Alternative disinfection methods to chlorine for use in the fresh-cut industry

Antibacterial mechanism of lysine against Escherichia coli O157:H7, its action on lettuce and in reducing the severity of murine colitis

The aim of the present study was to evaluate the mechanism of antimicrobial action of Lysine (Lys) against Escherichia coli (E. coli) O157:H7. Lys alters the permeability and morphology of bacterial cell membranes, leading to leakage of intracellular material. Using agarose gel electrophoresis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE), it was found that high concentrations of Lys disrupted the DNA and protein primary structure of E. coli O157:H7. Lys also inhibited the ability of E. coli biofilm formation in a concentration-dependent manner. Subinhibitory concentration of Lys reduces the swimming and swarming ability of E. coli O157:H7 and its ability to adhere and to invade Caco-2 cells. The use of Lys on lettuce inoculated with E. coli O157:H7 showed good disinfection efficiency. Further studies revealed that Lys had both preventive and therapeutic effects on the severity of colitis induced by E. coli O157:H7 infected mice, and that the preventive effect was greater than the therapeutic effect.

Role of advanced cleaning and sanitation techniques in biofilm prevention on dairy equipment

Biofilm formation on dairy equipment is a persistent challenge in the dairy industry, contributing to product contamination, equipment inefficiency, and economic losses. Traditional methods such as manual cleaning and basic chemical sanitation are discussed as foundational approaches, followed by an in-depth investigation of cutting-edge technologies, including clean-in-place systems, high-pressure cleaning, foam cleaning, ultrasonic and electrochemical cleaning, dry ice blasting, robotics, nanotechnology-based agents, enzymatic cleaners, and oxidizing agents. Enhanced sanitation techniques, such as dry steam, pulsed light, acidic and alkaline electrolyzed water, hydrogen peroxide vapor, microbubble technology, and biodegradable biocides, are highlighted for their potential to achieve superior sanitation while promoting sustainability. The effectiveness, feasibility, and limitations of these methods are evaluated, emphasizing their role in maintaining dairy equipment hygiene and reducing biofilm-associated risks. Additionally, challenges, such as equipment compatibility, cost, and regulatory compliance, are addressed, along with insights into future directions and innovations, including automation, smart cleaning systems, and green cleaning solutions. This review provides a comprehensive resource for researchers, industry professionals, and policymakers aiming to tackle biofilm formation in dairy production systems and enhance food safety, operational efficiency, and sustainability.

Comparative evaluation of sanitation strategies against Listeria monocytogenes on food-contact surfaces in enoki mushroom (Flammulina velutipes) processing facilities

We investigated strategies to reduce Listeria monocytogenes contamination on food contact surfaces during enoki mushroom processing. Chemical disinfectants and thermal treatments were evaluated on conveyor belts, stainless steel, plastic surfaces, and Velcro strips. Without organic matter, chemical disinfectants effectively reduced L. monocytogenes, with stainless steel showing the highest susceptibility. Organic matter decreased disinfectant efficacy, but sodium hypochlorite remained most effective on stainless steel. Peracetic acid was more effective on conveyor belts and plastic surfaces than on stainless steel. Combining peracetic acid with dry heating synergistically reduced L. monocytogenes on Velcro strips. Moist heat at 70 °C alone was insufficient, but when combined with hot air drying, it effectively reduced L. monocytogenes on Velcro strips. Our findings emphasize the importance of surface-specific strategies combining chemical disinfection and thermal treatment for eliminating L. monocytogenes in mushroom processing environments.

The ability of Salmonella enterica subsp. enterica strains to form biofilms on abiotic surfaces and their susceptibility to selected essential oil components

The ability of Salmonella enterica subsp. enterica to persist and form biofilms on different surfaces can constitute a source of food contamination, being an issue of global concern. The objective of this study was to understand the biofilm formation profile of 14 S. enterica strains among different serovars and sources and to evaluate the ability of essential oil (EO) components (carveol, citronellol, and citronellal) to disinfect the biofilms formed on stainless steel and polypropylene surfaces. All the strains were able to form biofilms with counts between 5.34 to 6.78 log CFU cm-2. Then, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of EO components were evaluated on two selected strains. All compounds inhibited the growth of Salmonella Typhimurium (strain 1; MIC = 800-1000 µg ml-1) and Salmonella Enteritidis (strain 5; MIC = 400-1000 µg ml-1) and only carveol showed bactericidal activity against strains 1 and 5 (MBC = 1200 µg ml-1). Biofilms were exposed to the EO components at 10 × MIC for 30 min and polypropylene surfaces were more difficult to disinfect showing reductions between 0.9 and <1.2 log CFU cm-2. In general, the S. enterica biofilms demonstrated a significant tolerance to disinfection, demonstrating their high degree of recalcitrance on food processing surfaces.

"Candidatus Liberibacter asiaticus" Infection Induces Citric Acid Accumulation and Immune Responses Mediated by the Transcription Factor CitPH4

Citrus huanglongbing (HLB), caused by "Candidatus Liberibacter" spp., is one of the most disastrous citrus diseases worldwide. HLB-affected citrus fruits are significantly more acidic than healthy fruits. However, the molecular mechanism behind this phenomenon remains to be elucidated. Here, we report that HLB-affected fruits have higher levels of citric acid (CA) than healthy fruits. Moreover, Citrus PH4 (CitPH4), which encodes a MYB transcription factor that functions as a key regulator of CA accumulation, was upregulated in HLB-affected fruits relative to healthy fruits. Heterologous overexpression of CitPH4 in tobacco (Nicotiana tabacum) plants enhanced tolerance to HLB. Subsequently, overexpression and gene-editing experiments indicated that CitPH4 can affect the salicylic acid (SA) pathway, which directly binds to and activates the promoter of CsPBS3, a key gene of SA biosynthesis. HLB-affected fruits had higher SA levels than healthy fruits. Furthermore, application of SA activated CA biosynthesis and application of CA activated SA biosynthesis and signalling in citrus fruits and decreased "Candidatus Liberibacter asiaticus" (CLas) titres in infected leaves. This work suggests that CitPH4 is a key node between CA and SA, thus revealing crosstalk between defence responses and fruit quality in citrus.

Characterization of the extracellular proteases from Bacillus inaquosorum strain E1-8 and its application in the preparation of hydrolysates from plant and animal proteins with antioxidant, antifreeze and anti-browning properties

BACKGROUND

Bacillus inaquosorum strains is widely recognized for their plant-growth-promoting and biocontrol capabilities, yet their roles in protease production remain unclear. The present study aimed to comprehensively assess the protease-producing performance of B. inaquosorum strain E1-8, at the same time as exploring the novel application of agricultural Bacillus proteases in the preparation of protein hydrolysates for fresh-cut fruits preservation.

RESULTS

First, genomic sequencing revealed the diversity of E1-8 proteases, indicating 15 putative extracellular proteases. Subsequently, the fermentation conditions for E1-8 protease production were optimized, with sweet potato powder and soybean meal identified as the most suitable carbon and nitrogen sources, respectively, resulting in a maximum protease activity of 321.48 U mL-1. Upon culturing the strain under these optimized conditions, only an S8 family serine protease and an M48 family metalloprotease were revealed by secretomic analysis and protease inhibitor assays. Additionally, the optimal protease conditions for generating protein hydrolysates from soy, pea, fish and porcine proteins were determined. The molecular weight of the hydrolysates primarily ranged from 2000 to 180 Da, with a total of 17 amino acids identified. The application of these hydrolysates demonstrated a 2,2-diphenyl-1-picrylhydrazyl (i.e. DPPH) scavenging activity ranging from 58.64% to 84.12%, significantly reducing of the melting peaks and the freezing points. Furthermore, the browning index of apple slices stored at 4 °C decreased by 14.81% to 22.15% on the second day, and similar effects were observed in fresh-cut banana stored at 4 °C for 7 days.

CONCLUSION

The protein hydrolysates obtained exhibit remarkable antioxidant, antifreeze and anti-browning properties for fresh-cut fruits. © 2024 Society of Chemical Industry.

Efficacy of Air and Oxygen Micro-nano Bubble Waters Against Colletotrichum gloeosporioides and Impacts on Postharvest Quality of 'Fan Retief' Guava Fruit

This study focused on the application of micro-nano bubbles (MNBs) water generated using air or oxygen (O2), as an alternative to chlorine-based wash for fruits. For the in vitro and in vivo investigation, 106 spore or conidia/mL Colletotrichum gloeosporioides suspension was used, and treated with solutions of air- or O2-MNB for 30- or 60-min, sodium hypochlorite (NaOCl), and untreated (as control). In the second experiment, freshly harvested guava fruits were washed with tap water (control), NaOCl (standard practice), air-, or O2-MNB (for 15- or 30-min). All samples were packaged, stored for 21 days at 13 °C, and monitored for changes in natural microbial population and quality attributes. Based on the confocal laser and transmission electron microscopy results, exposure of C. gloeosporioides to air-MNB for 60 min resulted in the lowest viable cell count (%) compared to control and other treatments (O2-MNB and NaOCl). Air- and O2-MNB treatments damaged cellular structures, disrupted cell membrane integrity, and deformed hyphal morphology. Washing 'Fan Retief' guava (Psidium guajava L.) in air- or O2-MNB (for 15 and/or 30 min), better-retained tissue strength, delayed changes in color, and total soluble solid (TSS) content. Notably, MNB treatments were as effective as NaOCl washing and significantly reduced microbial load on fruit surface by ≥2 Log (p < 0.05). Micro-nano bubble water treatment offers a new paradigm for decontamination and preservation of guava fruit quality.

Recent advances in examining the factors influencing the efficacy of biocides against Listeria monocytogenes biofilms in the food industry: A systematic review

Controlling Listeria monocytogenes and its associated biofilms in the food industry requires various disinfection techniques, including physical, chemical, and biological treatments. Biocides, owing to their ease of use, cost-effectiveness, dissolvability in water, and efficacy against a wide range of microorganisms, are frequently selected options. Nonetheless, concerns have been raised about their efficacy in controlling L. monocytogenes biofilm, as laboratory-based and commercial studies have reported the persistence of this bacterium after cleaning and disinfection. This review systematically examined scientific studies, sourced from the Web of Science, Scopus, and PubMed databases between January 2010 and May 2024, that investigated the effectiveness of the most commonly used biocides in the food industry against L. monocytogenes biofilms. A total of 92 articles which met the screening criteria, were included, with studies utilizing biocides containing sodium hypochlorite, quaternary ammonium compounds, and peroxyacetic acid being predominant. Studies indicated that several key factors may potentially influence biocides' efficacy against L. monocytogenes biofilms. These factors included strain type (persistent, sporadic), serotype, strain origin (clinical, environmental, or food), surface type (biotic or abiotic), surface material (stainless steel, polystyrene, etc.), incubation time (biofilm age) and temperature, presence of organic matter, biocide's active agent, and the co-culture of L. monocytogenes with other bacteria. The induction of the viable but nonculturable (VBNC) state following disinfection is also a critical concern. This review aims to provide a global understanding of how L. monocytogenes biofilms respond to biocides under different treatment conditions, facilitating the development of effective cleaning and disinfection strategies in the food industry.

Chitosan-based sustainable packaging and coating technologies for strawberry preservation: A review

Strawberry fruits are popular all over the world due to their rich organoleptic properties and enormous health benefits. However, it is highly susceptible to postharvest spoilage due to various factors, including moisture loss, nutrient oxidation, and microbial spoilage. Recently, various researchers have studied the effect of chitosan-based flexible films and surface coatings on the shelf life of strawberries. Despite various reviews providing general information on the effects of chitosan-based films and coatings on various food products, no review has focused solely on their effects on postharvest preservation and the shelf life of strawberries. The purpose of this review is to summarize the current research on chitosan-based formulations for extending the shelf life of strawberries. Chitosan, a cationic carbohydrate polymer, possesses excellent properties such as film formation, mechanical strength, non-toxicity, biodegradability, edibility, UV-blocking ability, antioxidant activity, and antibacterial functionality, justifying its potential as packaging/coating material for fresh agricultural products, including strawberries. This review covers the various factors responsible for strawberry spoilage and the properties of chitosan that help counteract these factors. Additionally, the advantages of chitosan-based preservation technology compared to existing strawberry preservation methods were explained, efficiency was evaluated, and future research directions were suggested.

Multimode ultrasonic-assisted decontamination of fruits and vegetables: A review

Fruits and vegetables (F&V) are a significant part of our diet consumption. Microbial and pesticide residues are the predominant safety hazards of F&V consumption. Ordinary water washing has a very limited effect on removing microorganisms and pesticide residues and requires high water usage. Ultrasound, as an environmentally friendly technology, shows excellent potential for reducing microbial contamination and pesticide residue. This paper summarizes the research on ultrasound application in F&V washing, including the removal of microbial and pesticide residues and the comprehensive effect on their physicochemical characteristics. Furthermore, multimode ultrasonic-assisted techniques like multi-frequency and sequential ultrasound, combined with novel and conventional methods, can enhance the ultrasound-based effect and be more effective and sustainable in preventing F&V from microbial contamination. Overall, this work explicitly establishes the background on the potential for ultrasound cleaning and disinfection in the food industry as a green, effective, and ultimate method of preventing foodborne illnesses.

Enhanced photodynamic inactivation against Escherichia coli O157:H7 provided by chitosan/curcumin coating and its application in food contact surfaces

Sterilisation technologies are essential to eliminate foodborne pathogens from food contact surfaces. However, most of the current sterilisation methods involve high energy and chemical consumption. In this study, a photodynamic inactivation coating featuring excellent antibacterial activity was prepared by dispersing curcumin as a plant-based photosensitiser in a chitosan solution. The coating generated abundant reactive oxygen species (ROS) after light irradiation at 420 nm, which eradicated ≥99.999 % of Escherichia coli O157:H7. It was also found that ROS damaged the cell membrane, leading to the leakage of cell contents and cell shrinkage on the basis of chitosan. In addition, the production of ROS first excited the bacterial antioxidant defence system resulting in the increase of peroxidase (POD) and superoxide dismutase (SOD). ROS levels exceed its capacity, causing damage to the defence system and further oxidative decomposition of large molecules, such as DNA and proteins, eventually leading to the death of E. coli O157:H7. We also found the curcumin/chitosan coating could effectively remove E. coli O157:H7 biofilms by oxidative of extracellular polysaccharides and proteins. All the contributors made the chitosan/curcumin coating an efficient detergent comparable with HClO.

Antimicrobial Activity of Hydrogen Peroxide for Application in Food Safety and COVID-19 Mitigation: An Updated Review

Hydrogen peroxide (H2O2) is a well-known agent with a broad-spectrum antimicrobial activity against pathogenic bacteria, fungi, and viruses. It is a colorless liquid and commercially available in aqueous solution over a wide concentration range. It has been extensively used in the food industry by virtue of its strong oxidizing property and its ability to cause cellular oxidative damage in microbial cells. This review comprehensively documents recent research on the antimicrobial activity of H2O2 against organisms of concern for the food industry, as well as its effect against SARS-CoV-2 responsible for the COVID-19 pandemic. In addition, factors affecting the antimicrobial effectiveness of H2O2, different applications of H2O2 as a sanitizer or disinfectant in the food industry as well as safety concerns associated with H2O2 are discussed. Finally, recent efforts in enhancing the antimicrobial efficacy of H2O2 are also outlined.

Small concentrations, big results: μM addition of photoactive iron oxides with PMS, PDS, or H2O2, leads to enhanced removal of viruses at near-neutral pH

The photo-Fenton process is effective for pathogen removal, and its low-cost versions can be applied in resource-poor contexts. Herein, a photo-Fenton-like system was proposed using low concentrations of iron oxides (hematite and magnetite) and persulfates (peroxymonosulfate - PMS, and peroxydisulfate - PDS), which exhibited excellent inactivation performance towards MS2 bacteriophages. In the presence of bacteria, MS2 inactivation was inhibited in H2O2 and PDS systems but promoted in PMS-involved systems. The inactivation efficacy of all the proposed systems for mixed bacteria and viruses was greater than that of the sole bacteria, showing potential practical applications. The inactivation performance of humic acid-incorporated iron oxides mediating photo-Fenton-like processes was also studied; except for the PMS-involved system, the inactivation efficacy of the H2O2- and PDS-involved systems was inhibited, but the PDS-involved system was still acceptable (< 2 h). Reactive species exploration experiments indicated that ·OH was the main radical in the H2O2 and PDS systems, whereas 1O2 played a key role in the PMS-involved system. In summary, hematite- and magnetite-mediated persulfate-assisted photo-Fenton-like systems at low concentrations can be used as alternatives to the photo-Fenton process for virus inactivation in sunny areas, providing more possibilities for point-of-use drinking water treatment in developing countries.

Advances in strawberry postharvest preservation and packaging: A comprehensive review

Strawberries spoil rapidly after harvest due to factors such as the ripening process, weight loss, and, most importantly, microbial contamination. Traditionally, several methods are used to preserve strawberries after harvest and extend their shelf life, including thermal, plasma, radiation, chemical, and biological treatments. Although these methods are effective, they are a concern from the perspective of safety and consumer acceptance of the treated food. To address these issues, more advanced environment-friendly technologies have been developed over the past decades, including modified and controlled atmosphere packaging, active biopolymer-based packaging, or edible coating formulations. This method can not only significantly extend the shelf life of fruit but also solve safety concerns. Some studies have shown that combining two or more of these technologies can significantly extend the shelf life of strawberries, which could significantly contribute to expanding the global supply chain for delicious fruit. Despite the large number of studies underway in this field of research, no systematic review has been published discussing these advances. This review aims to cover important information about postharvest physiology, decay factors, and preservation methods of strawberry fruits. It is a pioneering work that integrates, relates, and discusses all information on the postharvest fate and handling of strawberries in one place. Additionally, commercially used techniques were discussed to provide insight into current developments in strawberry preservation and suggest future research directions in this field of study. This review aims to enrich the knowledge of academic and industrial researchers, scientists, and students on trends and developments in postharvest preservation and packaging of strawberry fruits.

From rust to robust disinfectants: How do iron oxides and inorganic oxidants synergize with UVA light towards bacterial inactivation?

Pathogens in drinking water remain a challenge for human health, photo-Fenton process is a promising technique for pathogen inactivation, herein, two common iron oxides, hematite and magnetite mediate persulfate (peroxymonosulfate-PMS - and peroxydisulfate-PDS) involved photo-Fenton-like processes were constructed for E. coli inactivation, and the inactivation performance was investigated and compared with the photo-Fenton process under a low intensity UVA irradiation. Results indicated that with a low dose of iron oxides (1 mg/L) and inorganic peroxides (10 mg/L), PMS-involved photo-Fenton-like process is the best substitute for the photo-Fenton one over pH range of 5-8. In addition, humic acid (HA, one of the important components of natural organic matter) incorporated iron oxide-mediated photo-Fenton-like processes for bacteria inactivation was also studied, and facilitating effect was found in UVA/hematite/PMS and UVA/magnetite/PDS systems. Reactive oxygen species (ROS) exploration experiments revealed that ·OH was the predominant radical in H2O2- and PDS-containing systems, whereas 1O2 was one of the principal reactive species in the PMS systems. In addition to the semiconductor photocatalysis of iron oxides and UVA-activated oxidants, iron-complexes (iron-oxidant complexes and iron-bacteria complexes) mediated ligand-to-metal charge transfer (LMCT) processes also made contribution to bacterial inactivation. Overall, this study demonstrates that it is feasible to replace H2O2 with PMS in a photo-Fenton-like process for water disinfection using a low dose of reagents, mediated by cheap catalysts, such as hematite and magnetite, it is also hoped to provide some insights to practical water treatment.

Effects of washing with boric acid solutions on residual boric acid content, microbiological load, and quality of fresh-cut spinach

Insufficient disinfection of fresh-cut spinach poses significant health risks, along with potential issues like odor, color changes, and softening during short-term storage. To address these challenges, boric acid solutions were explored as an alternative to chlorine washes, which are known to produce toxic compounds. Among various concentrations, 1 % boric acid exhibited the most effective microbial inactivation, leading to substantial reductions in total mesophilic aerobic bacteria, total yeast and mold, and Enterobacteriaceae counts, with reductions of 1.64, 1.38, and 1.77 logs, respectively. Additionally, washing spinach leaves with this solution for 1 min maintained quality parameters, with enhanced antioxidant activity (55.26 mg kg-1 Trolox equivalent), increased total phenolic content (1214.06 mg kg-1 gallic acid equivalent), retention of chlorophyll a (839.16 mg kg-1), chlorophyll b (539.61 mg kg-1) and ascorbic acid content (264.72 mg kg-1). Mechanical properties such as puncture strength (1.81 N) and puncture distance (52.78 mm) also showed favorable outcomes, alongside optimal moisture content at 89.81 %. Notably, residual boric acid content was lowest in spinach leaves (1252.49 mg kg-1) and highest in the wash water (53.88 mg kg-1) after treatment. Scanning electron microscopy images demonstrated maintained tissue integrity, while Hunter Lab readings indicated minimal color changes post-washing. Additionally, sensory evaluations and various physicochemical analyses further supported the efficacy of boric acid washing. Consequently, washing spinach leaves with a 1 % boric acid solution for 1 min yielded favorable results across multiple quality parameters. These findings suggest the potential of boric acid as a safe and effective alternative disinfectant in the fresh-cut produce industry, highlighting its practical implications for food safety and quality. Future research should focus on exploring long-term effects and optimizing washing protocols for broader applications.

The Use of Ultraviolet Irradiation to Improve the Efficacy of Acids That Are Generally Recognized as Safe for Disinfecting Fresh Produce in the Ready-to-Eat Stage

Fresh-cut produce is usually produced under standardized disinfection processes, which are unavailable at the ready-to-eat stage. Currently, chemical sanitizers are used for washing, but their disinfection efficacy is limited. In this study, UV-C (1.03 kJ/m2) was combined with organic acids that are generally recognized as safe (GRAS), including citric, malic, acetic, and lactic acids (LAs), to wash lettuce and cherry tomatoes that are contaminated with Escherichia coli O157:H7 and Salmonella Typhimurium. The results showed that LA was the most effective treatment among the single treatments, with a pathogen reduction and cross-contamination incidence of 2.0-2.3 log CFU/g and 28-35%, respectively. After combining with UV-C, the disinfection efficacy and cross-contamination prevention capacity of the four GRAS acids significantly improved. Among the combination treatments, the highest pathogen reduction (2.5-2.7 log CFU/g) and the lowest cross-contamination incidence (11-15%) were achieved by LA-UV. The analyses of ascorbic acid, chlorophyll, lycopene, antioxidant capacity, and ΔE indicated that neither the single nor combination treatments negatively affected the quality properties. These results provide a potential hurdle technology for fresh produce safety improvement at the ready-to-eat stage.

Different electrolytic treatments for food sanitation and conservation simulating a wash process at the packinghouse

Microorganisms are predominantly responsible for food deterioration, necessitating the sanitization and removal of these entities from food surfaces. The packinghouse employs free chlorine in the sanitization process; however, free chlorine's propensity to react with organic matter, forming potentially toxic compounds, has led to its restriction or outright prohibition in several European countries. Therefore, this study aims to assess various washing methods, emulating packinghouse conditions, utilizing diverse forms of electrolyzed water to impede microbial proliferation and significantly enhance the food's shelf life. The subject of investigation was cherry tomatoes. The findings revealed that electrolyzed water containing NaCl exhibited superior efficacy compared to electrolysis with Na2SO4. Both forms of electrolyzed water demonstrated noteworthy effectiveness in inhibiting microorganisms, resulting in a reduction of 2.0 Log CFU mL-1 for bacteria and 1.5 Log CFU mL-1 for fungi. The electrolyzed water also exhibited a comparable capability to free chlorine in removing fecal coliforms from the tomato surfaces. Notably, both electrolyzed water treatments extended the shelf life of cherry tomatoes by at least three days, accompanied by minimal or negligible residues of free chlorine. Consequently, the electrolyzed water formulations proposed in this study present themselves as promising alternatives to traditional packinghouse sanitizers.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05882-1.

Competition quenching strategies reduce antibiotic tolerance in polymicrobial biofilms

Bacteria typically live in dense communities where they are surrounded by other species and compete for a limited amount of resources. These competitive interactions can induce defensive responses that also protect against antimicrobials, potentially complicating the antimicrobial treatment of pathogens residing in polymicrobial consortia. Therefore, we evaluate the potential of alternative antivirulence strategies that quench this response to competition. We test three competition quenching approaches: (i) interference with the attack mechanism of surrounding competitors, (ii) inhibition of the stress response systems that detect competition, and (iii) reduction of the overall level of competition in the community by lowering the population density. We show that either strategy can prevent the induction of antimicrobial tolerance of Salmonella Typhimurium in response to competitors. Competition quenching strategies can thus reduce tolerance of pathogens residing in polymicrobial communities and could contribute to the improved eradication of these pathogens via traditional methods.

Application of combined treatment of peracetic acid and ultraviolet-C for inactivating pathogens in water and on surface of apples

In this study, a combined treatment of peracetic acid (PAA) and 280 nm Ultraviolet-C (UVC) - Light emitting diode (LED) was applied for inactivating foodborne pathogens in water and apples. The combined treatment of PAA (50 ppm) and UVC-LED showed synergistic inactivation effects against Escherichia coli O157:H7 and Listeria monocytogenes in water. In mechanism analysis, PAA/UVC-LED treatment induced more lipid peroxidation, intracellular ROS, membrane, and DNA damage than a single treatment. Among them, membrane damage was the main synergistic inactivation mechanism of combination treatment. Cell rupture and shrink of both pathogens after PAA/UVC-LED treatment were also identified through scanning electron microscope (SEM) analysis. To examine inactivation of pathogens on the surface of apples by PAA, UVC-LED, and their combined treatment, a washing system (WS) was developed and used. Through applying the WS, PAA/UVC-LED treatment effectively inactivated two pathogens in washing solution and on the surface of apples below the detection limit (3.30 log CFU/2000 mL and 2.0 log CFU/apple) within 5 min. In addition, there was no significant difference in color or firmness of apples after PAA/UVC-LED treatment (p > 0.05).

Effects of benzalkonium chloride as a cationic surfactant on the physicochemical properties of adlay millet starch films

The effects of benzalkonium chloride (BC) as a cationic surfactant on the mechanical, water barrier, microstructural, and thermal properties of adlay millet starch (AS) films were investigated in this study. With increasing BC concentration, tensile strength (from 5.93 to 6.15 MPa) and elongation at break (from 41.39 to 45.48%) of AS-BC films significantly increased, whereas their moisture content, water solubility, and water vapor permeability were reduced, indicating water resistance improvement. Fourier transform infrared spectroscopy and scanning electron microscopy analysis showed that BC at concentrations below 1% did not cause noticeable changes in the microstructure of AS-BC films. In addition, the thermal stability of AS-BC films was not affected by BC, indicating good miscibility between AS and BC. Therefore, BC could improve the physicochemical properties of starch films, and AS-BC films developed in this study can be applied as novel biodegradable packaging materials in the food packaging industry.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01383-1.

One Health Perspectives on Food Safety in Minimally Processed Vegetables and Fruits: From Farm to Fork

While food markets and food production chains are experiencing exponential growth, global attention to food safety is steadily increasing. This is particularly crucial for ready-to-eat products such as fresh-cut salads and fruits, as these items are consumed raw without prior heat treatment, making the presence of pathogenic microorganisms quite frequent. Moreover, many studies on foodborne illnesses associated with these foods often overlook the transmission links from the initial contamination source. The prevention and control of the dissemination of foodborne pathogens should be approached holistically, involving agricultural production, processing, transport, food production, and extending to final consumption, all while adopting a One Health perspective. In this context, our objective is to compile available information on the challenges related to microbiological contamination in minimally handled fruits and vegetables. This includes major reported outbreaks, specific bacterial strains, and associated statistics throughout the production chain. We address the sources of contamination at each stage, along with issues related to food manipulation and disinfection. Additionally, we provide potential solutions to promote a healthier approach to fresh-cut fruits and vegetables. This information will be valuable for both researchers and food producers, particularly those focused on ensuring food safety and quality.

Efficacy of a New Alcohol-Free Organic Acid-Based Hand Sanitizer against Foodborne Pathogens

In light of the global health crisis triggered by the COVID-19 pandemic, numerous experts have deemed the utilization of hand sanitizers imperative as a precautionary measure against the virus. Consequently, the demand for hand sanitizers has experienced a substantial surge. Since the beginning of 2020, the utilization of alcohol-free hand sanitizers has been increasingly favored due to the potential risks associated with alcohol poisoning, flammability, as well as the adverse effects on skin lipid dissolution, dehydration, and sebum reduction, which can lead to severe cases of eczema and norovirus infections. In this study, we developed an aqueous hand sanitizer that does not contain alcohol. The sanitizer consists of naturally occurring, food-grade organic acids, including lactic, citric, and azelaic acids. Additionally, food-grade ammonium sulfate and a small amount of povidone-iodine (PVPI) were included in the formulation to create a synergistic and potent antibacterial effect. The effectiveness of the hand sanitizer was evaluated against four common foodborne pathogens, namely Clostridium botulinum, Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus, via in vitro testing. The organic acids exhibited a synergistic inhibitory function, resulting in a 3-log reduction in CFU/mL. Furthermore, the presence of povidone-iodine and ammonium sulfate enhanced their antibacterial effect, leading to a 4-log reduction in CFU/mL. The hand sanitizer solution remained stable even after 60 days of storage. During this period, the detection of additional triiodide (I3-) ions occurred, which have the ability to release broad-spectrum molecular iodine upon penetrating the cell walls. This alcohol-free hand sanitizer may offer extended protection and is anticipated to be gentle on the skin. This is attributed to the presence of citric and lactic acids, which possess cosmetic properties that soften and smoothen the skin, along with antioxidant properties.

Unveiling Fresh-Cut Lettuce Processing in Argentine Industries: Evaluating Salmonella Levels Using Predictive Microbiology Models

A survey was performed to gather information on the processing steps, conditions, and practices employed by industries processing ready-to-eat (RTE) leafy vegetables in Argentina. A total of seven industries participated in the survey. A cluster analysis of the data obtained was performed to identify homogeneous groups among the participating industries. The data collected were used as inputs of two predictive microbiology models to estimate Salmonella concentrations after chlorine washing, during storage and distribution of final products, and to rank the different practices according to the final estimated Salmonella levels. Six different clusters were identified by evaluating the parameters, methods, and controls applied in each processing step, evidencing a great variability among industries. The disinfectant agent applied by all participating industries was sodium hypochlorite, though concentrations and application times differed among industries from 50 to 200 ppm for 30 to 110 s. Simulations using predictive models indicated that the reductions in Salmonella in RTE leafy vegetables would vary in the range of 1.70-2.95 log CFU/g during chlorine-washing depending on chlorine concentrations applied, washing times, and vegetable cutting size, which varied from 9 to 16 cm2 among industries. Moreover, Salmonella would be able to grow in RTE leafy vegetables during storage and distribution, achieving levels of up to 2 log CFU/g, considering the storage and transportation temperatures and times reported by the industries, which vary from 4 to 14 °C and from 18 to 30 h. These results could be used to prioritize risk-based sampling programs by Food Official Control or determine more adequate process parameters to mitigate Salmonella in RTE leafy vegetables. Additionally, the information gathered in this study is useful for microbiological risk assessments.

Microbiological hazards associated with the use of water in the post-harvest handling and processing operations of fresh and frozen fruits, vegetables and herbs (ffFVHs). Part 1 (outbreak data analysis, literature review and stakeholder questionnaire)

The contamination of water used in post-harvest handling and processing operations of fresh and frozen fruit, vegetables and herbs (ffFVHs) is a global concern. The most relevant microbial hazards associated with this water are: Listeria monocytogenes, Salmonella spp., human pathogenic Escherichia coli and enteric viruses, which have been linked to multiple outbreaks associated with ffFVHs in the European Union (EU). Contamination (i.e. the accumulation of microbiological hazards) of the process water during post-harvest handling and processing operations is affected by several factors including: the type and contamination of the FVHs being processed, duration of the operation and transfer of microorganisms from the product to the water and vice versa, etc. For food business operators (FBOp), it is important to maintain the microbiological quality of the process water to assure the safety of ffFVHs. Good manufacturing practices (GMP) and good hygienic practices (GHP) related to a water management plan and the implementation of a water management system are critical to maintain the microbiological quality of the process water. Identified hygienic practices include technical maintenance of infrastructure, training of staff and cooling of post-harvest process water. Intervention strategies (e.g. use of water disinfection treatments and water replenishment) have been suggested to maintain the microbiological quality of process water. Chlorine-based disinfectants and peroxyacetic acid have been reported as common water disinfection treatments. However, given current practices in the EU, evidence of their efficacy under industrial conditions is only available for chlorine-based disinfectants. The use of water disinfection treatments must be undertaken following an appropriate water management strategy including validation, operational monitoring and verification. During operational monitoring, real-time information on process parameters related to the process and product, as well as the water and water disinfection treatment(s) are necessary. More specific guidance for FBOp on the validation, operational monitoring and verification is needed.

Disinfection of Clostridioides difficile on spinach with epigallocatechin-based antimicrobial solutions and sodium hypochlorite

The removal of C. difficile inoculated on fresh spinach leaves washed with antimicrobial solutions was investigated. In addition, the effect of washing solutions on the total aerobic mesophilic bacteria (TAMB) and Enterobacteriaceae in the fresh spinach was examined. The fresh spinach was washed through immersion in different concentrations (MIC, 2xMIC, and 4xMIC) of the natural disinfectant solution (NDS) consisting of EDTA, borax, and epigallocatechin gallate (EGCG) content developed in our laboratory and green tea extract-acetic acid (GTE-AA) for varying contact times (5 and 15 min). Different concentrations (50, 100, and 200 ppm) of sodium hypochlorite (NaOCl) and tap water as the control group were used to compare the effectiveness of the NDS. In addition, the effects of washing on the color, texture, and total phenol content of the spinach were determined. No statistical difference was observed in the washing of the spinach leaves with NDS prepared at 2xMIC and 4xMIC concentrations, while inhibition of C. difficile ranged between 2.11 and 2.32 logs. The highest inhibition was observed in the application of 50 ppm NaOCl for 15 min with a decrease of 2.88 logs in C. difficile spores. The GTE-AA and NDS decreased the number of TAMB by 2.27-3.08 log and, 3.21-3.66 log, respectively. Washing spinach leaves with natural disinfectant for 5 min caused a decrease of 2.58 logs in Enterobacteriaceae load, while washing with 50 ppm NaOCl for 15 min reduced Enterobacteriaceae load by 4 logs. Tap water was ineffective in reducing any microbial load. No difference was detected in the color parameters of the spinach through all washes. Although all antimicrobial washes made a difference in the texture of the spinach, the greatest loss in firmness was observed in the spinach washed with NaOCl. Washing spinach with epigallocatechin-based wash solutions can remove C. difficile in possible C. difficile contamination, thereby reducing the environmental load of C. difficile. Epigallocatechin-based disinfectants can be an alternative to chlorine-based disinfectants in improving the microbial quality of vegetables.

Biopreservative technologies of food: an alternative to chemical preservation and recent developments

Despite centuries of developing strategies to prevent food-associated illnesses, food safety remains a significant concern, even with multiple technological advancements. Consumers increasingly seek less processed and naturally preserved food options. One promising approach is food biopreservation, which uses natural antimicrobials found in food with a long history of safe consumption and can help reduce the reliance on chemically synthesized food preservatives. The hurdle technology method that combines multiple antimicrobial strategies is often used to improve the effectiveness of food biopreservation. This review attempts to provide a research summary on the utilization of lactic acid bacteria, bacteriocins, endolysins, bacteriophages, and biopolymers helps in the improvement of the shelf-life of food and lower the risk of food-borne pathogens throughout the food supply chain. This review also aims to evaluate current technologies that successfully employ the aforementioned preservatives to address obstacles in food biopreservation.

Determination of 25 quaternary ammonium compounds in sludge by liquid chromatography-mass spectrometry

With the pandemic of COVID-19, the application of quaternary ammonium compounds (QACs), which can be used in SARS-CoV-2 disinfection products, has increased substantially. QACs cumulated in sewer system are ultimately deposited and enriched in sludge. QACs in the environment can adversely affect human health and the environment. In this study, a liquid chromatography-mass spectrometry method was established for the simultaneous determination of 25 QACs in sludge samples. Ultrasonic extraction and filtration of the samples was performed using a 50 mM hydrochloric acid-methanol solution. The samples were separated by liquid chromatography and detected in multiple reaction monitoring mode. The matrix effects of the sludge on the 25 QACs ranged from - 25.5% to 7.2%. All substances showed good linearity in the range of 0.5-100 ng/mL, with all determination coefficients (R2) greater than 0.999. The method detection limits (MDLs) were 9.0 ng/g for alkyltrimethylammonium chloride (ATMAC), 3.0 ng/g for benzylalkyldimethylammonium chloride (BAC), and 3.0 ng/g for dialkyldimethylammonium chloride (DADMAC). The spiked recovery rates were in the range of 74-107%, while the relative standard deviations were in the range of 0.8-20.6%. Considering its sensitivity, accuracy, and easy operation, the proposed method in this study was used to determine 22 sludge samples collected from a comprehensive wastewater treatment plant. The results showed that the concentrations of ΣATMACs, ΣBACs, and ΣDADMACs were 19.684, 3.199, and 8.344 μg/g, respectively. The main components included ATMAC-C16, ATMAC-C18, ATMAC-C20, ATMAC-C22, BAC-C12, and DADMAC-C18:C18, with concentrations exceeding 1.0 μg/g. The concentration relationships of different components in the congeners showed that some components were of similar origin.

Association of resistance to quaternary ammonium compounds and organic acids with genetic markers and their relationship to Escherichia coli serogroup

Sanitizer resistance is being extensively investigated due to the potential for bacterial survival and cross-resistance with other antimicrobials. Similarly, organic acids are being used due to their microbial inactivation potential as well as being generally recognized as safe (GRAS). However, little is known about associations of genetic and phenotypic factors in Escherichia coli related to resistance to sanitizers and organic acids as well as differences between "Top 7" serogroups. Therefore, we investigated 746 E. coli isolates for resistance to lactic acid and two commercial sanitizers based on quaternary ammonium and peracetic acid. Furthermore, we correlated resistance to several genetic markers and investigated 44 isolates using Whole Genome Sequencing. Results indicate that factors related to motility, biofilm formation, and Locus of Heat Resistance played a role in resistance to sanitizers and lactic acid. In addition, Top 7 serogroups significantly differed in sanitizer and acid resistance, with O157 being the most consistently resistant to all treatments. Finally, mutations in rpoA, rpoC, and rpoS genes were observed, in addition to presence of a Gad gene with alpha-toxin formation in all O121 and O145 isolates, which may be related to increased resistance of these serogroups to the acids used in the present study.

Minimally Processed Vegetables in Brazil: An Overview of Marketing, Processing, and Microbiological Aspects

The global demand for minimally processed vegetables (MPVs) has grown, driven by changes in the population's lifestyle. MPVs are fresh vegetables that undergo several processing steps, resulting in ready-to-eat products, providing convenience for consumers and food companies. Among the processing steps, washing-disinfection plays an important role in reducing the microbial load and eliminating pathogens that may be present. However, poor hygiene practices can jeopardize the microbiological quality and safety of these products, thereby posing potential risks to consumer health. This study provides an overview of minimally processed vegetables (MPVs), with a specific focus on the Brazilian market. It includes information on the pricing of fresh vegetables and MPVs, as well as an examination of the various processing steps involved, and the microbiological aspects associated with MPVs. Data on the occurrence of hygiene indicators and pathogenic microorganisms in these products are presented. The focus of most studies has been on the detection of Escherichia coli, Salmonella spp., and Listeria monocytogenes, with prevalence rates ranging from 0.7% to 100%, 0.6% to 26.7%, and 0.2% to 33.3%, respectively. Foodborne outbreaks associated with the consumption of fresh vegetables in Brazil between 2000 and 2021 were also addressed. Although there is no information about whether these vegetables were consumed as fresh vegetables or MPVs, these data highlight the need for control measures to guarantee products with quality and safety to consumers.

Probiotic potential of Lactobacillus plantarum DMR14 for preserving and extending shelf life of fruits and fruit juice

The harmful effects of chemical preservatives are driving the need for natural ones. To meet this demand, probiotic lactic acid bacteria (LAB) were isolated from fermented oats in this study. The goals of this study were to separate and identify probiotic LAB from fermented oats, to determine how effective these LAB are at combating pathogenic microorganisms in vitro, and to investigate their preservative capacity by applying the bacterium's cell-free supernatant (CFS) to specific fruits and fruit juice. The isolated strain was identified as Lactobacillus plantarum DMR14 using morphological, biochemical, and molecular investigation. Antimicrobial, antibiofilm, anti-oxidant, pH tolerance, and antibiotic resistance assays were used to evaluate the strain's probiotic potential, showing that Lactobacillus plantarum DMR14 had the strongest antagonistic and anti-biofilm capacity against Shigella boydii. Furthermore, the bacteriocin-containing compounds, cell-free supernatant (CFS) of the LAB, were tested against three fruits and one fruit juice, with the cell-free supernatant (CFS) of the bacterium lengthening the shelf life of the fruits compared to the untreated ones. Furthermore, while the concentration of coliform bacteria decreased in the treated sugarcane juice, an increase in the concentration of lactic acid bacteria suggested that the strain may be used as a fruit preservative in food industries.

Effects of chlorine and peroxyacetic acid wash treatments on growth kinetics of Salmonella in fresh-cut lettuce

Fresh-cut produces are often consumed uncooked, thus proper sanitation is essential for preventing cross contamination. The reduction and subsequent growth of Salmonella enterica sv Thompson were studied in pre-cut iceberg lettuce washed with simulated wash water (SWW), sodium hypochlorite (SH, free chlorine 25 mg/L), and peroxyacetic acid (PAA, 80 mg/L) and stored for 9 days under modified atmosphere at 9, 13, and 18 °C. Differences in reduction between SH and PAA were non-existent. Overall, visual quality, dehydration, leaf edge and superficial browning and aroma during storage at 9 °C were similar among treatments, but negative effects increased with temperature. These results demonstrated that PAA can be used as an effective alternative to chlorine for the disinfection of Salmonella spp. in fresh-cut lettuce. The growth of Salmonella enterica sv Thompson was successfully described with the Baranyi and Roberts growth model in the studied storage temperature range, and after treatment with SWW, chlorine, and PAA. Subsequently, predictive secondary models were used to describe the relationship between growth rates and temperature based on the models' family described by Bělehrádek. Interestingly, the exposure to disinfectants biased growth kinetics of Salmonella during storage. Below 12 °C, growth rates in lettuce treated with disinfectant (0.010-0.011 log CFU/h at 9 °C) were lower than those in lettuce washed with water (0.016 log CFU/h at 9 °C); whereas at higher temperatures, the effect was the opposite. Thus, in this case, the growth rate values registered at 18 °C for lettuce treated with disinfectant were 0.048-0.054 log CFU/h compared to a value of 0.038 log CFU/h for lettuce treated with only water. The data and models developed in this study will be crucial to describing the wash-related dynamics of Salmonella in a risk assessment framework applied to fresh-cut produce, providing more complete and accurate risk estimates.

Application of essential oils as sanitizer alternatives on the postharvest washing of fresh produce

Growers commonly wash fresh produce with chemical sanitizers during postharvest handling. However, these sanitizers can be harsh to washing systems and pose a health risk to workers. Essential oils (EOs) can be used as alternatives to chemical sanitizers in produce washing. Previous studies reveal that the EOs from thyme, oregano, cinnamon, and clove are the main EOs evaluated in the studies as potential sanitizers for the washing of produce. The use of EOs and surfactants, such as tween80 and cetylpyridinium chloride, might be used to improve the antimicrobial activity of emulsions. However, studies are still required to evaluate the potential effect of different chemical components of EOs and preparations. Also, it is recommended that researchers focus on overcoming obstacles regarding EOs application in washing systems, including the high levels of EO required to reduce bacterial growth, undesired organoleptic impact on produce, and the poor solubility of EOs in aqueous solution.

Efficacy of combined caprylic acid and thymol treatments for inactivation of Listeria monocytogenes on enoki mushrooms in household and food-service establishments

Raw enoki mushroom is a high-risk vector for listeriosis, which led to foodborne outbreaks resulting in four deaths in the United States in 2020. This study aimed to investigate the washing method for the inactivation of L. monocytogenes in enoki mushrooms for household and food service establishments. Five methods of washing fresh agricultural products without using disinfectants were selected: (1) rinsing under running water (2 L/min, 10 min), (2-3) dipping in water (200 ml/20 g) at 22 or 40 °C for 10 min, and using (4) 10% NaCl or (5) 5% vinegar at 22 °C for 10 min. The antibacterial efficacy of each washing method along with the final rinse was tested with enoki mushrooms inoculated with a 3-strain cocktail of L. monocytogenes (ATCC 19111, 19115, 19117; ca. 6 log CFU/g). The 5% vinegar showed a significant difference in antibacterial effect compared to the other treatments except 10% NaCl (P < 0.05), with the maximum elimination of L. monocytogenes by 1.23 log CFU/g. Therefore, a disinfectant for enoki mushrooms that can complement the commonly used washing method was developed using antimicrobials (caprylic acid, CA: 0, 0.20, 0.40%; thymol, TM: 0, 0.075, 0.15%). By combined treatment of 0.40% CA and 0.15% TM at 22 °C for 10 min, L. monocytogenes was completely inactivated (>5.55 log reduction CFU/g) and did not recover after enrichment, although individual treatments of antimicrobials showed low bactericidal effects of <1.50 log reduction CFU/g. The bacterial membrane disintegration induced by the disinfectant was analyzed through flow cytometry. Additionally, the sensory scores (odor and appearance) and color parameters (L*, a*, and b*) of enoki mushrooms treated with the disinfectant were not significantly different from those of enoki mushrooms washed with water (P > 0.05). Our findings suggest a washing disinfectant consisting of low concentrations of CA and TM with synergistic antibacterial effects without quality deterioration that can ensure the safe consumption of raw enoki mushrooms in homes and food service establishments.

The application of adaptively evolved thermostable bacteriophage ΦYMFM0293 to control spp. in poultry skin

Bacteriophages, bacterial viruses, are now being re-highlighted as one of the promising alternative antimicrobial agents to control bacterial pathogens in various fields, including the food industry. However, wild-type (WT) phages isolated from nature are vulnerable to external stresses such as heat, limiting the usability of phages in thermal processing. Here, we applied an adaptive laboratory evolution approach to improving the heat stability of newly isolated Salmonella-infecting lytic phage ΦYMFM0293 and examined its application in the poultry scalding process. After 15 cycles of exposure to sub-lethal temperature, the obtained adaptively evolved (AE) phages maintained approximately 3-log more infectious particles at 73 or 74 °C than the WT and non-heat-treated control phages. Missense mutations mainly concentrated in the genes related to the phage tail module were identified from the independently obtained heat-challenged phages, regardless of host Salmonella's heat-shock protein chaperone induction. These results demonstrated the necessity and sufficiency of the phage exposures to heat for thermal adaptation and suggested the involvement of the phage tail in heat stability. No significant physiological or morphological changes except the mutually offsetting phage replication parameters were observed in the AE phages. Accordingly, hot water supplemented with the AE phages significantly reduced the number of artificially contaminated Salmonella cells on chicken and duck skin in the mimicked scalding process. The AE strategy used here could be applied to other WT phages to improve their usability as more feasible antimicrobials for food safety.

A review on egg pasteurization and disinfection: Traditional and novel processing technologies

Salmonella Enteritidis is a pathogen related to many foodborne outbreaks involving eggs and egg products. Regulations about whether eggs should be pasteurized are very different and inconsistent worldwide. In the United States, eggs are not required to be pasteurized. Hence, less than 3% of the eggs in the country are pasteurized. The standard pasteurization method (57°C, 57.5 min) uses a long thermal process that increases the cost of the product and affects its quality. Foodborne outbreaks can be reduced if eggs are properly pasteurized to inactivate Salmonella spp. However, the technology to pasteurize eggs needs to offer a faster and more reliable method that can be scaled up to industry settings at a low cost and without affecting product quality. Several novel technologies have been tested for eggshell disinfection and egg pasteurization. Some thermal technologies have been evaluated for the pasteurization of eggs. Microwave has limited penetration depth and is a technical challenge for egg pasteurization. However, radio frequency can penetrate eggshells effectively to inactivate Salmonella, considerably reduce processing time, and maintain the quality of the product. Nonthermal technologies such as ultraviolet, pulsed light, cold plasma, ozone, pressure carbon dioxide, electrolyzed water, and natural antimicrobials have been explored for surface cleaning of the intact egg as alternatives without affecting the internal quality. This review presents some of these novel technologies and the current challenges. It discusses the possible combination of factors to achieve the egg's internal pasteurization and the eggshell's disinfection without affecting the quality at a low cost for the consumer.

Intelligent detection for fresh-cut fruit and vegetable processing: Imaging technology

Fresh-cut fruits and vegetables are healthy and convenient ready-to-eat foods, and the final quality is related to the raw materials and each step of the cutting unit. It is necessary to integrate suitable intelligent detection technologies into the production chain so as to inspect each operation to ensure high product quality. In this paper, several imaging technologies that can be applied online to the processing of fresh-cut products are reviewed, including: multispectral/hyperspectral imaging (M/HSI), fluorescence imaging (FI), X-ray imaging (XRI), ultrasonic imaging, thermal imaging (TI), magnetic resonance imaging (MRI), terahertz imaging, and microwave imaging (MWI). The principles, advantages, and limitations of these imaging technologies are critically summarized. The potential applications of these technologies in online quality control and detection during the fresh-cut processing are comprehensively discussed, including quality of raw materials, contamination of cutting equipment, foreign bodies mixed in the processing, browning and microorganisms of the cutting surface, quality/shelf-life evaluation, and so on. Finally, the challenges and future application prospects of imaging technology in industrialization are presented.

Microbial and Parasitic Contamination of Vegetables in Developing Countries and Their Food Safety Guidelines

The safety of humans is of paramount importance in the vegetable production chain. Evidence of microbial and parasitic contamination of these products poses a great threat to consumers. This is an emerging issue the world is battling, and it is still in the process of unravelling. However, one of the contributing factors responsible for the rapid spread of these pathogens to millions of people among other factors is the distribution of food in our food systems. The purpose of this study was to draw the attention of producers, retailers, consumers, and various stakeholders to the occurrence and potential hazard of these organisms, their contamination origin, and food safety protocols. Among the food system, vegetables play a major role, and their consumption has increased as they form a larger portion of daily diets. This urge for healthy diets coupled with changing dietary habits and human population explosion has therefore accelerated their production. This has resulted in parasitic and microbial contamination gaining grounds in salad vegetables, and as such, a wide range of microbes such as Escherichia coli O157: H7, Listeria monocytogenes, Salmonella spp., Shigella, and Staphylococcus, and parasites such as Giardia lamblia, Entamoeba coli, Entamoeba histolytica, Cystoisospora belli, Toxoplasma gondii, Trichuris trichiura, and Ascaris lumbricoides have been isolated from them. Therefore, major routes for salad vegetable contamination and prevention methods have been pointed out in this review article. The topic of protective countermeasures will also be covered here in this review. Notwithstanding, several control measures have been reported to be effective and efficient in removing or eliminating pathogens, including treatment of irrigation water and fertilizers, use of disinfectants like vinegar and saltwater, irradiation, ozone, and bacteriophages. Though consumption of vegetables and salads is encouraged due to their nutritional advantage, appropriate systems should be put in place to ensure their safety.

Multi-Functional Potential of Lactic Acid Bacteria Strains and Antimicrobial Effects in Minimally Processed Pomegranate (Punica granatum L. cv Jolly Red) Arils

This study aimed to evaluate the antimicrobial activity of both cells, and cell-free supernatants (CFS) of 7 selected lactic acid bacteria (LAB) strains belonging to Limosilactobacillus fermentum (4 strains), Lacticaseibacillus paracasei (1 strain), Lacticaseibacillus rhamnosus (1 strain), and Enterococcus faecium (1 strain) species, against Listeria monocytogenes, Escherichia coli, Salmonella Typhimurium, Pseudomonas aeruginosa and Staphylococcus aureus, by both the agar-well diffusion and co-culture methods. In addition, probiotic and safety traits were also detected. Great variability was detected on antimicrobial effects, whereas all tested strains were found sensitive to most of the tested antibiotics, and without any DNase, gelatinase, or hemolytic activity. Moreover, strains showed excellent survival in acidic conditions and exhibited tolerance to pepsin and bile salts. Based on the in vitro results, the CFSs of two selected L. fermentum strains were applied, in a mixed solution, as bio-preservative into minimally processed pomegranate arils, inoculated with a cocktail of L. monocytogenes and E. coli. Samples, packaged in an ordinary atmosphere, were analyzed during refrigerated storage, for up to 12 days, for physicochemical (as weight loss, texture, color, pH, total soluble solids and organic acid content) and for microbiological traits. Results revealed the effectiveness of CFS, up to 12 days, in reducing weight loss and microbial growth, without any significant effect on texture, total soluble solid content and color, found comparable to the acid citric treatment, highlighting the multi-functional potential of selected probiotic strains.

Use of Ultrasonic Cleaning Technology in the Whole Process of Fruit and Vegetable Processing

In an era of rapid technological development, ultrasound technology is being used in a wide range of industries. The use of ultrasound technology in fruit and vegetable processing to improve production efficiency and product quality has been an important research topic. The cleaning of whole fresh fruits and vegetables is an important part of fruit and vegetable processing. This paper discusses the development process of components of the ultrasonic equipment, the application of ultrasonic technology in fruit and vegetable cleaning, and the research advances in ultrasonic cleaning technology. Moreover, the feasibility of ultrasonication of fruits and vegetables for cleaning from the perspectives of microbial inactivation, commodity storage, and sensory analysis were discussed. Finally, the paper identified the inevitable disadvantages of cavitation noise, erosion, and tissue damage in fruit and vegetable processing and points out the future directions of ultrasonic fruit and vegetable cleaning technology.

Switchgrass extractives to mitigate Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium contamination of romaine lettuce at pre- and postharvest

The antimicrobial potential of switchgrass extractives (SE) was evaluated on cut lettuce leaves and romaine lettuce in planta, using rifampicin-resistant Escherichia coli O157:H7 and Salmonella Typhimurium strain LT2 as model pathogens. Cut lettuce leaves were swabbed with E. coli O157:H7 or S. Typhimurium followed by surface treatment with 0.8% SE, 0.6% sodium hypochlorite, or water for 1 to 45 min. For in planta studies, SE was swabbed on demarcated leaf surfaces either prior to or after inoculation of greenhouse-grown lettuce with E. coli O157:H7 or S. Typhimurium; the leaf samples were collected after 0, 24, and 48 h of treatment. Bacteria from inoculated leaves were enumerated on tryptic soy agar plates (and also on MacConkey's and XLT4 agar plates), and the recovered counts were statistically analyzed. Cut lettuce leaves showed E. coli O157:H7 reduction between 3.25 and 6.17 log CFU/leaf, whereas S. Typhimurium reductions were between 2.94 log CFU/leaf and 5.47 log CFU/leaf depending on the SE treatment durations, from initial levels of ∼7 log CFU/leaf. SE treatment of lettuce in planta, before bacterial inoculation, reduced E. coli O157:H7 and S. Typhimurium populations by 1.88 and 2.49 log CFU after 24 h and 3 h, respectively. However, SE treatment after bacterial inoculation of lettuce plants decreased E. coli O157:H7 populations by 3.04 log CFU (after 0 h) with negligible reduction of S. Typhimurium populations. Our findings demonstrate the potential of SE as a plant-based method for decontaminating E. coli O157:H7 on lettuce during pre- and postharvest stages in hurdle approaches.

Consumers’ Knowledge and Handling Practices Associated with Fresh-Cut Produce in the United States

Previous studies have shown that three factors influence fresh-cut produce safety from farm to fork: (1) post-harvest practices in processing facilities, (2) employees’ handling practices in retail facilities, and (3) consumers’ handling practices in domestic kitchens or cooking facilities. However, few studies have examined consumers’ food safety knowledge, risk perceptions, and their handling practices associated with fresh-cut produce. To fill this gap, the present study conducted a nationwide survey to assess U.S. consumers’ food safety knowledge, practices, and risk perception associated with fresh-cut produce among various demographic groups and investigated factors influencing consumers’ food safety practices related to fresh-cut produce. The results showed that consumers lack the knowledge and safe handling practices toward fresh-cut produce regarding storage hierarchy, surface cleaning and sanitizing, and time and temperature control of fresh-cut produce. The men and millennial consumers exhibit a lower level of safe fresh-cut produce handling practices. In addition, a significant interaction was observed between food safety knowledge and risk perceptions on consumers’ fresh-cut produce handling practices, such that food safety knowledge can transfer to practice more effectively for consumers with high levels of risk perception. The results can be utilized to design effective consumer food safety education tools for targeted audiences.

Preparation of Acidic Electrolyzed Water by a RuO2@TiO2 Electrode with High Selectivity for Chlorine Evolution and Its Sterilization Effect

The food hygiene problems caused by bacterial biofilms in food processing equipment are directly related to human life safety and health. Therefore, it is of great strategic significance to study new food sterilization technology. An acidic electrolyzed water (AEW) disinfectant is an electrochemical sterilization technology which has the characteristics of wide adaptability, high efficiency, and environmental friendliness. However, since the sterilization efficiency of AEW for biofilms is not ideal, it is necessary to increase the available chlorine content (ACC) in AEW. A feasible method to increase the ACC is by increasing the chlorine evolution reaction (CER) selectivity of the electrode for AEW preparation. In this paper, the RuO₂@TiO₂ electrode was prepared by thermal decomposition combined with high-vacuum magnetron sputtering. Compared with the oxygen evolution reaction (OER) activity of an ordinary RuO₂ electrode, the OER activity of the RuO₂@TiO₂ electrode is significantly reduced. However, the CER activity of the RuO₂@TiO₂ electrode is close to the OER activity of RuO₂. The CER mechanism of the RuO₂@TiO₂ electrode is the second electron transfer, and the OER mechanism is the formation and transformation of OH_ads. The potential difference between the CER and OER of the RuO₂@TiO₂ electrode is 174 mV, which is 65 mV higher than that of the RuO₂ electrode, so the selectivity of the CER of the RuO₂@TiO₂ electrode is remarkably improved. During the preparation of AEW, the ACC obtained with the RuO₂@TiO₂ electrode is 1.7 times that obtained with the RuO₂ electrode. In the sterilization experiments on Escherichia coli and Bacillus subtilis biofilms, the logarithmic killing values of AEW prepared the by RuO₂@TiO₂ electrode are higher than those of AEW prepared by the RuO₂ electrode.

Use of a silver-based sanitizer to accelerate Escherichia coli die-off on fresh-cut lettuce and maintain produce quality during cold storage: Laboratory and pilot-plant scale tests

Outbreaks and product recalls involving romaine and iceberg lettuce are frequently reported in the United States. Novel technologies are needed to inactivate pathogens without compromising product quality and shelf life. In this study, the effects of a process aid composed of silver dihydrogen citrate, glycerin, and lactic acid (SGL) on Escherichia coli and Listeria monocytogenes concentrations on lettuce immediately after washing and during cold storage were evaluated. Sensory and quality attributes of fresh-cut iceberg lettuce were also evaluated. Laboratory results indicated that application of SGL solution for 30 s as a first step in the washing process resulted in a 3.15 log reduction in E. coli O157:H7 immediately after washing. For E. coli O157:H7 a significant difference between SGL treatment and all other treatments was maintained until day 7. On day zero, SGL led to a 2.94 log reduction of L. monocytogenes. However, there was no significant difference between treatments with or without SGL regardless of storage time. Pilot-plant results showed that samples receiving SGL spray followed by chlorinated flume wash exhibited a greater reduction (1.48 log) in nonpathogenic E. coli populations at the end of shelf life than other treatments (p < 0.05). Additional pilot plant tests were conducted to investigate the hypothesis that SGL residues could continue to impact microbial survival on the final washed lettuce. Results show that pathogens introduced subsequent to flume washing of lettuce pretreated with SGL solution were not affected by antimicrobial residues. The final quality and shelf life of flume washed lettuce were also unaffected by pretreatment with SGL. In conclusion, the results of this study demonstrate that this new technology has the potential to accelerate E. coli die-off on fresh-cut lettuce during cold storage and improve product safety, while not affecting quality throughout the shelf life of the finished products.