This study investigated how to reduce the content of N-hydroxyacetylneuraminic acid (Neu5Gc) in pork. By using Neu5Gc standard solution, porcine submandibular gland mucin (PSM) solution, meat pieces and minced meat as experimental subjects, and high performance liquid chromatography with fluorescence detection (HPLC-FLD) for quantitative analysis, the effect of pulsed electric field (PEF) treatment (with 50 cycles of electric shock at 1–4 kV/cm) on the content of total and free Neu5Gc and eating quality attributes (pH, color difference and texture quality) in pork was explored. The results showed that the content of free Neu5Gc in Neu5Gc standard solution showed a decreasing trend as PEF intensity increased, and significantly decreased at PEF intensity of 3 and 4 kV/cm (P < 0.05). The contents of total, free and bound Neu5Gc in PSM solution also decreased significantly (P < 0.05) with increasing intensity of PEF. The contents of total and bound Neu5Gc in meat pieces showed a decreasing trend while the content of free Neu5Gc increased, and the contents of total and bound Neu5Gc were significantly lower than those in the control group at 4 kV/cm (P < 0.05). The contents of total and bound Neu5Gc in minced meat showed a decreasing trend, and were significantly lower in all treatment groups than in the control group (P < 0.05). Compared with the control group, there was a significant difference (P < 0.05) in the pH of meat pieces treated at PEF intensity of 2 and 4 kV/cm. The brightness L* value of meat pieces and minced meat first increased and then decreased, reaching a maximum level at 3 kV/cm. The chewiness and elasticity of PEF-treated meat pieces were significantly lower than those of the control group (P < 0.05). The hardness and chewiness of minced meat tended to decrease, but there was no significant change in the elasticity (P > 0.05). Therefore, PEF can effectively reduce the content of Neu5Gc in pork and the chewiness and elasticity of pork pieces, but it also shows an adverse effect on the pH and color of pork.

In order to study the color stability and change mechanism of beef during postmortem storage, quantitative proteomic analysis was carried out on bovine Longissimus dorsi with high and low color stability at 75 min, 2 days and 8 days after slaughter. Proteomic results showed that a total of 1377 proteins were identified in the high and low color stability groups, including 136 differential proteins. Bioinformatics analysis found that the differential proteins were mainly involved in postmortem biochemical processes such as redox, glucose metabolism, signal transduction and apoptosis, which were closely related to the regulation of meat color stability during postmortem storage. By functional analysis of these differential proteins, four key differential proteins related to the respiratory electron transport chain were selected, namely, cytochrome complex subunit (UQCR10), cytochrome C oxidase subunit Ⅶa peptide 1 (COX7A1), mitochondrial ATP synthase subunit (ATP5MG), and mitochondrial ATP synthase subunit (ATP5MF). These proteins participated in the postmortem energy metabolism and redox processes and affected oxidoreductase activity, which in turn affected the color stability of beef during storage. This study provides an idea for the regulation of meat color stability in the future.

In order to improve the flavor quality and production efficiency of liquid-smoked bacon, the traditional use of liquid smoke was improved and the production process with liquid smoke-assisted curing was optimized by response surface methodology. The independent variables were volume fraction and addition level of liquid smoke, curing time and roasting time. The response was sensory scores. The quality of liquid-smoked bacon was compared with that of traditional bacon from west Hunan Province. Partial least squares-discriminant analysis (PLS-DA) was used to evaluate the changes of flavor substances during the roasting of liquid-smoked bacon. The results showed that the optimal process conditions were as follows: adding 2% of liquid smoke at a volume fraction of 70%, curing for 4 days and roasting for 8 days. Compared with commercially available west Hunan-style bacon, liquid-smoked bacon had higher moisture content and brightness value, and lower salt and nitrite contents (3.8% and 1.20 mg/kg respectively), and its sensory score was 84.56 ± 1.10 out of 100 points. The taste activity value (TAV) analysis showed that inosine monophosphate (IMP), guanosine monophosphate (GMP), alanine, glutamic acid, lysine, arginine, valine, histidine, and adenosine monophosphate (AMP) were mainly responsible for the taste of liquid-smoked bacon. PLS-DA showed that the content of taste substances varied depending on the roasting time, and citrulline, tryptophan, cysteine, hypoxanthine (Hx), GMP, glutamine, glycine, isoleucine, and leucine were the key indexes influencing the differences in the flavor of liquid-smoked bacon with different roasting times.