Development of antioxidant rich fruit supplemented probiotic yogurts using free and microencapsulated Lactobacillus rhamnosus culture.

Abstract

The present study reports the preparation of probiotic yogurt using Lactobacillus rhamnosus. The standard starter cultures used for yogurt fermentation were Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus and obtained from NDRI, Karnal, India. The prepared yogurt was supplemented with fruit pulp (10 % w/v) of apricot, raspberries, plum and jamun. These fruits were rich in antioxidant property as observed by DPPH, nitric oxide radical scavenging and ferric reducing antioxidant power assay methods. The probiotic yogurt products were prepared using free, alginate (2 %) and carrageenan (2 %) encapsulated probiotic L. rhamnosus culture. The microencapsulated beads were characterized by FTIR and alginate beads with bacteria showed characteristic wavelength major at 1424 and 1033 nm. The acidity increased (0.40 ± 0-0.76 ± 0.01 %) and pH of yogurts decreased (4.63 ± 0.06 - 2.83 ± 0.03) during storage. Probiotic L. rhamnosus count decreased during storage and alginate microencapsulated probiotic culture was more stable (8.85 ± 0.01 - 4.35 ± 0.03 log CFU/g) as compared with carrageenan encapsulated (8.79 ± 0.01 -2.56 ± 0.04 log CFU/g) and free culture (8.90 ± 0.01 - 2.26 ± 0.03 log CFU/g). The antioxidant power of fruits supplemented probiotic yogurts decreased successively during storage up to 15 days.