Brewtopia
"Greenwood Aged Beer"
What Are Hops?
Hops are cultivated flowers (humulus *****us), green in color with yellow *****in glands down between the petals, used for preservative and flavoring characteristics in beer. The bitterness of the hop is used to balance the sweetness of the malt, and the essential oils add a flavor/aroma which cannot be achieved by using any other plant. The hop plant is a perennial spiraling vine which will grow in almost any climate given enough water and sunlight. It can climb either string or poles and can reach heights of 40 feet. The flowers (or cones as they are often called) are usually dried before use.
Bittering Compounds
One of the major contributions hops give to beer is a characteristic bitterness that provides a counterpoint to the rich sweetness provided by the malt. This bitter flavor is extracted from the hops during the boil. It is during this time that virtually insoluble alpha acids are isomerized (rearranged without changing their composition) into more soluble and stable iso-alpha acids, the main bittering substance in beer. Five different naturally occurring alpha acids have been isolated from hops which are:
humulone
cohumulone
adhumulone
prehumulone
posthumulone
Although isomerized alpha acids are the biggest contributers, hops contain beta acids which also add bitterness to beer. The beta acids are similar to alpha acids both in structure and abundance. In contrast to alpha acids, it is not isomerized beta acids that add bitterness, it is the oxidation products of the beta acids, which are bitter and soluble, that make their presence felt. It should be noted that oxidized beta acids are not as bitter as isomerized alpha acids, and thus contribute much less to the final bitterness of the beer.
Both the alpha and beta acids are very susceptible to oxidation, especially at temperatures above freezing. Theoretical losses of alpha acids of up to 60% have been calculated for hops which are packaged and stored poorly. This is important because once alpha acids have been oxidized they can no longer be isomerized into iso-alpha acid, thus decreasing the hop's bittering potential. As stated above, oxidation components of beta acids contribute to bitterness, thus the bittering potential of oxidized hops may not decrease as much as is commonly thought. This does not, in any way, argue against storing hops well, since essential oils are dramatically and negatively altered by oxidation.
For these reasons, the "storageability" of each hop variety is sometimes provided, along with the alpha and beta acid levels, by the hop broker. This parameter is usually given as a percentage of the alpha acids present after 6 months at 20C. Some good storage hops (usually high alpha acid) lose only 15-20% of their alpha acids: Cluster and Galena are among the best. Most high quality aroma hops lose anywhere from 35-65% of their alpha acids unless anaerobic conditions and cold storage (< 0C) are provided. This is why it is imperative for brewers to buy the freshest hops available and store them in the coldest environment available, usually the freezer. It is also important to package the hops properly, which means removing as much oxygen as possible and containing them in an oxygen barrier material.
Aroma and Flavor Compounds
Hops bring a lot more to beer than bitterness. The volatile oils, usually 0.5 - 3.0% (vol/wt) of the hop cone, are an important flavor component of many types of beer. Brewers seeking to maximize hop flavor and aroma generally make late kettle additions (0-15 min. before cooling) with high quality "aroma" hops. Dry hopping, i.e. the addition of hops to the secondary fermenter or serving tank, is another way to add hop character to a beer although the aroma components retained by this method differ from those obtained in late kettle additions. The maximum oil utilization is about 10 - 15% which decreases with increased boiling time.
The essential oils are what give hops their unique aroma; each variety has its own distinct profile. The smell of hops freshly crushed in your hand is quite often different than that in a finished beer. This is due to the fact that the major components in hop oil, beta-pinene, myrcene, beta- caryophyllene, farnesene and alpha-humulene, are not usually found in beer. This is also the reason that measures of "total hop oil percentage" that some hop retailers provide are considered by some to be useless information. On the other hand, fermentation and oxidation products of these compounds, especially humulene epoxides and diepoxides are considered contributors to "hoppy" flavors and aroma. The exception here is with dry-hopping, where some of the hop oil components do survive into the beer intact.
Researchers have not been able to duplicate the complexities of hoppy character by adding pure chemicals in any proportion or combination. Consensus is that there is a synergistic blend of several compounds, some of which may have not yet been discovered.
Hop researchers, using capillary gas chromatography, have detected and identified more than 250 essential oil components in hops. Twenty two of these have been pinpointed as being good indicators of hoppiness potential. They are subdivided into 3 groups, humulene and caryophyllene oxidative products, floral/estery compounds, and citrus/piney compounds, as listed below:
Oxidation Products:
caryolan-1-ol
caryophyllene oxide
humulene diepoxide a
humulene diepoxide b
humulene diepoxide c
humulene epoxide I
humulene epoxide II
humulene epoxide III
humulenol II
humulol
Floral/Estery Compounds:
geraniol
geranyl acetate
geranyl isobutyrate
linalool
Citrus/Piney Compounds:
delta-cadinene
gamma-cadinene
citral
limonene
limonene-10-ol
alpha-muurolene
nerol
beta-selenene
Different Hop Products
Much has been written about what form of hops should be used. Loose hops are just that: loose cones which have been dried after picking. Plugs are loose hops which have been subsequently pressed into a bung under pressure, generally in 0.5 oz. sizes. Pellets are loose hops which have been ground to a fine powder and then pressed into rabbit-food-sized pellets.
Loose Hops
Advantages: They are the most natural form of the ingredient. They float, which is good for siphoning out from under, and form a natural filter bed. When they are fresh, they beat all other forms in delivering the original hop compounds to the beer (processing hops alters the volatile hop compounds in many ways).
Disadvantages: They float, so some contact with a still wort (as in dry hopping) is thought to be lost; this disadvantage is certainly arguable though, especially when it is considered that by using weighted hop bags, it is a non-issue. Since they are loose, exposure to air (oxygen) may be greater which could cause them to lose quality more quickly than the other forms of hops (note that this point is debatable). When stored in vacuum- sealed or CO2 or nitrogen purged Oxygen barrier bags or jars, this potential problem can be avoided. They are bulkier than other forms.
Plugs
Advantages: Are nearly the same as loose hops, in that, when hydrated, they become whole hop cones again. Like loose hops, they float. They may be better protected from air, but this is unproven.
Disadvantages: Few hop varieties come in this form. Currently, any domestic varieties are first shipped to England where they are made into plugs and then shipped back to the U.S. This probably negates any potential freshness advantage they have over loose hops (for U.S. varieties). It is difficult, but not impossible to separate into increments smaller than 0.5 oz. The compression of the hops into this form causes the *****in glands to burst, which causes a finite loss of the volatile hop aromatic compounds and could cause increased alpha acid oxidation.
Pellets
Advantages: Convenient to measure and may have better protection from air (another unproven assumption). They sink, so they get maximum contact in a still wort, as when used for dry hopping (may or may not be an advantage). If they are subsequently covered with dead yeast, wort contact is mostly lost, so careful timing is recommended when using them for dry hopping. They reportedly contribute 10% more alpha acids to the wort because of maximized surface area, so are a more efficient use of this relatively expensive ingredient. They are generally available in more varieties.
Disadvantages: They sink and are powdered, so it is difficult to avoid them when siphoning. The extra processing of chopping and compressing negatively affects hop compounds.
Given the pros and cons listed, the choice of which form of hop to use in a certain application is up to the individual brewer and dependent upon the individual brewhouse. With some kettle arrangements (those using a hopback, for instance) loose hops can form a utilitarian filter bed. In others, the mass of loose hops can be a nuisance and soak up a large quantity of wort which is lost to the brewer. It should be noted that fresh, whole hops are available today from many sources, including mail-order nationwide (US) from companies such as Just Hops, Freshops, and HopTech, which may negate many of the advantages of processed hops.
Hops are cultivated flowers (humulus *****us), green in color with yellow *****in glands down between the petals, used for preservative and flavoring characteristics in beer. The bitterness of the hop is used to balance the sweetness of the malt, and the essential oils add a flavor/aroma which cannot be achieved by using any other plant. The hop plant is a perennial spiraling vine which will grow in almost any climate given enough water and sunlight. It can climb either string or poles and can reach heights of 40 feet. The flowers (or cones as they are often called) are usually dried before use.
Bittering Compounds
One of the major contributions hops give to beer is a characteristic bitterness that provides a counterpoint to the rich sweetness provided by the malt. This bitter flavor is extracted from the hops during the boil. It is during this time that virtually insoluble alpha acids are isomerized (rearranged without changing their composition) into more soluble and stable iso-alpha acids, the main bittering substance in beer. Five different naturally occurring alpha acids have been isolated from hops which are:
humulone
cohumulone
adhumulone
prehumulone
posthumulone
Although isomerized alpha acids are the biggest contributers, hops contain beta acids which also add bitterness to beer. The beta acids are similar to alpha acids both in structure and abundance. In contrast to alpha acids, it is not isomerized beta acids that add bitterness, it is the oxidation products of the beta acids, which are bitter and soluble, that make their presence felt. It should be noted that oxidized beta acids are not as bitter as isomerized alpha acids, and thus contribute much less to the final bitterness of the beer.
Both the alpha and beta acids are very susceptible to oxidation, especially at temperatures above freezing. Theoretical losses of alpha acids of up to 60% have been calculated for hops which are packaged and stored poorly. This is important because once alpha acids have been oxidized they can no longer be isomerized into iso-alpha acid, thus decreasing the hop's bittering potential. As stated above, oxidation components of beta acids contribute to bitterness, thus the bittering potential of oxidized hops may not decrease as much as is commonly thought. This does not, in any way, argue against storing hops well, since essential oils are dramatically and negatively altered by oxidation.
For these reasons, the "storageability" of each hop variety is sometimes provided, along with the alpha and beta acid levels, by the hop broker. This parameter is usually given as a percentage of the alpha acids present after 6 months at 20C. Some good storage hops (usually high alpha acid) lose only 15-20% of their alpha acids: Cluster and Galena are among the best. Most high quality aroma hops lose anywhere from 35-65% of their alpha acids unless anaerobic conditions and cold storage (< 0C) are provided. This is why it is imperative for brewers to buy the freshest hops available and store them in the coldest environment available, usually the freezer. It is also important to package the hops properly, which means removing as much oxygen as possible and containing them in an oxygen barrier material.
Aroma and Flavor Compounds
Hops bring a lot more to beer than bitterness. The volatile oils, usually 0.5 - 3.0% (vol/wt) of the hop cone, are an important flavor component of many types of beer. Brewers seeking to maximize hop flavor and aroma generally make late kettle additions (0-15 min. before cooling) with high quality "aroma" hops. Dry hopping, i.e. the addition of hops to the secondary fermenter or serving tank, is another way to add hop character to a beer although the aroma components retained by this method differ from those obtained in late kettle additions. The maximum oil utilization is about 10 - 15% which decreases with increased boiling time.
The essential oils are what give hops their unique aroma; each variety has its own distinct profile. The smell of hops freshly crushed in your hand is quite often different than that in a finished beer. This is due to the fact that the major components in hop oil, beta-pinene, myrcene, beta- caryophyllene, farnesene and alpha-humulene, are not usually found in beer. This is also the reason that measures of "total hop oil percentage" that some hop retailers provide are considered by some to be useless information. On the other hand, fermentation and oxidation products of these compounds, especially humulene epoxides and diepoxides are considered contributors to "hoppy" flavors and aroma. The exception here is with dry-hopping, where some of the hop oil components do survive into the beer intact.
Researchers have not been able to duplicate the complexities of hoppy character by adding pure chemicals in any proportion or combination. Consensus is that there is a synergistic blend of several compounds, some of which may have not yet been discovered.
Hop researchers, using capillary gas chromatography, have detected and identified more than 250 essential oil components in hops. Twenty two of these have been pinpointed as being good indicators of hoppiness potential. They are subdivided into 3 groups, humulene and caryophyllene oxidative products, floral/estery compounds, and citrus/piney compounds, as listed below:
Oxidation Products:
caryolan-1-ol
caryophyllene oxide
humulene diepoxide a
humulene diepoxide b
humulene diepoxide c
humulene epoxide I
humulene epoxide II
humulene epoxide III
humulenol II
humulol
Floral/Estery Compounds:
geraniol
geranyl acetate
geranyl isobutyrate
linalool
Citrus/Piney Compounds:
delta-cadinene
gamma-cadinene
citral
limonene
limonene-10-ol
alpha-muurolene
nerol
beta-selenene
Different Hop Products
Much has been written about what form of hops should be used. Loose hops are just that: loose cones which have been dried after picking. Plugs are loose hops which have been subsequently pressed into a bung under pressure, generally in 0.5 oz. sizes. Pellets are loose hops which have been ground to a fine powder and then pressed into rabbit-food-sized pellets.
Loose Hops
Advantages: They are the most natural form of the ingredient. They float, which is good for siphoning out from under, and form a natural filter bed. When they are fresh, they beat all other forms in delivering the original hop compounds to the beer (processing hops alters the volatile hop compounds in many ways).
Disadvantages: They float, so some contact with a still wort (as in dry hopping) is thought to be lost; this disadvantage is certainly arguable though, especially when it is considered that by using weighted hop bags, it is a non-issue. Since they are loose, exposure to air (oxygen) may be greater which could cause them to lose quality more quickly than the other forms of hops (note that this point is debatable). When stored in vacuum- sealed or CO2 or nitrogen purged Oxygen barrier bags or jars, this potential problem can be avoided. They are bulkier than other forms.
Plugs
Advantages: Are nearly the same as loose hops, in that, when hydrated, they become whole hop cones again. Like loose hops, they float. They may be better protected from air, but this is unproven.
Disadvantages: Few hop varieties come in this form. Currently, any domestic varieties are first shipped to England where they are made into plugs and then shipped back to the U.S. This probably negates any potential freshness advantage they have over loose hops (for U.S. varieties). It is difficult, but not impossible to separate into increments smaller than 0.5 oz. The compression of the hops into this form causes the *****in glands to burst, which causes a finite loss of the volatile hop aromatic compounds and could cause increased alpha acid oxidation.
Pellets
Advantages: Convenient to measure and may have better protection from air (another unproven assumption). They sink, so they get maximum contact in a still wort, as when used for dry hopping (may or may not be an advantage). If they are subsequently covered with dead yeast, wort contact is mostly lost, so careful timing is recommended when using them for dry hopping. They reportedly contribute 10% more alpha acids to the wort because of maximized surface area, so are a more efficient use of this relatively expensive ingredient. They are generally available in more varieties.
Disadvantages: They sink and are powdered, so it is difficult to avoid them when siphoning. The extra processing of chopping and compressing negatively affects hop compounds.
Given the pros and cons listed, the choice of which form of hop to use in a certain application is up to the individual brewer and dependent upon the individual brewhouse. With some kettle arrangements (those using a hopback, for instance) loose hops can form a utilitarian filter bed. In others, the mass of loose hops can be a nuisance and soak up a large quantity of wort which is lost to the brewer. It should be noted that fresh, whole hops are available today from many sources, including mail-order nationwide (US) from companies such as Just Hops, Freshops, and HopTech, which may negate many of the advantages of processed hops.