Synergistic Evaluation of Lactobacilli on Probiotic Viability and Antioxidant Properties in Almond and Cow Milk

Lactobacilli are important probiotic groups recognized for their numerous health-promoting properties. This study investigated how four probiotic strains, Lacticaseibacillus rhamnosus (Lr), Lactobacillus acidophilus (La), Lactiplantibacillus plantarum (Lp), or Lacticaseibacillus casei (Lc), affected post-acidification, viable cell counts (VCCs), total phenolic and flavonoid contents (TPCs and TFCs, respectively), and antioxidant activity of fermented almond milk (FAM) and its combination with cow’s milk (CM) at different concentrations (75:25, 50:50, and 25:75) during 1, 7, 14, and 21 days of storage. All FAM and its mixture with CM showed significantly greater (p < 0.05) post-acidification than their respective controls throughout storage. Viable cell counts in all samples ranged from 5.9 to 6.8 log cfu/mL, which were higher than those of the controls (3–4 log cfu/mL; p < 0.05). Total phenolic contents in FAM/CM (75:25 and 50:50 and 25:75)-Lc increased more than twofold (95.82 ± 0.003 and 105.71 ± 0.008 and 101.02 ± 0.071 μg GAE/mL; p < 0.05) compared to the controls (19–40 μg GAE/mL) by the end of the third week. Lbs. rhamnosus enhanced (p < 0.05) TFCs in FAM/CM (25:75) after the first day of storage. All lactobacilli strains improved the antioxidant activity in all treated samples during storage. In conclusion, the combination of fermented almond milk with cow’s milk may serve as an excellent carrier for Lbs. rhamnosus, Lab. acidophilus, Lpb. plantarum, and Lbs. casei, which exhibit antioxidant activity.