88D-11 |
Metabolic patterns of spoilage microorganisms and biopreservative lactic acid bacteria in meat substrates |
M. SIGNORINI, E. Ponce-Alquicira, and I. Guerrero Legarreta. Departamento de Biotecnologia, Universidad Autonoma Metropolitana-Iztapalapa, Ap. Postal 55-535, Universidad Nacional del Litoral, Esperanza (CP 3080), Argentina, Mexico City, 09340, Mexico Use of lactic fermentation as a means to extend meat shelf life has been studied in conjunction of other techniques, preventing considerable alteration on sensory characteristics. Before studying the ability of lactic acid bacteria to successfully compete with spoilage microorganisms, the metabolic patter of spoilage microorganisms and bioprotective cultures must be elucidated. Four meat spoilage strains (Pseudomonas fluorescens, Pseudomonas fragi, Brochotrix thermosphacta and Lactobacillus minor) and three bioprotective strains (Lactobacillus carnis, L. pentosus and Staphylococcus carnosus) were inoculated to finely ground meat, vacuum packaged and stored at 4 and 20oC during a total study time of 12 days. Growth curves, meat pH, lipolytic and proteolytic activities were determined for meat samples separatly inoculated with the seven strains. Pseudomonds populations were considerably lower as compared to other microorganisms, especially biopreservative strains which showed very high counts. pH of meat inoculated with biopreservative strains and incubated at 4oC was rapidly reduced; in samples stored at 20oC pH increased from day 8. Beef inoculated with spoilage microorganisms showed an increasing trend in pH throughout the study time. Only B. thermosphacta showed lipolytic activity on the most abundant fatty acids present in meat. P. flurescens was the most active proteolytic strain on myofibrillar proteins, analyzed by SDS-PAGE electrophoresis. Once the metabolic pattern of the tested microorganisms was elucidated, changes in meat subjected to competition of spoilage microflora and bioprotective cultures will be understood.
Session 88D, Food Microbiology: General
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