HomeBrewTalk Wiki - User contributions [en]

Local Home Brew Store

2008-01-24T08:48:30Z

Mrkristofo: /* USA */

[[Category:Beer]]

'''Local Home Brew Stores''' are available as a source for supplies and advice. The following list contains home brew stores grouped by Country and region:

= Canada =

==Ontario==
; [http://www.brewtime.ca Brewtime], Hamilton, Ontario : A wine-making and brew-on-premises shop with helpful staff and a healthy supply of fresh ingredients and WhiteLabs yeast products.

=UK=
==Cheshire==
[http://www.zen37219.zen.co.uk/ The brew Shop]; Stockport,

=USA=
==California==
[http://www.morebeer.com/ Beer, Beer and More Beer]; Concord, CA

[http://www.homebrewmart.com/ Home Brew Mart]; San Diego, CA

[http://www.oakbarrel.com/ Oak Barrel]; Berkeley, CA

[http://www.sanfranciscobrewcraft.com/ San Francisco Brewcraft]; San Francisco, CA

[http://www.steinfillers.com/ Stein Fillers]; Long Beach, CA

==Colorado==
[http://www.beerathome.com/ Beer at Home]; Englewood and Westminster, CO

[http://www.stompthemgrapes.com/ Stomp Them Grapes]; Denver, CO
==Kentucky==
Wine makers & Beer makers Supply - Louisville, Ky
http://www.winebeersupply.com/about_us.htm

==Texas==
[http://www.austinhomebrew.com/ Austin Home Brew]; Austin, TX

==Utah==
[http://www.beernut.com/ The Beer Nut]; Salt Lake City, UT

==Washington==
Bob's Homebrew & Wine Supply; 2821 NE 55th St., Seattle, WA 98105 (206) 527-9283

=External Links=

;[http://beeradvocate.com/beerfly/ BeerFly]:A very complete listing of local homebrew shops around the world hosted by [[BeerAdvocate]].

Hop chemistry

2007-11-14T21:03:22Z

Mrkristofo: /* Iso-alpha acids */

[[Category:Beer]]
[[Category:Beer chemistry]]
[[Category:Beer ingredients]]
[[Category:Hops]]

The bittering, flavor, and aroma characteristics of [[hops]] are created by a two major types of chemical compound contained in the cone-shaped hop flower: acids and oils. The acids in question are '''alpha acids''' ('''humulone''', '''adhumulone''', and '''cohumulone'''), which for '''iso-alpha acids''' in the boil, and '''beta acids'''; the oils are the hop '''essential oils''' (primarily '''humulene''', '''myrcene''', '''caryophyllene''' and '''farnesene''').

==Alpha acids==
[[Image:alpha-acids.png|thumb|alpha acid]]

The '''alpha acids''' are the hop components most familiar to home brewers. Every package of hops sold to homebrewers indicates the alpha acid percentage to allow the brewer to calculate the [[bitterness]] he or she wants in the finished beer.
The alpha acid percentage represents the amount of the hop, by weight, that is composed of alpha acids. For more information on these calculations, see the article on [[bitterness]].

The "alpha acid" percentage actually encompasses multiple separate chemicals, each of which adds a unique flavor and style of bitterness. The primary alpha acids are:

===Humulone===

'''Humulone''' (R=isovaleryl) is the primary alpha acid occurring in most hops. It is thought to give a desirable "soft" bittering to the finished beer.

===Cohumulone===

Traditionally, '''cohumulone''' (R=isobutyryl) has been considered to add a harsh, unpleasant bitterness to beer, and so low-cohumulone varieties were considered more desirable for brewing purposes; most [[noble hops]] have relatively low cohumulone. For this reason, cohumulone is often the only alpha acid identified specifically by hop producers. Cohumulone is indicated as a percentage (by weight) of the total alpha acid content of a hop.

However, recently the role of cohumulone has been called into question, as new high-alpha [[hop varieties]] that are also high in cohumulone have come onto the market which are considered to impart a good bitterness.

===Adhumulone===

The third identified alpha acid is '''adhumulone''' (R=2-methylbutyryl), which usually occurs in relatively small amounts. Its effect on bitterness and flavor is not well understood.

==Iso-alpha acids==
[[Image:iso-alpha-acids.png|thumb|iso-alpha acid]]

When added to boiling [[wort]], alpha acids go into solution almost immediately. However, the bitterness they impart to beer appears only gradually, as the alpha acids are slowly isomerized in the boil to form '''isomerized alpha acids''' or '''iso-alpha acids'''. This is why bittering hop additions are normally done at the beginning of a boil of 60 minutes or longer.

Each alpha acid has a corresponding iso-alpha acid. The iso-alpha acid '''isohumulone''', the isomerized form of humulone, is important to brewers because it reacts with riboflavin in the presence of [[light]] to form [[MBT]] to form a skunk-like flavor and odor.

===Mechanism of Isomerization===
The formal structure of the isohumulones was published by De Keukeleire in 1971, as was a mechanism for the isomerization of humulone<ref>De Keukeleire, D., and Verzele, M. The absolute configuration of the isohumulones and the humulinic acids. ''Tetrahedron'' 27:4939-
4945, 1971. </ref>

[[Image:humulone-isomerization.png|thumb|mechanism of humulone isomerization]]

==Beta acids==

Along with alpha acids, hops contain '''beta acids''', principally '''lupulone''', '''colupulone''' and '''adlupulone'''. These are rarely considered separately, but the beta acids as a whole are important to a beer's flavor.

The beta acids do not produce as much bitterness during the boil as the alpha acids, but during fermentation and storage, as alpha acid bitterness breaks down, beta acids slowly create bitterness through [[oxidation]]. This affects the long-term character of aged and lagered beers.

Beta acids are given by hop producers as either a total percentage of beta acid in the hops by weight, or as a ratio of alpha to beta acids. Some people consider beta acid bitterness to be "harsher" than alpha acid (or at least humulone) bitterness, and look for hops with low total beta acids. However, the traditional [[noble hops]] generally have an alpha to beta acid ratio of close to 1:1, which is therefore considered desirable by some. Other brewers prefer a 2:1 ratio, which is thought to yield the most constant bitterness in aged beers.

==Essential oils==

While alpha acids contribute most of the bitterness to beer, most of the hop flavor and aroma is contributed by volatile '''essential oils'''. Hop producers generally indicate the total percentage of essential oils by weight in a given hop, and sometimes identify specific oils by percentage of total oil.

Because hop oils are highly volatile, traditionally the aroma and flavor characteristics of hops were obtained by late hop additions or [[dry hopping]], allowing the oils to be absorbed into the [[wort]] but not leaving them in the boil long enough to boil off. Traditionally flavor additions were made in the last fifteen minutes or less of the boil, while aroma additions were made with five minutes or less of boil remaining. However, recently home and craft brewers have been experimenting with the recently rediscovered technique of [[first wort hopping]], which allows hops added early in the brewing process to survive the boil and lend flavor and aroma to the finished beer.

The principal hop essential oils are:

===Humulene===

'''Humulene''' is thought to lend the distinctive "noble" character to [[noble hops]]; most varieties traditionally considered noble are high in humulene, while many bittering hop varieties have very low levels. The noble character is strongest when the hops are used in [[dry hopping]] or late hop additions; if boiled for longer periods, humulene lends the finished beer an herbal or spicy character.

===Myrcene===

'''Myrcene''' yields flavors that were not traditionally considered desirable by European brewers, and [[noble hops]] are very low in myrcene. However, many [[American hop varieties]] are very high in myrcene; it makes up up to 60% of total oil in [[Cascade]] and up to 70% in [[Amarillo]]. Also found in some citrus fruits, myrcene lends American hops many of their distinctive flavors.

When added late in, or after, the boil, myrcene adds the intense, pungent aroma associated with American dry-hopped beers. When boiled for longer periods, it yields the characteristic citrus and pine aromas of American craft beer.

===Caryophyllene===

'''Caryophyllene''' adds a spicy, herbal character similar to humulene when boiled. Its effect on flavor when fresh is not well understood.

===Farnesene===

'''Farnesene''' makes up a very low percentage of total oil in most [[hop varieties]]. However, it is considered significant because it makes up a substantial proportion of some [[noble hops]]. Its effect on flavor and aroma is unknown.

==References==

<references/>

Hop chemistry

2007-11-14T21:01:37Z

Mrkristofo: /* Humulone */

[[Category:Beer]]
[[Category:Beer chemistry]]
[[Category:Beer ingredients]]
[[Category:Hops]]

The bittering, flavor, and aroma characteristics of [[hops]] are created by a two major types of chemical compound contained in the cone-shaped hop flower: acids and oils. The acids in question are '''alpha acids''' ('''humulone''', '''adhumulone''', and '''cohumulone'''), which for '''iso-alpha acids''' in the boil, and '''beta acids'''; the oils are the hop '''essential oils''' (primarily '''humulene''', '''myrcene''', '''caryophyllene''' and '''farnesene''').

==Alpha acids==
[[Image:alpha-acids.png|thumb|alpha acid]]

The '''alpha acids''' are the hop components most familiar to home brewers. Every package of hops sold to homebrewers indicates the alpha acid percentage to allow the brewer to calculate the [[bitterness]] he or she wants in the finished beer.
The alpha acid percentage represents the amount of the hop, by weight, that is composed of alpha acids. For more information on these calculations, see the article on [[bitterness]].

The "alpha acid" percentage actually encompasses multiple separate chemicals, each of which adds a unique flavor and style of bitterness. The primary alpha acids are:

===Humulone===

'''Humulone''' (R=isovaleryl) is the primary alpha acid occurring in most hops. It is thought to give a desirable "soft" bittering to the finished beer.

===Cohumulone===

Traditionally, '''cohumulone''' (R=isobutyryl) has been considered to add a harsh, unpleasant bitterness to beer, and so low-cohumulone varieties were considered more desirable for brewing purposes; most [[noble hops]] have relatively low cohumulone. For this reason, cohumulone is often the only alpha acid identified specifically by hop producers. Cohumulone is indicated as a percentage (by weight) of the total alpha acid content of a hop.

However, recently the role of cohumulone has been called into question, as new high-alpha [[hop varieties]] that are also high in cohumulone have come onto the market which are considered to impart a good bitterness.

===Adhumulone===

The third identified alpha acid is '''adhumulone''' (R=2-methylbutyryl), which usually occurs in relatively small amounts. Its effect on bitterness and flavor is not well understood.

==Iso-alpha acids==
[[Image:iso-alpha-acids.png|thumb|iso-alpha acid]]

When added to boiling [[wort]], alpha acids go into solution almost immediately. However, the bitterness they impart to beer appears only gradually, as the alpha acids are slowly isomerized in the boil to form '''isomerized alpha acids''' or '''iso-alpha acids'''. This is why bittering hop additions are normally done at the beginning of a boil of 60 minutes or longer.

The formal structure of the isohumulones was published by De Keukeleire in 1971, as was a mechanism for the isomerization of humulone<ref>De Keukeleire, D., and Verzele, M. The absolute configuration of the isohumulones and the humulinic acids. ''Tetrahedron'' 27:4939-
4945, 1971. </ref>

[[Image:humulone-isomerization.png|thumb|mechanism of humulone isomerization]]

Each alpha acid has a corresponding iso-alpha acid. The iso-alpha acid '''isohumulone''', the isomerized form of humulone, is important to brewers because it reacts with riboflavin in the presence of [[light]] to form [[MBT]] to form a skunk-like flavor and odor.

==Beta acids==

Along with alpha acids, hops contain '''beta acids''', principally '''lupulone''', '''colupulone''' and '''adlupulone'''. These are rarely considered separately, but the beta acids as a whole are important to a beer's flavor.

The beta acids do not produce as much bitterness during the boil as the alpha acids, but during fermentation and storage, as alpha acid bitterness breaks down, beta acids slowly create bitterness through [[oxidation]]. This affects the long-term character of aged and lagered beers.

Beta acids are given by hop producers as either a total percentage of beta acid in the hops by weight, or as a ratio of alpha to beta acids. Some people consider beta acid bitterness to be "harsher" than alpha acid (or at least humulone) bitterness, and look for hops with low total beta acids. However, the traditional [[noble hops]] generally have an alpha to beta acid ratio of close to 1:1, which is therefore considered desirable by some. Other brewers prefer a 2:1 ratio, which is thought to yield the most constant bitterness in aged beers.

==Essential oils==

While alpha acids contribute most of the bitterness to beer, most of the hop flavor and aroma is contributed by volatile '''essential oils'''. Hop producers generally indicate the total percentage of essential oils by weight in a given hop, and sometimes identify specific oils by percentage of total oil.

Because hop oils are highly volatile, traditionally the aroma and flavor characteristics of hops were obtained by late hop additions or [[dry hopping]], allowing the oils to be absorbed into the [[wort]] but not leaving them in the boil long enough to boil off. Traditionally flavor additions were made in the last fifteen minutes or less of the boil, while aroma additions were made with five minutes or less of boil remaining. However, recently home and craft brewers have been experimenting with the recently rediscovered technique of [[first wort hopping]], which allows hops added early in the brewing process to survive the boil and lend flavor and aroma to the finished beer.

The principal hop essential oils are:

===Humulene===

'''Humulene''' is thought to lend the distinctive "noble" character to [[noble hops]]; most varieties traditionally considered noble are high in humulene, while many bittering hop varieties have very low levels. The noble character is strongest when the hops are used in [[dry hopping]] or late hop additions; if boiled for longer periods, humulene lends the finished beer an herbal or spicy character.

===Myrcene===

'''Myrcene''' yields flavors that were not traditionally considered desirable by European brewers, and [[noble hops]] are very low in myrcene. However, many [[American hop varieties]] are very high in myrcene; it makes up up to 60% of total oil in [[Cascade]] and up to 70% in [[Amarillo]]. Also found in some citrus fruits, myrcene lends American hops many of their distinctive flavors.

When added late in, or after, the boil, myrcene adds the intense, pungent aroma associated with American dry-hopped beers. When boiled for longer periods, it yields the characteristic citrus and pine aromas of American craft beer.

===Caryophyllene===

'''Caryophyllene''' adds a spicy, herbal character similar to humulene when boiled. Its effect on flavor when fresh is not well understood.

===Farnesene===

'''Farnesene''' makes up a very low percentage of total oil in most [[hop varieties]]. However, it is considered significant because it makes up a substantial proportion of some [[noble hops]]. Its effect on flavor and aroma is unknown.

==References==

<references/>

Hop chemistry

2007-11-14T21:01:21Z

Mrkristofo: /* Adhumulone */

[[Category:Beer]]
[[Category:Beer chemistry]]
[[Category:Beer ingredients]]
[[Category:Hops]]

The bittering, flavor, and aroma characteristics of [[hops]] are created by a two major types of chemical compound contained in the cone-shaped hop flower: acids and oils. The acids in question are '''alpha acids''' ('''humulone''', '''adhumulone''', and '''cohumulone'''), which for '''iso-alpha acids''' in the boil, and '''beta acids'''; the oils are the hop '''essential oils''' (primarily '''humulene''', '''myrcene''', '''caryophyllene''' and '''farnesene''').

==Alpha acids==
[[Image:alpha-acids.png|thumb|alpha acid]]

The '''alpha acids''' are the hop components most familiar to home brewers. Every package of hops sold to homebrewers indicates the alpha acid percentage to allow the brewer to calculate the [[bitterness]] he or she wants in the finished beer.
The alpha acid percentage represents the amount of the hop, by weight, that is composed of alpha acids. For more information on these calculations, see the article on [[bitterness]].

The "alpha acid" percentage actually encompasses multiple separate chemicals, each of which adds a unique flavor and style of bitterness. The primary alpha acids are:

===Humulone===

'''Humulone''' is the primary alpha acid occurring in most hops. It is thought to give a desirable "soft" bittering to the finished beer.

===Cohumulone===

Traditionally, '''cohumulone''' (R=isobutyryl) has been considered to add a harsh, unpleasant bitterness to beer, and so low-cohumulone varieties were considered more desirable for brewing purposes; most [[noble hops]] have relatively low cohumulone. For this reason, cohumulone is often the only alpha acid identified specifically by hop producers. Cohumulone is indicated as a percentage (by weight) of the total alpha acid content of a hop.

However, recently the role of cohumulone has been called into question, as new high-alpha [[hop varieties]] that are also high in cohumulone have come onto the market which are considered to impart a good bitterness.

===Adhumulone===

The third identified alpha acid is '''adhumulone''' (R=2-methylbutyryl), which usually occurs in relatively small amounts. Its effect on bitterness and flavor is not well understood.

==Iso-alpha acids==
[[Image:iso-alpha-acids.png|thumb|iso-alpha acid]]

When added to boiling [[wort]], alpha acids go into solution almost immediately. However, the bitterness they impart to beer appears only gradually, as the alpha acids are slowly isomerized in the boil to form '''isomerized alpha acids''' or '''iso-alpha acids'''. This is why bittering hop additions are normally done at the beginning of a boil of 60 minutes or longer.

The formal structure of the isohumulones was published by De Keukeleire in 1971, as was a mechanism for the isomerization of humulone<ref>De Keukeleire, D., and Verzele, M. The absolute configuration of the isohumulones and the humulinic acids. ''Tetrahedron'' 27:4939-
4945, 1971. </ref>

[[Image:humulone-isomerization.png|thumb|mechanism of humulone isomerization]]

Each alpha acid has a corresponding iso-alpha acid. The iso-alpha acid '''isohumulone''', the isomerized form of humulone, is important to brewers because it reacts with riboflavin in the presence of [[light]] to form [[MBT]] to form a skunk-like flavor and odor.

==Beta acids==

Along with alpha acids, hops contain '''beta acids''', principally '''lupulone''', '''colupulone''' and '''adlupulone'''. These are rarely considered separately, but the beta acids as a whole are important to a beer's flavor.

The beta acids do not produce as much bitterness during the boil as the alpha acids, but during fermentation and storage, as alpha acid bitterness breaks down, beta acids slowly create bitterness through [[oxidation]]. This affects the long-term character of aged and lagered beers.

Beta acids are given by hop producers as either a total percentage of beta acid in the hops by weight, or as a ratio of alpha to beta acids. Some people consider beta acid bitterness to be "harsher" than alpha acid (or at least humulone) bitterness, and look for hops with low total beta acids. However, the traditional [[noble hops]] generally have an alpha to beta acid ratio of close to 1:1, which is therefore considered desirable by some. Other brewers prefer a 2:1 ratio, which is thought to yield the most constant bitterness in aged beers.

==Essential oils==

While alpha acids contribute most of the bitterness to beer, most of the hop flavor and aroma is contributed by volatile '''essential oils'''. Hop producers generally indicate the total percentage of essential oils by weight in a given hop, and sometimes identify specific oils by percentage of total oil.

Because hop oils are highly volatile, traditionally the aroma and flavor characteristics of hops were obtained by late hop additions or [[dry hopping]], allowing the oils to be absorbed into the [[wort]] but not leaving them in the boil long enough to boil off. Traditionally flavor additions were made in the last fifteen minutes or less of the boil, while aroma additions were made with five minutes or less of boil remaining. However, recently home and craft brewers have been experimenting with the recently rediscovered technique of [[first wort hopping]], which allows hops added early in the brewing process to survive the boil and lend flavor and aroma to the finished beer.

The principal hop essential oils are:

===Humulene===

'''Humulene''' is thought to lend the distinctive "noble" character to [[noble hops]]; most varieties traditionally considered noble are high in humulene, while many bittering hop varieties have very low levels. The noble character is strongest when the hops are used in [[dry hopping]] or late hop additions; if boiled for longer periods, humulene lends the finished beer an herbal or spicy character.

===Myrcene===

'''Myrcene''' yields flavors that were not traditionally considered desirable by European brewers, and [[noble hops]] are very low in myrcene. However, many [[American hop varieties]] are very high in myrcene; it makes up up to 60% of total oil in [[Cascade]] and up to 70% in [[Amarillo]]. Also found in some citrus fruits, myrcene lends American hops many of their distinctive flavors.

When added late in, or after, the boil, myrcene adds the intense, pungent aroma associated with American dry-hopped beers. When boiled for longer periods, it yields the characteristic citrus and pine aromas of American craft beer.

===Caryophyllene===

'''Caryophyllene''' adds a spicy, herbal character similar to humulene when boiled. Its effect on flavor when fresh is not well understood.

===Farnesene===

'''Farnesene''' makes up a very low percentage of total oil in most [[hop varieties]]. However, it is considered significant because it makes up a substantial proportion of some [[noble hops]]. Its effect on flavor and aroma is unknown.

==References==

<references/>

Hop chemistry

2007-11-14T21:00:49Z

Mrkristofo: /* Cohumulone */

[[Category:Beer]]
[[Category:Beer chemistry]]
[[Category:Beer ingredients]]
[[Category:Hops]]

The bittering, flavor, and aroma characteristics of [[hops]] are created by a two major types of chemical compound contained in the cone-shaped hop flower: acids and oils. The acids in question are '''alpha acids''' ('''humulone''', '''adhumulone''', and '''cohumulone'''), which for '''iso-alpha acids''' in the boil, and '''beta acids'''; the oils are the hop '''essential oils''' (primarily '''humulene''', '''myrcene''', '''caryophyllene''' and '''farnesene''').

==Alpha acids==
[[Image:alpha-acids.png|thumb|alpha acid]]

The '''alpha acids''' are the hop components most familiar to home brewers. Every package of hops sold to homebrewers indicates the alpha acid percentage to allow the brewer to calculate the [[bitterness]] he or she wants in the finished beer.
The alpha acid percentage represents the amount of the hop, by weight, that is composed of alpha acids. For more information on these calculations, see the article on [[bitterness]].

The "alpha acid" percentage actually encompasses multiple separate chemicals, each of which adds a unique flavor and style of bitterness. The primary alpha acids are:

===Humulone===

'''Humulone''' is the primary alpha acid occurring in most hops. It is thought to give a desirable "soft" bittering to the finished beer.

===Cohumulone===

Traditionally, '''cohumulone''' (R=isobutyryl) has been considered to add a harsh, unpleasant bitterness to beer, and so low-cohumulone varieties were considered more desirable for brewing purposes; most [[noble hops]] have relatively low cohumulone. For this reason, cohumulone is often the only alpha acid identified specifically by hop producers. Cohumulone is indicated as a percentage (by weight) of the total alpha acid content of a hop.

However, recently the role of cohumulone has been called into question, as new high-alpha [[hop varieties]] that are also high in cohumulone have come onto the market which are considered to impart a good bitterness.

===Adhumulone===

The third identified alpha acid is '''adhumulone''', which usually occurs in relatively small amounts. Its effect on bitterness and flavor is not well understood.

==Iso-alpha acids==
[[Image:iso-alpha-acids.png|thumb|iso-alpha acid]]

When added to boiling [[wort]], alpha acids go into solution almost immediately. However, the bitterness they impart to beer appears only gradually, as the alpha acids are slowly isomerized in the boil to form '''isomerized alpha acids''' or '''iso-alpha acids'''. This is why bittering hop additions are normally done at the beginning of a boil of 60 minutes or longer.

The formal structure of the isohumulones was published by De Keukeleire in 1971, as was a mechanism for the isomerization of humulone<ref>De Keukeleire, D., and Verzele, M. The absolute configuration of the isohumulones and the humulinic acids. ''Tetrahedron'' 27:4939-
4945, 1971. </ref>

[[Image:humulone-isomerization.png|thumb|mechanism of humulone isomerization]]

Each alpha acid has a corresponding iso-alpha acid. The iso-alpha acid '''isohumulone''', the isomerized form of humulone, is important to brewers because it reacts with riboflavin in the presence of [[light]] to form [[MBT]] to form a skunk-like flavor and odor.

==Beta acids==

Along with alpha acids, hops contain '''beta acids''', principally '''lupulone''', '''colupulone''' and '''adlupulone'''. These are rarely considered separately, but the beta acids as a whole are important to a beer's flavor.

The beta acids do not produce as much bitterness during the boil as the alpha acids, but during fermentation and storage, as alpha acid bitterness breaks down, beta acids slowly create bitterness through [[oxidation]]. This affects the long-term character of aged and lagered beers.

Beta acids are given by hop producers as either a total percentage of beta acid in the hops by weight, or as a ratio of alpha to beta acids. Some people consider beta acid bitterness to be "harsher" than alpha acid (or at least humulone) bitterness, and look for hops with low total beta acids. However, the traditional [[noble hops]] generally have an alpha to beta acid ratio of close to 1:1, which is therefore considered desirable by some. Other brewers prefer a 2:1 ratio, which is thought to yield the most constant bitterness in aged beers.

==Essential oils==

While alpha acids contribute most of the bitterness to beer, most of the hop flavor and aroma is contributed by volatile '''essential oils'''. Hop producers generally indicate the total percentage of essential oils by weight in a given hop, and sometimes identify specific oils by percentage of total oil.

Because hop oils are highly volatile, traditionally the aroma and flavor characteristics of hops were obtained by late hop additions or [[dry hopping]], allowing the oils to be absorbed into the [[wort]] but not leaving them in the boil long enough to boil off. Traditionally flavor additions were made in the last fifteen minutes or less of the boil, while aroma additions were made with five minutes or less of boil remaining. However, recently home and craft brewers have been experimenting with the recently rediscovered technique of [[first wort hopping]], which allows hops added early in the brewing process to survive the boil and lend flavor and aroma to the finished beer.

The principal hop essential oils are:

===Humulene===

'''Humulene''' is thought to lend the distinctive "noble" character to [[noble hops]]; most varieties traditionally considered noble are high in humulene, while many bittering hop varieties have very low levels. The noble character is strongest when the hops are used in [[dry hopping]] or late hop additions; if boiled for longer periods, humulene lends the finished beer an herbal or spicy character.

===Myrcene===

'''Myrcene''' yields flavors that were not traditionally considered desirable by European brewers, and [[noble hops]] are very low in myrcene. However, many [[American hop varieties]] are very high in myrcene; it makes up up to 60% of total oil in [[Cascade]] and up to 70% in [[Amarillo]]. Also found in some citrus fruits, myrcene lends American hops many of their distinctive flavors.

When added late in, or after, the boil, myrcene adds the intense, pungent aroma associated with American dry-hopped beers. When boiled for longer periods, it yields the characteristic citrus and pine aromas of American craft beer.

===Caryophyllene===

'''Caryophyllene''' adds a spicy, herbal character similar to humulene when boiled. Its effect on flavor when fresh is not well understood.

===Farnesene===

'''Farnesene''' makes up a very low percentage of total oil in most [[hop varieties]]. However, it is considered significant because it makes up a substantial proportion of some [[noble hops]]. Its effect on flavor and aroma is unknown.

==References==

<references/>

Hop chemistry

2007-11-14T21:00:29Z

Mrkristofo: /* Cohumulone */

[[Category:Beer]]
[[Category:Beer chemistry]]
[[Category:Beer ingredients]]
[[Category:Hops]]

The bittering, flavor, and aroma characteristics of [[hops]] are created by a two major types of chemical compound contained in the cone-shaped hop flower: acids and oils. The acids in question are '''alpha acids''' ('''humulone''', '''adhumulone''', and '''cohumulone'''), which for '''iso-alpha acids''' in the boil, and '''beta acids'''; the oils are the hop '''essential oils''' (primarily '''humulene''', '''myrcene''', '''caryophyllene''' and '''farnesene''').

==Alpha acids==
[[Image:alpha-acids.png|thumb|alpha acid]]

The '''alpha acids''' are the hop components most familiar to home brewers. Every package of hops sold to homebrewers indicates the alpha acid percentage to allow the brewer to calculate the [[bitterness]] he or she wants in the finished beer.
The alpha acid percentage represents the amount of the hop, by weight, that is composed of alpha acids. For more information on these calculations, see the article on [[bitterness]].

The "alpha acid" percentage actually encompasses multiple separate chemicals, each of which adds a unique flavor and style of bitterness. The primary alpha acids are:

===Humulone===

'''Humulone''' is the primary alpha acid occurring in most hops. It is thought to give a desirable "soft" bittering to the finished beer.

===Cohumulone===

Traditionally, '''cohumulone''' (R=isovaleryl) has been considered to add a harsh, unpleasant bitterness to beer, and so low-cohumulone varieties were considered more desirable for brewing purposes; most [[noble hops]] have relatively low cohumulone. For this reason, cohumulone is often the only alpha acid identified specifically by hop producers. Cohumulone is indicated as a percentage (by weight) of the total alpha acid content of a hop.

However, recently the role of cohumulone has been called into question, as new high-alpha [[hop varieties]] that are also high in cohumulone have come onto the market which are considered to impart a good bitterness.

===Adhumulone===

The third identified alpha acid is '''adhumulone''', which usually occurs in relatively small amounts. Its effect on bitterness and flavor is not well understood.

==Iso-alpha acids==
[[Image:iso-alpha-acids.png|thumb|iso-alpha acid]]

When added to boiling [[wort]], alpha acids go into solution almost immediately. However, the bitterness they impart to beer appears only gradually, as the alpha acids are slowly isomerized in the boil to form '''isomerized alpha acids''' or '''iso-alpha acids'''. This is why bittering hop additions are normally done at the beginning of a boil of 60 minutes or longer.

The formal structure of the isohumulones was published by De Keukeleire in 1971, as was a mechanism for the isomerization of humulone<ref>De Keukeleire, D., and Verzele, M. The absolute configuration of the isohumulones and the humulinic acids. ''Tetrahedron'' 27:4939-
4945, 1971. </ref>

[[Image:humulone-isomerization.png|thumb|mechanism of humulone isomerization]]

Each alpha acid has a corresponding iso-alpha acid. The iso-alpha acid '''isohumulone''', the isomerized form of humulone, is important to brewers because it reacts with riboflavin in the presence of [[light]] to form [[MBT]] to form a skunk-like flavor and odor.

==Beta acids==

Along with alpha acids, hops contain '''beta acids''', principally '''lupulone''', '''colupulone''' and '''adlupulone'''. These are rarely considered separately, but the beta acids as a whole are important to a beer's flavor.

The beta acids do not produce as much bitterness during the boil as the alpha acids, but during fermentation and storage, as alpha acid bitterness breaks down, beta acids slowly create bitterness through [[oxidation]]. This affects the long-term character of aged and lagered beers.

Beta acids are given by hop producers as either a total percentage of beta acid in the hops by weight, or as a ratio of alpha to beta acids. Some people consider beta acid bitterness to be "harsher" than alpha acid (or at least humulone) bitterness, and look for hops with low total beta acids. However, the traditional [[noble hops]] generally have an alpha to beta acid ratio of close to 1:1, which is therefore considered desirable by some. Other brewers prefer a 2:1 ratio, which is thought to yield the most constant bitterness in aged beers.

==Essential oils==

While alpha acids contribute most of the bitterness to beer, most of the hop flavor and aroma is contributed by volatile '''essential oils'''. Hop producers generally indicate the total percentage of essential oils by weight in a given hop, and sometimes identify specific oils by percentage of total oil.

Because hop oils are highly volatile, traditionally the aroma and flavor characteristics of hops were obtained by late hop additions or [[dry hopping]], allowing the oils to be absorbed into the [[wort]] but not leaving them in the boil long enough to boil off. Traditionally flavor additions were made in the last fifteen minutes or less of the boil, while aroma additions were made with five minutes or less of boil remaining. However, recently home and craft brewers have been experimenting with the recently rediscovered technique of [[first wort hopping]], which allows hops added early in the brewing process to survive the boil and lend flavor and aroma to the finished beer.

The principal hop essential oils are:

===Humulene===

'''Humulene''' is thought to lend the distinctive "noble" character to [[noble hops]]; most varieties traditionally considered noble are high in humulene, while many bittering hop varieties have very low levels. The noble character is strongest when the hops are used in [[dry hopping]] or late hop additions; if boiled for longer periods, humulene lends the finished beer an herbal or spicy character.

===Myrcene===

'''Myrcene''' yields flavors that were not traditionally considered desirable by European brewers, and [[noble hops]] are very low in myrcene. However, many [[American hop varieties]] are very high in myrcene; it makes up up to 60% of total oil in [[Cascade]] and up to 70% in [[Amarillo]]. Also found in some citrus fruits, myrcene lends American hops many of their distinctive flavors.

When added late in, or after, the boil, myrcene adds the intense, pungent aroma associated with American dry-hopped beers. When boiled for longer periods, it yields the characteristic citrus and pine aromas of American craft beer.

===Caryophyllene===

'''Caryophyllene''' adds a spicy, herbal character similar to humulene when boiled. Its effect on flavor when fresh is not well understood.

===Farnesene===

'''Farnesene''' makes up a very low percentage of total oil in most [[hop varieties]]. However, it is considered significant because it makes up a substantial proportion of some [[noble hops]]. Its effect on flavor and aroma is unknown.

==References==

<references/>

File:Humulone-isomerization.png

2007-11-14T18:35:46Z

Mrkristofo: Mechanism of Humulone isomerization proposed by De Keukeleire, D., and Verzele, M. The absolute configuration of the isohumulones and the humulinic acids. Tetrahedron 27:4939-4945, 1971.

Mechanism of Humulone isomerization proposed by De Keukeleire, D., and Verzele, M. The absolute configuration of the isohumulones and the humulinic acids. Tetrahedron 27:4939-4945, 1971.

Hop chemistry

2007-11-14T18:34:48Z

Mrkristofo:

[[Category:Beer]]
[[Category:Beer chemistry]]
[[Category:Beer ingredients]]
[[Category:Hops]]

The bittering, flavor, and aroma characteristics of [[hops]] are created by a two major types of chemical compound contained in the cone-shaped hop flower: acids and oils. The acids in question are '''alpha acids''' ('''humulone''', '''adhumulone''', and '''cohumulone'''), which for '''iso-alpha acids''' in the boil, and '''beta acids'''; the oils are the hop '''essential oils''' (primarily '''humulene''', '''myrcene''', '''caryophyllene''' and '''farnesene''').

==Alpha acids==
[[Image:alpha-acids.png|thumb|alpha acid]]

The '''alpha acids''' are the hop components most familiar to home brewers. Every package of hops sold to homebrewers indicates the alpha acid percentage to allow the brewer to calculate the [[bitterness]] he or she wants in the finished beer.
The alpha acid percentage represents the amount of the hop, by weight, that is composed of alpha acids. For more information on these calculations, see the article on [[bitterness]].

The "alpha acid" percentage actually encompasses multiple separate chemicals, each of which adds a unique flavor and style of bitterness. The primary alpha acids are:

===Humulone===

'''Humulone''' is the primary alpha acid occurring in most hops. It is thought to give a desirable "soft" bittering to the finished beer.

===Cohumulone===

Traditionally, '''cohumulone''' has been considered to add a harsh, unpleasant bitterness to beer, and so low-cohumulone varieties were considered more desirable for brewing purposes; most [[noble hops]] have relatively low cohumulone. For this reason, cohumulone is often the only alpha acid identified specifically by hop producers. Cohumulone is indicated as a percentage (by weight) of the total alpha acid content of a hop.

However, recently the role of cohumulone has been called into question, as new high-alpha [[hop varieties]] that are also high in cohumulone have come onto the market which are considered to impart a good bitterness.

===Adhumulone===

The third identified alpha acid is '''adhumulone''', which usually occurs in relatively small amounts. Its effect on bitterness and flavor is not well understood.

==Iso-alpha acids==
[[Image:iso-alpha-acids.png|thumb|iso-alpha acid]]

When added to boiling [[wort]], alpha acids go into solution almost immediately. However, the bitterness they impart to beer appears only gradually, as the alpha acids are slowly isomerized in the boil to form '''isomerized alpha acids''' or '''iso-alpha acids'''. This is why bittering hop additions are normally done at the beginning of a boil of 60 minutes or longer.

The formal structure of the isohumulones was published by De Keukeleire in 1971, as was a mechanism for the isomerization of humulone<ref>De Keukeleire, D., and Verzele, M. The absolute configuration of the isohumulones and the humulinic acids. ''Tetrahedron'' 27:4939-
4945, 1971. </ref>

[[Image:humulone-isomerization.png|thumb|mechanism of humulone isomerization]]

Each alpha acid has a corresponding iso-alpha acid. The iso-alpha acid '''isohumulone''', the isomerized form of humulone, is important to brewers because it reacts with riboflavin in the presence of [[light]] to form [[MBT]] to form a skunk-like flavor and odor.

==Beta acids==

Along with alpha acids, hops contain '''beta acids''', principally '''lupulone''', '''colupulone''' and '''adlupulone'''. These are rarely considered separately, but the beta acids as a whole are important to a beer's flavor.

The beta acids do not produce as much bitterness during the boil as the alpha acids, but during fermentation and storage, as alpha acid bitterness breaks down, beta acids slowly create bitterness through [[oxidation]]. This affects the long-term character of aged and lagered beers.

Beta acids are given by hop producers as either a total percentage of beta acid in the hops by weight, or as a ratio of alpha to beta acids. Some people consider beta acid bitterness to be "harsher" than alpha acid (or at least humulone) bitterness, and look for hops with low total beta acids. However, the traditional [[noble hops]] generally have an alpha to beta acid ratio of close to 1:1, which is therefore considered desirable by some. Other brewers prefer a 2:1 ratio, which is thought to yield the most constant bitterness in aged beers.

==Essential oils==

While alpha acids contribute most of the bitterness to beer, most of the hop flavor and aroma is contributed by volatile '''essential oils'''. Hop producers generally indicate the total percentage of essential oils by weight in a given hop, and sometimes identify specific oils by percentage of total oil.

Because hop oils are highly volatile, traditionally the aroma and flavor characteristics of hops were obtained by late hop additions or [[dry hopping]], allowing the oils to be absorbed into the [[wort]] but not leaving them in the boil long enough to boil off. Traditionally flavor additions were made in the last fifteen minutes or less of the boil, while aroma additions were made with five minutes or less of boil remaining. However, recently home and craft brewers have been experimenting with the recently rediscovered technique of [[first wort hopping]], which allows hops added early in the brewing process to survive the boil and lend flavor and aroma to the finished beer.

The principal hop essential oils are:

===Humulene===

'''Humulene''' is thought to lend the distinctive "noble" character to [[noble hops]]; most varieties traditionally considered noble are high in humulene, while many bittering hop varieties have very low levels. The noble character is strongest when the hops are used in [[dry hopping]] or late hop additions; if boiled for longer periods, humulene lends the finished beer an herbal or spicy character.

===Myrcene===

'''Myrcene''' yields flavors that were not traditionally considered desirable by European brewers, and [[noble hops]] are very low in myrcene. However, many [[American hop varieties]] are very high in myrcene; it makes up up to 60% of total oil in [[Cascade]] and up to 70% in [[Amarillo]]. Also found in some citrus fruits, myrcene lends American hops many of their distinctive flavors.

When added late in, or after, the boil, myrcene adds the intense, pungent aroma associated with American dry-hopped beers. When boiled for longer periods, it yields the characteristic citrus and pine aromas of American craft beer.

===Caryophyllene===

'''Caryophyllene''' adds a spicy, herbal character similar to humulene when boiled. Its effect on flavor when fresh is not well understood.

===Farnesene===

'''Farnesene''' makes up a very low percentage of total oil in most [[hop varieties]]. However, it is considered significant because it makes up a substantial proportion of some [[noble hops]]. Its effect on flavor and aroma is unknown.

==References==

<references/>

Hop chemistry

2007-11-14T18:30:45Z

Mrkristofo: /* Iso-alpha acids */

[[Category:Beer]]
[[Category:Beer chemistry]]
[[Category:Beer ingredients]]
[[Category:Hops]]

The bittering, flavor, and aroma characteristics of [[hops]] are created by a two major types of chemical compound contained in the cone-shaped hop flower: acids and oils. The acids in question are '''alpha acids''' ('''humulone''', '''adhumulone''', and '''cohumulone'''), which for '''iso-alpha acids''' in the boil, and '''beta acids'''; the oils are the hop '''essential oils''' (primarily '''humulene''', '''myrcene''', '''caryophyllene''' and '''farnesene''').

==Alpha acids==
[[Image:alpha-acids.png|thumb|alpha acid]]

The '''alpha acids''' are the hop components most familiar to home brewers. Every package of hops sold to homebrewers indicates the alpha acid percentage to allow the brewer to calculate the [[bitterness]] he or she wants in the finished beer.
The alpha acid percentage represents the amount of the hop, by weight, that is composed of alpha acids. For more information on these calculations, see the article on [[bitterness]].

The "alpha acid" percentage actually encompasses multiple separate chemicals, each of which adds a unique flavor and style of bitterness. The primary alpha acids are:

===Humulone===

'''Humulone''' is the primary alpha acid occurring in most hops. It is thought to give a desirable "soft" bittering to the finished beer.

===Cohumulone===

Traditionally, '''cohumulone''' has been considered to add a harsh, unpleasant bitterness to beer, and so low-cohumulone varieties were considered more desirable for brewing purposes; most [[noble hops]] have relatively low cohumulone. For this reason, cohumulone is often the only alpha acid identified specifically by hop producers. Cohumulone is indicated as a percentage (by weight) of the total alpha acid content of a hop.

However, recently the role of cohumulone has been called into question, as new high-alpha [[hop varieties]] that are also high in cohumulone have come onto the market which are considered to impart a good bitterness.

===Adhumulone===

The third identified alpha acid is '''adhumulone''', which usually occurs in relatively small amounts. Its effect on bitterness and flavor is not well understood.

==Iso-alpha acids==
[[Image:iso-alpha-acids.png|thumb|iso-alpha acid]]

When added to boiling [[wort]], alpha acids go into solution almost immediately. However, the bitterness they impart to beer appears only gradually, as the alpha acids are slowly isomerized in the boil to form '''isomerized alpha acids''' or '''iso-alpha acids'''. This is why bittering hop additions are normally done at the beginning of a boil of 60 minutes or longer.

The formal structure of the isohumulones was published by De Keukeleire in 1971, as was a mechanism for the isomerization of humulone<ref>{{cite journal
| last = Keukeleire
| first = D.
| coauthors = Verzele, M.
| title = The absolute configuration of the isohumulones and the humulinic acids
| journal = Tetrahedron
| volume = 27
| pages = 4939-4945}}</ref>

[[Image:humulone-isomerization.png|thumb|mechanism of humulone isomerization]]

Each alpha acid has a corresponding iso-alpha acid. The iso-alpha acid '''isohumulone''', the isomerized form of humulone, is important to brewers because it reacts with riboflavin in the presence of [[light]] to form [[MBT]] to form a skunk-like flavor and odor.

==Beta acids==

Along with alpha acids, hops contain '''beta acids''', principally '''lupulone''', '''colupulone''' and '''adlupulone'''. These are rarely considered separately, but the beta acids as a whole are important to a beer's flavor.

The beta acids do not produce as much bitterness during the boil as the alpha acids, but during fermentation and storage, as alpha acid bitterness breaks down, beta acids slowly create bitterness through [[oxidation]]. This affects the long-term character of aged and lagered beers.

Beta acids are given by hop producers as either a total percentage of beta acid in the hops by weight, or as a ratio of alpha to beta acids. Some people consider beta acid bitterness to be "harsher" than alpha acid (or at least humulone) bitterness, and look for hops with low total beta acids. However, the traditional [[noble hops]] generally have an alpha to beta acid ratio of close to 1:1, which is therefore considered desirable by some. Other brewers prefer a 2:1 ratio, which is thought to yield the most constant bitterness in aged beers.

==Essential oils==

While alpha acids contribute most of the bitterness to beer, most of the hop flavor and aroma is contributed by volatile '''essential oils'''. Hop producers generally indicate the total percentage of essential oils by weight in a given hop, and sometimes identify specific oils by percentage of total oil.

Because hop oils are highly volatile, traditionally the aroma and flavor characteristics of hops were obtained by late hop additions or [[dry hopping]], allowing the oils to be absorbed into the [[wort]] but not leaving them in the boil long enough to boil off. Traditionally flavor additions were made in the last fifteen minutes or less of the boil, while aroma additions were made with five minutes or less of boil remaining. However, recently home and craft brewers have been experimenting with the recently rediscovered technique of [[first wort hopping]], which allows hops added early in the brewing process to survive the boil and lend flavor and aroma to the finished beer.

The principal hop essential oils are:

===Humulene===

'''Humulene''' is thought to lend the distinctive "noble" character to [[noble hops]]; most varieties traditionally considered noble are high in humulene, while many bittering hop varieties have very low levels. The noble character is strongest when the hops are used in [[dry hopping]] or late hop additions; if boiled for longer periods, humulene lends the finished beer an herbal or spicy character.

===Myrcene===

'''Myrcene''' yields flavors that were not traditionally considered desirable by European brewers, and [[noble hops]] are very low in myrcene. However, many [[American hop varieties]] are very high in myrcene; it makes up up to 60% of total oil in [[Cascade]] and up to 70% in [[Amarillo]]. Also found in some citrus fruits, myrcene lends American hops many of their distinctive flavors.

When added late in, or after, the boil, myrcene adds the intense, pungent aroma associated with American dry-hopped beers. When boiled for longer periods, it yields the characteristic citrus and pine aromas of American craft beer.

===Caryophyllene===

'''Caryophyllene''' adds a spicy, herbal character similar to humulene when boiled. Its effect on flavor when fresh is not well understood.

===Farnesene===

'''Farnesene''' makes up a very low percentage of total oil in most [[hop varieties]]. However, it is considered significant because it makes up a substantial proportion of some [[noble hops]]. Its effect on flavor and aroma is unknown.

File:Iso-alpha-acids.png

2007-11-14T05:27:55Z

Mrkristofo:

Hop chemistry

2007-11-14T05:27:27Z

Mrkristofo: /* Iso-alpha acids */

[[Category:Beer]]
[[Category:Beer chemistry]]
[[Category:Beer ingredients]]
[[Category:Hops]]

The bittering, flavor, and aroma characteristics of [[hops]] are created by a two major types of chemical compound contained in the cone-shaped hop flower: acids and oils. The acids in question are '''alpha acids''' ('''humulone''', '''adhumulone''', and '''cohumulone'''), which for '''iso-alpha acids''' in the boil, and '''beta acids'''; the oils are the hop '''essential oils''' (primarily '''humulene''', '''myrcene''', '''caryophyllene''' and '''farnesene''').

==Alpha acids==
[[Image:alpha-acids.png|thumb|alpha acid]]

The '''alpha acids''' are the hop components most familiar to home brewers. Every package of hops sold to homebrewers indicates the alpha acid percentage to allow the brewer to calculate the [[bitterness]] he or she wants in the finished beer.
The alpha acid percentage represents the amount of the hop, by weight, that is composed of alpha acids. For more information on these calculations, see the article on [[bitterness]].

The "alpha acid" percentage actually encompasses multiple separate chemicals, each of which adds a unique flavor and style of bitterness. The primary alpha acids are:

===Humulone===

'''Humulone''' is the primary alpha acid occurring in most hops. It is thought to give a desirable "soft" bittering to the finished beer.

===Cohumulone===

Traditionally, '''cohumulone''' has been considered to add a harsh, unpleasant bitterness to beer, and so low-cohumulone varieties were considered more desirable for brewing purposes; most [[noble hops]] have relatively low cohumulone. For this reason, cohumulone is often the only alpha acid identified specifically by hop producers. Cohumulone is indicated as a percentage (by weight) of the total alpha acid content of a hop.

However, recently the role of cohumulone has been called into question, as new high-alpha [[hop varieties]] that are also high in cohumulone have come onto the market which are considered to impart a good bitterness.

===Adhumulone===

The third identified alpha acid is '''adhumulone''', which usually occurs in relatively small amounts. Its effect on bitterness and flavor is not well understood.

==Iso-alpha acids==
[[Image:iso-alpha-acids.png|thumb|iso-alpha acid]]

When added to boiling [[wort]], alpha acids go into solution almost immediately. However, the bitterness they impart to beer appears only gradually, as the alpha acids are slowly isomerized in the boil to form '''isomerized alpha acids''' or '''iso-alpha acids'''. This is why bittering hop additions are normally done at the beginning of a boil of 60 minutes or longer.

Each alpha acid has a corresponding iso-alpha acid. The iso-alpha acid '''isohumulone''', the isomerized form of humulone, is important to brewers because it reacts with riboflavin in the presence of [[light]] to form [[MBT]] to form a skunk-like flavor and odor.

==Beta acids==

Along with alpha acids, hops contain '''beta acids''', principally '''lupulone''', '''colupulone''' and '''adlupulone'''. These are rarely considered separately, but the beta acids as a whole are important to a beer's flavor.

The beta acids do not produce as much bitterness during the boil as the alpha acids, but during fermentation and storage, as alpha acid bitterness breaks down, beta acids slowly create bitterness through [[oxidation]]. This affects the long-term character of aged and lagered beers.

Beta acids are given by hop producers as either a total percentage of beta acid in the hops by weight, or as a ratio of alpha to beta acids. Some people consider beta acid bitterness to be "harsher" than alpha acid (or at least humulone) bitterness, and look for hops with low total beta acids. However, the traditional [[noble hops]] generally have an alpha to beta acid ratio of close to 1:1, which is therefore considered desirable by some. Other brewers prefer a 2:1 ratio, which is thought to yield the most constant bitterness in aged beers.

==Essential oils==

While alpha acids contribute most of the bitterness to beer, most of the hop flavor and aroma is contributed by volatile '''essential oils'''. Hop producers generally indicate the total percentage of essential oils by weight in a given hop, and sometimes identify specific oils by percentage of total oil.

Because hop oils are highly volatile, traditionally the aroma and flavor characteristics of hops were obtained by late hop additions or [[dry hopping]], allowing the oils to be absorbed into the [[wort]] but not leaving them in the boil long enough to boil off. Traditionally flavor additions were made in the last fifteen minutes or less of the boil, while aroma additions were made with five minutes or less of boil remaining. However, recently home and craft brewers have been experimenting with the recently rediscovered technique of [[first wort hopping]], which allows hops added early in the brewing process to survive the boil and lend flavor and aroma to the finished beer.

The principal hop essential oils are:

===Humulene===

'''Humulene''' is thought to lend the distinctive "noble" character to [[noble hops]]; most varieties traditionally considered noble are high in humulene, while many bittering hop varieties have very low levels. The noble character is strongest when the hops are used in [[dry hopping]] or late hop additions; if boiled for longer periods, humulene lends the finished beer an herbal or spicy character.

===Myrcene===

'''Myrcene''' yields flavors that were not traditionally considered desirable by European brewers, and [[noble hops]] are very low in myrcene. However, many [[American hop varieties]] are very high in myrcene; it makes up up to 60% of total oil in [[Cascade]] and up to 70% in [[Amarillo]]. Also found in some citrus fruits, myrcene lends American hops many of their distinctive flavors.

When added late in, or after, the boil, myrcene adds the intense, pungent aroma associated with American dry-hopped beers. When boiled for longer periods, it yields the characteristic citrus and pine aromas of American craft beer.

===Caryophyllene===

'''Caryophyllene''' adds a spicy, herbal character similar to humulene when boiled. Its effect on flavor when fresh is not well understood.

===Farnesene===

'''Farnesene''' makes up a very low percentage of total oil in most [[hop varieties]]. However, it is considered significant because it makes up a substantial proportion of some [[noble hops]]. Its effect on flavor and aroma is unknown.

Peter Bouckaert

2007-10-08T04:42:27Z

Mrkristofo: New page: Brewmaster, New Belgium Brewing Co.

Brewmaster, New Belgium Brewing Co.

Hop chemistry

2007-10-08T04:18:54Z

Mrkristofo:

[[Category:Beer]]
[[Category:Beer chemistry]]
[[Category:Beer ingredients]]
[[Category:Hops]]

The bittering, flavor, and aroma characteristics of [[hops]] are created by a two major types of chemical compound contained in the cone-shaped hop flower: acids and oils. The acids in question are '''alpha acids''' ('''humulone''', '''adhumulone''', and '''cohumulone'''), which for '''iso-alpha acids''' in the boil, and '''beta acids'''; the oils are the hop '''essential oils''' (primarily '''humulene''', '''myrcene''', '''caryophyllene''' and '''farnesene''').

==Alpha acids==
[[Image:alpha-acids.png|thumb|alpha acid]]

The '''alpha acids''' are the hop components most familiar to home brewers. Every package of hops sold to homebrewers indicates the alpha acid percentage to allow the brewer to calculate the [[bitterness]] he or she wants in the finished beer.
The alpha acid percentage represents the amount of the hop, by weight, that is composed of alpha acids. For more information on these calculations, see the article on [[bitterness]].

The "alpha acid" percentage actually encompasses multiple separate chemicals, each of which adds a unique flavor and style of bitterness. The primary alpha acids are:

===Humulone===

'''Humulone''' is the primary alpha acid occurring in most hops. It is thought to give a desirable "soft" bittering to the finished beer.

===Cohumulone===

Traditionally, '''cohumulone''' has been considered to add a harsh, unpleasant bitterness to beer, and so low-cohumulone varieties were considered more desirable for brewing purposes; most [[noble hops]] have relatively low cohumulone. For this reason, cohumulone is often the only alpha acid identified specifically by hop producers. Cohumulone is indicated as a percentage (by weight) of the total alpha acid content of a hop.

However, recently the role of cohumulone has been called into question, as new high-alpha [[hop varieties]] that are also high in cohumulone have come onto the market which are considered to impart a good bitterness.

===Adhumulone===

The third identified alpha acid is '''adhumulone''', which usually occurs in relatively small amounts. Its effect on bitterness and flavor is not well understood.

==Iso-alpha acids==

When added to boiling [[wort]], alpha acids go into solution almost immediately. However, the bitterness they impart to beer appears only gradually, as the alpha acids are slowly isomerized in the boil to form '''isomerized alpha acids''' or '''iso-alpha acids'''. This is why bittering hop additions are normally done at the beginning of a boil of 60 minutes or longer.

Each alpha acid has a corresponding iso-alpha acid. The iso-alpha acid '''isohumulone''', the isomerized form of humulone, is important to brewers because it reacts with riboflavin in the presence of [[light]] to form [[MBT]] to form a skunk-like flavor and odor.

==Beta acids==

Along with alpha acids, hops contain '''beta acids''', principally '''lupulone''', '''colupulone''' and '''adlupulone'''. These are rarely considered separately, but the beta acids as a whole are important to a beer's flavor.

The beta acids do not produce as much bitterness during the boil as the alpha acids, but during fermentation and storage, as alpha acid bitterness breaks down, beta acids slowly create bitterness through [[oxidation]]. This affects the long-term character of aged and lagered beers.

Beta acids are given by hop producers as either a total percentage of beta acid in the hops by weight, or as a ratio of alpha to beta acids. Some people consider beta acid bitterness to be "harsher" than alpha acid (or at least humulone) bitterness, and look for hops with low total beta acids. However, the traditional [[noble hops]] generally have an alpha to beta acid ratio of close to 1:1, which is therefore considered desirable by some. Other brewers prefer a 2:1 ratio, which is thought to yield the most constant bitterness in aged beers.

==Essential oils==

While alpha acids contribute most of the bitterness to beer, most of the hop flavor and aroma is contributed by volatile '''essential oils'''. Hop producers generally indicate the total percentage of essential oils by weight in a given hop, and sometimes identify specific oils by percentage of total oil.

Because hop oils are highly volatile, traditionally the aroma and flavor characteristics of hops were obtained by late hop additions or [[dry hopping]], allowing the oils to be absorbed into the [[wort]] but not leaving them in the boil long enough to boil off. Traditionally flavor additions were made in the last fifteen minutes or less of the boil, while aroma additions were made with five minutes or less of boil remaining. However, recently home and craft brewers have been experimenting with the recently rediscovered technique of [[first wort hopping]], which allows hops added early in the brewing process to survive the boil and lend flavor and aroma to the finished beer.

The principal hop essential oils are:

===Humulene===

'''Humulene''' is thought to lend the distinctive "noble" character to [[noble hops]]; most varieties traditionally considered noble are high in humulene, while many bittering hop varieties have very low levels. The noble character is strongest when the hops are used in [[dry hopping]] or late hop additions; if boiled for longer periods, humulene lends the finished beer an herbal or spicy character.

===Myrcene===

'''Myrcene''' yields flavors that were not traditionally considered desirable by European brewers, and [[noble hops]] are very low in myrcene. However, many [[American hop varieties]] are very high in myrcene; it makes up up to 60% of total oil in [[Cascade]] and up to 70% in [[Amarillo]]. Also found in some citrus fruits, myrcene lends American hops many of their distinctive flavors.

When added late in, or after, the boil, myrcene adds the intense, pungent aroma associated with American dry-hopped beers. When boiled for longer periods, it yields the characteristic citrus and pine aromas of American craft beer.

===Caryophyllene===

'''Caryophyllene''' adds a spicy, herbal character similar to humulene when boiled. Its effect on flavor when fresh is not well understood.

===Farnesene===

'''Farnesene''' makes up a very low percentage of total oil in most [[hop varieties]]. However, it is considered significant because it makes up a substantial proportion of some [[noble hops]]. Its effect on flavor and aroma is unknown.

Hop chemistry

2007-10-08T03:18:11Z

Mrkristofo: /* Alpha acids */

[[Category:Beer]]
[[Category:Beer chemistry]]
[[Category:Beer ingredients]]
[[Category:Hops]]

The bittering, flavor, and aroma characteristics of [[hops]] are created by a two major types of chemical compound contained in the cone-shaped hop flower: acids and oils. The acids in question are '''alpha acids''' ('''humulone''', '''adhumulone''', and '''cohumulone'''), which for '''iso-alpha acids''' in the boil, and '''beta acids'''; the oils are the hop '''essential oils''' (primarily '''humulene''', '''myrcene''', '''caryophyllene''' and '''farnesene''').

==Alpha acids==
[[Image:alpha-acids.png|thumb|alpha acid]]

The '''alpha acids''' are the hop components most familiar to home brewers. Every package of hops sold to homebrewers indicates the alpha acid percentage to allow the brewer to calculate the [[bitterness]] he or she wants in the finished beer.
The alpha acid percentage represents the amount of the hop, by weight, that is composed of alpha acids. For more information on these calculations, see the article on [[bitterness]].

The "alpha acid" percentage actually encompasses multiple separate chemicals, each of which adds a unique flavor and style of bitterness. The primary alpha acids are:

==Iso-alpha acids==

When added to boiling [[wort]], alpha acids go into solution almost immediately. However, the bitterness they impart to beer appears only gradually, as the alpha acids are slowly isomerized in the boil to form '''isomerized alpha acids''' or '''iso-alpha acids'''. This is why bittering hop additions are normally done at the beginning of a boil of 60 minutes or longer.

Each alpha acid has a corresponding iso-alpha acid. The iso-alpha acid '''isohumulone''', the isomerized form of humulone, is important to brewers because it reacts with riboflavin in the presence of [[light]] to form [[MBT]] to form a skunk-like flavor and odor.

===Humulone===

'''Humulone''' is the primary alpha acid occurring in most hops. It is thought to give a desirable "soft" bittering to the finished beer.

===Cohumulone===

Traditionally, '''cohumulone''' has been considered to add a harsh, unpleasant bitterness to beer, and so low-cohumulone varieties were considered more desirable for brewing purposes; most [[noble hops]] have relatively low cohumulone. For this reason, cohumulone is often the only alpha acid identified specifically by hop producers. Cohumulone is indicated as a percentage (by weight) of the total alpha acid content of a hop.

However, recently the role of cohumulone has been called into question, as new high-alpha [[hop varieties]] that are also high in cohumulone have come onto the market which are considered to impart a good bitterness.

===Adhumulone===

The third identified alpha acid is '''adhumulone''', which usually occurs in relatively small amounts. Its effect on bitterness and flavor is not well understood.

==Beta acids==

Along with alpha acids, hops contain '''beta acids''', principally '''lupulone''', '''colupulone''' and '''adlupulone'''. These are rarely considered separately, but the beta acids as a whole are important to a beer's flavor.

The beta acids do not produce as much bitterness during the boil as the alpha acids, but during fermentation and storage, as alpha acid bitterness breaks down, beta acids slowly create bitterness through [[oxidation]]. This affects the long-term character of aged and lagered beers.

Beta acids are given by hop producers as either a total percentage of beta acid in the hops by weight, or as a ratio of alpha to beta acids. Some people consider beta acid bitterness to be "harsher" than alpha acid (or at least humulone) bitterness, and look for hops with low total beta acids. However, the traditional [[noble hops]] generally have an alpha to beta acid ratio of close to 1:1, which is therefore considered desirable by some. Other brewers prefer a 2:1 ratio, which is thought to yield the most constant bitterness in aged beers.

==Essential oils==

While alpha acids contribute most of the bitterness to beer, most of the hop flavor and aroma is contributed by volatile '''essential oils'''. Hop producers generally indicate the total percentage of essential oils by weight in a given hop, and sometimes identify specific oils by percentage of total oil.

Because hop oils are highly volatile, traditionally the aroma and flavor characteristics of hops were obtained by late hop additions or [[dry hopping]], allowing the oils to be absorbed into the [[wort]] but not leaving them in the boil long enough to boil off. Traditionally flavor additions were made in the last fifteen minutes or less of the boil, while aroma additions were made with five minutes or less of boil remaining. However, recently home and craft brewers have been experimenting with the recently rediscovered technique of [[first wort hopping]], which allows hops added early in the brewing process to survive the boil and lend flavor and aroma to the finished beer.

The principal hop essential oils are:

===Humulene===

'''Humulene''' is thought to lend the distinctive "noble" character to [[noble hops]]; most varieties traditionally considered noble are high in humulene, while many bittering hop varieties have very low levels. The noble character is strongest when the hops are used in [[dry hopping]] or late hop additions; if boiled for longer periods, humulene lends the finished beer an herbal or spicy character.

===Myrcene===

'''Myrcene''' yields flavors that were not traditionally considered desirable by European brewers, and [[noble hops]] are very low in myrcene. However, many [[American hop varieties]] are very high in myrcene; it makes up up to 60% of total oil in [[Cascade]] and up to 70% in [[Amarillo]]. Also found in some citrus fruits, myrcene lends American hops many of their distinctive flavors.

When added late in, or after, the boil, myrcene adds the intense, pungent aroma associated with American dry-hopped beers. When boiled for longer periods, it yields the characteristic citrus and pine aromas of American craft beer.

===Caryophyllene===

'''Caryophyllene''' adds a spicy, herbal character similar to humulene when boiled. Its effect on flavor when fresh is not well understood.

===Farnesene===

'''Farnesene''' makes up a very low percentage of total oil in most [[hop varieties]]. However, it is considered significant because it makes up a substantial proportion of some [[noble hops]]. Its effect on flavor and aroma is unknown.

File:Alpha-acids.png

2007-10-08T03:17:56Z

Mrkristofo: General structure of alpha acids in hops.

General structure of alpha acids in hops.

File:Alpha-acids.gif

2007-10-08T03:15:02Z

Mrkristofo: General structure of alpha-acids present in hops.

General structure of alpha-acids present in hops.

Acetaldehyde

2007-10-08T03:04:31Z

Mrkristofo:

__FORCETOC__
[[Category:Beer]]
[[Category:Troubleshooting]]
[[Category:Flavor problems]]
[[Category:Aroma problems]]

'''Acetaldehyde''' is a compound that causes [[:Category:Flavor problems|off flavors]] and [[:Category:Aroma problems|aromas]] in beer, often described as tasting and smelling like '''green apples''', '''cut grass''' or '''green leaves''', '''pumpkin''', or '''latex paint''', and is sometimes described as giving beer a '''green''' character.

[[Image:acetaldehyde.gif|thumb|acetaldehyde]]

==Acetaldehyde in beer==

While acetaldehyde is usually considered a fault in beer, some beer styles do use it as part of the flavor profile. The best-known example is Budweiser, but other beers such as EKU-28, Salvator and Ephemere also include acetaldehyde flavors.

==Causes of acetaldehyde==

Acetaldehyde is an compound formed by an intermediate step in the conversion of [[sugar]] to [[ethanol]] by [[yeast]]. Under ordinary circumstances, any acetaldehyde formed during [[fermentation]] will eventually be taken up and converted by the [[yeast]]. The most common cause is removing the beer from the yeast too early, before the yeast has a chance to complete fermentation.

In finished beer, the ethanol reaction can sometimes be reversed by [[oxidation]], resulting in acetaldehyde re-formation.

Adetaldehyde is also a byproduct of the conversion of [[ethanol]] to [[acetic acid]] ([[vinegar]]) by [[acetic acid bacteria]]. If this is the cause of your acetaldehyde problems, it will probably be accompanied by a [[vinegary]] or [[cidery]] flavor and aroma.

==Preventing acetaldehyde==

Because acetaldehyde is usually formed by an intermediate step in the [[ethanol]] reaction, in most cases it can be prevented by a longer [[cold conditioning]] process.

See the entries on [[acetic acid bacteria]] and [[oxidation]] if you think those are the source of your acetaldehyde problem.

==Creating acetaldehyde==

If you want an acetaldehyde character in your beer, the easiest method is to use a short [[cold conditioning]] period and then [[filtering|filter]] your beer to remove the [[yeast]].

To simulate acetaldehyde in beer for tasting or judging testing or calibration, add 3/4 tsp. of white wine vinegar to 12 ounces of beer.

File:Acetaldehyde.gif

2007-10-08T03:04:05Z

Mrkristofo:

MBT

2007-10-08T03:02:20Z

Mrkristofo:

__FORCETOC__
[[Category:Beer]]
[[Category:Beer chemistry]]
[[Category:Troubleshooting]]
[[Category:Flavor problems]]
[[Category:Aroma problems]]

'''MBT''' is the abbreviation for '''3-methyl-2-butene-1-thiol''', a compound formed by the reaction of [[isomerized alpha acids]], specifically [[isohumulone]], with riboflavin in the presence of certain wavelengths of '''light'''. MBT is very similar in chemical composition and odor to the spray of a '''skunk'''.
[[Image:MBT.gif|thumb|MBT]]
==MBT in Beer==

MBT is not generally considered appropriate in any beer style. However, some brands of lager, notably Heineken, are packaged in such a way that the creation of some amounts of MBT (and therefore skunk flavor and aroma) is almost inevitable. Many beer drinkers, especially in the United States, have come to associate this character with the beer itself and consider it part of the beer's character.

==Causes of MBT==

MBT is created when [[wort]] or [[beer]] containing [[isomerized alpha acids]], which are extracted from [[hops]] by boiling and contribute [[bitterness]] to beer, is exposed to certain wavelengths of ultraviolet and blue visible light. In the presence of light, one iso-alpha acid, [[isohumulone]], reacts with the riboflavin present in wort or beer to form MBT.

Because the reaction is specific to hop acids, [[mead]], [[wine]], and other [[fermented beverages]] that do not contain [[hops]] may be safely exposed to light.

==Preventing MBT==

MBT can be prevented by avoiding exposing [[wort]] or [[beer]] to the relevant wavelengths of light after the completion of the boil. Sunlight skunks beer faster than other kinds of light, and fluorescent light is also a problem; incandescent light contains less of the relevant wavelengths of light. Beer stored in clear, blue, or green carboys or bottles should never be exposed to sunlight or fluorescent light, and exposure to incandescent light should be limited. Beer should be bottled in brown bottles wherever possible to minimize skunking, but even brown bottles should not be left in sunlight for long periods of time. In clear or green glass, skunking can happen in a matter of minutes.

Some commercial breweries that bottle their beer in green or clear bottles avoid skunking by using special hop extracts which do not contain [[isohumulone]], thus eliminating the problem of skunking altogether. This is not practical or desirable for most homebrewers.

==Creating MBT==

To create an MBT character in beer for tasting or judging testing or calibration, leave a bottle of Heineken or another [[lager]] bottled in a green bottle in bright sunlight for fifteen minutes.

MBT

2007-10-08T02:57:46Z

Mrkristofo:

__FORCETOC__
[[Category:Beer]]
[[Category:Beer chemistry]]
[[Category:Troubleshooting]]
[[Category:Flavor problems]]
[[Category:Aroma problems]]

'''MBT''' is the abbreviation for '''3-methyl-2-butene-1-thiol''', a compound formed by the reaction of [[isomerized alpha acids]], specifically [[isohumulone]], with riboflavin in the presence of certain wavelengths of '''light'''. MBT is very similar in chemical composition and odor to the spray of a '''skunk'''.

[[Image:MBT.gif]]

==MBT in Beer==

MBT is not generally considered appropriate in any beer style. However, some brands of lager, notably Heineken, are packaged in such a way that the creation of some amounts of MBT (and therefore skunk flavor and aroma) is almost inevitable. Many beer drinkers, especially in the United States, have come to associate this character with the beer itself and consider it part of the beer's character.

==Causes of MBT==

MBT is created when [[wort]] or [[beer]] containing [[isomerized alpha acids]], which are extracted from [[hops]] by boiling and contribute [[bitterness]] to beer, is exposed to certain wavelengths of ultraviolet and blue visible light. In the presence of light, one iso-alpha acid, [[isohumulone]], reacts with the riboflavin present in wort or beer to form MBT.

Because the reaction is specific to hop acids, [[mead]], [[wine]], and other [[fermented beverages]] that do not contain [[hops]] may be safely exposed to light.

==Preventing MBT==

MBT can be prevented by avoiding exposing [[wort]] or [[beer]] to the relevant wavelengths of light after the completion of the boil. Sunlight skunks beer faster than other kinds of light, and fluorescent light is also a problem; incandescent light contains less of the relevant wavelengths of light. Beer stored in clear, blue, or green carboys or bottles should never be exposed to sunlight or fluorescent light, and exposure to incandescent light should be limited. Beer should be bottled in brown bottles wherever possible to minimize skunking, but even brown bottles should not be left in sunlight for long periods of time. In clear or green glass, skunking can happen in a matter of minutes.

Some commercial breweries that bottle their beer in green or clear bottles avoid skunking by using special hop extracts which do not contain [[isohumulone]], thus eliminating the problem of skunking altogether. This is not practical or desirable for most homebrewers.

==Creating MBT==

To create an MBT character in beer for tasting or judging testing or calibration, leave a bottle of Heineken or another [[lager]] bottled in a green bottle in bright sunlight for fifteen minutes.

File:MBT.gif

2007-10-08T02:56:34Z

Mrkristofo: