Production of nutty-like flavour from soybean protein isolate hydrolysate pretreated or assisted by microwave irradiation: impact of encapsulation on nutty flavour quality

The aim of this study was to prepare a nutty-like flavour from enzymatic hydrolysates of soybean protein isolate pretreated or assisted by microwave heating. In both cases the time of microwave heating was optimized and degree of hydrolysis (DH) and content of free amino acids in each hydrolysate were determined and compared with those of hydrolysate prepared by conventional method (E-HSC). The hydrolysates showed the best results were used as main precursors of nutty flavour. The generated volatiles were subjected to GC–MS analysis and odour evaluation. The effect of encapsulation and storage on the nutty flavour was evaluated. The results revealed that the hydrolysates pretreated (E-HSMP7) or assisted (E-HSMA6) by microwave at 7 and 6 min, respectively showed a significant increase in DH. The nutty flavour generated from these hydrolysates (NFMP7 and NFMA6) were dominated with pyrazines whereas, the volatiles from E-HSC (NFC) dominated with furans. NFMA6 showed the highest intensity of nutty and overall acceptability notes, compared with NFMP7 and NFC. Encapsulation resulted in a significant decrease in pyrazines, which are responsible for the nutty note. The significant increase in nutty aroma intensity of the stored encapsulated sample was correlated to the increase in pyrazines.