Effects of using different O2 scavengers on the qualitative attributes of bifidus yogurt during refrigerated storage

Abstract Among the factors that adversely influence the viability of probiotics, the oxygen content of the product and the permeation of oxygen molecules through the packaging system have a noticeable role in the viability loss during the manufacture and storage of fermented milk products. The objective of this study was to examine the qualitative attributes of probiotic yogurt containing different O2 scavengers, including the commercial O2 absorber and cysteine-ascorbic acid. Bifidobacterium lactis BIA-7 and B. longum BIA-8 were used as probiotic strains for the production of bio-yogurts. The biochemical parameters, including the changes in pH, titratable acidity, redox potential and incubation time, were determined throughout the fermentation period at 30-min intervals. Also, the changes in viable count, pH, redox potential, titratable acidity, and dissolved oxygen were evaluated at 7-day intervals during the 28 days of refrigerated storage. In addition, the evaluation of rheological and sensory properties measured in the freshly made samples was carried out. The results showed that the utilization of different oxygen scavengers has an effective impact on the decrement of oxygen content and improvement of probiotic viability. As such, the population of B. lactis in the treatments containing various oxygen scavengers was maintained above 7 log CFU/mL throughout the refrigerated storage. Notwithstanding the effective function of cysteine-ascorbic acid in the enhancement of viability, the containing treatments had not only weaker gel structure probably due to short incubation time (360 min) and fast acidification [22.20-22.35 (˚D/min) ×10-2], but also lower sensory acceptance. Overall, the yogurt treatment containing commercial O2 scavenger and B. lactis indicated a great potential for the industrial applications. To the best of our knowledge, there is no study on the efficiency of commercial O2 absorber as a potential factor to maintain the viability of probiotics in yogurt.