Research On Improvement Of Qula Traditional Processing And Application

Qula, the traditional Tibetan food and raw material of casein in China, which has a great demand and broad prospect. So far, the traditional processing is still used in processing of Qula, leading to serious oxidative browning, poor color and flavor, affecting edible value and economic value, and bringing many difficulties to downstream-processing of casein. This paper studied from fermentation and dehydration process mainly, by studying the influence of the fermentation degree and the heat coagulation conditions on Qula’s chroma(L*, a*, b*), determined by studying the end of fermentation and heat treatment condition of Qula. This experiment optimized the fermentation process of casein and improved the color quality. During the fermentation process, p H, titration acidity, the fat oxidation state(POV, TBA) and the concentent of flavor substances(acetaldehyde, diacetyl) were determined, to observe the change trend, then used kinetic data analysis to explore the change laws of the quality of Qula fermentation coagulum during the fermentation process. Different pressure gradients were put on wet Qula clot to complete the pre-dewatering process before drying. Qula made with optimization technique was used as raw material for the production of casein, then analyzed the influence on the color quality. The test results are as follows:(1) Chroma(L*, a*, b*) of Qula with the decrease of fermentation p H deteriorating, when the p H of fermentation terminal point is close to the isoelectric point(p I=4.6) of casein, Chroma is relatively better. When L* value is 79.38, a* value is 1.95, b* value is 22.72, the yield of Qula is highest. On the basis of this, the process parameters of heat coagulation process were selected. The results showed that, when the coagulation temperature is 63℃, the coagulation time is 30 min, the chroma of coagulation is better after drying. The L* value is 81.85, a* value is 1.25, b* value is 14.31.(2) The inoculation amount, fermentation temperature and fermentation time were screened, and the chroma value(L*, a *, b *) of dried products were taken as target parameters, and the three factors were scored by the comprehensive evaluation using the data standardization method. The order of various factors on Qula’s chroma is inoculum amount > fermentation time > Fermentation temperature. The optimal fermentation parameters are: inoculum amount is 0.3%, fermentation temperature is 40℃ and fermentation time is 9 h. On this condition, standardized score of chroma is 0.812. Chroma quality of Qula improved significantly.(3) In the process of fermentation, p H of fermented coagulation showes a downward trend, p H change with exponential model fitting effect is better, fitting regression coefficient was 0.8398. The acidity of the titration showes a gradual upward trend, the change with linear model fitting effect is better, fitting regression coefficient was 0.8781. POV and TBA of fermented coagulation showes a gradual upward trend, the change with exponential model fitting effect is better, fitting regression coefficient was 0.9847 and 0.9886 respectively. The concentent of acetaldehyde increase at first and then decrease, 0~14 h and 14~16 h, the change with exponential model fitting effect is better. The concentent of diacetyl showed a gradual upward trend, the change with linear model fitting effect is better.(4) Different pressure gradients were put on wet Qula clot to complete the pre-dewatering process before drying. The results showed that the optimal pre-dehydration pressure is 850 N, at this pressure the transition point of water content of coagulation is 32.15%, L* value is 95.70, a* value is 0.29, b* value is 7.33. The content of 5-HMF is 0.70 μg·m L-1, POV value is 0.33 meq·kg-1 and TBA value is 0.48 mg·kg-1, all are significantly better than other contrast group.(5) Qula made with optimization technique was used as raw material for production of casein, and did not add any bleach and antioxidants. Before drying different pressure gradients were put on wet casein clot to complete the pre-dewatering process. L* value is 96.15, a* value is 0.13, b* value is 5.97.