Comparative evaluation of drying methods on kinetics, biocompounds and antioxidant activity of Bacillus subtilis-fermented dehulled adlay

Abstract

The effects of five drying methods on kinetics, biocompounds and antioxidant activity of Bacillus subtilis-fermented dehulled adlay (BDA) were evaluated in this study. The Page model (MR = $\mathrm{A}{\mathrm{e}}^{{-\mathrm{kt}}^{\mathrm{B}}}$) was the best-fit model to describe the drying kinetics of all dried BDA. The shortest drying time and highest drying rate were observed in microwave-vacuum drying (MVD). The highest contents of tetramethylpyrazine (TMP), γ-aminobutyric acid (GABA), triterpenoids, coixol, and coixan were detected in freeze-vacuum dried samples. However, the highest levels of total phenolics, flavonoids, and antioxidant activity were found in hot air-dried BDA. Moreover, higher retention ratios of TMP (71.90%), GABA (94.56%), coixol (63.38%), and coixan (94.29%), as well as the highest coixenolide content were obtained in MVD samples. In conclusion, MVD should be given first priority in large-scale industrial practice due to shorter drying time and high health-beneficial components.

Keywords:

• Dehulled adlay
• Bacillus subtilis
• drying kinetics
• biocompounds
• antioxidant activity

Additional information

Funding

The research was supported by the Natural Science Foundation of Guizhou Province (grant No. (2019) 1111, (2014) 6023 & (2012) 4001), and Agriculture Committee of Guizhou Province (grant No. (2018) 81).