This study clarified the escape behavior of key volatile compounds in stewed beef with soy sauce during air-cooling process and refrigeration, aiming to provide the theoretical basis for the flavor preservation and conformity of stewed beef with soy sauce.
The volatile flavors in stewed beef with soy sauce were identified by the electronic nose (E-nose) and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME/GC-MS) combined with odor activity value (OAV) and principal component analysis (PCA), which defined the dynamic change of flavors during cold air-cooling process (the central temperature was reduced from 50 ℃ to 10 ℃, the wind speed was 2 m∙s-1, and the cooling time was 90 minutes) and refrigeration (0, 6, 18, 30, 42 and 54 h at 4 ℃). Then the escape behavior of key flavor active compounds in stewed beef with soy sauce were revealed.
According to the E-nose analysis, the flavor profiles of stewed beef with soy sauce exhibited significant differences among the three stages (“out of the pot”, before air-cooling and after air-cooling). Nitrogen oxides, alcohols, aldehydes, ketones, aromatics and organic sulfides were considered the main compounds for the discrepancy. On the other side, the stewed beef with soy sauce after 0, 42 and 54 h refrigeration showed differential flavor profiles, which mainly caused by the variety in nitrogen compounds, alcohols, aldehydes and ketones. However, there was no significant difference in the flavor profiles among 6, 18 and 30 h refrigeration. The HS-SPME-GC-MS results showed that 39, 31 and 33 volatile compounds were identified in three cold air-cooling stages, and the contents were 13 636.18, 9 799.21 and 8 213.86 μg∙kg-1, respectively, with total amounts reducing by 39.8%. Morever, 36, 36, 34, 34, 31 and 29 volatile compounds were identified on different refrigeration periods, the contents were 7 712.65, 6 196.00, 5 319.42, 4 732.69, 5 295.05 and 4 281.82 μg∙kg-1, respectively, and the total contents decreased by 44.5%. Therefore, the flavor escape of stewed beef with soy sauce mainly occurred in the refrigeration stage. Besides, OAV analysis showed stewed beef with soy sauce in the cold air-cooling stage had 18 key active compounds, while eucalyptol, lauryl alcohol, valeraldehyde, and L-carvone were all lost before cold air-cooling, and acetoin, phenethyl alcohol, geranyl acetone, as well as linalool escaped severely, with their OAV values reducing by 81.3%, 64.0%, 63.7% and 55.1%, respectively. 15 key active volatile compounds were identified during refrigeration. Among them, isobutyl acetate and ethyl heptanoate were lost after 6 h. Anethole, eugenol, 4-allylanisole, and linalool were severely escaped, and the OAV values decreased by 63.9%, 63.8%, 58.1% and 53.9%, respectively. Refrigeration was the main stage for the loss and dissipation of flavor compounds in stewed beef with soy sauce; alcohols, ketones, esters and phenolic ethers were more susceptible to lose and escape during air-cooling and refrigeration; the loss and dissipation of flavor compounds were mainly derived from spices.
This study revealed the escape behavior of flavor active compounds in stewed beef with soy sauce during air-cooling process and refrigeration, and provide the theoretical basis for stewed beef's flavor retention and regulation with soy sauce.