In order to better understand the impact of heating temperature on volatiles forming during linoleic acid heating process, volatile profiling was investigated by using thermal‐desorption cryo‐trapping combined with gas chromatography–mass spectrometry. As a result, a total of 42 volatile compounds were detected and identified during this process, including aldehydes (12), ketones (6), alcohols (5), furans (6) acids (10), and aromatic compounds (3). The forming temperature of each volatile was determined. It reveals most volatiles with shorter carbon chains were generated at lower temperatures, while volatiles with longer carbon chains were generated at higher temperatures. Simultaneously, principal component analysis was used to analyze the volatile composition characteristics of linoleic acid at each temperature points. Results show volatile characteristics of linoleic acid had a big difference among different temperatures. One conclusion was drawn the volatile compound formation from linoleic acid is a temperature‐dependent reaction rather than a time‐dependent one during heating. Novelty impact statement Thermal desorption combined with GC–MS could be an effective method for studying the volatile compounds forming mechanism of linoleic acid during heating. Temperature plays a crucial role in the heating process. Volatile compound formation from linoleic acid is a temperature‐dependent reaction rather than a time‐dependent one during heating.

Increasing the copy number of peptides is an effective method to genetically engineer recombinant expression and obtain umami peptides in large quantities. However, the umami taste value of multicopy number umami peptides is lower than the single ones, thus limiting the industrial application of recombinantly expressed umami peptides. With aims to solve this problem, modification of an umami beefy meaty peptide (BMP) with trypsin hydrolysis sites was carried out via homology modeling and molecular docking in this study. A total of 1286 modified peptide sequences were created and molecularly simulated for docking with the homology modeling-constructed umami receptor (T1R1/T1R3), and 837 peptides were found to be better docked than the BMP. Afterward, the MLSEDEGK peptide with the highest docking score was synthesized. And umami taste evaluation results demonstrated that this modified peptide was close to that of monosodium glutamate (MSG) and BMP, as confirmed by electronic tongue and sensory evaluation (umami value: 8.1 ± 0.2 for BMP; 8.2 ± 0.3 for MLSEDEGK peptide). Meanwhile, mock trypsin digestion of eight copies of MLSEDEGK peptide results showed that the introduced digestion sites were effective. Therefore, the novel modified BMP in this study has the potential for large-scale production by genetic engineering.

To better understand the mechanism of palmitoleic acid oxidation into volatile compounds during heating, volatile profiling was investigated by combining thermaldesorption cryo-trapping with gas chromatography-mass spectrometry. A total of 49 volatile compounds were detected and identified during this process, including aldehydes (18), ketones ( 14), alcohols (9), furans (3) and acids and ester (5). The forming temperature of each volatile was determined. Most of the volatiles with short carbon chains were generated at low temperatures, while those with long carbon chains were generated at high temperatures. Results of principal component analysis show that nearly all of the identified volatiles were considered as the characteristic ones of the high temperature points. Meanwhile, the oxidative products of the C7-C11 saturated and unsaturated aldehydes were also detected and identified during heating to intensively investigate the oxidative mechanism of palmitoleic acid during heating. Results demonstrated that only the C10 saturated and unsaturated aldehydes could continue to be oxidized during heating. Therefore, the oxidation reactions above the secondary level of lipids mainly occurred in the C10 saturated and unsaturated aldehydes.