Drying kinetics, physico-chemical properties, antioxidant activity and phenolic composition of foam-mat dried germinated rice bean (Vigna umbellata) hydrolysate

This research was aimed to study physico-chemical properties and antioxidant activities of foam-mat dried germinated rice bean (Vigna umbellata) hydrolysate. Germination led to an increase in released phenolic content and antioxidant activity (DPPH radical scavenging activity and FRAP) of rice bean hydrolysate. The hydrolysate obtained from germinated rice bean (GRB) and non-germinated rice beans (NGRBs) was foam-mat dried at 60 and 70 °C. Semi-theoretical and empirical model could suitably describe the drying characteristic of foamed bean hydrolysate. Total phenolic content and antioxidant activities of foam-mat dried samples decreased with increasing air-drying temperature (P ≤ 0.05). Gallic acid, catechol and epicatechin were major phenolic compounds in foam-mat dried samples prepared from both GRB and NGRB. The higher phenolic content and antioxidant activities were found in foam-mat dried hydrolysate of GRB. Electron spin resonance spectrometry revealed that foam-mat dried rice bean hydrolysate showed a strong ability to scavenge free radicals, especially carbon-centred radicals.