Inclusion of Yeast Cultures (<i>Saccharomyces cerevisiae</i>) to Dairy Cows’ Urea-Treated Rice Straw Diets Improves Mozzarella Cheese Processing and Yield

This research paper addresses the hypothesis that adding yeast cultures (Saccharomyces cerevisiae) to urea-treated cereal crop residues could improve milk composition to the level of milk produced on pastures for the manufacture of Mozzarella cheese. In three equal groups, Nine Friesian cows were randomly assigned to three treatment diets in a completely randomized design. The treatments were pasture (P), urea treated rice straw (UTRS), and urea treated rice straw with yeast inclusion (UTRS + Y). Urea inclusion was at 3.8% of the dry matter to treat rice straw, while yeast culture inclusion was 10 g/cow/day. The experimental period was 21 days, with 14 days of adaptation. Data analysis used general linear model procedure of SAS, fitting diet as a fixed effect and milk composition, syneresis, curd firmness and cheese yield as the response variables. Milk produced on UTRS diet yielded (p < 0.05) the highest fat content (4.79%) and the lowest density (1016.37 Kg·m-3) and casein-to-fat ratio (0.51). Yeast inclusion in the diet (UTRS + Y) significantly improved milk density (1022.68 Kg·m-3) with marginal reduction in milk fat content (4.53%). In cheese making, milk produced on URTS diets had significantly lower renneting time (1.4 minutes vs 3.47 minutes and 2.39 minutes), least viscous gel, lowest syneresis (755 mL vs 860 mL and 836 mL from 1000 mL), and lowest cheese yield (9.0% vs 11% and 10.5%) compared to P and UTRS + Y diets. Milk produced from P and UTRS + Y did not show any significant difference in cheese yield. The findings indicated that urea treated rice straw with yeast cultures improves syneresis, gel viscosity and Mozzarella cheese yield. Therefore, we recommend the inclusion of yeast to urea treated cereal crop residues to produce milk destined for Mozzarella cheese making.