18D-19 |
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N. L. RAMÍREZ-CHAVARIN1, E. Ponce-Alquicira1, M. C. Wacher-Rodarte2, I. Guerrero-Legarreta1, and M. L. Pérez-Chabela1. (1) Departamento de Biotecnología, Universidad Autónoma Metropolitana, Iztapalapa, Apartado Postal 55-535, Mexico D.F., 09340, Mexico, (2) Departamento de Alimentos, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico D.F., Mexico The use of bioprotective strains have been studied for several years as a means to extend meat products shelf life. Inoculation of sausages with strains highly competitive against undesirable microflora could play a double role: increasing sanitation and extending shelf life. However, in order to be efficient the bioprotector should be isolated from the same ecological niche where it will be applied. The objective of this work was to isolate and identified heat resistant lactic acid bacteria from meat products merchandised in Mexico City, aimed to extend cooked sausage shelf life. Strains were isolated from raw meat and cooked meat products sold in bulk in supermarkets. Biochemical tests were: Gram stain, catalase and oxidase activity, growth on 6.5% sodium chloride, arginine and esculine hydrolysis, nitrate reduction, CO2 production and acid production, growth on MRS medium at 20oC, motility, and growth on anaerobic conditions. In addition API 50 CHL kits were applied. Strains identified as presumptive lactic acid bacteria were inoculated in MRS broth and incubated until OD=1.0; cell suspension were then subjected to heating in a water bath at 50, 60 and 70oC during 15, 30, 45 and 60 min, cooled down to room temperature (approximately 18oC) and inoculated into MRS agar. Surviving cells were counted and reported. Nineteen strains were considered as presumptive lactic acid bacteria; however, after heat treatment only 11 survived. Five strains were discarded after the biochemical tests were carried out; the other 6 strains were identified by API 50 kits as Pediococcos pentosaceus (3 strains) and Lactobacillus plantarum (3 strains), no serotypes were specified. Isolation and characterization of native heat resistant strains aimed as bioprotectors have the advantage of being naturally selected, hence more efficient, in native meat products. At the same time of increasing shelf life, bioprotectors are considered as “natural” additives.
Session 18D, Food Microbiology: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |