In vitro angiotensin converting enzyme (ACE)-inhibitory and antioxidant activity of probiotic yogurt incorporated with orange fibre during storage

In the present work, the effects of orange fibre (OF) supplementation at four different concentrations (0.5%, 1%, 1.5% and 2%) on some quality properties of probiotic set yogurt produced with ABT-2 culture (containing Streptococcus thermophilus ST-20Y, Lactobacillus acidophilus LA-5 and Bifidobacterium lactis BB-12) were evaluated, during 21 days of storage. The in vitro angiotensin converting enzyme (ACE)-inhibitory activity and antoxidant capacity as well as some physicochemical and microbiological analyses of probiotic yogurts were analysed and compared with plain yogurt. At the beginning of storage, yogurt samples had high survivability for probiotic bacteria leading to viable counts (> 10(7) CFU/g) higher than the minimum therapeutic threshold (10(6) CFU/g). A significant influence (p < 0.05) of OF supplementation on S. thermophilus ST-20Y and B. lactis BB-12 counts was observed. While OF addition enhanced the viability of B. lactis BB-12, it caused a decrease in S. thermophilus ST-20Y counts. OF addition up to 1.5% concentration affected positively the syneresis, apparent viscosity and consistency index values of yogurt samples. ACE-inhibitory activity showed an increasing trend throughout the storage. Control yogurt had the lowest ACE-inhibitory activity at 1 day of storage, and the highest activity was obtained in yogurt containing 1% OF at the end of the storage. Also, yogurts with OF had higher antioxidant activity than the control sample at all days of storage (p < 0.05). Antioxidant activity increased until 14 days of storage in all yogurt batches, while it was decreased 21th days of storage. Briefly, this study reflected the performance of using OF as an alternative hydrocolloid to improve the quality properties and bioactivity of bio-yogurt.