Quality Difference Analysis Among Soy Whey Produced by Different Processing Methods

The objective of this study was to analyse the difference in sensory flavour and volatile compounds among the three processing methods of soy whey, as well as to establish an evaluation model representing the correlation between sensory flavour and volatile compounds. The results showed that the soy whey produced by the boiling-to-filtering method (BFM) exhibited a higher total soluble solid (TSS) content and total flavonoid content (TFC) compared to that of the repeated boiling-to-filtering method (RBFM) and the filtering-to-boiling method (FBM), while RBFM soy whey showed a higher total protein content (TPC). The sensory analysis showed that the FBM soy whey exhibited an intense beany flavour and grease odour. The SPME/GC–MS results showed that FBM soy whey exhibited more categories and higher contents of flavour compounds, particularly for alcohols and aldehydes. 1-Octen-3-ol, n-hexanol, hexanal and nonanal were the main volatile compounds influencing soy whey with different processing methods. The evaluation model revealed that the beany flavour was close to FBM soy whey and highly correlated with 1-octen-3-ol, n-hexanol, hexanal, heptanal and 2-ethyl furan. (E, E)-2,4-Heptadienal, (E, E)-2,4-nonadienal and octanal were close to FBM and highly correlated with grease and bean fragrance. Decanal, ethyl caproate and ethyl caprylate were highly correlated with the floral aroma and close to FBM soy whey. Sweet and fruity aromas were associated with RBFM soy whey and highly correlated with 3-methyl butanal, (E)-2-nonenal and nonanal. The milk aroma was close to BFM soy whey and highly correlated with 2-ethylfuran, decanal, ethyl caprylate and ethyl caproate. Overall, RBFM and BFM soy whey contained higher levels of protein and flavonoids and exhibited less beany flavour, potentially offering greater nutritional value. In contrast, the FBM soy whey exhibited a higher content of volatile flavour compounds, especially 1-octen-3-ol, n-hexanol, hexanal and 2-ethyl furan.