Improvement of overall quality of black rice by stabilization combined with solid-state fermentation

Abstract

The application of black rice in food industry is challenging due to its short shelf life, poor cooking and eating quality. Superheated steam (SS) and far infrared radiation (FIR) are effective ways of stabilization and might be beneficial to solid-state fermentation (SSF). Therefore, stabilization treatments (SS and FIR) combined with SSF by Aspergillus oryzae were applied to furtherly improve the overall quality of black rice in present study. Results indicated that combined treatments were more favorable to shorten cooking time, increase water absorption and solid loss, resulting improvement of cooking quality of black rice. Besides, the significant decrease in hardness and chewiness after combined treatments was also good for the texture improvement. Moreover, black rice after combined treatments showed significantly higher contents of free phenolics, flavonoids, antioxidant activities, and phenolic acids, while their contents in bound form were significantly decreased, leading to significant increase of nutritional properties. Furthermore, black rice after combined treatments had significantly lower acid value and peroxide value during accelerated storage. Particularly, far infrared radiation combined with SSF was the most valued to improve the overall quality of black rice. These improvements were mainly ascribed to the enhancement of hydrolase activities based on the synergistic effect between stabilization treatments and SSF, which led to more significant pasting viscosities decrease, crystal structure destruction, cell wall rupture and starch degradation. The above results will provide a favorable strategy to improve the overall quality of black rice and then promote its consumption and application in food industry.

Industrial relevance

The short shelf life, poor cooking and eating quality severely limit the utilities of black rice in food industry. Heat processing is one of the most efficient strategies used in food industry to improve quality and prolong shelf life. Superheated steam and far infrared radiation are typical innovative heating technologies, and they are more energy efficient and more effective than conventional heating methods. In our previous work, they were effective ways of stabilization to extend the shelf life of black rice, and the starch after above treatments was partially gelatinized, which might be beneficial to the solid-state fermentation and thereby furtherly improve the overall quality of black rice. The present study aims to provide a favorable strategy to improve the overall quality of black rice and then promote its consumption and application in food industry.