In order to explore the effect of clove essential oil on the quality and safety of dry fermented catfish sausage, sausage samples were prepared from catfish surimi added with different amounts of clove essential oil (0% as control, 0.02%, 0.03%, 0.04%, and 0.05%), and their moisture content, water activity (a_w), pH value, color difference, thiobarbituric acid reactive substance (TBARs) value, microbial load, biogenic amine content, nitrite residue, N-nitrosamine content, and sensory quality of dry sausages were determined. The results showed that the addition of clove essential oil had little effect on the moisture content, a_w and TBARs value of dry fermented fish sausages, but it could decrease the a_w compared with the control group. With the addition of 0.05% clove essential oil, the lightness value (L*) of sausages was the highest, and the redness value (a*) was improved with increasing concentration of clove essential oil. The pH value showed a trend of first decreasing and then increasing with increasing concentration of clove essential oil, reaching its minimum at an addition level of 0.03%. The residual amount of nitrite in air dried sausage decreased with increasing addition of clove essential oil, and the maximum inhibition percentage of 38.7% was observed at an addition level of 0.05%. Clove essential oil promoted the growth of lactic acid bacteria, but the effect did not significantly vary depending on its concentration. The count of Enterobacteriaceae in the 0.03% addition group was significantly lower than that in the control group. The total amount of biogenic amines decreased with increasing essential oil addition, and the inhibitory effect on putrescine and histamine was the highest. The 0.02% and 0.03% addition groups had the lowest N-nitrosamine content. The 0.03% addition group had the highest sensory score. Collectively, we concluded that that higher concentration of clove essential oil was more conducive to improving the quality and safety of dry fermented sausages. However, the addition of excess clove essential oil can mask the flavor. Therefore, it is considered appropriate to add 0.03% clove essential oil.

In order to explore the relationship between dehydrin (DHN) and core browning in late-harvested Yali pears, this study identified and characterized the PbDHN3 gene based on bioinformatics methods, and analyzed the expression pattern of this gene during the core browning process under rapid cooling and slow cooling conditions. The results showed that the open reading frame (ORF) of PbDHN3 was 564 bp in length, encoding 187 amino acids, and having a conserved domain of dehydrin superfamily comprising two Y segments, one S segment and three K segments (Y₂SK₃). Bioinformatics analysis showed that PbDHN3 was a hydrophilic stable protein with a molecular mass of 19.77 kDa and an isoelectric point of 7.98. The secondary structure consists of α-helix, irregular coil, extended chain and β-turn. PbDHN3 was located in the nucleus and contained no signal peptide or transmembrane structure. It was a non-secretory protein. The results of homology analysis showed that PbDHN3 was more than 89.74% similar to the DHN of five other plants such as apples. Phylogenetic analysis showed that PbDHN3 had the closest relationship with the DHN of Pyrus ussuriensis × Pyrus communis. The results of promoter analysis showed that PbDHN3 contained basic promoter elements and other cis-acting elements, which were consistent with the predicted results of the upland cotton GhDHN1 and the wheat TaDHN2 promoter regions, and all of them included hormone response elements and light response elements. The results of real-time fluorescence polymerase chain reaction (PCR) analysis showed that the expression of the DHN3 gene was significantly up-regulated during the core browning process of Yali pears under rapid cooling conditions, which was closely related to the browning of the core. This study provides a theoretical basis for further exploring the function of the PbDHN3 gene and clarifying the mechanism of core browning of Yali pears.

In order to explore the effects of different combinations of spice essential oils on the quality and safety of air-dried catfish sausages, sausages were prepared from marinated catfish surimi added with a 1:1 (m/m) blend of clove and star anise (CA), clove and perilla (CP), star anise and perilla (AP) or clove, star anise and perilla essential oil (CAP) at 0.03% or none as a control. Moisture content, water activity (a_w), pH, color difference, thiobarbituric acid reactive substance (TBARS) value, biological amine content, N-nitrosamine content, and microbial load were measured. Microbial community structure was analyzed by 16S rDNA high-throughput sequencing. The results showed that the moisture content of the AP group was 27.13%, and the a_w value was 0.765. The L^* and a^* values of the CA group were high, indicating typical characteristics of air-dried sausages. The pH of the four treatment groups was higher than that of the control group, and followed the descending order of CAP > AP > CA > CP. There was no significant difference in the inhibition of fat oxidation among different essential oil combinations (P > 0.05), but the TBARS value of air-dried sausages was significantly reduced by all combinations (P < 0.05). The contents of biogenic amine and N-nitrosamine in the AP group were low. The total number of bacteria, and the number of Enterobacteriaceae and Aeromonas were significantly lower in the AP group than in the control group (P < 0.05). High-throughput sequencing results showed low species richness in the AP and CAP groups and low relative abundance of pathogenic bacteria in the AP group. Overall analysis showed that AP was superior to the other groups in improving the quality and safety of air-dried catfish sausages.

This study was conducted in order to explore the effects of addition of a mixed spice essential oil of star anise and perilla (1:1, m/m) combined with inoculation of a commercial lactic acid bacterial starter culture (PRO-MIX5) on the quality and safety of dried catfish sausage. Uninoculated sausage with the mixed oil was used as control (AP). The quality and safety of sausages were evaluated in terms of water activity, water content, pH, thiobarbituric acid reactive substance (TBARS) value, nitrite residue, lactic acid bacteria, Enterobacteriaceae and Pseudomonas counts, biogenic amine content and N-nitrosamine content at the end of fermentation. The results showed that the water content and water activity of dried sausage were significantly reduced during the fermentation process, and the degree of fat oxidation was reduced. At the end of fermentation, higher Enterobacteriaceae and lower Pseudomonas counts were found in the inoculated sausage (AP-PRO). The content of lactic acid bacteria in the AP and AP-PRO groups was 8.4 and 8.7 (lg(CFU/g)), respectively. The contents of total biogenic amines and N-nitrosamines were 14.5% and 41.0% in the AP-PRO group, significantly lower than the AP group (P < 0.05), respectively. In conclusion, the AP-PRO group was superior to the AP group in terms of quality and safety.