Yeast Nutrients & Acidity for Fermentation

A slightly acidic environment is enjoyed by yeast, and also inhibits the development of bacterial contaminants. The pH of the brew should be adjusted to between 4.0 and 4.5 prior to fermentation, using citric or lactic acids. You can also use lemon juice rather than citric acid - it works great in distilling, but is bad in winemaking. Just use it on an equal volume basis- 1TBSP of acid blend = 1TBSP of lemon juice.
If using citric acid ....
To get a pH of you need to use grams per litre
ie grams in a L wash to use

This calculation seems on the low side practically - it must be that the citric acid sold in supermarkets / brewshops isn't 100% pure. Always double-check the pH using pH papers or some other test.

Nutrients also need to be present. Yeast cells require phosphorus, nitrogen and potassium, as well as amino acids and vitamins, for metabolic processes. The extent to how much is required depends on the feedstock being used. The nitrogen requirement may be supplied in the form of amino acids, ammonia, or ammonium salts. If the solids are separated from the sugar solution prior to fermentation (or say starting only with sugar) the bulk of the protein will be removed, and hence a potential nitrogen source lost. Ammonia or ammonium salts are the preferred source of of additional nitrogen if its needed, however avoid using excessive amounts because it can kill the yeast. Both nitrogen and phosphorus can be supplied by ammonium phosphate (commonly available as a fertilizer). Many fermentations will proceed satisfactorly without vitamin suppliments because the fermentation medium contains sufficient of these nutrients, however in most cases, cell growth is enhanced when B-vitamins are added.

Jack adds ...
    DAP (Diammonium phosphate) is also known as "yeast nutrient" among wine/beer makers. Yeast energizer is typically a yeast hull extract- an all-natural version of yeast nutrient- it doesn't work as well, because there just isn't enough free-amino nitrogen in it. Most homebrew shops (who know what they are doing) sell the DAP salt- it should look just like any other chemical salt (like table salt, but with bigger crystals)- if it's off-white, brown, or any other color- it's likely a mix of yeast nutrient, yeast energizer, some B vitamins and other assorted junk (ie trace minerals, folic acid). If your local homebrew shop has it's head up it's arse, try checking online for a domestic home-brew shop that sells it online. Most homebrew magazines have dozens of adds for places like this- just find the closest one to save on shipping.

One recipe for nutrient ale salts is
  • 58 g sodium chloride (common table salt)
  • 170 g citric acid
  • 7 g ammonium sulphate
  • 6 g magnesium sulphate
  • 2.5 g grape tannin
This mixture is hygroscopic (attracts water), so keep it in a cool dry place with a good lid.

The "Great New Zealand Home Wine Making Book" suggests to ... "buy some ammonium sulphate or ammonium phosphate, and some pottassium phosphate or potassium sulphate and add 2g (1/2 teaspoon) of each to every 4.5 L. Another valuable addition is vitamin B1. You can buy these as tiny 3 milligram tablets from your local chemist or pharmacy and add one of these each 4.5 L" ...
Darryl offers ...
    Before turbo yeasts came along, I would use a champagne yeast and my own nutient mix to ferement a sugar wash. For a 20 litre wash I would use 5 kg sugar plus the following nutrient mix:
    • 4 tsp winemakers' yeast nutrient salts
    • 4 tsp citric acid
    • 1/3 small jar molasses
    • 1 tsp marmite

Concerning the use of Urea in nutrients, Des writes :
    According to 'The Food Regulations 1984, Amendment No. 5' dated 2nd December 1991 regulation 235, General alcoholic drinks, subclause 3 says "General alcoholic drinks may contain any of the following:", paragraph (i) "Yeast nutrients, except urea"

    Which is what has been quoted in past correspondence and always referred to when discussing the issue, however: 'The Food Regulations 1984, Amendment No. 9' dated 10th of October 1994 regulation 101, (3) states "Regulation 235 of the principal regulations is hereby further amended by revoking paragraph (i) of subclause (3)." ie the exception to urea above is now revoked.

    On seeing this I contacted the New Zealand Health Department and requested, under the Official Information Act, all the paper work as to why the original banning and why the lifting of that ban. Of course, I got screeds of paper but the story is that the ban was instigated because of research done in England that pointed health risks of urea as an ingredient for fermentation. Thus it was banned.

    It was later realised that although these chemicals were present in the fermented wash, they were not present once the wash had been distilled. It appears that they are not carried over in the distillation process, thus the ban for this type of alcoholic product was lifted.
Mike adds ...
    Nothing wrong with urea in modest quantities... the human body excretes it daily, and in some quantity, so it is not a killer. However, only drawback with its use as a nutrient is that it encourages production of ammonia compounds, and that can taint a brew. This was a common complaint from people who had problems with early turbo mixes that used excessive urea. Current mixes appear to have overcome this problem, but addition of urea yourself should be governed by caution. A little goes a long way. DAP is a better nutrient to use as the ammonium radical is more tightly bound.
Also, don't use too much nutrient. It won't make the yeast work any faster, once you've supplied its needs ... but it can make your spirit turn blue. Mike explains ...
    ... alkaline washes that hold a lot of nitrogen-containing compounds that have been put in as nutrients will liberate ammonia and that, being a gas, will get to the top condenser and form an aqueous ammonia solution, which is alkaline. Normal oxidation of copper under heat forms cupric hydroxide in an alkaline solution. This turns black when boiled with water, and is commonly seen on copper components in stills. This, in turn, reacts with ammonia solution to form Schweitzer's solution, containing the tetrammino-cupric ion Cu[4NH3]++, which is deep blue. Don't worry ... it won't hurt you, and you might even think the colour attractive!

    Answer is to ensure that your wash is not alkaline, but acidic. This is the normal condition after a fermentation, as yeasts tend to acidify the wash with their by-products. You say that you added yeast nutrients, and I suspect that you were a bit too enthusiastic, as this can tipp the balnace the other way. Addition of citric acid is usually enough to neutralise and then acidify a solution made too alkaline by overdosing with nutrients, but without acid buffers to control the pH. In an acidic solution, those nitrogen-containing compounds will react with the acid to form salts, and so will not ne carried up to the top condenser.
If this happens, make sure you strip down your tower, and clean it well. The blue alcohol can be cleaned up by adding some citric acid (50g per 5L) (which will react with the ammonia to produce ammonium citrate which will precipitate out along with the copper leaving hydrogen sulphyte and or sulphide), and then filtering it through some coffee filters to collect the flocculant; the alcohol will then be ok to redistil.

Matt suggests
    The White Labs site (http://www.whitelabs.com/) mentions that they are now distributing Servomyces a nutrient which apparently even conforms with the Reinheitsgebot! It was developed in Europe, and seems aimed more at the beer brewing market, but it might still give interesting results for those doing a low-nutrient wash ferment.

    Wyeast Labs of Oregon, USA also offers a yeast nutrient: http://www.wyeastlab.com/nutrient/nunutrie.htm

Brians recommendation re nutrients is lallemand fermaid k; use at a d/r of circa 60/100 g /20 litres (http://www.lallemand.com)

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