[Evaluation of the activity of probiotic cultures over Listeria monocytogenes during the production and storage of yogurt].
The effect of probiotic cultures over Listeria monocytogenes during the production and storage of yogurt was evaluated. A yogurt mixture (10.6% non-fat solid liquids, 3% fat and 0.3% gelatin) was prepared, homogenized and pasteurized. Yogurt was inoculated with 0, 10(2), 10(4) and 10(6) CFU/mL of L. monocytogenes and 0.02% of traditional lactic culture YC 180 (Streptococcus thermophilus and Lactobacillus bulgaricus) and probiotic culture ABY-1 (Bifidobacterium longum, B. bifidum, B, infantis, Lactobacillus acidophilus, Streptococcus thermophilus y Lactobacillus delbrueckii subsp. bulgaricus). It was incubated for 3 h at 43 degrees C until pH reached an approximate value of 4.8, followed by refrigeration at 5 degrees C for 21 days. During fermentation, samples were taken every hour, and during storage every 3 days, analyzing pH and lactic, bifidobacteria and pathogen count for each time. It was demonstrated that there was no significant simple effect for the type of culture used (ABY-1 and YC 180) (p = 0.684) over the amount of L. monocytogenes present in yogurt during the fermentation and storage periods. The presence of bifidobacteria in the ABY-1 culture did not present a significant effect over L. monocytogenes. Neither the effect of time presented a significant effect over L. monocytogenes (p = 0.448). In this case, the ABY-1 and YC 180 cultures present a bacteriostatic effect over the pathogen. The probiotic cultures had a bacteriostatic but not bactericidal effect over L. monocytogenes. This is not related to the protective effect of these cultures in bowel, since in-vivo conditions favor the production of antimicrobial substances, such as bacteriocins that act over pathogens.
Berrocal
Darling
D
Facultad de Microbiología, Universidad de Costa Rica.
Arias
María Laura
ML
Henderson
Marjorie
M
Wong
Eric
E
D001644:Bifidobacterium / Q000254:growth & development / Q000378:metabolism; D015169:Colony Count, Microbial; D005511:Food Handling; D005516:Food Microbiology; D019344:Lactic Acid / Q000378:metabolism; D007778:Lactobacillus / Q000254:growth & development / Q000378:metabolism; D008089:Listeria monocytogenes / Q000254:growth & development* / Q000378:metabolism; D019936:Probiotics / Q000378:metabolism*; D013291:Streptococcus / Q000254:growth & development / Q000378:metabolism; D015014:Yogurt / Q000382:microbiology*
D019344:Lactic Acid