Abstract
This study was conducted to investigate the effect of lactic acid bacteria (LAB) activated lactoperoxidase system (LPs) on keeping quality of raw camel milk at room temperature. Camel milk samples were collected from Errer valley, Babile district of eastern Ethiopia. The level of hydrogen peroxide (H2O2) for activation of LPs was optimized using different levels of exogenous H2O2. Strains of LAB (Lactococcus lactis 22333, Weissella confusa 22308, W. confusa 22282, W. confusa 22296, S. Infatarius 22279 and S. lutetiensis 22319) with H2O2 producing properties were evaluated, and W. confusa 22282 was selected as the best strain to produce H2O2. Storage stability of the milk samples was evaluated through the acidification curves, titratable acidity (TA), total bacterial count (TBC) and coliform counts (CC) at storage times of 0, 6, 12, 18, 24 and 48 hours. The LP activity and the inhibitory effect of activated LPs were evaluated by growing E. coli in pasteurized and boiled camel milk samples as contaminating agent. Results indicated that the W. confusa 22282 activated LPs generally showed significantly (P < 0.05) slower rates of acidification, lactic acid production and lower TBC and CC during the storage time compared to the non-activated sample. The H2O2 producing LAB and exogenous H2O2 activated LPs in pasteurized camel milk significantly reduced the growth of E. coli population compared to non-activated pasteurized milk. Overall, the result of acid production and microbial analysis indicated that the activation of LPs by H2O2 producing LAB (i.e. W. confusa 22282) maintained the storage stability of raw camel milk. Therefore, it can be concluded that the activation of LPs by biological method using H2O2 producing LAB can substitute the chemical activation method of LPs in camel milk.
Highlights
Camels are important source of livelihood for millions of people living in the arid and semi-arid areas of many parts of the world, providing food, cash income and transport and have significant cultural values to the pastoral communities [1]
The current study showed that lactic acid bacteria (LAB) can produce H2O2 to activate the natural antimicrobial system in the milk
The optimization experiment indicated that W. confusa 22282 can produce sufficient amount of H2O2 in Mann Rogosa Sharpe (MRS) broth
Summary
Camels are important source of livelihood for millions of people living in the arid and semi-arid areas of many parts of the world, providing food, cash income and transport and have significant cultural values to the pastoral communities [1]. The changes in life styles such as fast-growing population, intensified growth of small towns and commercialization of pastoral products in the lowlands increased the demand for camel milk [5]. This condition opened market opportunities for the pastoral communities and peri-urban milk producers [6] [7]. Camel milk is usually transported without cooling facilities for long distances to reach to the consumers or processing point which increased concerns over the microbiological quality of the milk [8]. Cooling of fresh milk during collection and transportation is widely used in most parts of the world especially in the developed countries [12]
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