Activation of lactoperoxidase system and its potential for microbial inhibition and preservation of milk in the Great African Rift Valley climate

Abstract Raw milk preservation encourages for dairy producers and milk processing plants. This study aimed to investigate the preservative and microbial inhibitory potentials of lactoperoxidase systems (LPs), at natural storage temperature. The milk was collected from a Friesian dairy cows farm right after hand milking from individual cows, bulked to a 50-l milk can and sampled 6 l of milk. Raw milk was divided as activated and un-activated (control). LP enzyme was activated within 2 hours after milking by adding sodium thiocyanate 14 ml (1 mg/ml) and 10 ml hydrogen peroxide (1 mg/ml) per liter. Acidity development and microbial counts were assessed. Results revealed that LPs activation had significantly (P < 0.05) extended the shelf life 8 hours. Activated milk had titratable acidity (0.19) and pH (6.52) value within the acceptable level of Ethiopian Standard up to 12 hours, while lower pH (6.24) and higher titratable acidity (0.21) were recorded in control milk. Activated milk was significantly (p < 0.05) lower in the total bacteria, yeast and mould, coliform and Staphylococcus counts. After 6 hours, total bacterial count in the control group increased to 7.36 log cfu/ml, while in activated milk it was 6.24 log cfu/ml and significantly lower (p < 0.05) from the initial count. LPs decreased the coliform count by 0.45 log cfu/ml as compared to 0.49 log cfu/ml increased in control group. LPs reduced in the Staphylococcus count by 23.13% after 12 hours of storage. LPs can be used to prolong the shelf life and safeguard the microbiological quality of raw cow’s milk where cooling facilitates are unavailable.