87-11 |
Bacteriocin production using supplemented whey permeate and antagonistic studies in liquid medium and in a salad dressing |
B. E. GARCÍA-ALMENDÁREZ1, V. García-González, and C. Regalado-González. (1) Dpto. Investigación y Posgrado en Alimentos, PROPAC, Facultad de Química, Universidad Autónoma de Querétaro, CU, Cerro de las Campanas S/N, Querétaro, Qro., 76010, Mexico The market for minimally processed vegetables has increased recently. However, their safety relies mainly on refrigeration which is difficult to maintain throughout the food chain. Bacteriocins are natural antimicrobial agents which may be used as additional barriers to prevent growth of foodborne pathogens, especially those psychrotrophic like Listeria monocytogenes. The objective was to utilize a supplemented whey permeate (SWP), to produce bacteriocin from a lactic acid bacteria, and to study its antagonistic activity against L. monocytogenes on liquid medium and in a salad dressing. Whey permeate was supplemented with 1% yeast extract (YE), MgSO4/MnSO4 1:5 ratio, and 0.2% Tween 80. Lactococcus lactis UQ2 was inoculated to the SWP, an incubated in an orbital shaker at 30°C, pH 6.5, 150 rpm. Bacteriocin production was evaluated every 1.5 h, during 20 h, and also its pH (2-10) stability. A cell free extract (CFE) and a partially purified extract (PPE) were obtained. Each extract (300-1200 AU/mL) was added separately to a liquid medium (soy trypticasein plus 0.6% YE) and a white salad dressing inoculated with 105 cfu/mL of L. monocytogenes, at 4°C. The maximum bacteriocin activity was 3200 AU/mL, after 20 h. The bacteriocin stability was highest at pH 4.0. For the liquid medium, a dose dependent antimicrobial activity was found. Using 600 AU/mL of CFE, the maximum population reduction was 4.7 log, while using 300 AU/mL of PPE, the maximum reduction was 3.2 log. For the salad dressing, 300 AU/mL of the CFE produced a 2 log reduction, while similar results were found using 1200 AU/mL of the PPE. The application of PPE was less effective than CFE on reducing L. monocytogenes viable cells, for both the liquid medium and the salad dressing. The bacteriocin produced in the SWP may be used as an additional barrier in the safety of minimally processed foods.
Session 87, Food Microbiology: General
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