Rivera Reyes, Minerva

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    The inclusion and survival rate of a bifidobacterial strain added to a fermented milk -whey beverage
    (2012) Rivera Reyes, Minerva; Ponce de León González, Leyda; College of Agricultural Sciences; Ríos Velázquez, Carlos; Ríos Hernández, Luis A.; Negrón de Bravo, Edna; Department of Food Science and Technology; Vélez, Ana
    A fermented milk-whey beverage was developed using previously standardized formulations, namely 100% milk and 0% whey and 75%-25% milk-whey respectively. Titratable acidity (TA) and pH of the beverages was measured to asses the fermentation process and the quality of the beverage. The fermentation process was stopped once the pH reached an approximate value of 4.5. The TA was measured as percentage of lactic acid using a solution of 0.1N NaOH and final TA was comparable to previously reported values for fermented milk beverages. The evaluation of this beverage as a potential probiotic food product was assessed by incorporating probiotic bacteria from the genus Bifidobacteirum and monitoring it’s survival during refrigerated storage of 21 days. The strain used, Bifidobacterium animalis (Bb12) is among the most resistant to acidity, one of the factors known to adversely affect its survival next to oxygen toxicity. No significant difference was observed in the survival of bifidobacteria between the formulations. Results obtained showed that bifidobacteria maintained cell counts above those required for the label of “probiotic” (6 Log10) up until the 18 days. The mean cfu ml1 was of 1.03 x 107 for the 100% formulation and 5.73 x 106 for the 75-25% formulation on day 18. It can be concluded that there was no significant difference between treatments throughout the storage period. The bifidogenic effect of the recognized prebiotic inulin was assessed by the supplementation with 1% of this oligosaccharide in fresh milk, UHT milk and MRS lactobacilli broth. The results obtained showed that even at this low supplementation level a bifidogenic effect was still achieved. Bacterial cell counts for the UHT with prebiotic and MRS with prebiotic evidenced a significant increase in log counts for day 3. For UHT an increase to 8.43 Log10 was achieved, which was significantly higher than MRS with no prebiotic for the same day which was 2.08 Log10. Thus the supplementation of UHT milk with 1% inulin represents a viable growth media for bifidobacteria. The identification to genus and species level of several presumptive bifidobacterial isolates was attempted. Using a genus specific primer set (Bifid-F and Bifid-R), all isolates tested were found to be from the genus Bifidobacterium. The ribosomal DNA of the isolates was extracted and purified and PCR amplified the digested using EcoRI and DdeI. Results obtained were comparable to the results obtained insilico. All isolates showed bands of the same length comparable to the control Bifidobacterium animalis therefore it can be concluded all isolates are Bifidobacterium lactis ssp animalis or Bifidobacterium lactis ssp lactis.