Nang roasting is a traditional lamb processing method in Xinjiang (China) with a history of thousands of years. This study comprehensively evaluated the volatile and nonvolatile compounds of oyster cuts of roasted lamb at different processing stages of Nang roasting using gas chromatography mass spectrometry and amino acid automatic analyzer, respectively. Results indicated that aldehydes were the dominant profiles of volatile compounds, and hexanal, nonanal, octanal, (E)-2-nonenal, (E, E)-2,4-decadienal, (E, E)-2,4-nonadienal and 1-octen-3-ol were the key volatile compounds or aroma contributors to roasted oyster cuts. Isoamylol and 3-hydroxy-2-butanone could differentiate fresh and marinated oyster cuts from roasted ones; (E)-2-nonenal, (E, E)-2,4-decadienal, 1-octen-3-ol, hexanal, octanal, nonanal and (E, E)-2,4-nonadienal could differentiate Nang roasted oyster cuts of 60 min from those of 15, 30 and 45 min. Umami amino acids and sweet amino acids are the dominant profiles of nonvolatile compounds; glutamic acid, alanine and 5′-IMP were the key free amino acids or taste contributors to roasted oyster cuts. Glutamic acid, alanine and 5′-IMP could differentiate fresh and marinated oyster cuts from roasted samples. This work provided theoretical support for the control of flavor attributes of roasted lamb with traditional Nang roasting.

Litopenaeus vannamei protein (LVP) is a high-quality protein. However, its functional properties do not fully meet the needs of food processing. In this study, LVP-xylose conjugates were prepared by conventional wet heat method (GLVP) and ball-milling-assisted wet heat method (GBLVP), respectively. The changes in structure and functional properties of the glycosylated LVP were explored. The findings revealed that ball-milling pretreatment increased the grafting degree to 35.21%. GBLVP had a sparser surface structure and lower particle size than GLVP. FTIR spectra showed that xylose was grafted onto LVP successfully and GBLVP had the lowest α-helix content. Compared with GLVP, GBLVP had a decrease in intrinsic fluorescence intensity and surface hydrophobicity, and an increase in UV absorption intensity. Moreover, GBLVP had higher foaming capacity, solubility and water-holding capacity, and lower allergenicity than GLVP. However, ball-milling pretreatment had a negative impact on the vitro digestibility and oil-holding capacity of GBLVP. In conclusion, ball-milling-assisted treatment of glycosylation could effectively improve the functional properties of LVP, benefiting the broader application of LVP in the food industry.

To address the challenges associated with resource inefficiency, low extraction rates, environmental concerns, and high energy consumption in traditional fish oil production from dotted gizzard shad (Konosirus punctatus), a novel approach is needed. This study aimed to develop and evaluate two innovative methods for fish oil extraction and refinement, focusing on their effects on fish oil quality, fatty acid profile, and volatile compound composition throughout the respective processes. The findings of the study revealed that the ethanol-assisted enzymatic extraction method surpassed the conventional enzymatic approach in extraction efficiency, achieving an optimal extraction rate of 74.94% ± 0.45% under optimized process conditions. Moreover, the ethanol-NaOH one-step degumming and deacidification method proved effective in simultaneously removing phospholipids and free fatty acids. Under optimal conditions, a notable reduction in phospholipid content in dotted gizzard shad oil, from 6.80 ± 0.01 mg/g to 1.18 ± 0.01 mg/g, and a substantial decrease in acid value, from 3.31 mg/g to 0.31 mg/g, were observed. In summary, the study analyzed the physicochemical properties, fatty acid composition, and volatile components of fish oil before and after refinement. The refining process was found to preserve the fatty acid composition while efficiently eliminating hydroperoxides and reducing unpleasant odors in the crude oil.

Suanyu is a traditional natural fermented fish product from Southwest China that contains very complex microflora. The main purpose of this study was to explore the fungal community and its relationship with the physicochemical properties of Suanyu. The fungal community structure of Suanyu from the main provinces (Guizhou and Hunan) was studied via high-throughput sequencing. The correlation between dominant fungi and physicochemical characteristics was analyzed via Spearman’s correlation coefficient. The results showed that the pH value, total volatile base nitrogen content, and thiobarbituric acid reactive substance content ranges of Suanyu samples were 4.30–5.50, 17.11–94.70 mg/100 g, and 0.61 to 3.62 mg/kg, respectively. The average contents of total volatile base nitrogen, thiobarbituric acid reactive substance, and total BAs in Suanyu from Guizhou were lower than those from Hunan. The main BAs were phenethylamine, putrescine, cadaverine, histamine, and tyramine. Ascomycota was the dominant fungal phylum, and Kodamaea, Debaryomyces, Wallemia, Zygosaccharomyces, and unclassified Dipodascaceae were the dominant fungal genera in different samples. Moreover, high abundance levels of Kodamaea and Zygosaccharomyces were found in Suanyu from Guizhou. According to the correlation analysis, Kodamaea and Zygosaccharomyces were negatively correlated with TBARS (R² = −0.43, −0.51) and TVBN (R² = −0.37, −0.29), and unclassified Dipodascaceae was significant negatively correlated with tyramine (R² = −0.56). This study expands the understanding of the fungal community and the fermentation characteristics of the dominant fungi in Suanyu.

Chitooligosaccharides have important application value in the fields of food and agriculture. Chitosanase can degrade chitosan to obtain chitooligosaccharides. The marine metagenome contains many genes related to the degradation of chitosan. However, it is difficult to mine valuable genes from large gene resources. This study proposes a method to screen chitosanases directly from the marine metagenome. Chitosanase gene chis1754 was identified from the metagenome and heterologously expressed in Escherichia coli. The optimal temperature and pH of CHIS1754 were 55 °C and 5.5, respectively. A mutant, CHIS1754T, with 15 single point mutations designed based on molecular evolution data was also expressed in E. coli. The results indicated that the thermal stability of CHIS1754T was significantly improved, as the T_m showed an increase of ~ 7.63 °C. Additionally, the k_cat/K_m of CHIS1754T was 4.8-fold higher than that of the wild type. This research provides new theories and foundations for the excavation, modification, and industrial application of chitosanases. Key points A chitosanase gene, chis1754, was firstly identified from marine metagenome. A multi-site mutant was designed to improve enzyme stability and activity. The k_cat/K_mof the designed mutant was 4.8-fold higher than that of the wild type.