Probiotics combined with prickly pear seed flour as a mean to fortify fermented milk-based beverages

The application of processing waste/by-products along with probiotics could represent a possible strategy to confer functional aspects to food items. This study aimed to evaluate the impact on yogurt of incorporating prickly pear seed (PPS) flour, rich in fiber, minerals and phenolic compounds, together with individual commercial probiotic strains of lactobacilli (Lacticaseibacillus casei BGP93, Lacticaseibacillus casei LC4P1, Lacticaseibacillus rhamnosus LRB, Lactiplantibacillus plantarum LPAL). Preliminarily, we optimized the production protocol by examining various percentages of PPS flour added either before or after fermentation. The best result was achieved adding 5 % of PPS flour after fermentation, coinciding with the addition of probiotics. The ability of all probiotic strains to survive in the yogurt matrix and in the presence of the starter cultures was assessed, during 40 days of refrigerated storage. Probiotic lactobacilli and yogurt starters were quantified using both culture-dependent (plate count on MRS and M17 agar) and culture-independent (real-time qPCR) techniques. The inclusion of PPS flour resulted in elevated levels of fiber (more than 3 %) and minerals, especially for magnesium, potassium and phosphorus. Furthermore, the antioxidant capacity, measured in vitro (via DPPH∙ and FRAP assays) and in cell line studies, showed an increase in the yogurt added with PPS and L. casei BGP93. These findings suggest the suitability of integrating PPS flour and probiotics into yogurt formulations to obtain functional yogurt, leading to a greater availability of phenolic compounds. Further research is needed on consumer appreciation and willingness to pay.