Search

To investigate thermolysis kinetics and identify degradation compounds, alliin solutions were heated at 60, 80, and 89 °C. The degradation compounds of alliin were identified by high performance liquid chromatography–mass spectrometry (HPLC–MS), tandem mass spectrometry (MS/MS) and ultra-pressure liquid chromatography–high resolution mass spectrometry (UPLC–HRMS). The results showed that the thermal degradation kinetic of alliin could be described by a first-order reaction and k = 4.38 × 10 17 exp (−142494/RT), where k is the reaction rate constant, min −1 ; R is gas constant; T is the absolute temperature, K. Degraded compounds, including S-allyl- l -cysteine and ethers, such as allyl alanine disulfide, allyl alanine trisulfide, allyl alanine tetrasulfide, dialanine disulfide (cysteine), dialanine trisulfide and dialanine tetrasulfide, were identified by HPLC–MS, MS/MS and UPLC–HRMS. Allyl alanine tetrasulfide was identified for the first time in alliin. The results show that alliin is unstable and significant numbers of organosulfur compounds are generated under high temperature treatment. [ABSTRACT FROM AUTHOR]

• Three pehtze stages in sufu production were characterized by high enzyme activities. • Four aging stages in sufu production were characterized by the presence of diverse targeted volatile compounds. • Protease and esterase were strongly correlated with most of the targeted volatile compounds. • Esterase contributed to the formation of three high molecular weight esters. Dynamic changes and correlations between physicochemical properties, 14 targeted volatile compounds (TVCs) and six groups of enzyme activities during eight production stages of naturally fermented plain sufu were explored. Multiple factor analysis was used to discriminate between and group the samples into three clusters: cluster I comprised tofu and pehtze; cluster II comprised dried pehtze and salted pehtze; cluster III involved the aging stages. Clusters I and II were characterised by higher enzyme activities, while cluster III was characterised by the presence of diverse TVCs. Protease and esterase were strongly correlated with most of the TVCs. Esterase, in particular, contributed to the formation of three high molecular weight esters, namely, ethyl dodecanoate, ethyl (Z)-9-octadecenoate and ethyl (Z , Z)-9,12-octadecadienoate. The enzymes found contributed to the texture and flavour of naturally fermented sufu and will provide a good guide and control for using the enzymes directly to ripen sufu products. [ABSTRACT FROM AUTHOR]