Summary
Chinese rice wine, a traditional alcoholic beverage, is fermented from steamed rice with a starter culture of wheat Qu which is either inoculated spontaneously with various microorganisms in natural environment or inoculated artificially with certain microorganisms. The diversity of filamentous fungi in wheat Qu and the fermentation mashes of Chinese rice wine was studied by high‐throughput sequencing. The results indicated that filamentous fungi varied in wheat Qu and fermentation periods. Moreover, Aspergillus was the dominant filamentous fungi at genus levels. On that basis, quantitative real‐time PCR was used to quantify some dominant Aspergillus species. It was found that Aspergillus species in wheat Qu were more abundant than that in various fermentation mashes and continually decreased until the end of rice wine fermentation. Furthermore, it was found that different organic acids were produced by microorganisms at different fermentation stages might due to the changes of oxygen and nutrient content.
Background and objectives
Prolamins are the primary component of millet protein, constituting over 50% (w/w) of the total protein. This study aimed to prepare and identify bioactive peptides from millet prolamins (MP).
Findings
Ultrasonic and heat treatment could change the secondary structure conformation of the protein and invert part of the α‐helices into β‐sheets or β‐turns. After these treatments, the degree of hydrolysis increased. The alcalase‐hydrolyzed fraction with molecular weight <1 kDa exhibited the highest antioxidant activity. The bioactive peptides were separated and purified by gel‐filtration chromatography and reversed‐phase high‐performance liquid chromatography. Two novel peptides with molecular weights of 522.3 and 785.5 Da were identified as Pro‐Phe‐Leu‐Phe (PFLF) and Ile‐Ala‐Leu‐Leu‐Ile‐Pro‐Phe (IALLIPF), respectively. Both peptides showed high antioxidant activity, especially PFLF, the 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging ability (RSA) of which was 149 μM TE/g protein, and the Oxygen radical absorbance capacity (ORAC) value reached 1,180 μM TE/g protein.
Conclusions
The results demonstrate that ultrasonic and heat treatment could enhance hydrolysis of MP by protease and antioxidant peptides with high DPPH RSA as well as ORAC value were purified and obtained.
Significance and novelty
Ultrasonic and heat treatment increased degree of MP hydrolysis. Two antioxidant peptides were successfully obtained from millet prolamins.
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