Ethylene-vinyl acetate copolymer (EVA) was modified by hydrolysis using dielectric heating. The modified EVA was characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis (TG), 1 H Nuclear magnetic resonance (NMR), gel permeation chromatography, and small-angle X-ray scattering. The results showed that the EVA was hydrolyzed with degree between 36.1 and 42.6% according to 1 H NMR and TG results. The relative reaction rate for the sample prepared in the oil bath was 9%/h, while in the dielectric was 150%/h for 15 min. This significant improvement was due to the specific effect of microwave-assisted reactions through dipole rotation and ionic polarization contributions. The hydrolysis reaction promoted a reduction of the pendent group size of EVA backbone. This change directly contributed to increasing melt temperature, crystallization temperature, melt and crystallization enthalpies. Also, decreased the long period, increased the volume crystallinity, and caused reductions amorphous/ crystalline interface and two-phase model deviations.
In the present study, tannin extracts (rinsed or not) were compared to the use of sodium hypochlorite and tap water on fresh cut crisp leaf lettuce stored under modified atmosphere packaging. Effects of these sanitizers on total color difference and microbial levels of the product after sanitization and storage for 9 days at 3°C were evaluated. Performance of rinsed SM(r) tannin extract was comparable to the results of chlorine solution for all the analyzed parameters and; furthermore, that extract presented a high reduction in the initial bacterial count of minimally processed lettuce. However, storage of tannin extracts, did not impart better outcomes than the use of tap water. Therefore, the tannin extract storage SM(r) could be used in washing water to reduce the initial microbiological load, avoiding cross contamination in vegetables minimally processed.
Pseudomonas aeruginosa has been found in bottled natural mineral water, even though its presence is not allowed in this product by different food regulations. This study aimed to investigate the inactivation of P. aeruginosa present in mineral water by vB_PaeM_CEB_DP1 (short name DP1) bacteriophage immobilized on ethylene-vinyl acetate (EVA) copolymer used as seal caps of plastic bottles. EVA was chemically modified using microwave-assisted alcoholysis, improving polymer-phage binding. After that, DP1 phage was attached to EVA and EVA-OH copolymers and both surfaces were tested for plaque formation using P. aeruginosa. Then, both materials containing immobilized phages were used as seal caps of plastic bottles and its antimicrobial capacity was tested against P. aeruginosa contaminating mineral water.The EVA-OH resulted in higher hydrogen bond density that contributed significantly to the phage immobilization on the polymer surface. The polymers containing immobilized phages were able to reduce 0.53 log of P. aeruginosa population present inside mineral water bottles after 14 days.
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