Raspberry and Strawberry Addition Improves Probiotic Viability in Yogurt and Possess Antioxidant Activity

This study aimed to i) investigate probiotic potentials of raspberry and strawberry addition in yogurts, ii) explore antioxidant activity of berries extracted by microwave using oxygen radical absorbance (ORAC), and 2,2-diphenyl-1-picryhydrazyl radical (DPPH) as well as iii) determine the total phenolic content (TPC) of the berries. The probiotic potentials of those berry additions into yogurts containing different probiotics were determined by subsequent viable microorganism counts in each yogurt trial using selective media, pH and total titratable acidity (TTA) during 28 days of cold storage at 4ºC. Viable microbial counts in yogurt trials containing probiotic Lactobacillus acidophilus and raspberry increased (P<0.05) for 21 consecutive days of cold storage. The pH levels decreased (P<0.05) as the TTA increased over 28 days of cold storage in all yogurts containing the berries. ORAC results showed that raspberry had higher antioxidant activity (505.72 µmol TE/100g of fruit) than strawberry (495 µmol TE/100g of fruit). Also, DPPH scavenging activity results showed that raspberry (86.11%) had higher antioxidant activity than strawberry (85.69%). There was not a significant (P<0.05) difference in TPC values of raspberry (0.20 g GAE/kg) and strawberry (0.18 g GAE/kg). This study suggests that both berries have potential as a source of prebiotics with antioxidant activity for future functional foods and nutraceutical applications.