Viability of calcium alginate microencapsulated probiotic bacteria in Iranian yogurt drink (Doogh) during refrigerated storage and under simulated gastrointestinal conditions

Abstract

The effects of microencapsulation of AB-type culture (Lactobacillus acidophilus LA-5 and Bifidobacterium lactis Bb-12) with calcium alginate on cell survival in Iranian yogurt drink (Doogh) during storage at 4°C for 42 days, as well as under simulated gastrointestinal conditions, were studied. The pH of the product at the beginning of storage was 4.53 and the final pH at the end of storage were 4.52 and 3.78 for the samples containing encapsulated and free cells, respectively. The acetic acid content in the encapsulated-cellcontaining Doogh increased by 0.01% (from 0.05 to 0.06%) during the storage period, whereas for free-cell-containing Doogh the increase was 0.04% (from 0.05 to 0.09%). At day 42, the viable counts of L. acidophilus and bifidobacteria in the samples containing encapsulated cells were 5.5 and 4.0 log cycles higher than those containing free cells, respectively. To evaluate the protective impact of encapsulation on cell survival in in vivo situations, the product was subjected to three simulated gastrointestinal conditions, including extreme conditions (pH 1.5, 90 min/2% bile, 90 min), intermediate conditions (pH 1.5, 90 min/1% bile, 90 min) and normal conditions, i.e. the situation in the gastrointestinal tract of a normal healthy person after the consumption of a probiotic-containing dairy drink, when the stomach has not been free for a relatively long time (pH 2.0, 30 min/0.6% bile, 60 min). The viability of the probiotic cells increased from 0.6% and 0.2% (L. acidophilus and bifidobacteria, respectively) as free cells to 18.0% and 9.5% under the extreme gastrointestinal conditions, after encapsulation. Under normal gastrointestinal conditions, the cell survival rates were 16.1% for L. acidophilus and 21% for bifidobacteria before encapsulation, and 26.3 and 34.0% (L. acidophilus and bifidobacteria, respectively) after encapsulation.