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Production of Diacetyl Prom Citric Acid in Butter Cultures¹

ABSTRACT

In studies on the changes in the diacetyl and the acetylmethylcarbinol contents of butter cultures under a variety of conditions, the factors found to favor a high diacetyl content were:

1. Addition of citric acid to the milk used. About 0.15 per cent citric acid appeared to be a practical amount. Larger percentages, such as 0.30 per cent, did not give correspondingly higher diacetyl contents unless the ripened cultures were held cold for an extended period with sufficient aeration.
   
2. Aeration of the cultures. Shaking the ripened cultures produced significant increases in diacetyl and lack of aeration caused decreases. Under practical conditions, normal agitation undoubtedly gives the same effect.
   
3. Holding the ripened cultures. There were commonly increases in diacetyl during the holding of cultures at various temperatures, but holding in the cooler is apparently the most practical.
   
4. Addition of citric acid to the ripened cultures. As little as 0.08 per cent was effective, the agitation incident to the distribution presumably also being a factor.
   
5. Production of a low pH in the ripened cultures. Lowering the pH of ripened cultures, even with such an acid as sulfuric, tended to increase the diacetyl content.
   

In general, a high acetylmethylearbinol content was favored by similar conditions. The attainment of a relatively high content at low temperatures is slower with the carbinol than with diacetyl.

¹ Journal Paper J-573 of the Iowa Agricultural Experiment Station, Ames, Iowa. Project No. 127.

² The studies reported were largely financed through a grant from Chas. Pfizer and Co., Inc., which provided particularly for the services of Dr. Prill.