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Whilst it is not excluded that wort may contain a small amount of protein capable of causing yeast flocculation, this can be only a minor factor. It is shown that gelatin and wort precipitates (obtained either by ammonium sulphate fractionation or by pH adjustment) protect yeast against flocculation by humic acid which is considered to be of similar character to wort melanoidin. An outstanding role for melanoidins in flocculation is accordingly postulated, and it is shown that inverse correlation exists between concentration of wort protein and rate of yeast flocculation.
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M. Kijima (1954) studied this question.
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