Functional properties of a kefir-based probiotic dairy product enriched with red prickly pear ( Opuntia dillenii ) powder

There has been a growing interest in functional foods that contain probiotics and bioactive substance due to the increasing awareness of the link between nutrition and health. In this context, the current study aimed to develop a kefir-based probiotic dairy product enriched with Opuntia dillenii fruit powder (ODFP). The phenolics profile, chemical composition and functional properties of ODFP was studied. Then, the microorganisms’ growth, physico-chemical, sensory, color and antioxidant properties of the fermented dairy product were studied during cold storage for 21 days. LC-ESI-MS analysis resulted in the identification of 13 compounds in ODFP ethanolic extract, of which quinic acid (37.73 mg/g extract) was the main one. The ODFP extract also showed relatively important antioxidant potential in the DPPH• (IC 50 = 0.7 ± 0.02 mg/mL) scavenging activity and (Fe 3+ ) reducing power (EC 0.5 = 0.25 ± 0.01 mg/mL). The dairy product was fermented using both yogurt starter culture and kefir in the presence of ODFP (0.1, 0.2 and 0.3 g/100 g). The ODFP enrichment increased titratable acidity and reduced the pH. The product enriched with 0.3% ODFP showed an exudate loss of 46.38% against 68.19% for the control product. The red color ( a* ) significantly increased in ODFP-fortified products. The biotransformation of ODFP by fermentation process increased the microorganisms’ growth, phenolics content and antioxidant activity. The kefir-based dairy product enriched with 0.2% ODFP showed the highest score of overall acceptability. Overall, combining red prickly pear and kefir offers a promising avenue for producing a novel fermented dairy product with enhanced sensory and functional attributes. Graphical abstract