Quality and Chemo-Physical Properties of Yoghurt Supplemented with Soybean and Skim Milk Powders

This study examined the effect of supplementing yoghurt milk with soybean powder (SBP) and skim milk powder (SMP) with different concentrations on the resulting yoghurt's chemo-physical, microbiological, and sensory qualities. Based on the observed results, it can be stated that the fermentation duration increased proportionally with rising SBP content. Adding different concentrations of SBP and SMP raised TS and protein content significantly (P≤ 0.05). Adding SBP at a concentration of 3% with 1% SMP (T1) resulted in the highest fat content while the lowest pH value was recorded by T3 (1% SBP and 3% SMP). Adding SBP and SMP at varying doses caused Zn, Fe, and K concentrations to rise considerably. Adding 4%, SMP greatly boosted P and Ca. Adding a mixture of SBP and SMP much reduced wheying off, with the lowest values obtained by adding 4% SMP (T4) and 1% SBP and 3% SMP (T3). The exact opposite trend was observed for curd tension. The microbiological research revealed that adding various amounts of SMP and SBP considerably lowered the total bacterial counts (TBC) compared to the control. By combining 3% SBP with 1% SMP, anaerobic bacteria were drastically reduced. In contrast, aerobic bacteria increased significantly in all treated samples relative to the untreated sample. The number of points awarded for general appearance and smoothness grew as the amount of SMP rose. There were no obvious differences (P˃0.05) in the flavour rankings between the treated and untreated yoghurt; all samples were free of off-flavours.