Prickly pear seed flour and adjunct lactobacilli as additional ingredients to fermented milk with potential health and nutritional benefits

Fermentation of food by-products using lactic acid bacteria is a promising strategy for conferring functional properties to foods. Processing prickly pear fruits, which can be grow in marginal areas without specific agronomic input, generates significant quantity of by-products. These include the seeds, which can be dried and ground to produce a flour rich in fibre, minerals, and phenolic compounds. The impact of incorporating prickly pear seed flour (PPS) in combination with selected commercial lactobacilli (Lacticaseibacillus casei BGP93, L. casei LC4P1, Lacticaseibacillus rhamnosus LRB, Lactiplantibacillus plantarum LPAL), some of which exhibit probiotic potential, on the production of a fermented milk was investigated, and its nutritional properties were evaluated. Preliminary protocol optimization involved examining different percentages of PPS flour added before and after fermentation. The best formulation was obtained by adding 5% PPS flour after fermentation, along with the addition of commercial lactobacilli. Adjunct lactobacilli and yogurt starters were quantified using culture-dependent technique. The inclusion of PPS flour resulted in levels of fibre higher than 3%, as well as increased levels of minerals such as iron, magnesium, potassium, and phosphorus. In vitro antioxidant capacity (DPPH∙ and FRAP assays) was found to be higher in fermented milk supplemented with PPS and L. casei BGP93. Furthermore, fermented milk extracts were tested on Caco-2 cell lines, confirming the antioxidant and anti-inflammatory activities associated with the combined use of PPS and L. casei BGP93. These results suggest the suitability of supplementing PPS flour with adjunct lactobacilli to develop functional fermented milk with greater availability of phenolic compounds. Finally, sensory analysis was performed to evaluate the product's sensorial characteristics, demonstrating that the inclusion of PPS flour is a viable strategy for developing a novel functional yogurt with high consumer appeal.