The aim of this study was to evaluate the effect of combining marinating and γ-irradiation at doses of 1, 1.5 and 3 kGy on Escherichia coli O157:H7, Salmonella typhimurium and Clostridium sporogenes in raw meat packed under vacuum and stored at 4 °C and to estimate its safety and shelf-life. Further, the effect of combined treatments on sensorial, nutritional values (lipid oxidation, concentration of thiamin and riboflavin) and color was evaluated. The study demonstrated that the use of marinade in combination with a low dose of γ-irradiation (1.5 kGy) could act in synergy to reduce to undetectable level of pathogenic bacteria and increase the shelf-life of ready-to-cook meat loin without affecting its sensorial and nutritional quality.

The marine environment is a proven source of structurally complex and biologically active compounds. In this study, the antimicrobial effects of a small collection of marine-derived extracts and isolates, were evaluated against 5 foodborne pathogens using a broth dilution assay. Results demonstrated that algal extracts from Padina and Ulva species and cyanobacterial compounds antillatoxin B, laxaphycins A, B and B3, isomalyngamide A, and malyngamides C, I and J showed antimicrobial activity against Gram positive foodborne pathogens (Listeria monocytogenes, Bacillus cereus and Staphylococcus aureus) at low concentrations (⩽ 500 μg/ml). None of the algal extracts or cyanobacterial isolates had antibacterial activity against Gram negative bacteria (Escherichia coli and Salmonella enterica serovar Typhimurium).

The objective of this study was to evaluate the impact of seven independent factors consisting of sodium nitrite, pH, sodium chloride, sodium acetate, sodium lactate syrup, calcium propionate and a blend of nisin and hop alpha acids on the growth rate of Listeria monocytogenes in ham as a model of ready-to-eat (RTE) meat products. A central composite consisted of seven factors mentioned above was designed and the response surface methodology was applied for creating a mathematic model to predict the growth rate of L. monocytogenes in RTE meat products. Six parameters showed a significant (P ≤ 0.1) influence on the growth rate of L. monocytogenes. Only the blend of nisin and hop alpha acids did not show any significant effect (P > 0.1) in the concentrations used in this study. Increasing concentration of sodium chloride, sodium nitrite, sodium acetate, potassium lactate and calcium propionate in meat reduced bacterial growth rate while increasing pH in meat increased the growth rate of L. monocytogenes. The current mathematical equation will be an important tool in order to reduce the required number of challenge studies performed in order to ensure a safe food product.

Lactococcus lactis subsp lactis BSA (L. lactis BSA) was isolated from a commercial fermented product (BSA Food Ingredients, Montreal, Canada) containing mixed bacteria that are used as starter for food fermentation. In order to increase the bacteriocin production by L. lactis BSA, different fermentation conditions were conducted. They included different volumetric combinations of two culture media (the Man, Rogosa and Sharpe (MRS) broth and skim milk), agitation level (0 and 100 rpm) and concentration of commercial nisin (0, 0.15, and 0.30 µg/ml) added into culture media as stimulant agent for nisin production. During fermentation, samples were collected and used for antibacterial evaluation against Lactobacillus sakei using agar diffusion assay. Results showed that medium containing 50 % MRS broth and 50 % skim milk gave better antibacterial activity as compared to other medium formulations. Agitation (100 rpm) did not improve nisin production by L. lactis BSA. Adding 0.15 µg/ml of nisin into the medium-containing 50 % MRS broth and 50 % skim milk caused the highest nisin activity of 18,820 AU/ml as compared to other medium formulations. This activity was 4 and ~3 times higher than medium containing 100 % MRS broth without added nisin (~4700 AU/ml) and 100 % MRS broth with 0.15 µg/ml of added nisin (~6650 AU/ml), respectively.

This study investigated the effect of combined treatments involving low doses of gamma irradiation in combination with nisin and carvacrol as antimicrobial agents on the growth and potential toxicity of Bacillus cereus, during storage temperature abuse. The chicken rice was spiked with endospores and was incubated at 10 degrees C for 2 weeks. Microbial population was examined using plate counting on MYP agar. Toxigenic potential was measured through the record of enterotoxins and phosphatidylcholine-specific phospholipase C (PC-PLC) activity. The results showed that samples processed with a combination of low irradiation dose; (D-10, 1/2 D-10) and reduced concentration of antibacterial agents (MIC, 1/2 MIC), resulted in a significant decrease (p <= 0.05) of B. cereus count compared to the samples treated only with higher amount of antimicrobial agents (2 x MIC). Toxin production was also delayed by irradiation and a total absence of enterotoxin was observed in irradiated rice at 1.8 kGy in the presence of nisin alone or in combination with carvacrol until the 12th day of storage at 10 degrees C. Reduced proliferation of B. cereus obtained by combined treatment was associated with a limitation of toxin production and led systematically to significant decrease (p <= 0.05) of PC-PLC activity during storage. (C) 2016 Elsevier Ltd. All rights reserved.

The aim of this study was to evaluate the effect of γ-radiations on the heat shock proteins (Hsps) content of strains of Enterobacteriacea and Pantoea agglomerans. Radiation treatments (1 and 3.5 kGy) were performed to highlight the radiotolerance. Total proteins were extracted after irradiation treatments and heat shock proteins (Hsp) of interest (GroEL, GroES and DnaK) were visualized and quantified using Western blot analysis. It was found that GroEL synthesis was increased significantly (P ≤ 0.05) for both strains while the DnaK seemed to be down regulated for the strain from ATCC 49174. Basal level of GroEL proteins was much higher in the strain isolated from carrots. The obtained results indicated the modification effects of γradiations on the Hsps at cellular level.

The purpose of this research was to evaluate the application of commercially available essential oils (EOs) and oleoresins to control bacterial pathogens for ready to eat food. In this study, sixty seven commercial EOs, oleoresins (ORs) and pure compounds were used to evaluate in vitro their antimicrobial activity against six food pathogens. These products were first screened for their antimicrobial activity using disk diffusion assay. Forty one products were then chosen for further analysis to determine their minimum inhibitory concentration against 6 different bacteria. There were 5 different products (allyl isothiocyanate, cinnamon Chinese cassia, cinnamon OR, oregano and red thyme) that showed high antimicrobial activity against all tested bacteria. Further analysis examined the effect of four selected EOs on controlling the growth rate of mixed cultures of Listeria monocytogenes in ham. A reduction of the growth rate by 19 and 10% was observed when oregano and cinnamon cassia EOs were respectively added in ham at a concentration of 500 ppm.

Currently little information exists on the response of Bacillus cereus after repetitive exposure to combined mild treatments involving antimicrobials and gamma irradiation. Therefore, the aim of this present study was to evaluate the radiation stress on growth and physiology of B. cereus LSPQ 2872 vegetative cells at stationary phase, following exposure to single and repetitive sub-lethal gamma-radiation treatment at 1 kGy simultaneously with carvacrol alone or combined with nisin at sub-inhibitory concentrations. Results indicated that the combination of carvacrol and nisin significantly enhance the radiation sensitivity of B. cereus since lower D-10 values were recorded after both single and repetitive irradiation treatments. Flow cytometric analysis of radiation-stressed B. cereus cells following repetitive treatment revealed the heterogenic behaviour of the bacterium leading to the induction of a radiation tolerance response. When compared to carvacrol alone, the combination of carvacrol and nisin developed also increased radioresistance if repetitively processed with gamma-radiation at 1 kGy, since the decrease percentage of dead cells was accompanied by an increase in the number of injured cells. However, good agreement was not found between classical plate counting (log cfu reductions) and flow cytometry method. For both antimicrobials, the increase of radioresistance after repetitive mild treatment was not accompanied by augmentations of lag phase or growth rate. The structural changes of the outer membranes were assessed by TEM analysis and results revealed that radioresistance might be related to changes in the cell wall. (C) 2013 Elsevier Ltd. All rights reserved.

Carbon nanotube (CNT) reinforced (0.050.5% by wt) polycaprolactone (PCL)-based composites were prepared by compression molding. Addition of 0.2% CNT caused a 131% improvement of tensile strength (TS) of PCL films. The tensile modulus (TM) and elongation at break (Eb) of PCL were also significantly improved with the addition of CNT. The water vapor permeability of PCL was 1.51 g.mm/m2.day but 0.2% CNT containing PCL films showed 1.08 g.mm/m2.day. Similarly, the oxygen transmission rate (OTR) of PCL films was found to decrease with the addition of CNT. But, carbon dioxide transmission rate (CO2TR) of PCL film was improved due to incorporation of CNT. Effect of gamma radiation on PCL films and CNT reinforced PCL-based composites were also studied. The TS of the irradiated (10 kGy) PCL films gained to 75% higher than control sample. The TS of the 0.2% CNT reinforced composite film was reached to 41 MPa at 15 kGy dose. The barrier properties of non-irradiated and irradiated (10 kGy) PCL films and composites (0.2% CNT reinforced) were also measured. Both PCL films and composites showed lower values of WVP upon irradiation and indicated better water vapor barrier. The OTR and CO2TR of the irradiated (10 kGy) PCL films and composites were decreased compared to their counterparts. Surface and interface morphologies of the composites were studied by scanning electron microscopy. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Irradiation combined with other processes can contribute to insuring food safety to consumers and controlling severe losses during transportation and commercialisation. We have demonstrated that using in synergy with other treatments; a lower dose could be used to eliminate pathogenic bacteria and permit a better protection of the sensorial quality and to prolong the shelf life of foods. Results indicated that some bacteria are more sensitive to irradiation under modified atmosphere (MAP) and the presence of active compound can increase the bacterial radiosensitivity by more than 4 times under air and by more than 10 times under MAP. Mild heat treatment or addition of natural antimicrobial compounds before irradiation treatment has also permitted an increase of Bacillus cereus radiosensitization. An increase of the bacterial radiosensitization of 1.5 and 1.56 was respectively observed. The effectiveness of the use of edible coating containing natural antimicrobial compounds, modified atmosphere packaging (MAP) or mild treatment before irradiation treatment was demonstrated in order to inactivate Listeria monocytogenes, Salmonella typhimurium, Escherichia coli and Bacillus cereus growth or B. cereus spore germination, to increase the bacterial sensitivity to irradiation, to reduce the water loss and to extend the shelf life of the food when stored at 4 °C. Also, the use of edible coating previously crosslinked by irradiation have permitted a better control of the active compounds release. Studies of combined treatments were used in ready to eat vegetables, fruits and meat products.

Nanocrystalline cellulose (NCC) reinforced poly(caprolactone) (PCL) composites were prepared by compression molding. The NCC content varied from 2 to 10% by weight. NCC played a significant role in improving the mechanical properties of PCL. The addition of 5 wt % NCC caused a 62% improvement of the tensile strength (TS) value of PCL films. Similarly, tensile modulus (TM) values were also improved by NCC reinforcement but elongation at break (Eb) values decreased montonically with NCC content. The water vapor permeability (WVP) of PCL was 1.51 g center dot mm/m2 center dot day center dot kPa, whereas PCL films containing 5 wt % NCC showed a WVP of 1.22 g center dot mm/m2 center dot day center dot kPa. The oxygen transmission rate (OTR) and carbon dioxide transmission rate (CO2TR) of PCL decreased by 19 and 17%, respectively, with 5 wt % NCC incorporation. It was found that the mechanical and barrier properties of both PCL and PCL-NCC composites further improved with 10 kGy gamma irradiation treatment. The combination of NCC and radiation significantly increased the TS, TM, and Eb (by 156, 123, and 80%, respectively, compared to untreated PCL). The WVP, OTR, and CO2TR decreased by 25-35% with respect to untreated PCL. The surface and interface morphologies of the PCL-NCC composites were studied by scanning electron microscopy and suggested homogeneous distribution of NCC within the PCL matrix. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Chitosan (0.1–1%, w/w), dissolved in 2% acetic acid solution, was added into 1% methylcellulose (MC)-based formulation containing 0.5% vegetable oil, 0.25% glycerol and 0.025% Tween®80. Films were prepared by casting. Puncture strength (PS), puncture deformation (PD), viscoelasticity coefficient and water vapour permeability (WVP) of the films were measured. The PS value of 312 N/mm was observed for MC-based films containing 0.25% chitosan. Values of PD, viscoelasticity coefficient and WVP of these films were 5.0 mm, 44.1%, and 6.0 g mm/m2 day kPa, respectively. The MC-based films containing 0.25% chitosan were also exposed to gamma radiation (0.5–50 kGy). The PS of the treated films decreased significantly from 312 at 0 kGy to 201 N/mm when treated at a dose of 50 kGy. However, WVP values were not affected by increasing irradiation the dose used. The Fourier Transform Infrared spectroscopy supported the molecular interactions due to addition of chitosan in MC-based films. Thermo gravimetric analysis and differential scanning calorimetric experiments showed that thermal properties of the films were significantly improved by chitosan loading. Surface topography of the films was studied by scanning electron microscopy and found rougher due to chitosan addition.

Methylcellulose (MC)-based films were prepared by solution casting from its 1% aqueous suspension containing 0.25% glycerol. Trimethylolpropane trimethacrylate (TMPTMA) monomer (0.1-2% by wt) along with the glycerol was added to the MC suspension. The films were cast and irradiated from a radiation dose varied from 0.1 to 10 kGy. Then the mechanical properties such as tensile strength (TS), tensile modulus (TM), and elongation at break (Eb) and barrier properties of the films were evaluated. The highest TS (47.88 PMa) and TM (1791.50 MPa) of the films were found by using 0.1% monomer at 5 kGy dose. The lowest water vapor permeability (WVP) of the films was found to be 5.57 g·mm/m(2)·day·kPa (at 0.1% monomer and 5 kGy dose), which is 12.14% lower than control MC-based films. Molecular interactions due to incorporation of TMPTMA were supported by FTIR spectroscopy. A band at 1720 cm(-1) was observed due to the addition of TMPTMA in MC-based films, which indicated the typical (C═O) carbonyl stretching. For the further improvement of the mechanical and barrier properties of the film, 0.025-1% nanocrystalline cellulose (NCC) was added to the MC-based suspension containing 1% TMPTMA. Addition of NCC led to a significant improvement in the mechanical and barrier properties. The novelty of this investigation was to graft insoluble monomer using γ radiation with MC-based films and use of biodegradable NCC as the reinforcing agent.

Methylcellulose (MC)-based films were prepared by casting from its 1% aqueous solution containing 0.5% vegetable oil, 0.25% glycerol and 0.025% Tween®-80. Puncture strength (PS), puncture deformation (PD) and water vapor permeability (WVP) of the films were found to be 147N/mm, 3.46mm, and 6.34gmm/m2daykPa, respectively. The monomer, 2-hydroxyethyl methacrylate (HEMA) (0.1–1%, w/w) was incorporated into the MC-based solution and films were prepared by casting. Films were then exposed to gamma radiation (5–25kGy) and it revealed that 1% HEMA containing films showed the highest PS values (282N/mm at 10kGy). Silane monomer (3-aminopropyl tri-ethoxy silane) (0.1–1%, w/w) was also added into the MC-based films and were found to improve the strength of the films significantly. In comparison between HEMA and silane treatment onto MC-based films, it was observed that silane performed better strength and barrier properties. Surface morphology of the monomer treated films was examined by scanning electron microscopy and suggested better appearance than MC-based film.

Biodegradable films were prepared from a 1% aqueous solution of methylcellulose (MC) and 0.25% glycerol. Trimethylolpropane trimethacrylate (TMPTMA, 0.1% w/w) was added to the MC solution, and the resulting cast films, MC-g-TMPTMA, were gamma-irradiated at 0.1-10 kGy. Mechanical properties such as tensile strength (TS), tensile modulus (TM), elongation at break (Eb), and barrier properties of the films were compared after TMPTMA grafting. The incorporation of 0.025-1% cellulose nanocrystals (CNC), as a reinforcing agent in film-forming solution, led to significant improvement of some film properties. Mechanical measurements showed that 0.025% CNC filling made it possible to improve significantly the TS of films to 67 MPa under 1 kGy and their Eb to 31.8% under 0.5 kGy. In addition, WVP measurements indicated that the lowest WVP of films was determined for 1% CNC filling under 0.5 kGy, with a value of 4.03 g. mm/m(2). day. kPa corresponding to a 24% reduction compared to the control. This investigation made it possible to establish an optimal formulation of MC-g-TMPTMA-grafted films reinforced with 0.025% CNC under 0.5-1 kGy, with better mechanical and barrier properties obtained simultaneously.

Chitosan films were prepared by casting from its 1% (w/w) solution. Tensile strength (TS) and tensile modulus (TM) of chitosan films were found to be 30MPa and 450MPa, respectively. Silane monomer (3-aminopropyl tri-methoxysilane) (0.25%, w/w) was added into the chitosan solution (1%, w/w) and films were casted. Then films were exposed to gamma radiation (5–25kGy) and mechanical properties were investigated. It was found that at 10kGy, the values of TS and TM were improved significantly. Silane grafted chitosan film reinforced poly(caprolactone) (PCL)-based tri-layer composites were prepared by compression molding. Silane improved interfacial adhesion between chitosan and PCL in composites. Surface of the films was investigated by scanning electron microscope (SEM) and found better morphology for silane grafted films.

Chitosan was dissolved in 2 % aqueous acetic acid solution and the films were prepared by solution casting. Values of tensile strength (TS), tensile modulus (TM), elongation at break (Eb %) and water vapor permeability (WVP) of the chitosan films were found to be 30 MPa, 450 MPa, 8 % and 4.7 g mm/m(2) day kPa, respectively. Poly(caprolactone) (PCL) films were prepared from its granules by compression molding and the values of TS, TM, Eb and WVP were 14 MPa, 220 MPa, 70 % and 1.54 g mm/m(2) day kPa, respectively. PCL was reinforced with chitosan films, and composite films were prepared by compression molding. Amount of chitosan in the composite films varied from 10 to 50 % (w/w). It was found that with the incorporation of chitosan films in PCL, both the values of TS and TM of composite films increased significantly. The highest mechanical properties were found at 50 % (w/w) of chitosan content. The Oxygen transmission rate (OTR) of composite film was found to decrease significantly than PCL films. Thermal properties of the composite were also improved as compared to PCL. The water uptake test of the composite also showed promising results with a good stability of composite films. The interface of the composite was investigated by scanning electron microscopy and showed good interfacial adhesion between PCL and chitosan films.

The present study evaluated the response of Bacillus cereus LSPQ 2872 vegetative cells, following exposure to single and repetitive sublethal γ-radiation treatment at 1 kGy alone or in combination with nisin at its maximum tolerated concentration, in BHI broth supplemented with 0.5% glucose. Results showed that B. cereus has the capability to develop increased resistance to subsequent cycles of gamma irradiation and a significant increase (p ≤ 0.05) of the relative radiation resistance (D10) value was noticed after the fourth irradiation at 1 kGy. The sequence and the repetitive sublethal treatment of γ-radiation with nisin affected significantly (p ≤ 0.05) B. cereus radio-tolerance since lower D10 values were recorded. Our results showed that the response of B. cereus to repetitive mild bactericidal treatment was accompanied by relevant modifications in the cell properties leading to the increased resistance. Transmission electron microscopy revealed that resistance might be related to changes in the cell wall. Multiparameter flow cytometry revealed effectively diverse physiological changes that B. cereus underwent during development of radio-resistance. The development of increased resistance to gamma irradiation was accompanied by an increase of the percentage of injured and viable cells at the expense of dead cells. Nisin treated cells developed also increased radio-resistance if repetitively processed with γ-radiation at sublethal doses which was not demonstrated by plate counting.