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Aouidi F.,University of Carthage | Aouidi F.,French National Center for Scientific Research | Aouidi F.,Tunisian National Institute of Applied Sciences and Technology | Ayari S.,University of Carthage | And 4 more authors.
Food Chemistry | Year: 2011

Olive leaves are commercialized for their antioxidative value due to their valuable phenolic compounds. The present study aimed to evaluate the effect of gamma irradiation on microbial load, on antioxidative properties and on phenolic compounds of air-dried olive leaves. Irradiation was applied up to 25 kGy (5 kGy intervals) to powdered and intact samples. Total aerobic bacteria, yeast and mold, and lactic acid bacteria were counted after gamma irradiation. Decontamination was obtained at 20 kGy. The radioresistance of microbial population was high with D10 values between 9.74 and 25.12 kGy. Besides, gamma irradiation up to 25 kGy was found to maintain the antioxidant capacity, molecular mass distribution of polyphenolics, total phenolics, ortho-diphenols, flavonoids, oleuropein, verbascoside and rutin contents. To conclude, the improvement of the microbial quality of air-dried olive leaves, without affecting phenolic composition and antioxidative properties, can be successively achieved by the application of gamma irradiation treatment. © 2011 Elsevier Ltd. All rights reserved.

Ayari S.,INRS Institute Armand Frappier | Ayari S.,National Center for Nuclear science and Technologies | Ayari S.,Tunisian National Institute of Applied Sciences and Technology | Dussault D.,INRS Institute Armand Frappier | And 2 more authors.
Food Control | Year: 2013

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 γ-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 D10 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 γ-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. © 2013 Elsevier Ltd.

Benbettaieb N.,National Center for Nuclear science and Technologies | Benbettaieb N.,University of Burgundy | Assifaoui A.,University of Burgundy | Karbowiak T.,University of Burgundy | And 2 more authors.
Radiation Physics and Chemistry | Year: 2016

This work deals with the study of the release kinetics of antioxidants (ferulic acid and tyrosol) incorporated into chitosan-gelatin edible films after irradiation processes. The aim was to determine the influence of electron beam irradiation (at 60 kGy) on the retention of antioxidants in the film, their release in water (pH=7) at 25 °C, in relation with the barrier and mechanical properties of biopolymer films. The film preparation process coupled to the irradiation induced a loss of about 20% of tyrosol but did not affect the ferulic acid content. However, 27% of the ferulic acid remained entrapped in the biopolymer network during the release experiments whereas all tyrosol was released. Irradiation induced a reduction of the release rate for both compounds, revealing that cross-linking occurred during irradiation. This was confirmed by the mechanical properties enhancement which tensile strength value significantly increased and by the reduction of permeabilities. Although molecular weights, molar volume and molecular radius of the two compounds are very similar, the effective diffusivity of tyrosol was 40 times greater than that of ferulic acid. The much lower effective diffusion coefficient of ferulic acid as determined from the release kinetics was explained by the interactions settled between ferulic acid molecules and the gelatin-chitosan matrix. As expected, the electron beam irradiation allowed modulating the retention and then the release of antioxidants encapsulated. © 2015 Elsevier Ltd.

Benbettaieb N.,National Center for Nuclear science and Technologies | Benbettaieb N.,University of Burgundy | Kurek M.,University of Burgundy | Debeaufort F.,University of Burgundy
Journal of the Science of Food and Agriculture | Year: 2014

BACKGROUND: The increased use of synthetic packaging films has led to a high ecological problem due to their total non-biodegradability. Thus, there is a vital need to develop renewable and environmentally friendly bio-based polymeric materials. Films and coatings made from polysaccharide polymers, particularly chitosans and gelatins have good gas barrier properties and are envisaged more and more for applications in the biomedical and food fields, as well as for packaging. In this study a casting method was used to develop an edible plasticised film from chitosan and gelatin. Aiming to develop a blend film with enhanced properties, the effects of mixing chitosan (CS) and gelatin (G) in different proportions (CS:G, 75:25, 50:50, 25:75, w/w) on functional and physico-chemical properties have been studied. RESULTS: Mean film thickness increased linearly (R2 = 0.999) with surface density of the film forming solution. An enhancement of mechanical properties by increasing the tensile strength (38.7 ± 11 MPa for pure chitosan and 76.8 ± 9 MPa for pure gelatin film) was also observed in blends, due to gelatin content. When the gelatin content in blend films was increased an improvement of both water vapour barrier properties [(4 ± 0.3) × 10-10 g m-1 s-1 Pa-1 for pure chitosan and (2.5 ± 0.14) × 10-10 g m-1 s-1 Pa-1 for pure gelatin, at 70% RH gradient] and oxygen barrier properties ((822.62 ± 90.24) × 10-12 g m-1 s-1 Pa-1 for blend film chitosan:gelatin (25:75 w/w) and (296.67 ± 18.76) × 10-12 g m-1 s-1 Pa-1 for pure gelatin was observed. Fourier transform infrared spectra of blend films showed a shift in the peak positions related to the amide groups (amide-I and amide-III) indicating interactions between biopolymers. CONCLUSIONS: Addition of gelatin in chitosan induced greater functional properties (mechanical, barrier) due to chemical interactions, suggesting an inter-penetrated network. © 2014 Society of Chemical Industry.

BenBettaieb N.,National Center for Nuclear science and Technologies | BenBettaieb N.,University of Burgundy | Karbowiak T.,University of Burgundy | Debeaufort F.,University of Burgundy
Food Hydrocolloids | Year: 2015

The objective of this work was to better display the effect of electron beam accelerator doses (0, 20, 40 and 60kGy) on structural, mechanical and barrier properties of edible lightly plasticized chitosan-fish gelatin blend film. From Electron Spin Resonance (ESR), signal at 3500G for blend film was identified as free radical formation during irradiation, which might introduce intermolecular cross-linking into the polymer matrix, thus affecting structural properties. Tensile Strength (TS) for gelatin film significantly increased with growing irradiation doses (improved by 30% for 60kGy), but the TS of chitosan and blend films were not significantly affected. On the contrary, irradiation significantly reduced elongation at break (%E) for chitosan and blend film up to 50% whereas it twice increased the Young modulus. Moisture barrier efficiency (30-84% RH gradient) of blend films was slightly improved after irradiation. Oxygen permeability also decreased after 60kGy irradiation treatment, for both chitosan and blend films. Surface hydrophobicity tended to decrease after irradiation. From Fourier Transform Infra-Red (FTIR) spectra, some noticeable differences were observed after irradiation, in the relative intensity and position of bands in the region between 3600 and 2800cm-1 and between 1700 and 1500cm-1. UV-vis analysis shows that all films displayed an absorbance peak between 280 and 385nm. These peaks are shifted toward higher wavelengths after irradiation This clearly showed some modifications in the interactions (hydrogen bonds, amide groups) between polymer chains induced by the irradiation. © 2014 Elsevier Ltd.

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