Re: what does yeast need to grow? and what preservative keeps it from growing?

Hi Russ,

Let me provide some answers to your interesting questions. Like other 
microorganisms (bacteria, molds), yeast have some environmental conditions 
which influence their growth. They require a source of food that can supply 
nutrients (a source of nitrogen, vitamins, etc) for growth. They also need 
water, which is generally supplied by the food source. In addition the 
growth of yeast is influenced by the pH and temperature of the 
environment. Finally the presence or absence of oxygen will influence their 
growth as well as the metabolic products that they make through 
fermentation (acids or alcohol). Yeasts have been used for thousands of 
years to produce food and beverages through fermentation. They are used to 
produce wine, beer, cheeses, yogurt, sausages (pepperoni & genoa salami), 
sauerkraut, and some pickles to name a few. If your question on 
preservatives is refering to chemicals that can inhibit the growth of 
yeasts in foods, sorbic acid, potassium sorbate, sulfites, sulfur dioxide 
and benzoic acid are very effective. The amount that can be used in foods 
is regulated by the Food and Drug Administration. You can also prevent the 
growth of yeasts in foods by heating, reducing the amount of water 
[dehydrating or by binding the water to sugar(i.e. jams & jellies)], 
irradiating the food, etc. I hope this information hleps to answer your 
questions.

Sincerely,

Al Bushway
Professor of Food Science