Influences of different fermentation and ripeningtemperatures on enzyme activities, physicochemicaland sensory properties of salted egg white sufuduring processing

• Main Authors: Wei-Ting Wang, 王韋庭
• Other Authors: 譚發瑞
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/82616269105719296801

碩士 === 國立中興大學 === 動物科學系所 === 102 === Duck eggs, which are rich in nutrients, are mainly consumed as in forms of processed products. Salted egg white is seldom to be used due to its high salt content. Sufu is a well-accepted traditional fermented soybean product due to its unique flavor,cheese-like texture, and high nutritional values. In addition to commonly be used for a flavoring agent, douchi, which is also a traditional fermented soybean product, is commonly used as a starter culture during sufu manufacturing. In addition to substrates,fermentation temperature and time also influence sufu qualities greatly. Therefore, this study was attempted to investigate the influence of different fermentation and ripening temperatures (25°C, 35°C and 45°C) and processing time (0, 5, 12, 19, and 26 days) on the qualities of salted egg white sufu which applying salted egg white as substrate, and inoculated with douchi. The results showed that the protease activity in douchi koji was the highest at day 0 and then decreased rapidly during fermentation (day 0-5), whereas there was no significant (P > 0.05) difference during ripening (day 5-19) and extended-ripening (day19-26) between treatments. The protease activities in the infusions were increased during ripening and were then decreased until finish. The protease activities in the sufu were increased during fermentation. During ripening, the protease activity in 25°C samples was decreased then remained stable, while the one in 35°C samples remained stable and the one in 45°C samples was increased and then decreased. The total nitrogen content was increased during fermentation and then decreased (P < 0.05) during ripening. The total amino nitrogen content and degree of hydrolysis of protein were increased during fermentation, slightly decreased after adding the salty rice wine and then increased during ripening, and the ones in 35°C and 45°C treatments were significantly (P < 0.05) higher than the ones in 25°C treatment. Comparing with the samples at day 0, samples at day19 and day 26 had higher free amino acids, in which glutamic acid was the highest free amino acid in content. The 45°C samples had greater changes in L*, a*, and b* values (P < 0.05) as compared to the 25 and 35°C samples. The one processed at 45°C looked dark red in color while the ones processed at 25°C and 35°C were light-yellow in color. The pH values in all treatments were decreased during fermentation and less change during ripening and extended-ripening was observed. The pH values in 35°C and 45°C treatments were significantly (P < 0.05) lower than the one in 25°C treatment. The titratable acidity of samples was increased during fermentation and there was no significant (P > 0.05) difference between treatments during post-ripening and extended-ripening. The salinity of samples was increased during fermentation and there was no significant (P > 0.05) difference between treatments during ripening. The hardness and springiness of samples were decreased rapidly during fermentation and slightly decreased during ripening and no significant difference was observed during extended-ripening (P > 0.05) and adhesiveness was increased during fermentation and decreased during ripening. The water soluble nitrogen and nonprotein nitrogen content were increased significantly (P < 0.05) during fermentation while a decrease and then increase patten during ripening was observed. No significance (P > 0.05) was observed due to the influence of extended-ripening. The proximate composition of samples changed significant (P < 0.05)during processing. The sufu processed at 35°C and 45°C had significantly (P < 0.05) higher sensory results than the ones processed at 25°C. In conclusion, by fermented for 5 days and ripened for 14 days at 35°C, it is possible to manufacture salted egg white sufu with better qualities. Superior flavor and texture was observed in this sample probably due to its higher and stable proteolysis during processing. Our results clearly demonstrated it is possible to develop a novel animal protein-based fermented product for consumers. Not only possibly resolving the problem of under-utilizaion of salted egg white, but the results obtained in this study also can be beneficial for future industrial production.