In order to explore the influence of different heating temperatures on the composition of aroma substances and the sensory attribute intensity of Xinjiang spicy chicken seasoning sauce, descriptive sensory evaluation and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) were used to analyze the volatile components of the seasoning sauces without heating and heated at 100 and 150 ℃, and their sensory attribute intensities were quantitatively compared. In addition, orthogonal partial least squares-discriminant analysis (OPLS-DA) and variable importance in projection (VIP) values were used to select and verify the key differential substances among the sauces with different heat treatments. The results showed that different heating temperatures significantly affected the sensory characteristics of Xinjiang spicy chicken seasoning sauce. By GC-MS, 6 volatile substances including hydrocarbons, aldehydes, esters, alcohols, ketones and others were detected, and 16 key differential flavor substances which were significantly affected by heating temperature were selected by OPLS-DA, including terpenes (eucalyptol, terpinolene and α-pinacol), aldehydes and alcohols. With the increase in heating temperature, the contents of terpenes (such as limonene and basil) increased first and then decreased, which were positively correlated with the fresh aroma and tongue-numbing taste of Xinjiang spicy chicken seasoning sauce. However, the contents of aldehydes such as hexanal and (E)-2-octenal significantly increased, resulting in unpleasant off-flavors such as fatty and metallic odors. The above results show that temperature is one of the key factors in the directional control of flavor quality in the industrial processing of Xinjiang spicy chicken seasoning sauce. The findings of the present study provide a basic theoretical basis for the directional optimization of flavor quality and process improvement in the production of Xinjiang spicy chicken seasoning sauce.

In order to investigate the effect of frying time on the aroma of fried Hancheng pepper oil (HPO), four HPOs (HPOs 1, 2, 3 and 4) were prepared by frying Dahongpao pepper at 130 ℃ for 5, 15, 25 and 35 minutes with rapeseed oil as the carrier oil, respectively. Descriptive sensory analysis (DSA), an electronic nose (E-nose) system and gas chromatography-ion mobility spectrometry (GC-IMS) were employed to compare and analyze the volatile flavor compounds of the HPOs, and multivariate statistical analysis was used to explore differential volatile compounds between these four HPOs. Both DSA and E-nose results indicated that significant differences were observed between the HPOs; among them, HPO2 showed very strong herbal, lemon-like and pine-like aromas, with moderate fatty and green attributes and a very weak burnt. A total of 46 volatile compounds, including 19 aldehydes, 15 terpenes, 8 alcohols, 3 esters and 1 ketone, were identified from the four HPOs by GC-IMS. The types of volatile compounds in the HPOs were similar, in spite of significant differences in peak intensities. The contents of aldehydes including hexanal, heptanal and (E)-2-heptanal showed an increasing trend with increasing frying time; the contents of α-terpinene, phellandrene, 4-terpineol, ethyl 3-methylbutyrate and acetal showed an increasing and then decreasing trend, while a reverse trend was observed for alcohols and esters; however, the contents of terpenoids did not change so much. Principal component analysis (PCA) showed that the four HPOs were classified into two groups; one group contained HPO1 and HPO2, and another group contained HPO3 and HPO4, which was consistent with the results of linear discriminant analysis (LDA) from the E-nose data. The results of partial least square discriminant analysis (PLS-DA) showed that limonene, α-phellandrene, acetal, α-pinene and ethyl 3-methylbutyrate were the characteristic aroma compounds of HPO2, and 20 compounds were identified as differential markers, mainly including linalool, β-pinene, α-pinene, limonene, α-phellandrene, hexanal, heptanal, (E)-2-hexanal, (E)-2-heptenal, furfural, 2-methylbutanal, methylpropanal, 2-propenal, 1-propanol and ethyl-3-methylbutanoate.

To investigate the effects of thyme (Thymus vulgaris L.) addition on the flavor modification of mutton broth during boiling, three mutton-broth samples with various thyme contents 0.06% (S1), 0.30% (S2), and 1.50% (S3) were analyzed and compared, without thyme as control (0.00%, S0). The meaty, fatty, pastoral flavor and spicy were chosen as sensory attributes to evaluate the flavor of the mutton-broth samples. Sensory results were significantly different (P < 0.001), with S2 having the optimum overall acceptability. A total of 99 volatile compounds were identified by gas chromatography-mass spectrometry, among which 19 compounds were considered as the odor-active compounds according to their odor activity values. Significant changes (P < 0.05) appeared in most volatiles in S0 with thyme addition, especially aldehydes. Free fatty acids (FFAs) were also identified, and all of them significantly increased with increased thyme (P < 0.05). Correlation analysis of odor-active compounds, FFAs, and sensory attributes through partial least squares regression (PLSR) indicated the important volatiles and FFAs remarkably contributed to the mutton broth samples, and further confirmed that the 0.30% of thyme may be a desirable addition amount for the sensory characteristics of mutton broth.