Background Due to rapid senescence and disease, a large amount of economic losses of fresh fruits and vegetables (F&V) occurs during postharvest stage. As a non-residue physical sterilization and preservation method, many scientists have recently applied electrolyzed water (EW) to postharvest F&V storage. Scope and approach This article reviews recent applications of EW in postharvest storage of F&V, including effects on sterilization and removal of pesticide residues. Moreover, this work summaries the effect of EW treatment on improving postharvest F&V quality during storage including suppressing browning, delaying senescence, maintaining nutraceutical/bioactive compounds and alleviating chilling injury. Key findings and conclusions This work reviews the application of EW as a disinfectant to postharvest F&V in recent years, and concludes that EW controls the postharvest diseases caused by fungal infections not only through the direct inhibition to pathogen, but also seems to be related to the increased resistance of host induced by EW. In addition, this article also summarizes the application of EW as a pesticide remover in postharvest F&V and reveals the types as well as molecular structures of target pesticides that acidic electrolyzed water (AEW) and alkaline electrolyzed water (ALEW) may act on. Particular finding is that in addition to the efficacy of disinfection and removing pesticide residues, EW also gets involved in regulating the physiological metabolism of postharvest F&V, which plays an important role in improving the quality and extending the shelf life of fresh products. The main applications of EW in improving the quality of postharvest F&V include (Ⅰ) suppress browning, (Ⅱ) delay senescence, (Ⅲ) maintain bioactive compounds, and (Ⅳ) alleviate chilling injury. In addition, the potential biochemical mechanisms of EW on improving quality of postharvest F&V are also discussed.

Application of electrolyzed water in postharvest fruits and vegetables storage: A review

Microbiological contamination of vegetables leading to foodborne disease is a serious public health problem. Slightly acidic electrolyzed water (SAEW) and ultraviolet-light emitting diode (UV-LED) are considered to have good bactericidal effect. However, the limitations of SAEW in application include its instability and the great dependence on equipment and that of UV-LED remains poorly characterized. To improve decontamination efficiency and explore the combined bactericidal efficacy, the coriander, immerged in different concentration SAEW in advance, were studied under various UV-LED intensity: 80, 160, 240 μW/cm2 for different times. Additionally, the coriander was evaluated for total viable counts and general quality. The result showed that UV-LED-SAEW combined treatment has better decontamination efficiency than that of single factor and the inactivation efficacy was related to the concentration of SAEW, intensity of UV-LED and their treating time. The 240 μW/cm2 UV-LED irradiation for 30 min combined with SAEW (ACC of 60 mg/L) 5-min-washing led to 2.72 log CFU/g Salmonella reduction and 2.42 log CFU/g E. coli reduction. The SAEW and UV-LED treatment cause no significant negative effect on overall coriander quality and prolonged the shelf-life of coriander. UV-LED with SAEW pretreatment shows potential for reducing foodborne pathogens on coriander without effects on its quality.

Effect of slightly acidic electrolyzed water (SAEW) and ultraviolet light illumination pretreatment on microflora inactivation of coriander

Chronic and recurrent bacterial infections are frequently associated with the formation of biofilms on biotic or abiotic materials that are composed of mono- or multi-species cultures of bacteria/fungi embedded in an extracellular matrix produced by the microorganisms. Biofilm formation is, among others, regulated by quorum sensing (QS) which is an interbacterial communication system usually composed of two-component systems (TCSs) of secreted autoinducer compounds that activate signal transduction pathways through interaction with their respective receptors. Embedded in the biofilms, the bacteria are protected from environmental stress stimuli, and they often show reduced responses to antibiotics, making it difficult to eradicate the bacterial infection. Besides reduced penetration of antibiotics through the intricate structure of the biofilms, the sessile biofilm-embedded bacteria show reduced metabolic activity making them intrinsically less sensitive to antibiotics. Moreover, they frequently express elevated levels of efflux pumps that extrude antibiotics, thereby reducing their intracellular levels. Some efflux pumps are involved in the secretion of QS compounds and biofilm-related materials, besides being important for removing toxic substances from the bacteria. Some efflux pump inhibitors (EPIs) have been shown to both prevent biofilm formation and sensitize the bacteria to antibiotics, suggesting a relationship between these processes. Additionally, QS inhibitors or quenchers may affect antibiotic susceptibility. Thus, targeting elements that regulate QS and biofilm formation might be a promising approach to combat antibiotic-resistant biofilm-related bacterial infections.

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Targeting the Holy Triangle of Quorum Sensing, Biofilm Formation, and Antibiotic Resistance in Pathogenic Bacteria

A removable photothermal antibacterial “warm paste” target for cariogenic bacteria

Dental caries is one of the most common microbe-mediated oral diseases in human beings. At present, the accepted etiology of caries is based on a four-factor theory that includes oral microorganisms, oral environment, host, and time. Excessive exposure to dietary carbohydrates leads to the accumulation of acid-producing and acid-resistant microorganisms in the mouth. Dental caries is driven by dysbiosis of the dental biofilm adherent to the enamel surface. Effective preventive methods include inhibiting the cariogenic microorganisms, treatment with an anti-biofilm agent, and sugar intake control. The goal is to reduce the total amount of biofilm or the levels of specific pathogens. Natural products could be recommended for preventing dental caries, since they may possess fewer side effects in comparison with synthetic antimicrobials. Herein, the mechanisms of oral microbial community development and functional specialization are discussed. We highlight the application of widely explored natural products in the last five years for their ability to inhibit cariogenic microorganisms.

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Microbial Etiology and Prevention of Dental Caries: Exploiting Natural Products to Inhibit Cariogenic Biofilms.

Free radical-induced oxidative stress is the root cause of many diseases, such as diabetes, stress and cardiovascular diseases. The objective of this research was to screen GABA levels, antioxidant activities and bioactive compounds in brown rice. In this study, we first fermented brown rice with different lactic acid bacteria (LABs), and the best LAB was selected based on the levels of GABA in the fermentate. Lactobacillus reuterii generated the highest levels of GABA after fermentation. To ascertain whether germination can improve the GABA levels of brown rice, we compared the levels of GABA in raw brown rice (Raw), germinated brown rice (Germ), fermented brown rice (Ferm) and fermented-germinated brown rice (G+F) to identify the best approach. Then, antioxidant activities were investigated for Raw BR, Germ BR, Ferm BR and G+F BR. Antioxidant activity was calculated using a 2,2-diphenyl-1-picryl hydrazile radical assay, 2,2-azino-bis-(3-ethylene benzothiozoline-6-sulfonic acid) radical assay and ferric-reducing antioxidant power. In Ferm BR, DPPH (114.40 ± 0.66), ABTS (130.52 ± 0.97) and FRAP (111.16 ± 1.83) mg Trolox equivalent 100 g, dry weight (DW), were observed as the highest among all samples. Total phenolic content (97.13 ± 0.59) and total flavonoids contents (79.62 ± 1.33) mg GAE/100 g and catechin equivalent/100 g, DW, were also found to be highest in fermented BR. Furthermore, an untargeted metabolomics approach using ultra-high-performance liquid tandem chromatography quadrupole time of flight mass spectrometry revealed the abundance of bioactive compounds in fermented BR, such as GABA, tryptophan, coumaric acid, L-ascorbic acid, linoleic acid, β-carotenol, eugenol, 6-gingerol, etc., as well as bioactive peptides which could contribute to the health-promoting properties of L. reuterii fermented brown rice.

Untargeted Metabolomics of Korean Fermented Brown Rice Using UHPLC Q-TOF MS/MS Reveal an Abundance of Potential Dietary Antioxidative and Stress-Reducing Compounds.

The initiation and development of cariogenic (that is, caries-related) biofilms are the result of the disruption of homeostasis in the oral microenvironment. There is a daily accumulation of dental biofilm on the surface of teeth and its matrix of extracellular polymers supports the host in its defense against invading microbes, thus helping to achieve oral microbial homeostasis. However, the homeostasis can be broken down under certain circumstances such as during long-term exposure to a low pH environment which results in the dominance of acidogenic and acid-tolerating species in the dental biofilm and, thus, triggers the shift of harmless biofilm to an acidic one. This work aims to explore microbial diversity and the quorum sensing of dental biofilm and their important contributions to oral health and disease. The complex and multispecies ecosystems of the cariogenic biofilm pose significant challenges for the modulation of the oral microenvironment. Promising treatment strategies are those that target cariogenic niches with high specificity without disrupting the balance of the surrounding oral microbiota. Here, we summarized the recent advances in modulating cariogenic biofilm and/or controlling its pathogenic traits.

https://www.mdpi.com/2076-2607/9/6/1311/pdf

Cariogenic Biofilm: Pathology-Related Phenotypes and Targeted Therapy

The objective of this study was to investigate the efficacy of slightly acidic electrolyzed water (SAEW) combined with fumaric acid (FA) and calcium oxide (CaO) treatment on the microbial disinfection of fresh fruits including apple, mandarin, and tomato at the industrial scale. The combined treatments can significantly (p < 0.05) reduce the population of natural microbiota from the fruit surfaces and the treated samples showed good sensory qualities during refrigeration storage. In addition, decontamination of inoculated foodborne pathogens (Escherichia coli O157:H7 and Listeria monocytogenes) was carried out in the laboratory, and the combined treatments resulted in a reduction ranging from 2.85 to 5.35 log CFU/fruit, CaO followed by SAEW+FA treatment that resulted in significantly higher reduction than for SAEW+FA treatment. The technology developed by this study has been used in a fresh fruit industry and has greatly improved the quality of the products. These findings suggest that the synergistic properties of the combination of SAEW, FA, and CaO could be used in the fresh fruit industry as an effective sanitizer.

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Disinfection Efficacy of Slightly Acidic Electrolyzed Water Combined with Chemical Treatments on Fresh Fruits at the Industrial Scale.

Oxidative stress has been postulated to play a role in several diseases, including cardiovascular diseases, diabetes, and stress-related disorders (anxiety/depression). Presently, natural plant-derived phytochemicals are an important tool in reducing metabolomic disorders or for avoiding the side effects of current medicinal therapies. Brown Rice (Oryza sativa L.) is an important part of Asian diets reported as a rich source of bioactive phytonutrients. In our present study, we have analyzed the effect of different lactic acid bacteria (LABs) fermentation on antioxidant properties and in the enhancement of bioactive constituents in Korean brown rice. Therefore, the antioxidant activities and phytochemical analysis were investigated for raw brown rice (BR) and different fermented brown rice (FBR). BR fermented with Limosilactobacillus reuteri, showed the highest antioxidant activities among all samples: DPPH (121.19 ± 1.0), ABTS (145.80 ± 0.99), and FRAP (171.89 ± 0.71) mg Trolox equiv./100 g, dry weight (DW). Total phenolic content (108.86 ± 0.63) mg GAE equiv./100 g, DW and total flavonoids content (86.79 ± 0.83) mg catechin equiv./100 g, DW was also observed highest in Limosilactobacillus reuteri FBR. Furthermore, phytochemical profiling using ultra-high-performance liquid tandem chromatography quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS) and cell antioxidant assay (CAA) revealed L. reuteri FBR as a strong antioxidant with an abundance of bioactive compounds such as gamma-aminobutyric acid, coumarin, cinnamic acid, butanoic acid, ascorbic acid, nicotinic acid, and stearic acid. This study expanded current knowledge on the impact of fermentation leading to the enhancement of antioxidant capacity with an abundance of health-related bioactive compounds in BR. The results obtained may provide useful information on functional food production using fermented brown rice.

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Xiuqin Chen

Papers

Microbial Etiology and Prevention of Dental Caries: Exploiting Natural Products to Inhibit Cariogenic Biofilms.

Untargeted Metabolomics of Korean Fermented Brown Rice Using UHPLC Q-TOF MS/MS Reveal an Abundance of Potential Dietary Antioxidative and Stress-Reducing Compounds.

Cariogenic Biofilm: Pathology-Related Phenotypes and Targeted Therapy

Disinfection Efficacy of Slightly Acidic Electrolyzed Water Combined with Chemical Treatments on Fresh Fruits at the Industrial Scale.

Limosilactobacillus reuteri Fermented Brown Rice: A Product with Enhanced Bioactive Compounds and Antioxidant Potential.