Xiao Mo Xiang You (XMXY) is a traditional Chinese sesame oil variety that is obtained through a hot water flotation process. This unique process gives the oil a unique aroma, health benefits, and excellent product stability. Although XMXY is always the most expensive among all the sesame oil varieties, it is usually used as a flavoring in many traditional Chinese daily food products and is increasingly popular. In order to reveal the characteristics of the oil, the volatile components, sensory evaluation, and oxidation stability of five XMXY samples were, respectively, analyzed by using headspace solid-phase microextraction/gas chromatography–mass spectrometry, an electronic nose, sensory evaluation, and RapidOxy. Comparisons and multidimensional statistical analysis were also carried out to distinguish XMXY from roasted sesame oil (RSO) and cold-pressed sesame oil (CSO) samples. In total, 69 volatiles were identified from XMXY, RSO, and CSO samples. Some compounds possessed high odor activity value (OAV > 1) in XMXY, including heterocyclic compounds, phenols, and sulfur-containing compounds. Additionally, they were also the main volatile components that distinguish XMXY from RSO and CSO. Roasted and nutty aromas were the dominant aroma attributes of XMXY. XMXY had better flavor intensity and oxidation stability than the other two sesame oil samples. These results are very valuable for the quality control and product identification of traditional Chinese sesame oil.

Visible-light-induced monofunctionalization and difunctionalization of MCPs via ring-opening and cyclization processes have been developed for the syntheses of difluoromethyl compounds, alkyl compounds, halides, and sulfonyl compounds.

It is well known that organic acids (OAs) could affect the flavour of fruit juices and beverages. However, the molecular mechanism of aroma release is still unclear. In this study, the effects of citric acid (CA), L-(-)-malic acid (MA) and L-lactic acid (LA) on the release of six selected esters and their sensory perception were investigated by means of HS-GC-MS analyses and odour detection threshold determination, respectively. Meanwhile, the density functional theory (DFT) calculation was employed to explore the interaction modes between esters and OAs. HS-GC-MS analyses showed that the concentration and the type of OAs regulated the release of esters. The results were basically consistent with the detection threshold change of those esters. The DFT calculation suggested that the main intermolecular interaction was hydrogen bonds, and several esters could form a ternary ring structure with OAs through hydrogen bonds. The interactions can induce the different release behaviours of esters in OAs water solution. The number of carboxyl functional groups in OAs and the spatial conformation of esters appeared to influence the magnitude of the interaction. The above results demonstrated the mechanism of OAs affecting the release of esters and indicated a possible flavour control way by using different OAs and OA concentrations.

Surface browning plays a major role in the quality loss of fresh-cut potatoes. Untargeted metabolomics were used to understand the metabolic changes of fresh-cut potato during the browning process. Their metabolites were profiled by ultra-high performance liquid chromatography coupled with high resolution mass spectrometry (UHPLC-HRMS). Data processing and metabolite annotation were completed by Compound Discoverer 3.3 software. Statistical analysis was applied to screen the key metabolites correlating with browning process. Fifteen key metabolites responsible for the browning process were putatively identified. Moreover, after analysis of the metabolic causes of glutamic acid, linolenic acid, glutathione, adenine, 12-OPDA and AMP, we found that the browning process of fresh-cut potatoes was related to the structural dissociation of the membrane, oxidation and reduction reaction and energy shortage. This work provides a reference for further investigation into the mechanism of browning in fresh-cut products.

Cyclic dipeptides represent a class of intriguing molecules with a wide range of biological activities, but their potential application as flavor precursors has not been previously reported. In this study, a flavor-producing bacterium Bacillus velezensis was screened out from 35 isolated endophytic bacteria. Gas chromatography-mass spectrometry (GC-MS) analysis suggested that the fermentation broth of B. velezensis contained flavor compounds and high amount of cyclic dipeptide flavor precursors. Three cyclic dipeptide flavor precursors, namely cyclo (L-prolyl-L-valine) (1), cyclo (L-prolyl-L-isoleucine) (2), and cyclo (L-prolyl-L-leucine) (3), were further isolated from the fermentation broth extraction through Sephadex LH-20 column chromatography and semi-preparative high-performance liquid chromatography (HPLC), and were identified by nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). Flavor precursors can generate aroma components during pyrolysis, and the pyrolysis of compounds 1 and 3 were performed using pyrolysis GC-MS (Py-GC-MS) to analyze the flavor products. According to the relative odor activity value (ROAV) analysis, the key pyrolysis flavor compounds were revealed as 6-heptyl-5,6-dihydro-2H-pyran-2-one, isobutyric acid, 4-methyl-2-oxo-pentanoic acid ester, pyrrole derivatives, and pyrazine derivatives, which could give great contributions to milky, roasting, fruity, sweetness, and nutty aromas. The pyrolysis formation pathway of these flavor compounds was also proposed in detail. Addition of fermentation broth from the flavor-producing bacteria on cigar tobacco leaves significantly enhanced the milky, roasting, fruity, sweetness, and nutty aromas, which further demonstrated the flavor enhancing ability of cyclic dipeptides. This is the first report of flavor enhancing effects of cyclic dipeptides utilized as flavor precursors.