| Summary: | 碩士 === 臺灣大學 === 農業化學研究所 === 95 === Abstract
This thesis includes three parts, 1) Utilization of recovered shoyu mash residue, 2) Studies on the hydrolysis of soy sauce koji, 3) Studies on the hydrolysis of soy protein.
1. Utilization of recovered shoyu mash residue.
The shoyu mash residue (or referred as soy sauce cake) is the main by-product during soy sauce manufacturing. It is mainly used as an ingredient for preparing feeds. Although shoyu mash residue has been used as a digestible protein, it is incinerated due to the declining livestock industry. A shoyu mash residue contains relatively high amount of salt; therefore, incineration results in corrosion of the furnace and environmental problems. The desalted shoyu mash residue has the excellent physical properties for a good dietary fiber. The purpose of this research is to produce good dietary fiber products from the recovered shoyu mash residue and to increase the yield of soy sauce product. Desalted shoyu mash residue fiber was prepared and their composition and physical properties were measured. In the experiments, the aqueous shoyu mash residue infusion was recycled as the saline water for preparing next batch soy sauce and measurements were carried out. The results indicate that the degree of the hydrolysis is 59.3 % and is higher than the control one (56.7 %) about 2.6 %. The total nitrogen utilization rate is 83.6 % and is higher than the control one (79.7 %) about 4 %. This demonstrates that the waste water from washing the shoyu mash residue can be recovered and reused and thereby reduce the cost of salt and increase the productivity of soy sauce.
2. Studies on the hydrolysis of soy sauce koji.
The production of soy sauce is time-consuming. To shorten the time needed for its production the rate of soy sauce koji hydrolysis must be increased. In addition, the salt-free and low-salt soy sauce products are also required as health foods by the consumers. The aim of this part of study is to develop an efficient method for the products. The changes of protein hydrolysis rates during the anaerobic fermentation of the koji were studied. The angiotensin converting enzyme inhibition activities of the peptides of various hydrolysis rates were analyzed. The results indicate that the best temperature for soy sauce koji hydrolysis under anaerobic fermentation is 45 oC. Under this temperature, a hydrolysate of 42.6 % degree of hydrolysis with 9 hours hydrolysis can be achieved. The results of angiotensin converting enzyme test show that hydrolysis for 9 hours at 45 oC can reach a 55.6 % inhibition. However, for a better quality control, condition at 50 oC with 6-12 hours hydrolysis is suggested.
3. Studies on the hydrolysis of soy protein.
Recently, peptides have elicited great interest for their multiple bio-functionalities. Among them, especially the peptides made from soy protein are the most popular subjects. The purpose of this research is to employ the koji proteases to produce the peptides of desirable degree of hydrolysis. Four kinds of food grade proteases (Bromelain, Flavourzyme, Neutrase and Papain) were used to hydrolyze soy protein. The angiotensin converting enzyme inhibition activities of the peptides of various hydrolysis rates were analyzed. The results indicate that the best protease for hydrolyze soy protein among the four proteases is Flavourzyme. A hydrolysate of 45.3 % degree of hydrolysis with 10 hours hydrolysis can be achieved. The results of angiotensin converting enzyme test show that by using Flavourzyme hydrolysis for 6 hours 58.2 % inhibition can be attained.
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