15C-2 |
Comparison of growth performance of lactic acid bacteria and Bacillus sp. in a non-heated milk based media using a non traditional microbial detection system |
M. M. ARENDTS1, R. M. Bertoldo, and R. R. Jiménez-Flores. (1) Dairy Products Technology Center, DPTC, California Polytechnic State University, 1 Grand Ave Bldg. 18-02, San Luis Obispo, CA 93407 Many microorganisms are a concern in processing and milk powder quality. Specific organisms play a positive role in product development due to their fermentative abilities, whereas others can be detrimental to product quality. The models used were: 1) lactic acid bacteria (LAB) isolated from the DPTC library of probiotic strains and 2) Bacillus sp., in the form of endospores, from our DPTC library that were isolated from California milk powder. Our objectives were to evaluate a non traditional microbial detection system for quality control analysis of dairy products and to develop a milk-based media that could facilitate subsequent molecular methods based on nucleic acid extraction. To evaluate the non traditional system in the analysis of LAB, samples containing a serial dilution between 102 and 105 CFU/mL were injected into bottles containing commercial anaerobic media and analyzed. The same samples were injected into milk-based media bottles for comparison. Detection times were plotted against initial inoculums. The Bacillus strains were heat shocked prior to injection into commercial media or milk-based media bottles in concentrations from 102 to 107 spores/mL. The spore counts were determined initially by direct microscopic count. Growth curves were generated as validation of this system using a 96 well plate with a continuous monitoring of turbidity (Absorbance at 405 nm). Growth curves generated by both systems demonstrated good correlation between time of detection and rate of growth from our growth curves. Optimization of this method using a milk based media that is filter sterilized has two advantages, 1) maintenance of all the nutrients and 2)the absence of heated proteins or sugars allows easier and more efficient nucleic acid extractions.
Session 15C, Dairy Foods
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