| As a primary dietarycondiment, the fermented vinegar has been welcomed by consumers for its abundant nutrients and unique pharmacological effects(such as relieving fatigue, regulating blood lipids, reducing blood pressure, antioxidant, anti-cancer, promoting appetite, preventing osteoporosis and so on). In recent years, ―The unique composition and nutritional function of crops‖, ―The new product development of flavor nutrition crops‖ and ―Microbial fermentation for improvement of product quality and biological functions‖ have become the research focus in tartary buckwheat or other crops industry domestically and globally. As a new product, tartary buckwheat vinegar has shown great market potential. In this paper, the processing byproducts of tartary buckwheat(the broken tartary buckwheat and skin powder) were used as raw material for brewing high-quality tartary buckwheat vinegar. The optimizing of processing techniques and the analysis of quality included:①The effects of three chinese herbs(Magnolia(HP), Mint(BH) and Sophora(KS)) on the quality of bran koji were studied based on liquefaction ability, glucoamylase activity, esteriyfing power, protease activity, total number of bacteria and moisture content. ②The optimal methods for saccharification of broken tartary buckwheat and skin powder by bran and glucoamylase were screened out based on the consumption ratio of reduing sugar, conversation of sugar to ethanol and retention of flavonoids. According to total acid and total flavonoids content, the brewing technology for liquid tartary buckwheat vinegar was optimized by orthogonal test. ③ The broken tartary buckwheat and skin powder undergone solid-liquid mixed fermentation by using the bran koji and spores of Aspergillus, respectively. In order to compare the effect of different fermentation techniques on the tartary buckwheat vinegar, the change of contents in total acid, volatile acid, unvolatile acid, ammonia nitrogen, flavonoids, dissolublesaltless substance in vinegar culture were monitored. ④ Principal component and aroma components of four kinds of tartary buckwheat vinegars were analyzed by SPME-GC-MS and Electronic tongue. The results showed as follows:1. The best quality of bran koji was with the addition of sophora and the main characters were demonstrated as follows: liquefaction ability was 0.84 g/(g·h), glucoamylase activity was 533 U/g, protease activity was 390.4 U/g, esteriyfing power was 29.38 mg/100 m L, the moisture content was 9.35%, the total viable count was 2.6×1013 CFU/g. The indicators of finished bran koji are as follows: volume weight of bulky starter was 0.58 g/cm3, starter production rate was 0.77, dehydration rate was 65%.2. Bran and glucoamylase saccharification methods were compared between the broken tartary buckwheat and skin powder. The recovery ratios of general flavones were 5.1% and 4.6%, the consumption ratios of substrate were 76.8% and 83.1%, the conversion ratios of sugar to alcohol were 45.6% and 33.8%, respectively, indicating that the bran is much better in saccharification. The optimal acetification conditions were liquid loading volume 1/2, acetic acid bacteria 0.6%, culture temperature 31℃. Under this condition, the total acids was 3.65g/100 m L, total flavonoids reached up to 3.53mg/g.3. Compared with solid state fermentation, the solid-liquid mixed fermentation of total acid, volatile acid, dissoluble saltless substance and ammonia nitrogen increased by 0.4g/100 m L, 0.41g/100 m L, 1.53g/100 g and 0.07g/100 g respectively. Compared with spores of Aspergillus, the bran koji of total acid and flavonoids increased by 0.72g/100 m L and 0.47g/100 m L, respectively.4. The principal component of PC1 and PC2 with TS-5000 Z Electronic tongue had good separation on four kinds of tartary buckwheat vinegars. The flavors of tartary buckwheat vinegar by fermentation with bran koji and commercial spores of Aspergillus were similar. However, solid-liquid mixed fermentation and solid state fermentation by commercial spores of Aspergillus generated different flavors because of its fermentation process.The 2-d scatter plot showed that the solid-liquid mixed fermentation tartary buckwheat vinegars had the heaviest sourness, while the liquid tartary buckwheat vinegar had the weakest which is in accordance with the taste radar chart.5. The aroma components of four kinds of tartary buckwheat vinegars were analyzed by SPME-GC-MS. Seventy-eight aroma components were detected, including acids, esters, alcohols, ketones and heterocyclic compounds. Among them, the amount of acetic acid, ethyl acetate, benzaldehyde, furfural and tetramethyl pyrazine were the highest, which constituted the main aroma of tartary buckwheat vinegar. The acid compounds of the solid-liquid mixed fermentation of bran koji and Spores of Aspergillus were 58.726% and 55.836% respectively, while the solid fermentation by adding Spores of Aspergillus was only 53.902%. Therefore, the quality of tartary buckwheat vinegar fermented by bran koji was better than that of solid state fermentation. Solid-liquid mixed fermentation process was better than solid-state fermentation process. |
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