Debittering and Improving Flavour of Enzymatic Soy Protein Hydrolysate Using the Maillard Reaction of Arabinose

The optimum reaction conditions (temperature 95°C, pH 6.5, time 70 min and cysteine 0.2 g) and significant influence factors were found by response surface model (RSM) experimentation to reduce bitterness and increase overall acceptability of soybean protein hydrolysate (SPH) using the Maillard reaction of arabinose. Three reaction products of different response values and sensory profiles were selected to be investigated further. Fourier transform infrared (FTIR) spectra and UV 294 and 420 nm analyses revealed their different extents of the Maillard reaction. Partial least squares regression analysis (PLSR) for free amino acids and molecular weight distribution and aroma compounds versus the used reaction conditions of the three samples suggested that reaction conditions of higher pH plus less Cys could cause more bitter amino acids (Leu, Val) and 500–1000 Da peptides, while those of more cysteine plus longer times under low temperatures benefitted formation of the umami amino acid of glutamic acid and > 1000 Da peptides. In particular, the reaction conditions of higher temperatures and more cysteine would generate more volatile compounds with roasted and meaty aromas unfavourable for overall acceptability. Furthermore, Pearson coefficient analysis revealed the key taste and aroma components and exposed that the fatty and caramel aromas contributed positively to overall acceptability. This study can provide references for debittering and improving the flavour of SPH.