Study of the optimized conditions for baker's yeast lysis and its utilization
1997
Supot Boonraeng
Response surface methodology (RSM) was used to determine optimum condition of baker's yeast lysis. The optimized values of temperature was 54 deg C, pH was 5.2 and yeast concentration was 13 percent (dry wt) and will give maximum yields from predicted equations of protein 58.35 percent, total carbohydrate 44.78 percent and autolysate 50.85 percent. The effects of chemical, biochemical and physical treatments to yeast autolysis were studied optimum concentration of ethanol and sodium chloride were 5 percent v/v and 5 percent w/v respectively, papain was 0.1 percent of compressed yeast weight and the homoginizing condition was two time of passing at 8,000 psi were the best conditions for breaking yeast cells. When comparing among three treatments the highest of solubilization yields from sample using both ethanol and NaCl obtained 61.90 percent protein, the sample treated by homogenization obtained 42.45 percent carbohydrate and the sample treated by papain obtained 46.53 percent autolysate. The important enzymes involved yeast autolysis are proteinase, glucanase and carboxypeptidase. Proteinase and glucanase increase to be maximum activity at 4-8 hrs of autolysis time but carboxypeptidase increased in the last period. The results of chemical analysis of yeast extract composition (g/100 g dry solid) showed highest values of protein 57.50 and amino nitrogen 8.22 from sample using papain; carbohydrate 27.60 from sample using ethanol; nucleic acid 14.69 from alkaline extraction sample; ash content 28.89 from NaCl treated sample. The glutamic acid content was highest among those amino acids analysed. When using yeast extract prepared noodle soups for sensory evaluation they were not significant (P0.05) from standard sample. The marketing potential of yeast extract in food industry of Thailand is very good, the import values of both sauces and soups were more than 500 millian bahts per year and marketing values of dry soups and powder soups were more than 850 millian bahts per year.
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