Natural approach of using nisin and its nanoform as food bio-preservatives against methicillin resistant Staphylococcus aureus and E.coli O157:H7 in yoghurt.

BACKGROUND: Natural antimicrobial agents such as nisin were used to control the growth of foodborne pathogens in dairy products. The current study aimed to examine the inhibitory effect of pure nisin and nisin nanoparticles (nisin NPs) against methicillin resistant Staphylococcus aureus (MRSA) and E.coli O157:H7 during the manufacturing and storage of yoghurt. Nisin NPs were prepared using new, natural, and safe nano-precipitation method by acetic acid. The prepared NPs were characterized using zeta-sizer and transmission electron microscopy (TEM). In addition, the cytotoxicity of nisin NPs on vero cells was assessed using the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The minimum inhibitory concentrations (MICs) of nisin and its nanoparticles were determined using agar well-diffusion method. Further, fresh buffalo's milk was inoculated with MRSA or E.coli O157:H7 (1 × 106 CFU/ml) with the addition of either nisin or nisin NPs, and then the inoculated milk was used for yoghurt making. The organoleptic properties, pH and bacterial load of the obtained yoghurt were evaluated during storage in comparison to control group. RESULTS: The obtained results showed a strong antibacterial activity of nisin NPs (0.125 mg/mL) against MRSA and E.coli O157:H7 in comparison with control and pure nisin groups. Notably, complete eradication of MRSA and E.coli O157:H7 was observed in yoghurt formulated with nisin NPs after 24 h and 5th day of storage, respectively. The shelf life of yoghurt inoculated with nisin nanoparticles was extended than those manufactured without addition of such nanoparticles. CONCLUSIONS: Overall, the present study indicated that the addition of nisin NPs during processing of yoghurt could be a useful tool for food preservation against MRSA and E.coli O157:H7 in dairy industry.

Common food preservatives impose distinct selective pressures on Salmonella Typhimurium planktonic and biofilm populations.

Food preservatives are crucial in controlling microbial growth in processed foods to maintain food safety. Bacterial biofilms pose a threat in the food chain by facilitating persistence on a range of surfaces and food products. Cells in a biofilm are often highly tolerant of antimicrobials and can evolve in response to antimicrobial exposure. Little is known about the efficacy of preservatives against biofilms and their potential impact on the evolution of antimicrobial resistance. In this study we investigated how Salmonella enterica serovar Typhimurium responded to subinhibitory concentrations of four food preservatives (sodium chloride, potassium chloride, sodium nitrite or sodium lactate) when grown planktonically and in biofilms. We found that each preservative exerted a unique selective pressure on S. Typhimurium populations. There was a trade-off between biofilm formation and growth in the presence of three of the four preservatives, where prolonged preservative exposure resulted in reduced biofilm biomass and matrix production over time. All three preservatives selected for mutations in global stress response regulators rpoS and crp. There was no evidence for any selection of cross-resistance to antibiotics after preservative exposure. In conclusion, we showed that preservatives affect biofilm formation and bacterial growth in a compound specific manner. We showed trade-offs between biofilm formation and preservative tolerance, but no antibiotic cross-tolerance. This indicates that bacterial adaptation to continuous preservative exposure, is unlikely to affect food safety or contribute to antibiotic resistance.

Convergent adaptation of Saccharomyces uvarum to sulfite, an antimicrobial preservative widely used in human-driven fermentations.

Different species can find convergent solutions to adapt their genome to the same evolutionary constraints, although functional convergence promoted by chromosomal rearrangements in different species has not previously been found. In this work, we discovered that two domesticated yeast species, Saccharomyces cerevisiae, and Saccharomyces uvarum, acquired chromosomal rearrangements to convergently adapt to the presence of sulfite in fermentation environments. We found two new heterologous chromosomal translocations in fermentative strains of S. uvarum at the SSU1 locus, involved in sulfite resistance, an antimicrobial additive widely used in food production. These are convergent events that share similarities with other SSU1 locus chromosomal translocations previously described in domesticated S. cerevisiae strains. In S. uvarum, the newly described VIIXVI and XIXVI chromosomal translocations generate an overexpression of the SSU1 gene and confer increased sulfite resistance. This study highlights the relevance of chromosomal rearrangements to promote the adaptation of yeast to anthropic environments.

Emulsified and Nanoemulsified Essential Oils in the Control of Clostridium botulinum and Clostridium sporogenes in Mortadella.

Clostridium botulinum is a foodborne pathogen responsible for severe neuroparalytic disease associated with the ingestion of pre-formed toxin in food, with processed meats and canned foods being the most affected. Control of this pathogen in meat products is carried out using the preservative sodium nitrite (NaNO2), which in food, under certain conditions, such as thermal processing and storage, can form carcinogenic compounds. Therefore, the objective was to use nanoemulsified essential oils (EOs) as natural antimicrobial agents, with the aim of reducing the dose of NaNO2 applied in mortadella. The antimicrobial activity of nanoemulsions prepared with mixtures of EOs of garlic, clove, pink pepper, and black pepper was evaluated on endospores and vegetative cells of C. botulinum and Clostridium sporogenes (surrogate model) inoculated in mortadella prepared with 50 parts per million NaNO2. The effects on the technological (pH, water activity, and color) and sensory characteristics of the product were also evaluated. The combinations of EOs and their nanoemulsions showed sporicidal effects on the endospores of both tested microorganisms, with no counts observed from the 10th day of analysis. Furthermore, bacteriostatic effects on the studied microorganisms were observed. Regarding the technological and sensorial characteristics of the product, the addition of the combined EOs had a negative impact on the color of the mortadella and on the flavor/aroma. Despite the strong commercial appeal of adding natural preservatives to foods, the effects on flavor and color must be considered. Given the importance of controlling C. botulinum in this type of product, as well as the reduction in the amount of NaNO2 used, this combination of EOs represents a promising antimicrobial alternative to this preservative, encouraging further research in this direction.

Rapid detection of tertiary butylated hydroquinone in food samples using Mn-MOF@f-CNF composite-modified screen-printed electrode.

Hydroquinone-based organic molecules are often used as unavoidable preservatives in the food industry. Among these additives, tertiary butylated hydroquinone (TBHQ) is widely employed as a preservative in various processed foods. However, the potential health risks associated with the excessive presence of TBHQ in food products have raised significant concerns. To address this pressing issuea novel binder-free composite composed of a manganese metal-organic framework and functionalized carbon nanofibers (Mn-MOF/f-CNF) has been developed as an electrode modifier for the ultrasensitive detection of TBHQ in food samples. The Mn-MOF/f-CNF composite was achieved using the ultrasonication method, revealing a lamellar sheet-like structure of the Mn-MOF and the curly thread-like fibrous structure of f-CNF. The developed Mn-MOF/f-CNF/SPE sensor system resulted in well-defined redox signals for TBHQ detection in a neutral pH solution. Compared to the unmodified SPE system, the modified system showed approximately a 300 mV reduction in overpotential and a twofold increase in peak current signal for TBHQ detection. The Mn-MOF/f-CNF/SPE sensor system showed a linear concentration window of 0.01 to 800 µM with a sensitivity of 6.28 µA µM-1 cm-2 and the obtained detection limit was 1.36 nM. Additionally, the proposed sensor displayed excellent reproducibility and repeatable results with an RSD of less than 5%. The real-time applicability of the Mn-MOF/f-CNF/SPE sensor system was demonstrated using real samples such as potato chips and instant noodles, showing excellent results with a recovery range of 95.1-98.5%.

Determination of Post-Fermentation Waste from Fermented Vegetables as Potential Substitutes for Preservatives in o/w Emulsion.

Post-fermentation wastes are rich sources of various biologically active compounds with antimicrobial activity, whose potential is not being fully exploited. One of the possible applications of post-fermentation waste may be its use as a natural preservative that effectively combats pathogens found in formulations. The study aims included the following: (1) compare the antimicrobial and antioxidant activity of fermented vegetable extracts (FVEs), (2) examine the inhibition of cosmetic-borne pathogens by FVEs, and (3) estimate the preservative effectiveness of FVEs in o/w emulsions. It was found that fermented white cabbage, cucumber, celery, and the mixture of fermented white cabbage, cucumber, and celery (1:1:1) showed antibacterial and antifungal activity against all the tested reference microbial strains. The addition of fermented cucumber, celery, and the mixture of fermented white cabbage, cucumber, and celery (1:1:1) to the o/w emulsion fulfilled criterion A of the preservative effectiveness test for S. aureus, E. coli, and A. brasiliensis, but did not fulfill the criterion for P. aeruginosa and C. albicans. The tested FVEs have comparable activity to inhibit pathogens in o/w emulsion as sodium benzoate. The results of our study prove that FVEs can be valuable raw materials supporting the preservative system, which, in turn, can significantly reduce the concentration of preservatives used in o/w emulsion.

Enhancing food preservation with postbiotic metabolites γ-aminobutyric acid (GABA) and bacteriocin-like inhibitory substances (BLIS) produced by Lactobacillus brevis C23 co-cultures in plant-based medium.

Lactic acid bacteria (LAB) can produce γ-aminobutyric acid (GABA) with antioxidant properties and sedative effects when it binds to the GABA receptor in the human brain. LAB can also produce bacteriocin-like inhibitory substances (BLIS) with antimicrobial capabilities during carbohydrate fermentation. GABA and BLIS are natural compounds with potential health benefits and food preservation properties. Lactobacillus brevis C23 was co-cultured with three different LABs as inducers, which produced the highest GABA content and BLIS activity. They were cultured in various plant-based media to obtain an edible and better-tasting final product over commercially available media like MRS broth. A coconut-based medium with additives was optimized using response surface methodology (RSM) to increase GABA and BLIS production. The optimized medium for maximum GABA production (3.22 ± 0.01 mg/mL) and BLIS activity (84.40 ± 0.44%) was a 5.5% coconut medium containing 0.23% glucose, 1.44% Tween 20, 0.48% L-glutamic acid, and 0.02% pyridoxine. Due to the presence of GABA, the cell-free supernatant (CFS) as a postbiotic showed higher antioxidant activity than other food preservatives like nisin and potassium sorbate. Finally, microbiological tests on food samples showed that the postbiotic was more effective than other preservatives at combating the growth of LAB, molds and coliform bacteria, making it a possible food preservative.

Research progress on natural preservatives of meat and meat products: classifications, mechanisms and applications.

Meat and meat products are highly susceptible to contamination by microorganisms and foodborne pathogens, which cause serious economic losses and health hazards. The large consumption and waste of meat and meat products means that there is a need for safe and effective preservation methods. Furthermore, toxicological aspects of chemical preservation techniques related to major health problems have sparked controversies and have prompted consumers and producers to turn to natural preservatives. Consequently, natural preservatives are being increasingly used to ensure the safety and quality of meat products as a result of customer preferences and biological efficacy. However, information on the current status of these preservatives is scattered and a comprehensive review is lacking. Here, we review current knowledge on the classification, mechanisms of natural preservatives and their applications in the preservation of meat and meat products, and also discuss the potential of natural preservatives to improve the safety of meat and meat products. The current status and the current research gaps in the extraction, application and controlled-release of natural antibacterial agents for meat preservation are also discussed in detail. This review may be useful to the development of efficient food preservation techniques in the meat industry. © 2024 Society of Chemical Industry.

Combined application of hot water and hexanal-based formulations preserves the postharvest quality of mango fruits.

BACKGROUND: Mango fruits undergo numerous postharvest quality losses during storage. Hence, the present study aimed to increase the shelf life of mango fruits by applying hexanal-based enhanced freshness formulations (EFF) in combination with hot water treatment (HWT). RESULTS: The findings revealed that, among all the tested applications, the combination of EFF 1.0% + HWT reduced the weight loss, decay incidence, and activity of cell wall degrading enzymes of mango fruits. Also, the combined treatment was effective in maintaining the fruit quality parameters such as soluble solid contents, titratable acidity, ascorbic acid and activity of antioxidant compounds. CONCLUSION: The present study concludes that the postharvest application of EEF 1.0% in combination with HWT can be used in extending the shelf life of mango cv. 'Langra,' fruits stored at 12° C and 85-90% relative humidity for 35 days. © 2024 Society of Chemical Industry.

The inhibitory action of lactocin 63 on deterioration of seabass (Lateolabrax japonicus) during chilled storage.

BACKGROUND: The bacteriocins, particularly derived from lactic acid bacteria, currently exhibit potential as a promising food preservative owing to their low toxicity and potent antimicrobial activity. This study aimed to evaluate the efficacy of lactocin 63, produced by Lactobacillus coryniformis, in inhibiting the deterioration of Lateolabrax japonicas during chilled storage, while also investigating its underlying inhibitory mechanism. The measurement of total viable count, biogenic amines, and volatile organic compounds were conducted, along with high-throughput sequencing and sensory evaluation. RESULTS: The findings demonstrated that treatment with lactocin 63 resulted in a notable retardation of bacterial growth in L. japonicas fish fillet during refrigerated storage compared with the water-treated and nisin-treated groups. Moreover, lactocin 63 effectively maintained the microbial flora balance in the fish fillet and inhibited the proliferation and metabolic activity of specific spoilage microorganisms, particularly Shewanella, Pseudomonas, and Acinetobacter. Furthermore, the production of unacceptable volatile organic compounds (e.g. 1-octen-3-ol, hexanal, nonanal), as well as the biogenic amines derived from the bacterial metabolism, could be hindered, thus preventing the degradation in the quality of fish fillets and sustaining relatively high sensory quality. CONCLUSION: The results of this study provide valuable theoretical support for the development and application of lactocin 63, or other bacteriocins derived from lactic acid bacteria, as potential bio-preservatives in aquatic food. © 2024 Society of Chemical Industry.

Effect of cinnamon essential oil/γ-cyclodextrin inclusion complex on papaya quality and shelf-life.

BACKGROUND: Papaya, a highly nutritious and economically significant fruit, is susceptible to infections caused by phytopathogenic fungi. Cinnamon essential oil, derived from Cinnamomum cassia (CC), shows promise in preserving papaya due to its antifungal properties. However, CC is volatile, sensitive to environmental factors, and carries a strong aroma. γ-Cyclodextrin (γ-CD) is known for encapsulating hydrophilic molecules, shielding them from environmental influences, reducing odor, and enabling controlled release due to its unique channel structure. This study aimed to tackle these challenges by preparing and characterizing an inclusion complex of CC with γ-CD (CC-γ-CD), and subsequently evaluating its efficacy in preserving papaya fruits. RESULTS: Analyses, including Fourier-infrared, powder X-ray diffraction, thermal gravity analysis, differential scanning calorimeter, and scanning electron microscopy, revealed successful encapsulation of CC components within the γ-CD cavity. Evaluations of the CC-γ-CD complex's impact on papaya fruit shelf life and quality showed notable enhancements. Fruits treated with CC-γ-CD inclusion complex at a dose of 10 g kg-1 exhibited a 55% extension in shelf-life, evidenced by reduced disease severity index compared with untreated fruit in the same storage conditions. Detailed physicochemical and bromatological assessments highlighted significant improvements, particularly in fruit treated with CC-γ-CD inclusion complex at a dose of 10 g kg-1. CONCLUSION: The application of CC-γ-CD inclusion complex at 10 g kg-1 extended the shelf-life of papaya fruit, significantly and markedly improved the overall quality. These findings underscore the potential of the CC-γ-CD inclusion complex as an effective preservative for papaya, offering a promising solution for its postharvest management and marketability. © 2024 Society of Chemical Industry.

Pre- and postharvest chitosan coatings extend the physicochemical and bioactive qualities of minimally processed 'Crimson Seedless' grapes during cold storage.

BACKGROUND: Food marketers desire residue-free fresh grapes although grapes have a short postharvest life. This study was performed to determine the influences of pre- and/or postharvest chitosan (Ch) coatings on postharvest quality of minimally processed (stem-detached) organic 'Crimson Seedless' berries. Berries were sorted as: (a) control (untreated berries); (b) preharvest Ch (dipping the clusters on the vine into 1% Ch 10 days before harvest at 20% soluble solid content (SSC)); (c) postharvest Ch (dipping the stem-detached berries into 1% Ch); and (d) pre + postharvest Ch. Berries were stored in 12 × 15 cm rigid polypropylene cups for up to 42 days at 1.0 ± 0.5 °C. RESULTS: Pre- and/or postharvest Ch coating reduced weight loss during storage. Pre- + postharvest Ch was the best treatment for restricting polygalacturonase (PG) activity, extending the visual quality, color features (L*, C and h°), skin rupture force, biochemical (SSC, titratable acidity, maturity index and pH) and bioactive (total phenol content, antioxidant activity) features. Pre- or postharvest Ch was also significantly effective in maintaining many quality features. CONCLUSION: Pre- and/or postharvest 1% Ch coatings effectively maintained the quality of minimally processed grape berries of organically produced 'Crimson Seedless' grapes by delaying weight loss and PG activity and keeping the postharvest physical, biochemical and bioactive features for 42-day cold storage at 1.0 ± 0.5 °C. The combined use of pre- and postharvest Ch found to be more effective than single treatment. Thus, pre- + postharvest 1% Ch coating could be recommended as an ecofriendly sustainable methodology for extending the postharvest quality of minimally processed fresh grapes. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Cooperative effects of three preservatives on physiological quality, endophytic bacterial community and volatile organic compounds of postharvest Codonopsis pilosula var. modesta roots.

BACKGROUND: Codonopsis pilosula var. modesta (CPVM) is a famous medicinal and edible plant of Campanulaceae. However, fresh CPVM roots (FCPVR) are prone to softening, browning and spoilage after concentrated harvesting in the main production area of Gansu Province, China in autumn, which poses great challenges to their large-scale storage and modern processing. In this study, effects of chitosan (CS), natamycin (NA) and modified atmosphere agent (MA) on the postharvest quality of FCPVR were first investigated. The roots after different treatments were stored at 4 °C and relative humidity of 75 ± 5% for 100 days. Their overall quality changes were evaluated from three perspectives: physiological quality, endophytic bacterial community and volatile organic compounds. RESULTS: The clustering heatmap and principal component analysis results indicated that CS (2 g kg-1), NA (0.5 g kg-1) and MA (5 g) had a synergistic effect on physiological quality. The roots in the CS + NA + MA group maintained better physiological state, effective components and antioxidant capacity throughout the storage process. On this basis, compared with room temperature storage, the relative abundance of the main spoilage bacterium Pseudomonas in the CS + NA + MA group roots decreased by 44% on the 100th day of storage. Furthermore, after CS + NA + MA composite treatment, the roots produced richer esters with fruit aroma during low-temperature storage. CONCLUSIONS: The CS + NA + MA composite treatment could maintain the physiological quality and flavor of FCPVR, inhibit spoilage by microbial contamination and maintain the optimal quality during low-temperature storage for up to 100 days. © 2024 Society of Chemical Industry.

Improving blueberry cold storage quality: the effect of preharvest hexanal application on chilling injuries and antioxidant defense mechanisms.

Blueberries are vulnerable to chilling injury (CI). This can lead to limited longevity when they are subjected to cold storage conditions. This study investigated the effectiveness of a preharvest spray containing 0.02% hexanal in reducing CI and improving the postharvest storage quality of 'Star' and 'Biloxi' blueberries. The blueberries were stored for a period of 5 weeks at 2 °C and in 90% relative humidity (RH). The findings revealed that the preharvest hexanal spraying of both cultivars delayed senescence by mitigating CI, as evidenced by the bolstering of the antioxidant defense system through increased superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POD), catalase (CAT), and phenylalanine ammonia lyase (PAL) enzyme activity. The treated fruit also maintained elevated levels of total phenol content (TPC), total flavonoids (TFC), and vitamin C, demonstrating enhanced free radical scavenging capacity (FRSC), while exhibiting reduced polyphenoloxidase (PPO) activity, and reduced malondialdehyde (MDA), and H2O2 content in comparison with the control group. The preharvest hexanal treatment also suppressed fruit softening by maintaining greater firmness and higher membrane stability index (MSI) scores, inhibiting the activity of polygalacturonase (PG), pectinmethylesterase (PME), xylanase, and α-amylase, and reducing microbial counts (MC) and incidence of decay (DI) in comparison with the control. Preharvest hexanal treatment also improved the overall storage quality by reducing weight loss, total soluble solids (TSS), pH, and the TSS/acid ratio, while increasing titratable acidity (TA) in comparison with the control during cold storage. The findings suggest that hexanal, as a preharvest application, delays senescence effectively and preserves overall quality by enhancing cold tolerance through antioxidant defense mechanisms in blueberry storage under cold conditions. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Nanoscale Pickering emulsion food preservative films/coatings: Compositions, preparations, influencing factors, and applications.

Pickering emulsion (PE) technology effectively addresses the issues of poor compatibility and low retention of hydrophobic active ingredients in food packaging. Nonetheless, it is important to recognize that each stage of the preparation process for PE films/coatings (PEFCs) can significantly influence their functional properties. With the fundamental considerations of environmental friendliness and human safety, this review extensively explores the potential of raw materials for PEFC and introduces the preparation methods of nanoparticles, emulsification technology, and film-forming techniques. The critical factors that impact the performance of PEFC during the preparation process are analyzed to enhance food preservation effectiveness. Moreover, the latest advancements in PE packaging across diverse food applications are summarized, along with prospects for innovative food packaging materials. Finally, the preservation mechanism and application safety have been systematically elucidated. The study revealed that the PEFCs provide structural flexibility, where designable nanoparticles offer unique functional properties for intelligent control over active ingredient release. The selection of the dispersed and continuous phases, along with component proportions, can be customized for specific food characteristics and storage conditions. By employing suitable preparation and emulsification techniques, the stability of the emulsion can be improved, thereby enhancing the effectiveness of the films/coatings in preserving food. Including additional substances broadens the functionality of degradable materials. The PE packaging technology provides a safe and innovative solution for extending the shelf life and enhancing the quality of food products by protecting and releasing active components.

Production, characterization, and potential applications of lipopeptides in food systems: A comprehensive review.

Lipopeptides are a class of lipid-peptide-conjugated compounds with differing structural features. This structural diversity is responsible for their diverse range of biological properties, including antimicrobial, antioxidant, and anti-inflammatory activities. Lipopeptides have been attracting the attention of food scientists due to their potential as food additives and preservatives. This review provides a comprehensive overview of lipopeptides, their production, structural characteristics, and functional properties. First, the classes, chemical features, structure-activity relationships, and sources of lipopeptides are summarized. Then, the gene expression and biosynthesis of lipopeptides in microbial cell factories and strategies to optimize lipopeptide production are discussed. In addition, the main methods of purification and characterization of lipopeptides have been described. Finally, some biological activities of the lipopeptides, especially those relevant to food systems along with their mechanism of action, are critically examined.

Recent approaches in the application of antimicrobial peptides in food preservation.

Antimicrobial peptides (AMPs) are small peptides existing in nature as an important part of the innate immune system in various organisms. Notably, the AMPs exhibit inhibitory effects against a wide spectrum of pathogens, showcasing potential applications in different fields such as food, agriculture, medicine. This review explores the application of AMPs in the food industry, emphasizing their crucial role in enhancing the safety and shelf life of food and how they offer a viable substitute for chemical preservatives with their biocompatible and natural attributes. It provides an overview of the recent advancements, ranging from conventional approaches of using natural AMPs derived from bacteria or other sources to the biocomputational design and usage of synthetic AMPs for food preservation. Recent innovations such as structural modifications of AMPs to improve safety and suitability as food preservatives have been discussed. Furthermore, the active packaging and creative fabrication strategies such as nano-formulation, biopolymeric peptides and casting films, for optimizing the efficacy and stability of these peptides in food systems are summarized. The overall focus is on the spectrum of applications, with special attention to potential challenges in the usage of AMPs in the food industry and strategies for their mitigation.

Peroxidase-Like FeCoZn Triple-Atom Catalyst-Based Electronic Tongue for Colorimetric Discrimination of Food Preservatives.

Recently, single-atom catalysts are attracting much attention in sensor field due to their remarkable peroxidase- or oxidase-like activities. Herein, peroxidase-like FeCoZn triple-atom catalyst supported on S- and N-doped carbon derived from ZIF-8 (FeCoZn-TAC/SNC) serves as a proof-of-concept nanozyme. In this paper, a dual-channel nanozyme-based colorimetric sensor array is presented for identifying seven preservatives in food. Further experiments reveal that the peroxidase-like activity of the FeCoZn TAzyme enables it to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) and o-phenylenediamine (OPD) in the presence of H2 O2 , yielding the blue oxTMB and yellow oxOPD, respectively. However, food preservatives are adsorbed on the nanozyme surface through π-π stacking interaction and hydrogen bond, and the reduction in catalytic activity of FeCoZn TAzyme causes differential colorimetric signal variations, which provide unique "fingerprints" for each food preservative.

Antimicrobial and anti-aflatoxigenic activities of nanoemulsions based on Achillea millefolium and Crocus sativus flower extracts as green promising agents for food preservatives.

BACKGROUND: Although the mechanism of action of nanoemulsion is still unclear, the modern use of nanoemulsions made from natural extracts as antimicrobial and anti-aflatoxigenic agents represents a potential food preservation and a safety target. METHODS: Two natural nanoemulsion extracts of Crocus sativus (the saffron flower) and Achillea millefolium (the yarrow flower) were produced in the current study using a low-energy method that included carboxymethylcellulose and Arabic gum. The synthesized nanoemulsion was fully identified by different analytical methods. Detection of the volatile content was completed using GC-MS analysis. The antioxidant potential, and phenolic compounds content were analyzed in the extractions. The synthesized nanoemulsions were screened for their antimicrobial potential in addition to their anti-aflatoxigenic activity. RESULTS: The droplet size of Saffron flowers was finer (121.64 ± 2.18 nm) than yarrow flowers (151.21 ± 1.12 nm). The Zeta potential measurements of the yarrow flower (-16.31 ± 2.54 mV) and the saffron flower (-18.55 ± 2.31 mV) both showed high stability, along with low PDI values (0.34-0.41). The nanoemulsion of yarrow flower revealed 51 compounds using gas chromatography-mass spectrometry (GCMS), with hexanal (16.25%), ß-Pinene (7.41%), ß-Myrcene (5.24%), D-Limonene (5.58%) and Caryophyllene (4.38%) being the most prevalent. Additionally, 31 compounds were detected in the saffron nanoemulsion, with D-limonene (4.89%), isophorone (12.29%), 4-oxy isophorone (8.19%), and safranal (44.84%) being the most abundant. Compared to the nanoemulsion of the yarrow flower, the saffron nanoemulsion had good antibacterial and antifungal activity. Saffron nanoemulsion inhibited total fungal growth by 69.64-71.90% in a simulated liquid medium and demonstrated the most significant decrease in aflatoxin production. Infected strawberry fruits coated with nanoemulsion extracts exhibited high antimicrobial activity in the form of saffron flower and yarrow flower extract nanoemulsions, which inhibited and/or controlled the growth of Aspergillus fungi. Due to this inhibition, the lag phase was noticeably prolonged, the cell load decreased, and the stability time increased. CONCLUSION: This study will contribute to expanding the theoretical research and utilization of nanoemulsions as green protective agents in agricultural and food industries for a promising protection from the invasion of some pathogenic bacteria and fungi.

Phenolic compounds in Nordic berry species and their application as potential natural food preservatives.

An increasing demand for natural food preservatives is raised by consumers. For Nordic berry species, abundance of phenolic compounds and potent activities of anti-oxidation and anti-bacteria enables a great potential as food preservatives. This review provides a systematic examination of current literature on phenolic profiles, anti-oxidative and anti-bacterial activities of various extracts of Nordic berry species, as well as the impact of various structure features of phenolics on the bioactivities. Special attention is placed on exploitation of leaves of berry species and pomaces after juice-pressing as side-streams of berry production and processing. The current progress and challenges in application of Nordic berry species as food preservatives are discussed. To fully explore the potential application of Nordic berry species in food industry and especially to valorize the side-streams of berry cultivation (leaves) and juice-pressing industry (pomaces), it is crucial to obtain extracts and fractions with targeted phenolic composition, which have high food preserving efficacy and minimal impact on sensory qualities of food products.