Quality attributes of set yogurt made from lactoperoxidase system activated cow's milk

The study aimed to assess the quality attributes of set yoghurt made from cow's milk preserved by lactoperoxidase system (LPs). Fresh cow's milk was collected from Datto milk collection center and samples were grouped to control and LPs activated. Set yoghurt was prepared immediately for the controlled samples, but in LPs activated milk, sample was kept for 9 h at 25 °C ± 2 before yoghurt was made. LP enzyme was activated within 2 h after milking by adding 1 mg/ml of sodium thiocyanate (SCN^_) and hydrogen peroxide (H₂O₂). Totally, 36 L of cow's milk was used and the experiment was done in triplicates. Titratable acidity (TA) and pH were assessed every 30 min until coagulation formed. Yoghurt samples were stored for 21 days and different parameters were assessed including incubation duration, pH, TA, microbiological quality and sensory attributes. The results revealed that LPs partially suppressed the rate of acid production during incubation of cultured milk. Yoghurt made from LPs treated milk had significantly (P < 0.05) higher pH and lower TA values. Similarly, yoghurt made from LPs treated milk had lower total bacterial counts at 24-h, 72-h and 7-days of storages. Additionally, yoghurt from LPs activated milk had lower yeast and mold counts at 24-h and 7-days. Yoghurt made from LPs activated milk received better scores for the sensory attributes. In general, LPs activated milk can be used for making set yoghurt without a negative effect. Further studies are needed to illustrate the LPs activated milk fitness in making other cultured milk products.