Effects of Alkaline Protease and Transglutaminase on Flavor Characteristics of Gluten-free Grain Steamed Buns during Fermentation

The taste and flavor of gluten-free grain steamed buns which were made of soybean flour and rice flour during fermentation were extracted, identified and analyzed by electronic tongue, electronic nose and solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) respectively. Gluten-free grain steamed buns were made by fermentation twice, which alkaline protease (adding amount was 2.0% of the dry base of the raw materials) was added and fermented for 60 min at 40℃ firstly and transglutaminase (TG enzyme) (adding amount was 2.0% of the dry base of the raw materials) was added and fermented for 90 min at 50℃ secondly. The results of electronic tongue showed that the accumulative variance contribution rate of the first principal component (PC1) and the second principal component (PC2) was 93.60%, which could represent the original taste information of the sample. After the second fermentation, the saltiness and freshness of steamed buns increased, while the bitterness and astringency decreased. The results of electronic nose showed that the accumulative variance contribution rate of the first principal component (PC1) and the second principal component (PC2) was 99.99%, which could distinguish the flavor difference between samples, and the sensor was sensitive to nitrogen oxides, hydrocarbons, alcohols and aromatic compounds. GC-MS results showed that after the secondary fermentation of gluten-free grain steamed buns by alkaline protease and TG enzyme compared with the control group, alcohol, ketone and aromatic substances increased by 12.04%, 1.13% and 0.32%, respectively, and the aroma of fruit, oil and wood were more obvious. The experimental results showed that the alkaline protease and TG enzyme could effectively improve the taste and flavor of gluten-free grain steamed buns, which would provide reference for the development of gluten-free grain food.