The effects of different mass fractions of L-arginine (0.0%, 0.5%, 1.0%, and 1.5%) on the emulsifying characteristics of pork sarcoplasmic protein were studied. The findings indicated that addition of L-arginine (≥ 1%) significantly enhanced the emulsifying activity and emulsion stability of sarcoplasmic protein (P < 0.05) and decreased the particle size (D_4,3, D₅₀, and D₉₀) of sarcoplasmic protein-stabilized emulsion (P < 0.05). The Turbiscan stability index (TSI) decreased after addition of L-arginine. The results of interfacial rheology showed that L-arginine increased the oil-water interfacial tension. The results of surface hydrophobicity and ultraviolet (UV) absorption spectroscopy implied that L-arginine promoted the exposure of protein hydrophobic groups (tryptophan and tyrosine residues). Raman spectroscopy showed that L-arginine was beneficial for the secondary structure transformation of sarcoplasmic protein from α-helix to β-turn. The results of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that the basic composition of sarcoplasmic protein was not affected by L-arginine. In summary, L-arginine could significantly improve the emulsifying properties of sarcoplasmic protein by changing emulsion physicochemical properties, protein interfacial characteristics, and protein secondary and tertiary structures.

Myofibrillar protein (MP) extracted from thawed pork was treated with plasma-activated water (PAW) generated by low-temperature plasma treatment. The effect of PAW obtained at different discharge times (0, 5, 10, 15, 20 and 25 s) on the emulsifying activity, emulsion stability, particle size, zeta potential, amount of adsorbed protein and rheological properties of MP-stabilized emulsion was investigated. The results showed that compared with the control group, PAW treatments significantly improved the emulsifying activity and emulsion stability, and reduced the turbiscan stability index (TSI) (P < 0.05). Additionally, after PAW treatments, the particle size of MP-stabilized emulsion significantly decreased and the zeta potential increased; PAW 20 s resulted in the smallest particle size and the highest absolute value of the zeta potential, 34.22 μm and 11.36 mV. Compared with PAW 20 s, PAW 25 s reduced the emulsion stability. The results of rheological properties showed that after PAW treatments, the elasticity, apparent viscosity and viscoelasticity increased. In conclusion, PAW treatment could significantly improve the emulsifying properties of MP from thawed pork, the effect being most pronounced with PAW 20 s.

Konjac glucomannan (KGM) gel was frozen by air freezing, immersion freezing and ultrasonic-assisted freezing, separately and analyzed for changes in its properties and structure by a texture analyzer, an X-ray diffractometer (XRD), low field nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), and cold field scanning electron microscopy (SEM). The results showed that compared with air freezing and immersion freezing, ultrasonic-assisted freezing increased the cooling rate of the gel, reduced the syneresis rate, and increased the gel strength without changing the crystallinity of KGM. When the ultrasonic power was 300 W, the syneresis rate and strength of the gel reached their best level. Compared with air freezing, ultrasonic-assisted freezing reduced the syneresis rate by 23.56% and increased the gel strength by 61.23%. The DSC heat flow curves showed that ultrasonic-assisted freezing increased the eutectic point of the gel and lowered its thawing temperature. The microscopic images showed that the network structure of the gel frozen at an ultrasonic power of 300 W was the densest, with the smallest pores. In conclusion, 300 W ultrasonic-assisted freezing can effectively improve the gel characteristics of KGM, which provides a theoretical foundation for the production of new KGM gel foods.

Postmortem ovine Longissimus dorsi muscle was treated by dielectric barrier discharge (DBD) low-temperature plasma with different intensities (0, 30, 60, 90 and 120 s) and then stored 4 ℃. The changes in the pH, color, juice loss, shear force, total bacterial count and protein oxidation indicators of the samples during storage were analyzed to explore the effect of DBD low-temperature plasma treatment on the quality of lamb meat. The results showed that during storage, the pH of the treated samples was lower than that of the untreated ones. The L^* and b^* values of the samples increased firstly and then decreased with treatment time. DBD low-temperature plasma treatment had no significant influence on the color or shear force, but could accelerate protein oxidation in lamb meat. Furthermore, this treatment significantly (P < 0.05) reduced the total count of bacteria during storage. After five days of storage, the total count of bacteria in the control group was 6.10 (lg (CFU/g)), which was far beyond the limit. However, the total count of bacteria the treatment group exceeded the limit value after seven days, indicating that DBD low-temperature plasma treatment can extend the shelf life of lamb meat. DBD low-temperature plasma treatment for 60 s had the least negative impact on lamb meat quality during storage.

In an attempt to investigate the effects of different freezing pretreatments on the emulsification and gelation properties of myofibrillar protein (MP), this study aimed to analyze changes in the emulsifying activity index (EAI), emulsifying stability index (ESI), emulsion particle size, rheological properties, gel strength, cooking loss, water distribution and morphology of MP extracted from porcine Longissimus dorsi muscle pretreated by air freezing (AF), immersion freezing (IF) or ultrasonic-assisted immersion freezing (UIF). The results showed that AF and IF remarkably lowered the emulsifying activity and emulsion stability of MP compared with the control group (held at 4 ℃ for 6 h) and resulted in significantly larger and non-uniform sizes of emulsion droplets. UIF markedly increased the emulsifying activity but did not change the emulsion stability or droplet size. UIF improved the viscoelasticity and gel strength of heat-induced MP gels and reduced the cooking loss compared with the other treatment groups, and water distribution in the gel network was more uniform. high-resolution field-emission scanning electron microscopic (FE-SEM) observation revealed that the network structure of UIF-treated MP gels was more compact than that of the other treatment groups, closer to that of fresh MP gels. In summary, UIF-treated MP had better emulsification and gelation properties, indicating that UIF could maintain the processing quality of frozen meat better.

Ultraviolet C light-emitting diodes (UVC-LEDs) are a new UV light source with various advantages, such as environmental friendliness, high efficiency, and long life span. In the past few years, UVC-LEDs have shown great potentials in the food industry. This work aimed to investigate the inactivation kinetics of foodborne bacteria on the surface of food contact materials by UVC-LEDs and the factors influencing it. The results showed that UVC-LEDs caused higher inactivation of Escherichia coli O157:H7 than Listeria monocytogenes inoculated on food contact materials. The number of L. monocytogenes inoculated on glass, oriented polypropylene (OPP) film, stainless steel, and kraft paper decreased from an initial value of 5.45, 5.56, 5.11, and 5.47 (lg (CFU/cm²)) to 0.60, 0.70, 1.04, and 5.08 (lg (CFU/cm²)), respectively, after UVC-LEDs treatment at 800 mJ/cm². Similar results were obtained for E. coli O157:H7 inactivation on these food contact materials. Both Weibull model (R² > 0.922) and Biphasic model (R² > 0.960) fitted well the inactivation curves of both bacteria. The bactericidal effect of UVC-LEDs against bacteria on glass, OPP film, stainless steel and kraft paper decreased in that order, which might be related to the surface roughness and hydrophilicity of food contact materials. The above results indicate that the antimicrobial effect of UVC-LEDs may be affected by microbial species as well as surface characteristics of food contact materials.

In order to improve the production process of sour meat, a traditional fermented meat product of some ethnic minorities in China, this work studied the effect of commercial acidic protease on the microbial structure, physicochemical characteristics and flavor quality of sour meat during its fermentation. Using high-throughput sequencing, the bacterial and fungal community compositions were analyzed. The results showed that the addition of protease affected the relative abundance of Lactobacillus, Bacillus and Staphylococcus during the fermentation of sour meat, reduced fungal species richness, and promoted the release of free amino acids (FAAs). Gas chromatography-mass spectrometry (GC-MS) analysis showed that the addition of protease increased the number and contents of volatile compounds, such as alcohols, acids, esters, ketones and aldehydes in ripened sour meat. Correlation analysis showed that Staphylococcus was correlated positively with 3-hydroxy-2-butanone and Bacillus was correlated positively with 1-octen-3-ol. The sensory evaluation showed protease addition improved the taste, smell and overall acceptability of sour meat samples. Therefore, acidic protease has an important effect on the microbial community composition and flavor quality of sour meat, which provides a theoretical basis for improving the production process of sour meat.

In order to investigate the effect and underlying mechanism of deacetylated konjac glucomannan (DKGM) on the structure and gel properties of pork myofibrillar protein (MP), the changes in the gel strength, water retention, water distribution, microstructure, secondary and tertiary structures and gel molecular forces of MP were analyzed after the addition of DKGM at different levels (0%, 0.125%, 0.25%, 0.5% and 1%). The results showed that the gel strength of MP increased with the increase of DKGM addition, reaching the maximum at an addition level of 0.25%, which was 1.55 times higher than that of the control group. The addition of DKGM could retard the flow of water, thus improving the gel water-holding capacity. Cold-field scanning electron microscopy revealed that the addition of DKGM could promote the formation of more uniform and dense network structures in MP gels. The structure and force analysis showed that the addition of an appropriate amount of DKGM could promote the unfolding of MP molecules and the exposure of hydrophobic groups, increase the content of active sulfhydryl groups, induce α-helix-to-β-fold transition, enhance the hydrophobic interactions and disulfide bonds of MP gels, and thus improve the gel strength and water-holding capacity.

In this study, magnetic metal organic framework composites as capture probe and immunofunctionalized gold nanoparticles as signal probe were used to develop a rapid colorimetric method for the detection of Listeria monocytogenes. Under optimal conditions, the visual detection limit for L. monocytogenes was 1.2 × 10³ CFU/mL. The results of ultraviolet spectroscopy showed a good linear relationship in the range of 1.2 × 10¹-1.2 × 10⁸ CFU/mL (Y = 0.519 - 0.043X, R² = 0.978), the detection limit was as low as 0.45 CFU/mL, and the intra-batch coefficient of variation of all concentration gradients was between 0.31% and 1.30%. The recoveries for spiked chicken breast were 91.1%-108.7% with coefficient of variation less than 7.4%, and the result was consistent with that of the plate counting method. In conclusion, the proposed assay is rapid, accurate sensitive, and highly applicable to the detection of foodborne pathogens.

In this study, the effects of different mass fractions of whey protein isolate (WPI) on the physicochemical properties, physical stability, rheological properties and microstructure of Antarctic krill oil (AKO, 30%, m/m)-in-water emulsion were compared and analyzed. The results showed that the mean particle size and zeta potential of AKO emulsion without WPI were 516.67 nm and −14.03 mV, respectively. As the mass fraction of WPI increased from 0% to 6%, the mean particle size of the emulsion decreased by 42.28% (P < 0.05), and the absolute value of zeta potential significantly increased by 18.05% (P < 0.05). The physical stability of the emulsion was obviously improved. Shear rheological test showed that the apparent viscosity of the emulsion increased with an increase in WPI mass fraction. Microrheological test showed that the introduction of WPI in the emulsion system slowed down the droplet movement speed, increased the elastic behavior, and decreased the fluidity. The microstructure observation showed that WPI addition caused the emulsion to form a more complete and uniform network structure, binding more lipid droplets to maintain the stability of the emulsion. The excessive addition (greater than 6%) of WPI caused the flocculation of the emulsion, thereby weakening its stability. Therefore, the addition of appropriate amounts of WPI can effectively improve the stability of AKO emulsion by reducing the particle size, increasing the charge repulsion force of lipid droplets, and enhancing the viscoelasticity and protein network structure binding. This study is expected to provide guidance for constructing high-load and high-stability AKO emulsion system and broadening its application in health foods.