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The flavor release mechanism related to the interaction of aroma compounds with proteins is still unclear. In this study, the interaction of protein with pyrazine homologues, such as 2-methylpyrazine (MP), 2,5-dimethylpyrazine (DP), 2,3,5-trimethylpyrazine (TRP) and 2,3,5,6-tetramethylpyrazine (TEP), was investigated to elucidate the effect of alkyl distribution in a pyrazine ring on its flavor release in bovine serum albumin (BSA) solution (pH 7.4). The results of SPME-GC-MS indicated that methyl distribution in a pyrazine ring significantly affected its release from BSA solution. The pyrazines released from BSA solution with an increasing order of MP, DP, TRP and TEP. The inhibition mechanism of alkyl-pyrazine release was further elucidated by the interaction between alkyl-pyrazines and BSA using multiple spectroscopic methods. The non-covalent interaction between alkyl-pyrazines and BSA was confirmed as the main interaction force by the value of the bimolecular quenching constant (Kq > 2 × 1010 L mol−1 s−1). A decrease in the hydrophobicity of the microenvironment between the alkyl-pyrazine and BSA was detected by synchronous fluorescence spectra, which revealed that alkyl-pyrazines were mainly bound on the sites of tyrosine and tryptophan in BSA. The UV-vis absorption spectra and circular dichromatic (CD) spectrum revealed that alkyl-pyrazines could induce polarity and conformation change of BSA. The above results indicated that the structure of the flavor homologues can affect their release in food matrices.

Dried Lentinus edodes (Berk.) sing stipe (LES) is mostly discarded owing to its high fibre content and bad palatability, causing significant waste of resources. The aim of this study is to sustainably use LES for the production of flavour soybean oil using the supercritical CO2 fluid extraction (SFE) method. The quality properties of the obtained soybean oil flavoured by LES (OFLS) were evaluated in this study. Profiles obtained with an electronic nose and gas chromatography results obtained by quadrupole time-of-flight mass spectrometry and with a mass-selective detector indicated that mushroom-like aroma compounds were mainly concentrated into the OFLSs from separation kettle A (9 MPa). Interestingly, off-flavour compounds from soybean oil, such as o-xylene and trans-2-nonenal, were mostly distilled into separation kettle B (4 MPa). More importantly, the developed SFE method effectively improved the colour quality of the OFLSs. Additionally, the decrease of the viscosity of the OFLSs indicated that the thermal stability of the edible oil could be improved. In summary, the OFLSs prepared by the green and sustainable SFE method significantly improved the quality of the edible oil.