Author : Parichart Vatana

Summary : Biochemical, nutritional, and sensory evaluation tests were carried out in fermented rice-shrimp mixture (balao-balao) starting from zero day daily up to the 10th day of fermentation. During fermentation, the acidic and ester odor of the product became stronger, the shell of the shrimps turned red and soft; the rice portion became watery and soft. The reactions occured from the action of microoganisms and enzymes of shrimps. Titratable acidity increased with the corresponding decrease in pH. Lactic acid, the only non-volatile acid produced, increased from the beginning until the 10th day; however, the volatile acids were produced in only small amounts reaching a maximum on the eighth day. Ethyl alcohol was produced in a small quantity and follwed the pattern of the volatile acid. Diacetyl was not-detectable in the products. Starch hydrolysis occurred with the formation of reducing sugars which reached a peak on the seventh day. Sugars found were glucose and maltose, the highest levels of which were produced on the sixth and seventh days, respectively. Amylolytic enzymes had a pH optimum at 6.1 and temperature at 50-60 degree C. The protein fractions, particularly soluble-nitrogen, increased from the beginning until the end of the fermentation period. The same pattern also occurred with amino-nitrogen formation concomitant with the reduction of molecular weight (MW) of shrimp protein. Cathepsin D in shrimp had an optimum pH of 3.5 and optimum temperature of 40 degree C. The activity of the enzyme decreased with fermentation time. The changes in sensory factors of the product and degree of softness of the shrimp-shell followed the same pattern. Samples fermented for four days got the highest scores and was chosen as the finished product.