Quality Characteristics of Probiotic Soy Yoghurts with Enzyme Hydrolyzed African Breadfruit and Rice Additives

Abstract

Effect of enzyme hydrolyzed African breadfruit (HABF) and culture type on the physicochemical and nutrient composition of soy yoghurt sweetened with rice syrup was evaluated. The effect of the HABF on the final counts of the cultures; Bifidobacterium bifidum (ATCC 11883) and Lactobacillus acidophilus in mono- and co-cultured soy yoghurt was also determined. African breadfruit (ABF) flour was hydrolysed with a mixture of cell wall degrading enzymes: Xylanase [endo-1,4-] and [endo-1,3(4)-] Beta-glucanase (UltraflowmaxR). HABF was added at concentrations of 0 - 5 % into soymilk containing 25 % hydrolysed rice syrup and then pasteurized at 80 °C for 30 min in a water bath. Probiotic B. bifidum and L. acidophillus as mono- and co-cultures were separately inoculated into the soy-HABF milk and fermented at 42°C for 6 - 8 h. Samples were analyzed using standard methods. The pH (4.46 - 4.30) and syneresis index (32.35 - 25.00) decreased significantly (P ≤ 0.05) with increase in HABF concentration for the cultures, while TTA (0.62 - 0.93 % lactic acid) and viscosity (1.20 - 1.84 Pa.s-1) increased significantly (P ≤ 0.05). No significant (P ≤ 0.05) effect on moisture (85.79 - 89.16 %), crude protein (3.44 - 3.75 %) and crude fat (1.24 - 1.58 %) content of the soy yoghurt was observed. The ash (0.17 - 0.50 %), crude fibre (0.24 - 0.47 %) and carbohydrate (7.10 - 8.53 %) varied significantly (P ≤ 0.05) amongst the cultures with HABF concentrations. B. bifidum and L.acidophillus monoculture counts ranged from 7.36 - 7.69 and 7.16 - 8.49 Log10 CFU/ml respectively, and 6.52 - 7.66 and 7.79 - 8.92 Log10 CFU/ml respectively in co-culture fermentation. Viable cells were > 106 recommended for probiotic products. This work therefore reveals the possibility of the production of probiotic yoghurt with soymilk and at least 4% HABF inclusion and rice syrup as sweetner.