Evaluation of Milk Drinks Fermented by Probiotic Bacteria and Fortified with Zinc Salts

Fermented milk drinks were made with buffalo's milk produced by three probiotic bacteria Lactobacillus acidophilus L-a-5, Bifidobacterium bifidum and Lactococcus lactis ss lactis biovar diacetilactis MD 099(1:1:1). Four treatments fortified with 10 and 20 mg zinc element/L (as zinc sulphate or zinc acetate), respectively, were studied in comparison with a control sample for 10 days of storage at 5°C. The sensory properties and cell viability of the fermented products were evaluated. The gross chemical composition, pH, flavor components (acetaldehyde and diacetyl) and viscosity were determined. The results showed that zinc salts activated the development of bacterial counts. Counts were increasing gradually during the first day of incubation till the end of the 5th day, then were gradually decreasing. The control and treatment samples contained the recommended levels of survival cells (106-107 CFU/g) of probiotic bacteria at the end of the 10th day. Statistical analysis of odour intensity, acidity, sweetness, bitterness, saltiness, creaminess, feeling after swallowing for fatty, astringency and metallic taste were sensory evaluated. A correlation was observed between sensory properties characteristics of fortified fermented milk drinks as affected by the addition of different levels of zinc salts.