Nitrogen Content

[iamatuna]

Hey guys

ive been doing some research into ester, phenol and jusy other compound production and have a quick question.

Everything i have read says that yeast needs a source of nitrogen for growth for amino acid/protein production, cell wall components, etc etc etc. However the souce of this nitrogen can dtermine flavour. I have read that almost all flavour compounds are a modification of amino acids or other cellular components.

My question is that add ammonium salts, providing more readily avaliable and favorable nitrogen source to the yeast giving the yeast an excess of soluable protein, will this excess proteins be used to generate more flavour compounds by the yeast?

Any input would be helpfull

Cheers

 

[ACbrewer]

Wine makers add yeast nutrient to their musts. Wine from grape, fruit or other sugar source is just that -sugar not much else.

But for beer the malt is supposed to carry in not just sugars, but some other compounds that contain the nitrogen. you shouldn't need to add anything. If you are currious, a brew experiment of a batch where you did same receipe and try one with some extra nitrogen and one without

 

[ajdelange]

The commonly sold yeast nutrients usually contain DAP (diammonium phosphate (NH4)2PO4) and urea (H2N-CO-NH2). A molecule of DAP furnishes, at wort pH, 2 ammonium ions (NH4+) when dissolved in water as does urea: H2N-CO-NH2 + 2H+ + H2O --> CO2 + 2NH4+. Thus these 2 compounds provide readily assimilable nitrogen which the yeast can use to fulfill whatever nitrogen demands they need to.

The sufficiency of nitrogen makes for healthy yeast and therefore should not be a source of off flavors. If they were, brewers wouldn't use nitrogen in the formulations of their yeast nutrients. Most of the flavor compounds that come to mind (vicinal diketones, aldehydes, alcohols (fusels and EtOH), esters do not contain nitrogen but there are certainly nitrogen compounds in beer i.e. the proteins which sustain the foam and mounthfeel as well as some volatile amines (dimethyl amine) but these are not, apparently, very flavorful.

With a properly managed mash (including protein rest though fewer and fewer brewers believe in the need for these) you should have plenty of FAN going into the fermenter. Nonetheless, many use the DAP/urea nutrients. These also contain yeast hulls and zinc salts and these may actually be of more benefit than the extra nitrogen but I don't know enough to make that assertion.

 

[iamatuna]

would the addition of DAP increase the amount of flavour compounds derived from proteins though??

has anyone ever tried to make a beer with as many proteins removed as possible (as in 2-3 hour boil and almost freezing to get as much hot and col break out of solution reducing the amount of FAN?

 

[ajdelange]

Looking at the big picture I would have to guess that if DAP does increase flavor compounds derived from proteins that they would have to be beneficial ones as if the converse were true brewers would not be adding DAP to their fermenting beers. But, as noted in the last post, I don't think there are many flavor active nitrogen compounds in beer. Protein in general is there for the benefit of foam and body but these are proteins from the grain, not the yeast.

To withhold nitrogen from yeast results in a poor ferment and problem beer. The infamous low FAN of extracts and the resulting poor quality of a lot of extract beers attest to this.