Background: When designing new probiotic products, one of the most important aspects is the selection of bacterial strains with high survival rates in the matrix of the product concerned. The aim of the present research was to evaluate the potential of selected strains of probiotic bacteria for the production of fruit-whey beverages.
Methods: Orange, apple and blackcurrant whey beverages were produced, and each was inoculated with one of the following probiotic strains: Bifidobacterium lactis HN019TM; Lactobacillus aci- dophilus NCFM®; Lactobacillus paracasei Lpc-37TM; Lactobacillus rhamnosus HN001TM. The count of probiotic bacteria as well as pH and total acidity were evaluated at the 1st, 7th, 14th, 21st and 28th day of storage.
Results: Beverages containing L. paracasei Lpc-37TM or L. rhamnosus HN001TM were characterized by a sig- nificantly higher average number of viable cells (7.02 or 7.05 log cfu/g, respectively) than products with lactis HN019TM or L. acidophilus NCFM® (6.43 or 6.37 log cfu/g, respectively). The use of L. paracasei Lpc-37 and L. rhamnosus HN001 strains in orange and apple drinks allows the recommended count for probiotic products, 106 cfu/g for 28 days of storage, to be exceeded. Survival of the B. lactis HN019 strain fulfills the above requirements only in the orange drink. The L. acidophilus NCFM® strain was found to be the least suitable for the production of beverages, as it did not reach 6 log cfu/g in any products after 28 days of stor- age. The highest average number of bacteria was found in the orange beverages (7.14 log cfu/g). In terms of bacteria viability, blackcurrant juice was the least suitable for the production of whey probiotic drinks, due to its high acidity.
Conclusions: The results of the present study indicate that careful selection of the fruit juice component, especially in terms of its acidity, is key to designing successful probiotic fruit-whey beverages. Other factors which should be taken into account to ensure a sufficient number of live probiotic cells, i.e. their therapeutic level in fruit-whey drinks, are the choice of probiotic strain and determination of the maximal shelf life.
Keywords: acidity; fruit drink; probiotics; viability; whey.