Plant extracts for the control of bacterial growth: efficacy, stability and safety issues for food application

Antibacterial activity and mode of action of selected glucosinolate hydrolysis products against bacterial pathogens

Plants contain numerous components that are important sources of new bioactive molecules with antimicrobial properties. Isothiocyanates (ITCs) are plant secondary metabolites found in cruciferous vegetables that are arising as promising antimicrobial agents in food industry. The aim of this study was to assess the antibacterial activity of two isothiocyanates (ITCs), allylisothiocyanate (AITC) and 2-phenylethylisothiocyanate (PEITC) against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Listeria monocytogenes. The antibacterial mode of action was also characterized by the assessment of different physiological indices: membrane integrity, intracellular potassium release, physicochemical surface properties and surface charge. The minimum inhibitory concentration (MIC) of AITC and PEITC was 100 μg/mL for all bacteria. The minimum bactericidal concentration (MBC) of the ITCs was at least 10 times higher than the MIC. Both AITC and PEITC changed the membrane properties of the bacteria decreasing their surface charge and compromising the integrity of the cytoplasmatic membrane with consequent potassium leakage and propidium iodide uptake. The surface hydrophobicity was also non-specifically altered (E. coli and L. monocytogenes become less hydrophilic; P. aeruginosa and S. aureus become more hydrophilic). This study shows that AITC and PEITC have strong antimicrobial potential against the bacteria tested, through the disruption of the bacterial cell membranes. Moreover, phytochemicals are highlighted as a valuable sustainable source of new bioactive products.

Inhibiting Microbial Toxins Using Plant-Derived Compounds and Plant Extracts

Many pathogenic bacteria and fungi produce potentially lethal toxins that cause cytotoxicity or impaired cellular function either at the site of colonization or other locations in the body through receptor-mediated interactions. Various factors, including biotic and abiotic environments, competing microbes, and chemical cues affect toxin expression in these pathogens. Recent work suggests that several natural compounds can modulate toxin production in pathogenic microbes. However, studies explaining the mechanistic basis for their effect are scanty. This review discusses the potential of various plant-derived compounds for reducing toxin production in foodborne and other microbes. In addition, studies highlighting their anti-toxigenic mechanism(s) are discussed.

Dietary oregano essential oil alleviates experimentally induced coccidiosis in broilers

An experiment was conducted to determine the effects of oregano essential oil on growth performance and coccidiosis prevention in mild challenged broilers. A total of 250 1-d-old chicks were used in a completely randomized design with 5 treatments and 5 replicates with 10 birds in each replication. Experimental treatments included: (1) negative control (NC; unchallenged), (2) positive control (PC; challenged with sporulated oocysts of Eimeria), (3) PC fed 200 ppm Diclazuril in diet, (4) PC fed 300 ppm oregano oil in diet, and (5) PC fed 500 ppm oregano oil in diet. At 22 d of age, all the experimental groups except for NC were challenged with 50-fold dose of Livacox T as a trivalent live attenuated coccidiosis vaccine. On d 28, two birds were slaughtered and intestinal coccidiosis lesions were scored 0-4. Moreover, dropping was scored in the scale of 0-3, and oocysts per gram feces (OPG) were measured. Oregano oil at either supplementation rate increased body weight gain (P=0.039) and improved feed conversion ratio (P=0.010) from d 22 to 28, when compared with PC group. Using 500 ppm oregano oil in challenged broilers diet increased European efficiency factor than PC group (P=0.020). Moreover, challenged broilers fed 500 ppm oregano oil or Diclazuril in diets displayed lower coccidiosis lesions scores in upper (P=0.003) and middle (P=0.018) regions of intestine than PC group, with the effect being similar to unchallenged birds. In general, challenged birds fed 500 ppm oregano oil or Diclazuril in diets had lower OPG (P=0.001), dropping scores (P=0.001), litter scores (P=0.001), and pH of litter (P=0.001) than PC group. It could be concluded that supplementation of oregano oil at the dose of 500 ppm in diet may have beneficial effect on prevention of coccidiosis in broilers.

Antimicrobial property and microstructure of micro-emulsion edible composite films against Listeria

Edible antimicrobial composite films from micro-emulsions containing all natural compounds were developed and their antimicrobial properties and microstructures were investigated. Chitosan, allyl isothiocyanate (AIT), barley straw arabinoxylan (BSAX), and organic acids (acetic, lactic and levulinic acids) were used as film-forming agent, antimicrobial agent, emulsifier, and solvent, respectively. Micro-emulsions were obtained using high pressure homogenization (HPH) processing at 138MPa for 3cycles. The composite films made from the micro-emulsions significantly (p<0.05) inactivated Listeria innocua in tryptic soy broth (TSB) and on the surface of ready-to-eat (RTE) meat samples, achieving microbial reductions of over 4logCFU/ml in TSB after 2days at 22°C and on meat samples after 35days at 10°C. AIT was a major contributor to the antimicrobial property of the films and HPH processing further enhanced its antimicrobial efficacy, while the increase of chitosan from 1.5% to 3%, or addition of acetic acid to the formulations didn't result in additional antimicrobial effects. This study demonstrated an effective approach to developing new edible antimicrobial films and coatings used for food applications.

Identification of didecyldimethylammonium salts and salicylic acid as antimicrobial compounds in commercial fermented radish kimchi

Daikon radish (Raphanus sativus) fermented with lactic acid bacteria, especially Leuconostoc or Lactobacillus spp., can be used to make kimchi, a traditional Korean fermented vegetable. Commercial Leuconostoc/radish root ferment filtrates are claimed to have broad spectrum antimicrobial activity. Leuconostoc kimchii fermentation products are patented as preservatives for cosmetics, and certain strains of this organism are reported to produce antimicrobial peptides (bacteriocins). We examined the antimicrobial agents in commercial Leuconostoc/radish root ferment filtrates. Both activity-guided fractionation with Amberlite XAD-16 and direct extraction with ethyl acetate gave salicylic acid as the primary agent with activity against Gram-negative bacteria. Further analysis of the ethyl acetate extract revealed that a didecyldimethylammonium salt was responsible for the Gram-positive activity. The structures of these compounds were confirmed by a combination of (1)H- and (13)C NMR, high-performance liquid chromatography, high-resolution mass spectrometry, and tandem mass spectrometry analyses. Radiocarbon dating indicates that neither compound is a fermentation product. No antimicrobial peptides were detected.

Medicinal plants for the treatment of hypertrophic scars

Hypertrophic scar is a complication of wound healing and has a high recurrence rate which can lead to significant abnormity in aesthetics and functions. To date, no ideal treatment method has been established. Meanwhile, the underlying mechanism of hypertrophic scarring has not been clearly defined. Although a large amount of scientific research has been reported on the use of medicinal plants as a natural source of treatment for hypertrophic scarring, it is currently scattered across a wide range of publications. Therefore, a systematic summary and knowledge for future prospects are necessary to facilitate further medicinal plant research for their potential use as antihypertrophic scar agents. A bibliographic investigation was accomplished by focusing on medicinal plants which have been scientifically tested in vitro and/or in vivo and proved as potential agents for the treatment of hypertrophic scars. Although the chemical components and mechanisms of action of medicinal plants with antihypertrophic scarring potential have been investigated, many others remain unknown. More investigations and clinical trials are necessary to make use of these medical plants reasonably and phytotherapy is a promising therapeutic approach against hypertrophic scars.

Bioactivity of essential oils: a review on their interaction with food components

Essential oils (EOs) are liquid preparations, produced from plant materials. Although EOs showed a promising bioactivity in vitro, they could interact in foods with some components (fats, proteins, carbohydrates) and pH, thus many authors have reported that a significant effect of EOs toward spoiling and pathogenic microorganisms could be achieved in vivo by using higher amounts of oils. Different methods can be used to assess the bioactivity of EOs (disk diffusion and agar or broth dilution methods); however, there is not a standardized test and researchers propose and use different protocols (evaluating the Minimal Inhibitory Concentration, studying the survival curves, analysis through the scanning electron microscopy, etc.). Thereafter, the scope of this review is a focus on interactions of EOs with proteins, carbohydrates, oils, NaCl, and pH, as well as a brief description on the different protocols to assess their bioactivity both under in vivo and in vitro conditions.

Use of herbs, spices and their bioactive compounds in active food packaging

Natural additives obtained from herbs and spices are being increasingly used in the food packaging industry.

Antimicrobial activity and acute and chronic toxicity of the essential oil of Lippia origanoides

Currently, there is a growing interest in medicinal plants, because of an increased demand for alternate therapies. In this study, the antimicrobial activity and toxicity of the essential oil of Lippia origanoides (L. origanoides) were investigated. The essential oil of L. origanoides was extracted by steam-dragging distillation and its constituents were identified by chromatography coupled with mass spectrometry. Among the 15 compounds identified, the most abundant were carvacrol (29.00%), o-cymene (25.57%), and thymol methyl ether (11.50%). The essential oil was studied in antimicrobial assays to determine the MIC and MBC. The results indicated that a concentration of 120μL/mL of oil was sufficient to inhibit the growth of the following microorganisms: Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923) and Salmonella cholerasuis (ATCC 10708). Acute and chronic toxic effects of orally administered oil were investigated in Wistar rats by using standard methods. Doses of 30, 60 and 120mg/kg of the essential oil did not induce significant changes in weight, behavior or hematological and biochemical parameters in the animals. There were no signs of any histopathological changes to the liver, kidneys or heart of the treated rats, suggesting that Lippia origanoides oil is non-toxic after oral administration in acute or chronic toxicity studies. The results obtained in this study show that the essential oil of L. origanoides has a high safety margin, with no detectable toxic effects in rats treated with doses to 120mg/kg. In addition, L. origanoides oil demonstrated potent antimicrobial activity against S. aureus, E. coli and S. cholerasuis. Based on these findings, this essential oil may have practical application as a veterinary antimicrobial.

Antibacterial activity of cinnamaldehyde and clove oil: effect on selected foodborne pathogens in model food systems and watermelon juice

Natural additives for the control of microbial growth are in demand because consumers prefer them over synthetic ones. In the present investigation, the antibacterial activity of two natural preservatives, cinnamaldeyde and clove oil alone or in combinations was studied, and their potential as food preservative in model food systems and watermelon juice was evaluated. The cinnamaldehyde and clove essential oil showed minimum inhibitory concentration (MIC) at or below 5000 mg/l, and fractional inhibitory studies using both the oils showed synergistic effect. In artificially inoculated barley model food system and cabbage model food system, 2 MIC of oils was able to reduce the growth of the tested bacteria (more than 5 log) during 4 weeks storage at 37 °C, and similar reduction was also observed when combinations of oils were used at one eighth of MIC against Bacillus cereus and Yersinia enterocolitica, and one fourth of MIC against Staphylococcus aureus and Escherichia coli. Natural contaminants of watermelon juice were also reduced by the combination of one fourth of MIC of the oils, which was more effective than individual 2 MICs. These findings may be useful for food applications, but their effect on sensory quality of various foods need to be studied.

Reduction of microbiological risk in minced meat by a combination of natural antimicrobials

BACKGROUND

Responsibility for food safety must be taken through the entire food-production chain, to avoid consumer cross-contamination. The antimicrobial activities of an Alpinia katsumadai seed extract and epigallocatechin gallate (EGCG), and their combination, were evaluated against individual food-borne pathogenic strains of Listeria monocytogenes, Escherichia coli and Campylobacter jejuni, individually and as a cocktail, in chicken-meat juice and sterile minced meat as food models, and in minced meat with the naturally present microflora, as an actual food sample.

RESULTS

The antimicrobial combination of the A. katsumadai extract and EGCG was the most efficient for C. jejuni growth inhibition, followed by inhibition of L. monocytogenes, which was reduced more efficiently in the bacterial cocktail than as an individual strain. The antimicrobial combination added to minced meat at refrigeration temperatures used in the food chain (8 °C) revealed inhibition of these pathogens and inhibition of the naturally present bacteria after 5 days.

CONCLUSIONS

The antibacterial efficiencies of the tested combinations are influenced by storage temperature. Food safety can be improved by using the appropriate combination of natural antimicrobials to reduce the microbiological risk of minced meat.

2(5H)-Furanone, epigallocatechin gallate, and a citric-based disinfectant disturb quorum-sensing activity and reduce motility and biofilm formation of Campylobacter jejuni

Brominated furanone and epigallocatechin gallate (EGCG) are naturally occurring polyphenolic compounds that can be derived from sources such as Delisea pulchra algae and green tea, respectively. These compounds may have potential health benefits and antimicrobial properties. Biofilm formation and bacterial motility are virulence factors that seem to be involved in the autoinducer 2 (AI-2)-mediated quorum sensing (QS) response of Campylobacter. In this study, the anti-QS activities of 2(5H)-furanone, EGCG, and a citric-based disinfectant were tested against Campylobacter jejuni. The minimal bactericidal concentration (MBC) was determined by a microdilution method, and the AI-2 activity was measured by bioluminescence. For motility tests, subinhibitory concentrations of each compound were mixed with semisolid Muller Hinton agar. Biofilm formation was quantified in broth-containing microplates after staining with safranin. The MBC of tested compounds ranged from 0.3 to 310 μg/mL. Subinhibitory concentrations of all of the antimicrobial compounds significantly decreased (19 to 62 %) the bacterial motility and reduced biofilm formation. After treatment with EGCG, furanone, and the disinfectant, AI-2 activity was decreased by 60 to 99 % compared to control. In conclusion, 2(5H)-furanone, EGCG, and the disinfectant exert bactericidal effects against C. jejuni and disturb QS activity and reduce motility and biofilm formation. These compounds may be naturally occurring alternatives to control C. jejuni.

Combating pathogenic microorganisms using plant-derived antimicrobials: a minireview of the mechanistic basis

The emergence of antibiotic resistance in pathogenic bacteria has led to renewed interest in exploring the potential of plant-derived antimicrobials (PDAs) as an alternative therapeutic strategy to combat microbial infections. Historically, plant extracts have been used as a safe, effective, and natural remedy for ailments and diseases in traditional medicine. Extensive research in the last two decades has identified a plethora of PDAs with a wide spectrum of activity against a variety of fungal and bacterial pathogens causing infections in humans and animals. Active components of many plant extracts have been characterized and are commercially available; however, research delineating the mechanistic basis of their antimicrobial action is scanty. This review highlights the potential of various plant-derived compounds to control pathogenic bacteria, especially the diverse effects exerted by plant compounds on various virulence factors that are critical for pathogenicity inside the host. In addition, the potential effect of PDAs on gut microbiota is discussed.

Phytotoxic and antibacterial metabolites from Fusarium proliferatum ZS07 isolated from the gut of long-horned grasshoppers

In the proceeding of screening new bioactive natural products, the ethyl acetate extract of the fermentation broth of Fusarium proliferatum ZS07, a fungus residing in the gut of long-horned grasshoppers (Tettigonia chinensis), was found possessing selective phytotoxic activity against the radicle growth of Amaranthus retroflexus L. Bioactivity-guided fractionation lead to the isolation of six fungal metabolites 1-6, including a new polyketide derivate O-methylated SMA93 (2) and five known compounds SMA93 (1), rhodolamprometrin (3), radicinin (4), dehydroallogibberic acid (5), and 3-methyl-6,8-dihydroxyisocoumarin (6). Their structures were identified on the basis of spectroscopic analysis and by comparison of the corresponding data to those reported in the literature previously. Phytotoxic effects of the four isolated compounds 1-4 on the radicle growth of A. retroflexus L. seeds were investigated under laboratory conditions, and compounds 2 and 4 showed good phytotoxic activity in the concentration of 100 μg/mL, with the inhibition rates of 83.0 and 65.2%, respectively. Furthermore, the antibacterial activity of compounds 1-5 were evaluated against selected bacteria. Compounds 1-3 were found to possess potent antibacterial activity against Bacillus subtilis (ATCC 6633), with the minimum inhibitory concentration (MIC) values of 3.13-12.50 μg/mL, while Escherichia coli (ATCC 8739) and Salmonella typhimurium [CMCC(B) 50115] were not susceptible. These results suggest that the new polyketide derivate 2 and known compounds 1, 3, and 4 have potential to be used as biocontrol agents in agriculture.

Volatile compounds of Van Herby cheeses produced with raw and pasteurized milks from different species

Levels of volatile compounds in Van herby cheeses manufactured from raw and pasteurized; 100 % ewes', 50 % ewes'+50 % cows' and mixture of 50 % ewes'+25 % cows'+25 % goats' milks were investigated over 180 days of ripening at 4 °C. The volatile compounds levels of herby cheese samples increased throughout the 180 days storage period. Samples produced from pasteurized milk showed lower volatile contents than their counterparts produced from raw milk. The volatile compounds profile of herby cheese samples detected by headspace solid-phase microextraction (HS-SPME) consisted of 8 esters, 5 ketones, 5 aldehydes, 9 acids, 6 alcohols and 14 hydrocarbons and terpenes. Acetic acid was the most abundant volatile compound in HS-SPME of ripened cheeses, followed by hexanoic, octanoic and butanoic acids.

Inhibition of microbial pathogens using fruit and vegetable peel extracts

The aim of the present work is to evaluate the antimicrobial potency of some vegetable and fruit peels. The extraction was done by individual cold percolation method using various solvents with increasing polarity (Hexane, ethyl acetate, acetone, methanol and aqueous). The antimicrobial activity was done by agar well diffusion assay against five Gram positive bacteria, five Gram negative bacteria and four fungi. All extracts demonstrated varied level of antimicrobial activity. The peel extracts showed highest zone of inhibition against Gram negative bacteria as compared to Gram positive bacteria and fungi. Amongst studied peel extracts Citrus limon followed by Manilkara zapota and Carica papaya showed good antimicrobial activity indicating its potency as a promising source of natural antimicrobics. The results confirm the belief that agro waste can be therapeutically used.

Natural additives and agricultural wastes in biopolymer formulations for food packaging

The main directions in food packaging research are targeted toward improvements in food quality and food safety. For this purpose, food packaging providing longer product shelf-life, as well as the monitoring of safety and quality based upon international standards, is desirable. New active packaging strategies represent a key area of development in new multifunctional materials where the use of natural additives and/or agricultural wastes is getting increasing interest. The development of new materials, and particularly innovative biopolymer formulations, can help to address these requirements and also with other packaging functions such as: food protection and preservation, marketing and smart communication to consumers. The use of biocomposites for active food packaging is one of the most studied approaches in the last years on materials in contact with food. Applications of these innovative biocomposites could help to provide new food packaging materials with improved mechanical, barrier, antioxidant, and antimicrobial properties. From the food industry standpoint, concerns such as the safety and risk associated with these new additives, migration properties and possible human ingestion and regulations need to be considered. The latest innovations in the use of these innovative formulations to obtain biocomposites are reported in this review. Legislative issues related to the use of natural additives and agricultural wastes in food packaging systems are also discussed.

Antimicrobial activity of acid-hydrolyzed Citrus unshiu peel extract in milk

Citrus fruit (Citrus unshiu) peels were extracted with hot water and then acid-hydrolyzed using hydrochloric acid. Antimicrobial activities of acid-hydrolyzed Citrus unshiu peel extract were evaluated against pathogenic bacteria, including Bacillus cereus, Staphylococcus aureus, and Listeria monocytogenes. Antilisterial effect was also determined by adding extracts at 1, 2, and 4% to whole, low-fat, and skim milk. The cell numbers of B. cereus, Staph. aureus, and L. monocytogenes cultures treated with acid-hydrolyzed extract for 12h at 35°C were reduced from about 8log cfu/mL to <1log cfu/mL. Bacillus cereus was more sensitive to acid-hydrolyzed Citrus unshiu peel extract than were the other bacteria. The addition of 4% acid-hydrolyzed Citrus unshiu extracts to all types of milk inhibited the growth of L. monocytogenes within 1d of storage at 4°C. The results indicated that Citrus unshiu peel extracts, after acid hydrolysis, effectively inhibited the growth of pathogenic bacteria. These findings indicate that acid hydrolysis of Citrus unshiu peel facilitates its use as a natural antimicrobial agent for food products.

Natural additives and agricultural wastes in biopolymer formulations for food packaging

The main directions in food packaging research are targeted toward improvements in food quality and food safety. For this purpose, food packaging providing longer product shelf-life, as well as the monitoring of safety and quality based upon international standards, is desirable. New active packaging strategies represent a key area of development in new multifunctional materials where the use of natural additives and/or agricultural wastes is getting increasing interest. The development of new materials, and particularly innovative biopolymer formulations, can help to address these requirements and also with other packaging functions such as: food protection and preservation, marketing and smart communication to consumers. The use of biocomposites for active food packaging is one of the most studied approaches in the last years on materials in contact with food. Applications of these innovative biocomposites could help to provide new food packaging materials with improved mechanical, barrier, antioxidant, and antimicrobial properties. From the food industry standpoint, concerns such as the safety and risk associated with these new additives, migration properties and possible human ingestion and regulations need to be considered. The latest innovations in the use of these innovative formulations to obtain biocomposites are reported in this review. Legislative issues related to the use of natural additives and agricultural wastes in food packaging systems are also discussed.

Antibacterial and antimutagenic activities of novel zerumbone analogues

Zerumbone, the key constituent of Zingiber zerumbet Smith, is a very important bioactive phytochemical. Two new compounds viz. azazerumbone 1 and azazerumbone 2 were synthesised by ZnCl2-catalysed Beckmann rearrangement of the zerumbone oxime. The structure elucidation of these analogues of zerumbone was carried out by 1D ((1)H NMR and (13)C NMR) and 2D-NMR (COSY, HSQC and NOESY) spectral analysis. Studies on the antibacterial activity established that azazerumbone 2 had better activity than zerumbone. Among the tested bacteria, Bacillus cereus was the most sensitive and Yersinia enterocolitica was found to be the most resistant. These compounds exhibited strong protection against sodium azide induced mutagenicity of Salmonella typhimurium strains TA 98 and TA 1531. Azazerumbone 2 showed better antibacterial and antimutagenic activity than azazerumbone 1. The antibacterial and antimutagenic activities exhibited by zerumbone and its analogues demonstrate their potential for use as nutraceuticals and in food preservation.

Controlling Vibrio vulnificus and spoilage bacteria in fresh shucked oysters using natural antimicrobials

This study evaluated the efficacy of grape seed extract (GE), citric acid (CA) and lactic acid (LA) on the inactivation of Vibrio vulnificus and inherent microflora in fresh shucked oysters. The minimum inhibitory concentration (MIC) of GE, CA or LA against V. vulnificus was determined. Furthermore, the shucked oysters were artificially inoculated with V. vulnificus. The inoculated shucked oysters (25 g) were then dipped in 250 ml GE, CA or LA solutions for 10 min. The population of V. vulnificus in shucked oysters was determined. The effects of the treatments with GE, CA or LA solutions on the inherent microbiota in fresh shucked oysters during storage at 5°C for 20 days were also studied. The MICs of GE, CA or LA against V. vulnificus were 10.0, 5.0 or 1.0 mg ml(-1), respectively. The concentrations of 500, 300 or 150 mg ml(-1) GE, CA or LA solutions were needed to reduce the population of V. vulnificus to below the detection level (1.0 log g(-1)). Treatment with 500, 300, 150 mg ml(-1) GE, CA or LA significantly reduced the initial inherent microbiota in fresh shucked oysters, and inherent levels were significantly (P < 0.05) lower than the control sample throughout refrigerated storage for 20 days.

SIGNIFICANCE AND IMPACT OF THE STUDY

Oysters filter large volume of seawater during their feeding activities that concentrate bacteria such as Vibrio vulnificus in their body. The presence of V. vulnificus in oysters has a serious impact on public health and international trade. There is increasing concern over the use of chemical preservatives. Furthermore, the food industry is looking for new natural preservation methods. This study indicated that lactic acid and citric acid wash solutions could offer an inexpensive, natural and strong approach to control V. vulnificus and spoilage bacteria in fresh shucked for the oyster industry.

Effect of the icing with thyme, oregano and clove extracts on quality parameters of gutted and beheaded anchovy (Engraulis encrasicholus) during chilled storage

The effect of ice containing thyme (0.04% w/v), oregano (0.03% w/v) and clove (0.02% w/v) extracts on the quality parameters of anchovy (Engraulis encrasicholus) was assessed through the chemical, sensory and microbiological methods. According to sensory analyses, anchovy stored in ice prepared with each plant extracts had a shelf life of 12 days, while batch stored in traditional ice had a shelf life of 9 days. pH were not significantly affected by the presence of plant extracts in the ice. However, a marked antioxidant effect (P<0.05) could be detected with fish kept under plant extract icing systems, according to peroxide (PV) and thiobarbituric acid (TBA) values. Moreover, the employment of such icing systems led to lower (P<0.05) total volatile base-nitrogen (TVB-N) value and free fatty acid (FFA) formation. Thus, TVB-N proved to be a suitable index for the spoilage of anchovies during chilled storage. The employment of such icing systems also led to significantly lower counts of aerobic mesophiles and psychrotrophic bacteria in anchovy muscle with skin, as compared with the traditional ice batch. This work demonstrates that the use of ice with plant extracts for the storage of gutted and beheaded anchovy can be recommended to improve the quality and extend the shelf life.

Antimicrobial potential of flavoring ingredients against Bacillus cereus in a milk-based beverage

Natural ingredients--cinnamon, cocoa, vanilla, and anise--were assessed based on Bacillus cereus vegetative cell growth inhibition in a mixed liquid whole egg and skim milk beverage (LWE-SM), under different conditions: ingredient concentration (1, 2.5, and 5% [wt/vol]) and incubation temperature (5, 10, and 22 °C). According to the results obtained, ingredients significantly (p<0.05) reduced bacterial growth when supplementing the LWE-SM beverage. B. cereus behavior was mathematically described for each substrate by means of a modified Gompertz equation. Kinetic parameters, lag time, and maximum specific growth rate were obtained. Cinnamon was the most bacteriostatic ingredient and cocoa the most bactericidal one when they were added at 5% (wt/vol) and beverages were incubated at 5 °C. The bactericidal effect of cocoa 5% (wt/vol) reduced final B. cereus log10 counts (log Nf, log10 (colony-forming units/mL)) by 4.10 ± 0.21 log10 cycles at 5 °C.

Reaction of 2,6-dichloroquinone-4-chloroimide (Gibbs reagent) with permethrin - an optical sensor for rapid detection of permethrin in treated wood

Background

A novel optical sensor for the rapid and direct determination of permethrin preservatives in treated wood was designed. The optical sensor was fabricated from the immobilisation of 2,6-dichloro-p-benzoquinone-4-chloroimide (Gibbs reagent) in nafion/sol–gel hybrid film and the mode of detection was based on absorption spectrophotometry. Physical entrapment was employed as a method of immobilisation.

Results

The sensor gave a linear response range of permethrin between 2.56–383.00 μM with detection limit of 2.5 μM and demonstrated good repeatability with relative standard deviation (RSD) for 10 μM at 5.3%, 100 μM at 2.7%, and 200 μM at 1.8%. The response time of the sensor was 40 s with an optimum response at pH 11.

Conclusions

The sensor was useful for rapid screening of wood or treated wood products before detailed analysis using tedious procedure is performed. The validation study of the optical sensor against standard method HPLC successfully showed that the permethrin sensor tended to overestimate the permethrin concentration determined.

Effect of postharvest UV-C treatment on the bacterial diversity of Ataulfo mangoes by PCR-DGGE, survival of E. coli and antimicrobial activity

Since Mexico is the second largest exporter of mangoes, its safety assurance is essential. Research in microbial ecology and knowledge of complex interactions among microbes must be better understood to achieve maximal control of pathogens. Therefore, we investigated the effect of UV-C treatments on bacterial diversity of the Ataulfo mangoes surface using PCR-DGGE analysis of variable region V3 of 16S rRNA genes, and the survival of E. coli, by plate counting. The UV-C irradiation reduced the microbial load on the surface of mangoes immediately after treatment and the structure of bacterial communities was modified during storage. We identified the key members of the bacterial communities on the surface of fruits, predominating Enterobacter genus. Genera as Lactococcus and Pantoea were only detected on the surface of non-treated (control) mangoes. This could indicate that these genera were affected by the UV-C treatment. On the other hand, the treatment did not have a significant effect on survival of E. coli. However, genera that have been recognized as antagonists against foodborne pathogens were identified in the bands patterns. Also, phenolic compounds were determined by HPLC and antimicrobial activity was assayed according to the agar diffusion method. The main phenolic compounds were chlorogenic, gallic, and caffeic acids. Mango peel methanol extracts (UV-C treated and control mangoes) showed antimicrobial activity against strains previously isolated from mango, detecting significant differences (P < 0.05) among treated and control mangoes after 4 and 12 days of storage. Ps. fluorescens and Ps. stutszeri were the most sensitive.

Screening and identification of the antibacterial bioactive compounds from Lonicera japonica Thunb. leaves

Our aim was to screen for antibacterial bioactive compounds from Lonicera japonica leaves. Staphylococcus aureus and Escherichia coli were used as the indicator bacteria. Bacteriostatic assay-guided extraction and stepwise partitioning of the samples yielded five compounds of interest. Antimicrobial activities of the compounds were determined using a disk diffusion assay. Extracts, fractions, and compounds from L. japonica leaves possessed considerable antibacterial activities against the tested bacterial strains and the most active fraction was attributed to J3B2, which primarily contained 3,5-di-O-caffeoylquinic acid and 4,5-di-O-caffeoylquinic acid. Meanwhile, five bacteriostatic constituents were isolated (3-O-caffeoylquinic acid, secoxyloganin, luteoloside, 3,5-di-O-caffeoylquinic acid and 4,5-di-O-caffeoylquinic acid), among which, secoxyloganin was isolated for the first time from leaves. The antibacterial activity of the compounds was in the order of 3,5-bis-O-caffeoyl quinic acid, 4,5-bis-O-caffeoylquinic acid, luteoloside>3-O-caffeoylquinic acid>secoxyloganin. Our results suggested that the phenolic compounds might significantly contribute to antibacterial activity and were the most responsible for the bacteriostatic activity of L. japonica leaves.

Predicting and preventing mold spoilage of food products

This article is a review of how to quantify mold spoilage and consequently shelf life of a food product. Mold spoilage results from having a product contaminated with fungal spores that germinate and form a visible mycelium before the end of the shelf life. The spoilage can be then expressed as the combination of the probability of having a product contaminated and the probability of mold growth (germination and proliferation) up to a visible mycelium before the end of the shelf life. For products packed before being distributed to the retailers, the probability of having a product contaminated is a function of factors strictly linked to the factory design, process, and environment. The in-factory fungal contamination of a product might be controlled by good manufacturing hygiene practices and reduced by particular processing practices such as an adequate air-renewal system. To determine the probability of mold growth, both germination and mycelium proliferation can be mathematically described by primary models. When mold contamination on the product is scarce, the spores are spread on the product and more than a few spores are unlikely to be found at the same spot. In such a case, models applicable for a single spore should be used. Secondary models can be used to describe the effect of intrinsic and extrinsic factors on either the germination or proliferation of molds. Several polynomial models and gamma-type models quantifying the effect of water activity and temperature on mold growth are available. To a lesser extent, the effect of pH, ethanol, heat treatment, addition of preservatives, and modified atmospheres on mold growth also have been quantified. However, mold species variability has not yet been properly addressed, and only a few secondary models have been validated for food products. Once the probability of having mold spoilage is calculated for various shelf lives and product formulations, the model can be implemented as part of a risk management decision tool.