Studies On Fermentative Microflora, Flavours And Melanoidins Of Long-ripined Douchiba

Soybean (Glycine max (L.) Merrill) has received increasing attention as the best non-meat sources of high-quality protein and edible oil without cholesterol as well as functional foodstuffs because of its rich nutrition and specific bioactive phytochemicals. Soybean-fermented food, which accounted about 30 to 40 % of the total worldwide food consumption, has remarkable values in nutrition, healthy style and many advantageous properties over other foods due to biochemical modification of microorganisms, and has gradually become global popular food.As a special fermented condiment in Guizhou, long-ripened Douchiba has exhibited great potential for marketability recently because of its everlasting flavor and black shining texture by exclusive manufacture technology. Therefore, this study was conducted to address the following aspects regarding traditional Guizhou long-ripened Douchiba: (1) Biochemical basis of flavor development; (2) Optimal physical and chemical properties of raw materials; (3) Identification of dominant microflora and fermentative isolates; (4) Extraction of functional ingredients of melanoidins and determination of its skeleton compositions as well as bioactivity. The results indicated that:The main advantage of Guizhou soybean over Northest China's soybean in the manufacture of Douchiba lay in its high protein content and small grain. Based on a force-deformation (time) curve determined by texture analyzer, the maximal height peak value (g) was a better quantity parameter than peak area (F.S) for the hardness of soaked and steamed soybean seed.The dominant microflora in the manufacture of Qianxi Douchiba only consisted of Bacillus such as Bacillus subtilis, Bacillus coagalans etc, while the dominant microflora in Dafang Douchiba had a combination of Bacillus and Moulds. Twelve strains of Bacillus were screened for the manufacture of long-ripened Douchiba from 40 strains obtained from Qianxi and Dafang after comprehensive evaluation including extracellular proteolytic activity and lipidolytic activity, salt tolerance etc.The headspace volatile compounds in Qianxi Douchiba and Dafang Douchiba included alcohols, acids, esters, aldehydes, ketones, phenols, sulfur-containing compounds, heterocyclic compounds. These compounds mainly derived from lipid oxidation, amino acid catabolism, carbohydrate fermentation, Maillard reaction and Strecker reduction. A total of 81 and 122 volatile compounds were identified from Qianxi and Dafang Douchiba, respectively, among which 35 volatile compounds were repeatedly detected, and 21 were presented in both Douchiba products. Aromatic flavor of long-ripened Douchiba was...