Inhibitory effects of microencapsulated allyl isothiocyanate (AIT) against Escherichia coli O157:H7 in refrigerated, nitrogen packed, finely chopped beef

Synthesis, characterization, biological potency, and molecular docking of Co2+, Ni2+ and Cu2+ complexes of a benzoyl isothiocyanate based ligand

The primary objective of the present study was to produce metal complexes of H4DAP ligand (N,N'-((pyridine-2,6-diylbis(azanediyl))bis(carbonothioyl))dibenzamide) derived from 2,6-diaminopyridine and benzoyl isothiocyanate with either ML or M2L stoichiometry. There are three distinct coordination complexes obtained with the formulas [Co(H2DAP)]·H2O, [Ni2(H2DAP)Cl2(H2O)2]·H2O, and [Cu(H4DAP)Cl2]·3H2O. The confirmation of the structures of all derivatives was achieved through the utilization of several analytical techniques, including FT-IR, UV-Vis, NMR, GC-MS, PXRD, SEM, TEM analysis, and QM calculations. Aiming to analyze various noncovalent interactions, topological methods such as QTAIM, NCI, ELF, and LOL were performed. Furthermore, the capacity of metal-ligand binding was examined by fluorescence emission spectroscopy. An in vitro investigation showed that the viability of MDA-MB-231 and HepG-2 cells was lower when exposed to the manufactured Cu2+ complex, in comparison to the normal cis-platin medication. The compounds were further evaluated for their in vitro antibacterial activity. The Ni2+ complex has shown promising activity against all tested pathogens, comparable to the reference drugs Gentamycin and Ketoconazole. Furthermore, a computational docking investigation was conducted to further examine the orientation, interaction, and conformation of the recently created compounds on the active site of the Bcl-2 protein.

Antibacterial activity and main action pathway of benzyl isothiocyanate extracted from papaya seeds

The development of natural antimicrobial agents has attracted long-term attention due to the increasing demand for food preservation. Papaya, a widely cultivated nutritious tropical fruit, has benzyl isothiocyanate (BITC) as one of the most important secondary metabolites in its seeds. And the antibacterial activity of BITC toward different strains and the main antibacterial pathway remain unclear. The current study focused on characterizing the antibacterial effect and exploring the major bacteriostatic pathway of BITC. BITC was shown to have a broad-spectrum antibacterial effect, with a minimum inhibitory concentration of 1 µL/mL for Escherichia coli, Bacillus subtilis, and Aspergillus niger, and 0.5 µL/mL for Salmonella enterica, Staphylococcus aureus, and Penicillium citrinum. Additionally, BITC was identified to affect the integrity of the biological oxidation system rather than the permeability or morphology of cell membranes. Furthermore, BITC was found not only to affect ATP production but also to hinder a series of important chemical reactions of the coenzymes involved in the transfer of hydrogen ions in the respiratory chain. The bacteriostatic pathway of BITC was shown to be implicated in an incomplete respiratory chain and the deregulation of the metabolism system. These results indicate the potential of BITC as a natural preservative in the food industry. PRACTICAL APPLICATION: BITC is present in papaya seeds and can be extracted and purified. Exploring its antibacterial activity and main action pathway may facilitate its application as a new bacteriostatic agent in food industry.

Control of pathogenic and spoilage bacteria in meat and meat products by high pressure: Challenges and future perspectives

High-pressure processing is among the most widely used nonthermal intervention to reduce pathogenic and spoilage bacteria in meat and meat products. However, resistance of pathogenic bacteria strains in meats at the current maximum commercial equipment of 600 MPa questions the ability of inactivation by its application in meats. Pathogens including Escherichia coli, Listeria, and Salmonelle, and spoilage microbiota including lactic acid bacteria dominate in raw meat, ready-to-eat, and packaged meat products. Improved understanding on the mechanisms of the pressure resistance is needed for optimizing the conditions of pressure treatment to effectively decontaminate harmful bacteria. Effective control of the pressure-resistant pathogens and spoilage organisms in meats can be realized by the combination of high pressure with application of mild temperature and/or other hurdles including antimicrobial agents and/or competitive microbiota. This review summarized applications, mechanisms, and challenges of high pressure on meats from the perspective of microbiology, which are important for improving the understanding and optimizing the conditions of pressure treatment in the future.

Development of a Bioactive Sauce Based on Oriental Mustard Flour with Antifungal Properties for Pita Bread Shelf Life Improvement

Ochratoxin A (OTA) is a mycotoxin produced in the secondary metabolism of fungus belonging to the genus Aspergillus and Penicillium. In this study, the employment of oriental mustard flour (OMF) as an ingredient in a packaged sauce was evaluated for the generation in situ of the antimicrobial compound allyl isothiocyanate (AITC) in order to preserve pita bread contaminated with Penicillium verrucosum VTT D-01847, an OTA producer, in an active packaging system. Four different concentrations (8, 16, 33 and 50 mg/g) were tested. Mycelium formation, mycotoxin production, AITC absorbed by the food matrix, and volatilization kinetics were studied for each concentration. The results obtained were compared with bread treated with the commercial additive calcium propionate (E-282). The results showed a shelf life increase of two and three days with the employment of 33 and 50 mg/g of OMF, with a significant reduction of the fungal population (3.1 and 5.7 logs, respectively) in comparison with the control experiment. The use of 16 and 33 mg/g of OMF in the sauce formulation decreased the concentration of OTA in the bread samples while no OTA production was detected employing 50 mg/g of OMF.

Generation of antibacterial peptides from crude cheese whey using pepsin and rennet enzymes at various pH conditions

BACKGROUND

The current study aimed to prepare antimicrobial agents for food preservation from crude cheese whey. Crude cheese whey was digested with porcine pepsin, and calf and fungal rennets at various pHs. The digests were assessed for antibacterial activities against Escherichia coli and Bacillus subtilis.

RESULTS

The calf rennet digest at pH 3.0 showed the highest antibacterial activity. Three antibacterial peptides that acted against B. subtilis lactoferrin f(20-30), and β-lactoglobulin f(14-22) and f(92-103) were identified in the calf rennet digest. Only lactoferrin f(20-30) also exerted bactericidal activity against E. coli. LC-MS/MS analysis revealed that the three peptides were generated by the porcine pepsin at pH 2.5, whereas the calf rennet generated them at a wider pH (pH 2.5-3.5). Fungal rennet generated only β-lactoglobulin f^14-22 at pH 3.5. The pepsin and calf rennet digests at pH 2.5 and 3.0, respectively, reduced the E. coli and B. subtilis populations by approximately 2 log at 6000 µg mL^-1 in milk at 4 °C.

CONCLUSION

The calf rennet and porcine pepsin digests of cheese whey, at a specific acidic pH, which can be prepared from food-grade materials, have the potential to be used as natural food preservatives due to the presence of the three antibacterial peptides. © 2018 Society of Chemical Industry.

Inactivation of Escherichia coli O157:H7 and Salmonella and Native Microbiota on Fresh Strawberries by Antimicrobial Washing and Coating

Antimicrobial washing (AW), antimicrobial coating (AC), and a combination of washing followed by coating (AW+AC) were evaluated for their ability to inactivate artificially inoculated foodborne pathogens and native microbiota on strawberries stored at 4°C. Strawberries were inoculated with a six-strain composite of Escherichia coli O157:H7 and Salmonella; treated by AW, AC, or AW+AC; and stored at 4°C for 3 weeks. The washing solution contained 90 ppm of peracetic acid, and the coating solution consisted of chitosan (1%, w/v), allyl isothiocyanate (1%, v/v), and corn-bio fiber gum (5%, w/v). The effectiveness of the antimicrobial treatments against E. coli O157:H7 and Salmonella pathogens and native microflora on strawberries and their impact on fruit quality (appearance, weight loss, color, and firmness) were determined. By the end of storage, pathogen populations on strawberries were 2.5 (AW+AC), 2.9 (AC), 3.8 (AW), and 4.2 log CFU for the positive (untreated) control. AW+AC treatments also inactivated the greatest population of native microflora, followed by the AC treatment alone. AW+AC treatments showed additional antimicrobial effectiveness against these two pathogens and native microflora. Both AW+AC and AC treatments preserved the color, texture, and appearance of strawberries throughout storage. The coating treatments (AW+AC and AC alone) further reduced the loss of moisture throughout storage. The AW treatment was the least effective in reducing populations of pathogens and native microflora and in maintaining the quality of strawberries throughout storage. This study demonstrates a method to improve the microbiological safety, shelf life, and quality of strawberries.

Control of Salmonella enterica and Listeria monocytogenes in hummus using allyl isothiocyanate

Hummus (chickpea dip) is a ready-to-eat product which has been implicated in several foodborne outbreaks and food recalls. This study aimed to screen the antimicrobial activity of allyl isothiocyanate (AITC) against 5 strains of each of Salmonella enterica and Listeria monocytogenes using a disc diffusion method. Additionally, the antimicrobial activity of 0.1-1.5% (v/w) AITC against both pathogens and aerobic bacteria in hummus was also investigated. The inhibition zones of AITC were 8.5-15 and 7.0-8.5 mm against the S. enterica and L. monocytogenes strains, respectively, at 37 °C. S. enterica numbers were reduced by >6 log₁₀ CFU/g in hummus containing ≥0.5% AITC by 3 days at both 4 and 10 °C. While 0.1-0.25% AITC reduced S. enterica by 2.5-5.1 log₁₀ CFU/g at 4 °C or by 4.7-6.0 log₁₀ CFU/g at 10 °C by 10 days. Similarly, L. monocytogenes numbers decreased by >6 log₁₀ CFU/g in hummus with ≥0.5% or ≥1.0% AITC at 4 or 10 °C, respectively, by 3 days. Further, 0.25% AITC significantly reduced L. monocytogenes in hummus by 2.7 and 4.3 log₁₀ CFU/g at 4 and 10 °C, respectively. Moreover, 0.1% AITC reduced L. monocytogenes by 1.8 log₁₀ CFU/g in hummus at 10 °C and inhibited the growth at 4 °C for up to 10 days. The aerobic bacterial count also significantly decreased in un-inoculated hummus treated with 1.0-1.5% AITC at both 4 and 10 °C, while a concentration of 0.25-0.5% AITC inhibited their growth at 4 °C. AITC can be used to reduce the risk of salmonellosis or listeriosis in hummus and extend its shelf-life.

Preparation and Characterization of Ternary Antimicrobial Films of β-Cyclodextrin/Allyl Isothiocyanate/Polylactic Acid for the Enhancement of Long-Term Controlled Release

Allyl isothiocyanate (AITC) are natural essential oil components that have outstanding antimicrobial activities. However, low water solubility, high volatility, and easy degradation by heat, restricting their application in food packing industry. Development of the inclusion complex of β-cyclodextrin/AITC (β-CD/AITC) is a promising solution. Furthermore, the incorporation of β-CD/AITC complex into polylactic acid (PLA) films would be an attractive method to develop food antimicrobial materials. The aim of this study was to evaluate the enhancement in physicochemical properties, antimicrobial activities, and controlled release of β-CD/AITC from such films. The addition of β-CD/AITC significantly increased the flexibility and thermal stability of films. The Fourier transform infrared (FTIR) results revealed that the interactions between β-CD/AITC and PLA films occurred. The controlled release of AITC encapsulated in β-CD was significantly affected by relative humidity and temperature. The PLA films containing β-CD/AITC can be applied as an effective antimicrobial packing material for food and non-food applications.

Antimicrobial edible coatings and films from micro-emulsions and their food applications

This study focused on the use of antimicrobial edible coatings and films from micro-emulsions to reduce populations of foodborne pathogens in foods. Corn-Bio-fiber gum (C-BFG) was used as an emulsifier with chitosan. Allyl isothiocyanate (AIT) and lauric arginate ester (LAE) served as antimicrobials. Micro-emulsions were obtained from a solution consisting of 1% chitosan, 0.5% C-BFG, and 1-4% AIT or LAE which was subject to high pressure homogenization (HPH) processing at 138MPa for 3cycles. Coatings and films produced from the micro-emulsions had micro-pores with sizes ranging from 100 to 300nm and micro-channels that hold antimicrobials effectively and facilitate the release of antimicrobials from the center to the surface of the films or coatings, thus enhancing their antimicrobial efficacy. The coatings and films with 1% AIT reduced populations of Listeria innocua by over 5, 2, and 3 log CFU in culture medium (Tryptic soy broth, TSB), ready-to-eat meat, and strawberries, respectively. The coatings and films with 1% LAE reduced populations of Escherichia coli O157:H7 and Salmonella spp. by over 5 and 2 log CFU in TSB and strawberries, respectively. This study provides an innovative approach for the development of effective antimicrobial materials to reduce food borne pathogenic contaminants on ready-to-eat meat, strawberries, or other food.

Novel food packaging systems with natural antimicrobial agents

A new type of packaging that combines food packaging materials with antimicrobial substances to control microbial surface contamination of foods to enhance product microbial safety and to extend shelf-life is attracting interest in the packaging industry. Several antimicrobial compounds can be combined with different types of packaging materials. But in recent years, since consumer demand for natural food ingredients has increased because of safety and availability, these natural compounds are beginning to replace the chemical additives in foods and are perceived to be safer and claimed to alleviate safety concerns. Recent research studies are mainly focused on the application of natural antimicrobials in food packaging system. Biologically derived compounds like bacteriocins, phytochemicals, enzymes can be used in antimicrobial food packaging. The aim of this review is to give an overview of most important knowledge about application of natural antimicrobial packagings with model food systems and their antimicrobial effects on food products.

Preliminary Investigation on the Use of Allyi Isothiocyanate to Increase the Shelf-Life of Gilthead Sea Bream (Sparus Aurata) Fillets

The aim of this work is to evaluate the activity of allyl isothiocyanate (AITC) against fish spoilage bacteria (specific spoilage organisms; SSOs) as well as its possible use in gilthead sea bream (Sparus aurata) fillets to extend their shelf-life. In this regard, in vitro tests are carried out in order to evaluate the inhibitory activity of AITC and its vapours on several strains of SSOs. The AITC effect on the shelf-life of sea bream fillets was made by putting them in plastic trays hermetically closed with the addition AITC. Microbiological and sensorial evaluations were made on fish fillets during storage. Treated fillets maintained microbial populations at a significantly lower level compared with the control samples during storage, showing better sensorial characteristics. Therefore, the use of AITC's vapours seems to be a new and interesting alternative way to increase fish product shelf-life.

Effect of the oriental and yellow mustard flours as natural preservative against aflatoxins B1, B2, G1 and G2 production in wheat tortillas

Reduction of the AFs produced by Aspergillus parasiticus CECT 2681 in wheat tortillas by isothiocyanates (ITCs) from oriental and yellow mustard flours was evaluated in this study. Polyethylene plastic bags were introduced with wheat tortillas contaminated with A. parasiticus and treated with 0, 0.1, 0.5 or 0.1 g of either oriental or yellow mustard flour added with 2 ml of water. The wheat tortillas were stored at room temperature during 1 month. The quantification of the AFs produced was analyzed by liquid chromatography (LC) coupled to the mass spectrometry detection in tandem (MS/MS). Gaseous allyl isothiocyanate (AITC) from oriental mustard was more effective than p-hydroxybenzyl isothiocyanate (p-HBITC) from yellow mustard to inhibit the production of AFs. More importantly, 1 g of AITC was able to reduce >90 % of AFs B1, B2, G1 and G2. p-HBITC is less stable and volatile than AITC, leading to a much lower AFs (average of 17.7 to 45.2 %). Further studies should investigate the use of active packaging using oriental mustard flour and water to reduce the production of AFs by Aspergillus species in bakery goods.

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.

Use of allyl isothiocyanate and carbon nanotubes in an antimicrobial film to package shredded, cooked chicken meat

We developed antimicrobial packaging incorporated with allyl isothiocyanate (AIT) and carbon nanotube (CNT), and this packaging was used for shredded cooked chicken meat inoculated with Salmonella Choleraesuis. The following parameters were analysed during the 40 days of storage: microbial counts, colour characteristics and changes in the oxidation of the meat as well as changes in the mechanical properties of the film, the structure of the antimicrobial film and the diffusion of the antimicrobial agent into the food. The incorporation of AIT into the films increased the elongation at the break (E) value of the films and decreased the tensile strength (TS) value of the films. The CNT was important to retain the AIT which is a volatile substance in the film. The diffusion of the AIT from the film into the chicken reduced the microbial contamination, controlled oxidation and reduced the colour changes. Thus, these packages were effective for the 40 days of storage.

Inactivation of Salmonella enterica serovar Typhimurium and quality maintenance of cherry tomatoes treated with gaseous essential oils

The antimicrobial activity of the essential oils (EOs) from cinnamon bark, oregano, mustard, and of their major components cinnamaldehyde, carvacrol, and allyl isothiocyanate (AIT) was evaluated as a gaseous treatment to reduce Salmonella enterica serovar Typhimurium in vitro and on tomatoes. In vitro tests showed that mustard EO and AIT had the greatest inhibition of Salmonella, followed by cinnamon EO and cinnamaldehyde, while oregano and carvacrol showed the least inhibition. Scanning electron microscopy images of S. Typhimurium on tomatoes suggest that the EOs and their major components damaged the bacteria, and the damage was more obvious after posttreatment storage at 10 °C for 4 and 7 d. Salmonella on inoculated tomatoes was reduced by more than 5 log colony forming units (CFU)/g by mustard EO and AIT, by 4.56 and 3.79 log CFU/g following cinnamon EO and cinnamaldehyde treatments, respectively, and 1.54 and 3.37 log CFU/g after oregano EO and carvacrol treatments, respectively. Mustard EO and AIT induced discoloration, softening, and loss of the vitamin C and lycopene during 21 d of storage at 10 °C, while treatment with cinnamon EO and cinnamaldehyde did not result in significant changes in tomato quality. Tomatoes treated with oregano EO had better quality than nontreated samples after storage. Therefore, treatment with cinnamon and oregano EO and their major components appeared to be feasible for inactivation of Salmonella on tomatoes and maintaining quality.

Antimicrobial activity of allyl isothiocyanate used to coat biodegradable composite films as affected by storage and handling conditions

We evaluated the effects of storage and handling conditions on the antimicrobial activity of biodegradable composite films (polylactic acid and sugar beet pulp) coated with allyl isothiocyanate (AIT). Polylactic acid and chitosan were incorporated with AIT and used to coat one side of the film. The films were subjected to different storage conditions (storage time, storage temperature, and packed or unpacked) and handling conditions (washing, abrasion, and air blowing), and the antimicrobial activity of the films against Salmonella Stanley in tryptic soy broth was determined. The films (8.16 μl of AIT per cm(2) of surface area) significantly (P < 0.05) inhibited the growth of Salmonella during 24 h of incubation at 22°C, while the populations of Salmonella in controls increased from ca. 4 to over 8 log CFU/ml, indicating a minimum inactivation of 4 log CFU/ml on films in comparison to the growth on controls. Statistical analyses indicated that storage time, storage temperature, and surface abrasion affected the antimicrobial activity of the films significantly (P < 0.05). However, the differences in microbial reduction between those conditions were less than 0.5 log cycle. The results suggest that the films' antimicrobial properties are stable under practical storage and handling conditions and that these antimicrobial films have potential applications in food packaging.

The bactericidal effects of allyl isothiocyanate in water

This study investigated the potential application of allyl isothiocyanate (AITC) for the disinfection of water by examining the bactericidal effects of this compound against inoculated Escherichia coli in autoclaved, de-chlorinated tap water and against the natural microbiota (heterotrophic plate count bacteria, HPCs) in a surface water. Bacteriostatic trials for AITC demonstrated growth inhibition against E. coli in tryptone soy broth, with AITC concentrations of 47.5, 63.3 and 126.6 mg/l inhibiting growth over two hours of contact time and 505.5 mg/l achieving complete growth inhibition for seven days. These AITC concentrations were then used to assess the bactericidal effect of AITC in water matrices, through which at least a 1.22-log10 reduction of both E. coli and HPCs was achieved in all trials, and up to a maximum of 2.93-log10 reduction of E. coli with 126.6 mg/l of AITC and two hours of contact time. AITC was consistently less effective against the HPCs in the surface water compared to the inoculated E. coli in tap water. Under the conditions that were tested, AITC was unable to reduce the HPC values below 100 CFU/ml, the World Health Organization guideline for safe drinking water, suggesting that AITC should not be used as a potable water disinfectant on its own; however, there may be applications for AITC as a biocide for non-potable water storage or treatment.

Inactivation of Salmonella on whole cantaloupe by application of an antimicrobial coating containing chitosan and allyl isothiocyanate

This study investigated the antimicrobial effect of a chitosan coating+allyl isothiocyanate (AIT) and nisin against Salmonella on whole fresh cantaloupes. Cantaloupes were inoculated with a cocktail of three Salmonella strains and treated with chitosan, chitosan+AIT, chitosan+nisin, and chitosan+AIT+nisin coatings. With AIT concentrations increasing from 10 to 60 μl/ml, the antibacterial effects of coating treatments against Salmonella increased. Chitosan coatings with 60 μl/ml AIT (chitosan+60AIT) reduced more than 5 log₁₀ CFU/cm² of Salmonella. The addition of nisin to the chitosan-AIT coating synergistically increased the antibacterial effect; coatings with nisin (25 mg/ml or 25,000 IU/ml)+30 μl/ml AIT resulted in a 4.8 log₁₀ reduction of Salmonella. The chitosan+60AIT coating significantly (p<0.05) reduced populations of native bacteria on cantaloupes to ca. 2 log₁₀ CFU/cm² during the first 6 days and populations remained unchanged through day 14 at 10 °C. The same coating treatment completely inactivated mold and yeast on cantaloupe at day 1 and no regrowth occurred even up to 14 days of storage. Scanning electron microscopy revealed that cell membrane damage and leakage of intercellular components occurred as a result of the chitosan-AIT coating treatments. No visual changes in overall appearance and color of cantaloupe rind and flesh due to coating treatments were observed. These results indicate that the application of an antimicrobial coating may be an effective method for decontamination of cantaloupes.

Effects of microencapsulated Allyl isothiocyanate (AITC) on the extension of the shelf-life of Kimchi

Allyl isothiocyanate (AITC) is a well-recognized antimicrobial agent but, application of AITC to food systems is limited due to its high volatility and strong odor. This study was performed to overcome the volatility of AITC by encapsulation using gum Arabic and chitosan and to investigate the effect of microencapsulated AITC as a natural additive on the shelf-life and quality of Kimchi. AITC loaded microparticles were prepared using gum Arabic and chitosan and were added to Kimchi at various concentrations (0-0.02%, w/w). The titratable acidity, pH, microbial changes, and sensory test of Kimchi were examined for 15days at different fermentation temperatures (4 and 10°C). The pH of Kimchi containing AITC microparticles was significantly higher than that of control and the higher the quantity of added AITC, the higher the pH became. The titratable acidity of Kimchi increased during storage especially, titratable acidity of control increased significantly higher than those of Kimchi with added AITC microparticles. The number of Leuconostoc and Lactobacillus species in Kimchi decreased with an increase in the concentration of AITC. The addition of AITC induced reduction of sour taste and improvement of the texture of Kimchi during fermentation. However, as the content of AITC increased, the scores of overall acceptability decreased due to the odor of AITC. These results indicate that addition of AITC (less than 0.1%) to Kimchi is an effective way of enhancing the shelf-life of Kimchi without reducing quality.

Antimicrobial activity of cyclodextrin entrapped allyl isothiocyanate in a model system and packaged fresh-cut onions

The aim of this work was to determine the antimicrobial effect of allyl isothiocyanate (AIT) entrapped in alpha and beta cyclodextrin inclusion complexes (ICs). In model experiments, AIT formulations were applied to filter paper discs fixed inside the lid of Petri dishes, where the agar surface was inoculated with the target organism (Penicillium expansum, Escherichia coli or Listeria monocytogenes). Solid phase microextraction coupled with gas chromatography was used to determine static headspace concentrations of AIT formulations. The antimicrobial effect of beta IC was determined during aerobic storage of packaged fresh-cut onions at 5 °C for 20 days. AIT entrapped in beta IC exhibited a significantly (p < 0.05) better antimicrobial effect compared to unentrapped AIT. AIT vapour concentrations in the static system were highest for unentrapped AIT followed by beta IC and alpha IC. Application of beta IC (200 μl/l) to packaged fresh-cut onions effectively decreased numbers of L. monocytogenes, which were also decreased at slower rates to undetectable levels on untreated cut onion. After 10 days, total aerobic counts were ca. 4 log CFU/g lower on onions treated with beta IC (100 and 200 μl/l) compared to untreated controls. This work demonstrates the utility of beta IC as an antimicrobial treatment with potential applications in packaged fresh-cut vegetable products.

Evaluation of antibacterial activity of 3-butenyl, 4-pentenyl, 2-phenylethyl, and benzyl isothiocyanate in Brassica vegetables

This study investigated antibacterial activities of 4 isothiocyanates (3-butenyl, 4-phentenyl, 2-phenylethyl, and benzyl isothiocyanate) against 4 Gram-positive bacteria (Bacillus cereus, Bacillus subtilis, Listeria monocytogenes, and Staphylococcus aureus) and 7 Gram-negative bacteria (Aeromonas hydrophila, Pseudomonas aeruginosa, Salmonella choleaesuis, Salmonella enterica, Serratia marcescens, Shigella sonnei, and Vibrio parahaemolyticus) by an agar disc diffusion assay. Benzyl isothiocyanate (> 90.00 mm inhibition zone diameter at 0.1 μL/mL) and 2-phenylethyl isothiocyanate (58.33 mm at 0.2 μL/mL) showed large inhibition zones especially against B. cereus. Also, 3-butenyl isothiocyanate (21.67 mm at 1.0 μL/mL) and 4-pentenyl isothiocyanate (19.67 mm at 1.0 μL/mL) displayed potent antibacterial activity against A. hydrophila. Benzyl and 2-phenylethyl isothiocyanate indicated higher activity against most of the pathogenic bacteria than 3-butenyl and 4-pentenyl isothiocyanate, and were more effective against Gram-positive bacteria than Gram-negative bacteria.

Inactivation of Salmonella in liquid egg albumen by antimicrobial bottle coatings infused with allyl isothiocyanate, nisin and zinc oxide nanoparticles

AIMS

To develop an antimicrobial bottle coating effective at inhibiting the growth of Salmonella in liquid egg albumen (egg white) and reduce the risk of human Salmonellosis.

METHODS AND RESULTS

Four-ounce glass jars were coated with a mixture of polylactic acid (PLA) polymer and antimicrobial compounds containing 100-500 μl allyl isothiocyanate (AIT), 250 mg nisin, 250 mg zinc oxide nanoparticles per jar or their combinations. The coated jars contained 100 ml of liquid egg white (LEW) inoculated with a three-strain Salmonella enterica ssp. enterica cocktail at populations of 10(3) or 10(7) CFU ml(-1) and stored at 10°C for 28 days. The PLA coating with 500 μl AIT completely inactivated 3 and 7 log CFU ml(-1) of Salmonella after 7 and 21 days of storage, respectively. The PLA coating with 200 μl AIT in combination with 250 mg nisin reduced Salmonella populations to an undetectable level (<10 CFU ml(-1) ) after 21 days of storage.

CONCLUSIONS

PLA coatings containing AIT alone or in combination with nisin effectively inactivated salmonellae in LEW.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study demonstrated the commercial potential of applying the antimicrobial bottle coating method to liquid eggs and possibly other fluid food products.

Stability and antimicrobial activity of allyl isothiocyanate during long-term storage in an oil-in-water emulsion

This study investigated the stability and antimicrobial activity of allyl isothiocyanate (AITC) in medium chain triglyceride (MCT) or soybean oil (SBO) dispersed in an oil-in-water (o/w) system during long-term storage. Oil type, content, and oxidative stability affect the stability and antimicrobial activity of AITC during storage. High oil content is favorable for AITC stability in the emulsion. Notably, AITC with MCT is more stable than AITC with SBO with the same oil content. Consequently, AITC with MCT is more effective than AITC with SBO in inhibiting G(-) bacteria (E. coli O157:H7, Salmonella enterica, and Vibrio parahaemolyticus) and G(+) bacteria (Staphylococcus aureus and Listeria monocytogenes).

Active packaging of fresh chicken breast, with allyl isothiocyanate (AITC) in combination with modified atmosphere packaging (MAP) to control the growth of pathogens

Listeria monocytogenes and Salmonella typhimurium are major bacterial pathogens associated with poultry products. Ally isothiocyanate (AITC), a natural antimicrobial compound, is reportedly effective against these pathogenic organisms. A device was designed for the controlled release of AITC with modified atmosphere packaging (MAP), and then evaluated for its ability to control the growth of L. monocytogenes and S. typhimurium on raw chicken breast during refrigerated storage. In order to obtain controlled release during the test period, a glass vial was filled with AITC and triglyceride. It was then sealed using high-density polyethylene film. The release of AITC was controlled by the concentration (mole fraction) of AITC in the triglyceride and by the AITC vapor permeability through the film. The fresh chicken samples were inoculated with one or the other of the pathogens at 10(4) CFU/g, and the packages (with and without AITC-controlled release device) were flushed with ambient air or 30% CO(2)/70% N(2) before sealing, and then stored at 4 degrees C for up to 21 d. The maximum reduction in MAP plus AITC (compared to MAP alone) was 0.77 log CFU/g for L. monocytogenes and 1.3 log CFU/g for S. typhimurium. The color of the chicken breast meat was affected by the concentration of AITC. Overall, a release rate of 0.6 microg/h of AITC was found to not affect the color, whereas at 1.2 microg/h of AITC the surface of the chicken was discolored.