Influence of the combination of cinnamon essential oil nanoemulsions and epsilon-polylysine on microbial community and quality of pork during refrigerated period and radio frequency cooking

Preparation and characterization of carvacrol/ε-polylysine loaded antimicrobial nanobilayer emulsion and its application in mango preservation

Carvacrol is well-known natural antimicrobial compounds. However, its usage in fruit preservation is restricted owing to poor water solubility. Our study aims to address this limitation by combining carvacrol with whey protein isolate (WPI) to form nanoemulsion and enhancing antimicrobial properties and stability of nanoemulsion through ε-polylysine addition, thereby improving their application in fruit preservation. The results indicated that the nanoemulsion exhibited a double-layer structure. The physicochemical properties and storage stability were found to be favorable under the conditions of WPI (0.3 wt% v/v), Carvacrol (0.5 % v/v), and ε-polylysine (0.3 wt% v/v). In addition, the nanoemulsion had inhibitory effects on Staphylococcus aureus, Escherichia coli, and Aspergillus niger at concentrations of minimal inhibition concentration (32, 32, and 200 μg/mL, respectively). In addition, during a 7-day storage period, the nanoemulsion effectively preserved mangoes. Therefore, nanoemulsion could serve as a candidate for control of postharvest mangoes spoilage and extend its period of storage.

Insights into the antibacterial effectiveness of linalool against Shigella flexneri on pork surface: Changes in bacterial growth and pork quality

Shigella flexneri has the ability to contaminate pork and cause foodborne diseases. This study aimed to examine the effectiveness of linalool (a natural preservative) against S. flexneri and explore its potential application in contaminated pork. The results showed that linalool was capable of damaging the cell membrane and binding to the DNA of S. flexneri, and inhibiting biofilm formation and disrupting mature biofilms. The antibacterial effectiveness of linalool on the surface of pork was further demonstrated by analyzing the physicochemical properties of the pork (i.e., weight loss rate, pH value, color index, and TVB-N value) and its protein profiles. Linalool did not completely kill S. flexneri in pork at minimum bactericidal concentration (MBC) concentration and its antibacterial effect of linalool was stronger during the initial stage of storage. During storage, linalool influenced the abundance of specific proteins in the pork, particularly those involved in pathways related to fat metabolism. These findings offer novel insights into the antibacterial efficacy of linalool and its underlying mechanism in pork.

Application of essential oils as slow-release antimicrobial agents in food preservation: Preparation strategies, release mechanisms and application cases

Food spoilage caused by foodborne microorganisms will not only cause significant economic losses, but also the toxins produced by some microorganisms will also pose a serious threat to human health. Essential oil (EOs) has significant antimicrobial activity, but its application in the field of food preservation is limited because of its volatile, insoluble in water and sensitive to light and heat. Therefore, in order to solve these problems effectively, this paper first analyzed the antibacterial effect of EOs as an antimicrobial agent on foodborne bacteria and its mechanism. Then, the application strategies of EOs as a sustained-release antimicrobial agent in food preservation were reviewed. On this basis, the release mechanism and application cases of EOs in different antibacterial composites were analyzed. The purpose of this paper is to provide technical support and solutions for the preparation of new antibacterial packaging materials based on plant active components to ensure food safety and reduce food waste.

Synergistic bactericidal mechanisms of RF energy simultaneously combined with cinnamon essential oil or epsilon-polylysine against Salmonella revealed at cellular and metabolic levels

Radio frequency (RF) heating and antimicrobials are considered to be effective methods for inactivating food pathogens. This study explored the bactericidal effects against Salmonella of RF heating combined with two kinds of natural antimicrobials possessing different hydrophobic properties and their synergistic bactericidal mechanisms. Results showed that RF heating caused sublethal damage to bacterial cells and enhanced the interaction of cells and antimicrobials, leading to synergistic bactericidal effects of the simultaneous combination of RF heating and antimicrobials. The combination of RF heating and ε-polylysine (ε-PL) further promoted cell morphological alteration, raised membrane permeability, intracellular adenosine triphosphate (ATP) leakage and intracellular reactive oxygen species (ROS) accumulation compared to individual treatment. The simultaneous combination of RF heating and cinnamon essential oil nanoemulsion (CEON) also further enhanced membrane permeability and ROS accumulation compared to individual treatment, but impacts were less than those in the combination of RF heating and ε-PL. The major synergistic bactericidal mechanism of RF heating and CEON was significantly inhibiting intracellular ATP synthesis. The untargeted metabolomics analysis revealed that the combined treatments enhanced disturbances to multiple intracellular metabolisms compared to individual treatment, thus leading to synergistic bactericidal effects against Salmonella. These results provide an in-depth understanding of the synergistic bactericidal mechanisms of the combination of RF heating and natural antimicrobials from cellular and metabolic levels.

Deciphering the growth responses and genotypic diversity of bioluminescent Photobacterium phosphoreum on chicken meat during aerobic refrigerated storage

The advent of high-throughput sequencing technologies in recent years has revealed the unexpected presence of genus Photobacterium within the chicken meat spoilage ecosystem. This study was undertaken to decipher the occurrence, the growth patterns and the genotypic biodiversity of Photobacterium phosphoreum on chicken breast fillets stored aerobically at 4 °C through conventional microbiological methods and molecular techniques. Samples were periodically cultured on marine broth agar (MA; supplemented with meat extract and vancomycin) for the enumeration of presumptive bioluminescent Photobacterium spp. In total, 90 bioluminescent bacteria were recovered from the initial (time of first appearance), middle and end stages of storage. Concomitantly, 95 total psychrotrophic/psychrophilic bacteria were isolated from the same medium to assess the presence and diversity of non-luminous photobacteria. Genetic diversity between bioluminescent isolates was assessed with two PCR-based DNA fingerprinting methods, i.e. RAPD and rep-PCR. Moreover, the characterization of selected bacterial isolates at the genus and/or species level was performed by sequencing of the 16S rRNA and/or gyrB gene. Bioluminescent bacteria were scarcely encountered in fresh samples at population levels of ca. 2.0 log CFU/g, whilst total psychrotrophic/psychrophilic bacteria were found at levels of ca. 4.4 log CFU/g. As time proceeded and close to shelf-life end, bioluminescent bacteria were encountered at higher populations, and were found at levels of 5.3 and 7.0 log CFU/g in samples from the second and third batch, respectively. In the first batch their presence was occasional and at levels up to 3.9 log CFU/g. Accordingly, total psychrotrophic/psychrophilic bacteria exceeded 8.4 log CFU/g at the end of storage, suggesting the possible underestimation of bioluminescent populations following the specific cultivation conditions. Sequence analysis assigned bioluminescent isolates to Photobacterium phosphoreum, while genetic fingerprinting revealed high intra-species variability. Respectively, total psychrotrophs/psychrophiles were assigned to genera Pseudomonas, Shewanella, Psychrobacter, Acinetobacter, Vibrio and Photobacterium. Non-luminous photobacteria were not identified within the psychrotrophs/psychrophiles. Results of the present study reveal the intra- and inter-batch variability on the occurrence and growth responses of P. phosphoreum and highlight its potential role in the chicken meat spoilage consortium.

Encapsulation and delivery systems of cinnamon essential oil for food preservation applications

Food safety threats and deterioration due to the invasion of microorganisms has led to economic losses and food-borne diseases in the food industry; so, development of natural food preservatives is urgently needed when considering the safety of chemically synthesized preservatives. Because of its outstanding antioxidant and antibacterial properties, cinnamon essential oil (CEO) is considered a promising natural preservative. However, CEO's low solubility and easy degradability limits its application in food products. Therefore, some encapsulation and delivery systems have been developed to improve CEO efficiency in food preservation applications. This work discusses the chemical and techno-functional properties of CEO, including its key components and antioxidant/antibacterial properties, and summarizes recent developments on encapsulation and delivery systems for CEO in food preservation applications. Since CEO is currently added to most biopolymeric films/coatings (BFCs) for food preservation, most studies have shown that encapsulation systems can improve the food preservation performance of BFCs containing CEOs. It has been confirmed that various delivery systems could improve the stability and controlled-release properties of CEO, thereby enhancing its ability to extend the shelf life of foods. These encapsulation techniques include spray drying, emulsion systems, complex coacervation (nanoprecipitation), ionic gelation, liposomes, inclusion complexation (cyclodextrins, silica), and electrospinning.