Originally By Tony Ackland
Yeast Nutrients & Acidity for FermentationA 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.
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 ...
One recipe for nutrient ale salts is
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 ...
Concerning the use of Urea in nutrients, Des writes :
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.
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.
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)