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Effect of the addition of various additives on the irradiation sensitivity of Escherichia coli and Salmonella typhi present in ground beef.

Chiasson, Francine (2003). Effect of the addition of various additives on the irradiation sensitivity of Escherichia coli and Salmonella typhi present in ground beef. Mémoire. Québec, Université du Québec, Institut National de la Recherche Scientifique, Maîtrise en microbiologie appliquée, 172 p.

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Résumé

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Ground beef is an easily perishable food product. It is linked to severa} cases of food poisoning. Severa} foodbome pathogens can be found at a very high concentration. One way to assure the innocuity and to improve the bacterial quality of ground beef is the use of irradiation. Since December 1997, the United States of America has approved the use of irradiation to control or eliminated pathogenic bacteria. This research was aimed to evaluate the effect of severa} additives on the irradiation sensitivity of E. coli and S. typhi. The goal was to find additives that would have a synergical effect with the irradiation treatment. The irradiation sensitivity (010) of each bacteria was determined in the presence of each active compound. Following that, the best combination of additives was determined. Also, the irradiation sensitivity of each bacteria in ground beef was determined in the presence of the best combination of additives packed under different temperature and atmospheres. Results from this study demonstrated that the best active compound was trans-cinnamaldehyde (at a concentration of 1.5 % forE. coli and 0.89% for S. typhi), with a D10 of 0.037 kGy forE. coli and of 0.139 kGy for S. typhi. Effectiveness of other additives in decreasing order were : carvacrol (0.88 % for E. coli and 1.15 % for S. typhi), thymol (1.14 % for E. coli and 1.60 % for S. typhi) and thyme (2.33 % forE. coli and 2.75 % for S. typhi), where the D10 measured were 0.103 kGy, 0.087 kGy and 0.090 kGy respective}y for E. coli and 0.208 kGy, 0.210 kGy and 0.260 kGy respectively for S. typhi. Not ali the additives tested increased the irradiation sensitivity of E. coli and S. typhi. Addition of ascorbic acid increased the irradiation resistance of E coli with a D10 value of 0.141 kGy compared to 0.126 kGy for the control, and had no effect on S. typhi (D10 : 0.521kGy). Thus, of the nine additives tested, carvacrol, ascorbic acid and tetrasodium pyrophosphate were selected to be the best. Trans-cinnamaldehyde was not selected for its inappropriate odour. Results also indicated that the best bioactive additives were carvacrol alone or in combination with tetrasodium pyrophosphate. The D10 were respectively 0.057 kGy and 0.057 kGy forE. coli. For S. typhi, the Dto with carvacrol and the mixture of carvacrol (1.0 %) and tetrasodium pyrophosphate (0.1 %) were respectively 0.235 kGy and 0.254 kGy. The mixture of carvacrol and tetrasodium pyrophosphate was used for the determination of the irradiation sensitivity under various atmospheres and irradiation temperatures. The best results were obtained under MAP (60% 02 - 30 % C02 - 10 % N2) in the presence of the mixture of additives, with Dto of 0.046 kGy forE. coli and 0.053 kGy for S. typhi respectively. Under frozen conditions, both E. coli and S. typhi were more resistant to irradiation than under refrigerated condition, as the D10 under frozen conditions increased from 0.055 kGy to 0.128 kGy for E. coli and from 0.254 kGy to 0.297 kGy for S. typhi.

Type de document: Mémoire
Directeur de mémoire/thèse: Lacroix, Monique
Informations complémentaires: Résumé avec symboles
Mots-clés libres: dehalogenation ; irradiation ; additif ; bacterie
Centre: Centre INRS-Institut Armand Frappier
Date de dépôt: 12 mai 2014 20:52
Dernière modification: 18 déc. 2015 16:58
URI: http://espace.inrs.ca/id/eprint/2086

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