Abstract:
Yeast autolysate is a product from self-digestion of yeast cells. It can be used as meat like flavor and flavor enhancer in food. In this study, yeast autolysate was made from spent brewer's yeast (Saccharomyces carlsbergensis) by first reducing the bitterness with alkaline washing and then improving the meat like flavor of yeast autolysate by adding non yeast protein; i.e. wheat gluten, soy protein isolate and soy bean meal; along with the addition of exogenous enzymes, i.e. Neutrase(R) 0.5L or Flavourzyme(R) 1000L, in the autolysis process. Alkaline washing with 2% sodium carbonate at 25ํC for 20 minutes reduced the bitterness of yeast 90.8% which gave the final bitterness in the bitterness unit of 12.65 and the yeast loss of 14.94% Addition of non-yeast protein and exogenous enzymes in the autolysis process increased the yield, protein content and carbohydrate content of yeast autolysate. The addition of 10% (w/v) wheat gluten and 1.0% (v/v) Flavourzyme(R) 1000L at 45ํC and pH 5.5 with autolysis time of 20 hours gave the highest yield, protein content and carbohydrate content at 70.72%, 27.53 mg./ml. and 12.17 mg./ml., respectively. The yeast autolysate was dried at 100ํC to the moisture content of 3-5%. Addition of 0.05%(w/v) of the dried yeast autolysate to the vegetable soup stock resulted in soup with the high score in meat like flavor. The production of yeast autolysate which contained high 5'-nucleotides was prepared by hydrolysing RNA in the mixture of yeast autolysate and non-yeast protein with phosphodiesterase. Incubation of 0.2% (w/v) 5'-Phosphodiesterase RP(R)-1 (PDE) with the yeast autolysate plus wheat gluten at pH 6.5 and 55ํC for 2 hours gave the high content of 5'-GMP, 5'-AMP and 5'-IMP at 71.76, 361.51 and 21.60 microg./ml., respectively. While incubation of 0.2% (w/v) 5'-Phosphodiesterase RP(R)-1 with the yeast autolysate plus soy bean meal at the same condition gave the high content of 5'-GMP, 5'-AMP and 5'-IMP at 67.40, 416.06 and 10.97 microg./ml., respectively. Improvement of meat like flavor was done with the addition of cysteine, methionine and thiamine at 0.3, 0.2 and 0.1 part per thousand of the dry matter content in the case of the concentrated yeast autolysate plus wheat gluten or the addition of cysteine, methionine and thiamine at 0.1, 0.1 and 0.1 part per thousand of the dry matter content in the case of the concentrated yeast autolysate plus soy bean meal. Addition of 0.05% (w/v) of the dried yeast autolysate mixture to the vegetable soup stock resulted in soup with the high score in meat like flavor. Using yeast autolysate mixture powder as food flavor in vegetarian meat ball was performed at the level of 1.0, 2.0 and 3.0% (w/w) of the main ingredient used. The best result was 2.0%.