Our previous results have shown that some genes such as PDIDSM_85260 and PDIDSM_08010 may be partly responsible for limonene biotransformation to α-terpineol as determined by analysis of genomic and transcriptomic data, protein separation and purification, and mass spectrometry. In order to explore the biological functions of the genes, RNA interference (RNAi) vectors for PDIDSM_85260 and PDIDSM_08010 were constructed and transformed into Penicillium digitatum DSM62840 by Agrobacterium tumefaciens-mediated transformation. RANi strains were obtained by a series of experiments, and the functions of the two genes were analyzed in P. digitatum DSM62840. It was found that the amount of α-terpineol produced by the silenced transformants obviously decreased compared to the wild-type strain, suggesting that PDIDSM_85260 and PDIDSM_08010 may participate in limonene biotransformation to α-terpineol.

The key enzyme involved in the biotransformation of limonene into α-terpineol by Penicillium digitatum DSM62840 was extracted and purified by sequential ultracentrifugation, ammonium sulfate precipitation, hydroxyapatite chromatography and gel filtration chromatography after high pressure disruption of cells. The results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed an obvious protein band with a molecular mass of approximatelty 50 kDa. This protein was tentatively identified as dihydrolipoyl dehydrogenase (PDIDSM_08010) by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results of this study may provide a basis and reference for α-terpineol production.

Identification of odor compounds in fresh sea buckthorn juice (FSBJ) and pulp (SBP) was performed by gas chromatography-mass spectrometry-olfactometry (GC-MS-O). A total of 39 and 36 odor compounds were identified in FSBJ and SBP, respectively. Further findings revealed that ethyl hexanoate, ethyl 2-methylbutyrate, ethyl 3-methylbutyrate, and 3-methylbutyl 3-methylbutanoate had high flavor dilution (FD) factors and were identified as the key odor compounds in FSBJ. In addition, the contents of ester compounds contributing to the fruity odor were significantly reduced in SBP after pasteurization. Sensory evaluation and electronic tongue analysis revealed that the sweetness and overall taste of SBP were superior to those of FSBJ. The contents of vitamin C and total flavonoids were significantly lower in SBP than in FSBJ, indicating that pasteurization reduces the nutritional quality of FSBJ. The results of the study can provide theoretical references for the flavor and nutritional quality optimization of sea buckthorn products.

In order to investigate the effects of different reheating methods (microwave, steam, water bath, and open flame) on the quality of quick-frozen prepared pork rib soup with carrot and corn, heating characteristics, texture, soup color, taste substances, volatile components, and sensory quality were determined. The results demonstrated that microwave reheating was the most efficient, providing uniform heating. In terms of texture, microwave and water bath reheating had less effects on the hardness, stickiness, and meat firmness of pork ribs, while microwave and open-flame reheating maintained the hardness and stickiness of corn and carrot significantly better (P < 0.05). The steam reheated soup was golden and clear in color, whereas the open-flame reheat soup became thick and milky white due to oil emulsification. The steam reheated soup exhibited a good combination of umami amino acids and nucleotides, presenting the strongest umami taste with an equivalent umami concentration (EUC) of 178.4 g/100 g, followed by those reheated by microwave, open flame, and water bath (EUC of 109.9, 100.2, and 56.5 g/100 g, respectively). A total of 61 volatile components were identified across all samples. In total, 29, 33 and 32 volatile components were found in the microwave, steam and open-flame reheated samples, respectively, with aromatic substances being the major ones; 31 volatile components in the water bath reheated sample, alcohols being the major ones. There were significant differences in the contents of some volatile components (P < 0.05). Sensory evaluation showed that the microwave and steam reheated soups were more favored by consumers in terms of color and taste (P < 0.05), with the highest overall sensory score. In summary, steam and microwave reheating are ideal reheating methods for frozen pork rib soup with carrot and corn.

In order to determine good jujube varieties for the production of vinegar, databases of soluble solids, total acid, transmittance, color, total phenols, total flavonoids, antioxidant properties and volatile flavor components were constructed for jujube vinegars made from four different varieties, Ruoqiang grey jujube from Xinjiang, Zanhuang jujube from Hebei, Tanzao jujube from Shanxi, and Tongxin round jujube from Ningxia. By comparing quality indexes and combining the results of principal component analysis (PCA) and sensory evaluation, it was concluded that Tanzao jujube vinegar was significantly superior to the other three jujube vinegars in terms of total acid content, total flavonoid content, 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging capacity, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cationic radical scavenging capacity, hydroxyl radical scavenging capacity, and volatile flavor components, and scored highest in both PCA and sensory evaluation. Therefore, Tanzao jujube was the most suitable raw material for jujube vinegar production. The results of this research provide a reference for raw material selection for and nutritional quality optimization of jujube vinegar.