Determination of Ethanol in Whey-Sugar Solutions by Freezing

The composition of solutions undergoing yeast fermentation was simulated by using direct-acid-set cottage cheese whey containing increasing amounts of ethanol (0 to 5.4%) with decreasing amounts of sucrose (10 to 0%). Each decrease of 1 g of sucrose per 100 ml of whey accompanied by an increase of 0.54 g of ethanol decreased specific gravity 0.0046 unit and lowered the freezing point 0.159 H. Whey containing 10% added sucrose was treated as follows: (a) inoculated with Kluyveromyces fragilis , (b) carbohydrate splitting enzymes added and inoculated with K. fragilis and (c) carbohydrate splitting enzymes added and inoculated with Saccharomyces cerevisiae . All mixtures were incubated 48 h at 32 C during which six samples from each treatment were analyzed for total solids, specific gravity and freezing point. No difference (P>.05) was noted between samples treated with enzymes or those treated with the two yeasts cultures as related to decrease in total solids concentration or specific gravity. Each 0.001-H decrease in freezing point was accompanied by a total solids decrease of0.006 g per 100 g of whey in the non-enzyme treated sample, and 0.008 g and 0.010 g per 100 g whey in the enzyme-treated samples inoculated with K. fragilis and S. cerevisiae , respectively. Each 0.001-H change in freezing point was equivalent to a change of 0.00003 specific gravity unit in the non-enzyme treated sample and 0.000043 and 0.000048 specific gravity unit in the enzyme-treated samples inoculated with K. fragilis and S. cerevisiae , respectively. The precision with which freezing point can be determined suggests its use in evaluating the amount of ethanol produced during fermentation.