Activation of Lactoperoxidase System: Evaluation of the Acidification Rate, Microbial Quality, and Shelf Life of Camel and Cow Milk
Abstract: Camel milk is produced in areas where there is lack of milk cooling facilities coupled with high
ambient temperature that exacerbates milk spoilage before it reaches the ultimate market and consumers.
To overcome this problem lactoperoxidase system (LPS) is one the methods to preserve freshness of milk
until it is marketed or reaches where there is milk cooling facilities. This study was conducted with the
objectives of assessing the effect LPS activation on preservation of raw camel and cow milk and to
comparing acidification rate of LPS activated camel and cow milk. The effect of LPS activation on
inhibition of selected pathogens (i.e. Escherichia coli and Staphylococcus aureus) was also studied. The treatments
consisted of a 2 x 4 factorial experiment (LPS activated and non LPS activated with 0, 6, 12, and 24 hrs
storage time at 30°C treatments) in a Completely Randomized Design (CRD) with a factorial arrangement
and three replications per treatment. Twenty-four camel and cow milk samples obtained from Errer valley
ago-pastoralists and Haramaya University Dairy farm, respectively were examined for titratable acidity, total
bacterial count (TBC) and coliform count (CC). The result revealed that titratable acidity, CC and TBC in
LPS activated milk samples were significantly lower (P< 0.05) than their respective values in non LPS
activated milk samples for both cow and camel milk, stored for 6, 12 and 24 hrs. The percent of acidity
were not significantly (P>0-05) different than that of the initial acidity level in LPS activated cow and camel
milk up to 12hrs of storage. LPS activated milk showed bactericidal effect against TBC and CC both in
cow and camel milk. In the current experiment, activation of LPS in camel milk reduced the growth rate
of E. coli as compared to non LPS activated milk samples. The bactericidal effect of the LPS suggests that
activation of the LPS would be of paramount importance in controlling the growth of microorganisms and
improving the microbial quality of both cow and camel milk in the study area. Cow milk with activated LPS
showed a slight delay in acidification rate compared to the non LPS activated cow and camel milk using a
thermophilic starter culture. From the study, we can suggest that LPS activation of both cow and camel
milk helps to extend the shelf life of fresh milk up to 6 and 12 hours, respectively and enables milk
producers to sell fresh milk within this time frame and reduce milk wastage. LPS activation can be used in
improving the microbiological quality and the shelf-life of raw camel and cow milk where milk cooling
facilities are not available. LPS activated milk could also be used for manufacturing of fermented milk
Keyword: Camel milk; cow milk; hydrogen peroxide; lactoperoxidase system; thiocyanate
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