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   This study investigated the antibacterial capacity and mechanism of surfactin (prepared by fermenting soybean meal with Bacillus subtilis SOPC5) against Staphylococcus aureus by examining its influences on the bacterial morphology, cell wall and membrane, as well as metabolic activity. The efficiency of surfactin in pork preservation was also investigated. HPLC-MS analysis showed that surfactin’s purity reached 97.4%, containing five congeners. The minimal inhibition concentration (MIC) and minimal bactericidal concentration (MBC) of surfactin against S. aureus were 1.6 and 3.2 mg/mL, respectively. The result of scanning electron microscopy observation revealed that 4 h of surfactin exposure resulted in deformation and even collapse of S. aureus . AKP assay, membrane potential analysis, extracellular protein and nucleic acid content measurement, and PI staining intensity assay showed that surfactin destroyed the cell wall and cell membrane of S. aureus. Decreases in iodonitrotetrazolium chloride levels and ATP enzyme activity indicated that surfactin could inhibit the metabolic ability of S. aureus . Furthermore, surfactin demonstrated an excellent antibacterial action on S. aureus within 5 days of pork storage without changing its texture. These findings suggest that sufactin has a great application potential in pork preservation. Graphical Abstract

Pork is perishable due to oxidation and microbial spoilage. Edible coating based on biopolymers and phenolic compounds is an effective way to preserve the quality of pork. In this study, ferulic acid-grafted-CS (ferulic acid-g-CS) with strong antioxidant and antimicrobial activities was synthesized through a carbodiimide-mediated coupling reaction. The obtained ferulic acid-g-CS was used as an edible coating material for fresh pork. The effect of ferulic acid-g-CS coating on the quality of pork during storage was investigated at 4 °C for 8 days. As compared to the uncoated pork, pork coated with CS and ferulic acid-g-CS showed lower total viable counts, total volatile basic nitrogen values, pH values, thiobarbituric acid reactive substances, and drip losses. Besides, pork coated with CS and ferulic acid-g-CS presented more compact microstructures than the uncoated pork at the eighth day. Sensory evaluation assay showed pork coated with CS and ferulic acid-g-CS had better color, odor, and over acceptance in comparison with the uncoated pork. Ferulic acid-g-CS coating, due to its relatively higher antioxidant and antimicrobial activities compared to CS coating, had a better performance in refrigerated pork preservation. Ferulic acid-g-CS coating effectively extended the shelf life of refrigerated pork to 7 days. This study revealed ferulic acid-g-CS coating was a promising technology for refrigerated pork preservation.

Riboflavin (RF) was considered to be possessed of photoactivity to generate reactive oxygen species (ROS) under ultraviolet (UV) light, which is thought to be a favorable antibacterial candidate. Herein, RF was incorporated into chitosan (CS) coatings and treated under UV with different exposure times (2, 4, and 6 h) to improve the physicochemical and antibacterial properties. The results showed that the light transmittance and antibacterial performance of chitosan coatings gradually increased with the extension of the UV irradiation time. The antibacterial ability of chitosan coatings correlated with the generation of ROS: ∙OH and H2O2, which achieved 1549.08 and 95.48 μg/g, respectively, after 6 h irradiation. Furthermore, the chitosan coatings with UV irradiation also reduced the pH value, total volatile basic nitrogen (TVB-N), ΔE, and total viable counts (TVC) and improved sensory attributes of pork. In conclusion, the UV irradiated chitosan coatings could be used as an environmentally friendly antimicrobial packaging material to effectively delay the spoilage of pork, maintain its sensory quality and prolong its shelf life.

Antibiotic resistance to pathogenic bacteria is becoming an increasing public health threat, and identifying alternatives to antibiotics would be an effective solution to the problem of drug resistance. Antimicrobial peptides are small peptides produced by various organisms; they are considered to be adequate antibiotic substitutes because they have intense, broad−spectrum antibacterial activity and stability, are widely available, and target strains do not quickly develop resistance. Recent research on antimicrobial peptides has shown that they have broad potential for applications in medicine, agriculture, food, and animal feed. Turgencin A is a potent antimicrobial peptide isolated from the Arctic sea squirt. We established a His-tagged expression system for Pichia pastoris and developed a rTurgencin A using the recombinant expression in Pichia pastoris with nickel column purification. This antimicrobial peptide showed intense antimicrobial activity against Gram-positive and Gram-negative bacteria and a good stability at most temperatures and pHs, as well as in various protease and salt ion concentrations, but underwent a significant decrease in stability in high-temperature and low-pH environments. Turgencin A induced bacterial membrane rupture, resulting in content leakage and subsequent cell death. It was also shown to have low hemolytic activity. This study provides primary data for the industrial production and application of the antimicrobial peptide Turgencin A.

This study aimed to prepare a degradable bacteriostatic aerogel pad using nanocellulose (CNC) as a matrix material, chitosan (CTS) as cross-linking agent, and graphene oxide (GO) as a reinforcement phase using a freeze-drying technique to absorb pork exudate and extend pork’s shelf life. With an increase in GO concentration, the network structure in CNC/CTS/GO aerogel was more uniform, and the mechanical properties, water adsorption capacity, and bacterial inhibition were gradually enhanced. Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) showed that adding of GO affected the chemical structure and thermal stability of the aerogels. Based upon effects of GO concentration on the structure and properties of the CNC/CTS/GO aerogel, 0.4 wt% of GO was selected to prepare aerogels for use as packaging pads for fresh pork. At 4 °C, the aerogel pads in of the GO-0.4 group could absorb the juices released throughout the pork storage process, delay pork color deterioration, and inhibit microorganism growth as well as decrease in pH and the total volatile basic nitrogen (TVB-N) content, thus prolonging the fresh pork’s shelf life.

In this work, a lemon essential oil–rutin composite nanoemulsion was formed and integrated into a chitosan (CS) matrix to form a coating for pork preservation. The introduction of rutin decreased the particle size of the nanoemulsion and suppressed the volatilization of the encapsulated essential oil. The rheological properties of the coating showed that it was a pseudoplastic fluid with shear-thinning behavior, and the apparent viscosity of the system was lower than 0.7 Pa·s. The incorporation of the nanoemulsion significantly (p < 0.05) increased the antioxidant and bacteriostatic properties of the CS coating, which was positively correlated with the content of the incorporated nanoemulsion. Pork preservation experiments revealed that the changes in color, the increase in pH, drip loss, thiobarbituric acid-reactive substances, total volatile basic nitrogen and total viable count were significantly (p < 0.05) delayed by the coating treatment. These results suggest that the formed lemon essential oil/rutin/CS coating has promising applications in pork preservation.

The development of biodegradable food packaging materials with active functionalities presents a sustainable alternative to conventional plastic films. This study developed a bioactive complex film through solvent casting technique using potato starch (PS) and κ-carrageenan (κC) as the matrix, incorporated with ethanol extract of crab-apple peel (EEC). Fourier-transform infrared analysis confirmed the formation of hydrogen bonds between the film-forming constituents. Scanning electron microscopy revealed that higher concentrations of EEC led to a relatively rough film surface. XRD indicated that the incorporation of EEC reduced the crystallinity of the potato starch. The addition of EEC significantly increased the a and b values of the complex film (p < 0.05), while the L value and opacity decreased significantly (p < 0.05). The TS, Young′s modulus, and WVP of the complex films decreased significantly with increasing EEC concentration (p < 0.05). The DPPH and ABTS radical scavenging abilities of PS-κC-EEC film were enhanced from 12.35% to 75.48% and from 10.26% to 72.52%, respectively. PS-κC-EEC film exhibited strong antimicrobial activity against Staphylococcus aureus and Escherichia coli. The application of the PS-κC-EEC film for the refrigerated preservation of pork demonstrated that the lipid oxidation level of wrapped pork was reduced. These results suggest that the fabricated PS-κC-EEC film could be utilized for the preservation of pork and extends its shelf life.

Chitosan films containing cinnamon essential oil Pickering emulsions (CEO-PEs) stabilized by methyl tetrahydrophthalic anhydride esterified corn starch (MeCS) were prepared and characterized. The incorporation of CEO-PEs was confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy. The cinnamon essential oil content affected the color of film significantly (p < 0.05), with higher concentrations resulting in a higher yellowness value. The films containing CEO-PEs had lower transparency and water vapor permeability. The antimicrobial activity of films against and was enhanced by incorporating CEO-PEs When used for pork preservation, the films containing CEO-PEs were more effective in limiting lipid oxidation, proteins decomposition, as well as total microbial growth. All these effects were proportional to the cinnamon essential oil content in the films. These results suggested that chitosan/MeCS-stablized CEO-PEs composite film have great potential in pork packaging.

Staphylococcus aureus (S. aureus) can contaminate food by forming biofilms, leading to significant food safety concerns. Amomum tsaoko essential oil (AEO) has been shown to be an effective plant-derived antibacterial agent. This study investigated the antibiofilm activity of AEO and evaluated its potential benefit in pork preservation. The results showed that AEO solution (2 mg/mL) can effectively remove the biofilm of S. aureus on food contact materials, achieving a removal rate of over 90%. Scanning electron microscopy (SEM) revealed that the S. aureus biofilm structure was disrupted after treatment with AEO. Meanwhile, AEO treatment significantly reduced the initial formation of S. aureus biofilms and extracellular polymeric substance (EPS) production. In addition, AEO down-regulated the expression of key biofilm-associated genes, including icaA, icaB, agrA, cidA, cidB, and cidC, thereby regulating formation. AEO also exhibited significant antibiofilm activity in pork preservation, effectively controlling key indicators associated with pork spoilage. This study revealed the potential of AEO in food preservation, demonstrating its ability to disrupt S. aureus biofilms by inhibiting initial formation, reducing the release of EPS secretion, and regulating the expression of biofilm-associated genes.

First, the antibacterial, antibiofilm effect and chemical composition of burdock (Arctium lappa L.) leaf fractions were studied. Then, the efficiency of burdock leaf fractions in pork preservation was evaluated. The results showed that burdock leaf fraction significantly inhibited the growth and biofilm development of Escherichia coli and Salmonella Typhimurium. MICs of burdock leaf fractions on E. coli and Salmonella Typhimurium were both 2 mg/ml. At a concentration of 2.0 mg/ml, the inhibition rates of the fraction on growth and development of E. coli and Salmonella Typhimurium biofilms were 78.7 and 69.9%, respectively. During storage, the log CFU per gram of meat samples treated with burdock leaf fractions decreased 2.15, compared with the samples without treatment. The shelf life of pork treated with burdock leaf fractions was extended 6 days compared with the pork without treatment, and the sensory property was obviously improved. Compared with the control group, burdock leaf fraction treatment significantly decreased the total volatile basic nitrogen value and pH of the meat samples. Chemical composition analysis showed that the burdock leaf fraction consisted of chlorogenic acid, caffeic acid, p-coumaric acid, rutin, cynarin, crocin, luteolin, arctiin, and quercetin. As a vegetable with an abundant source, burdock leaf is safe, affordable, and efficient in meat preservation, indicating that burdock leaf fraction is a promising natural preservative for pork.