ASSESSMENT OF THE EFFECTS OF ACTIVATED LACTOPEROXIDASE SYSTEM ON MICROBIOLOGICAL QUALITY OF RAW COW MILK ON DIFFFERENT CLIMATIC ZONE OF ETHIOPIA
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Date
2018-06
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Abstract
The objective of this study was to assess the antimicrobial effect of the Lactoperoxidase system
(LPS) in milk under different agro-climatic zones taking into account the variability of
environmental temperatures toward improving milk quality and safety in Ethiopia. Experimental
study design was employed to assess the antimicrobial effect of LPS on the keeping quality of
raw cow milk. Milk samples were collected from Addis Ababa University Business enterprise
Bishoftu fattening, dairy and poultry farm. A total of 12 liters of milk samples were collected and
grouped into activated (treated with sodium thiocyante and Hydrogen peroxide) and nonactivated
(control). The activated and non-activated milk samples were subjected to four
treatment groups based on temperature. The treatments were designed to represent the average
temperatures of the four agro-ecology of the country namely cool to cold humid zone (14oC),
warm to cool, semi-humid zone (18°C), warm to hot, semi-arid zone (24oC) and hot, arid zone
(37oC). The samples were incubated in adjustable incubator at each temperature. The effect of
the system was evaluated using alcohol tests, total plate count and analysis of the composition of
the milk every two hours. LPS activation has resulted in decrease of the number of microbial
load significantly. Its effect tended to be more efficient as storage temperature decreases. There
was significant reduction of microbial load in LPS activated milk samples as compared to the
control group (P<0.05). The microbial load was decreased by 66.7%, 75%, 67.9% and 64.3% in
activated milk samples kept at 370c, 240c, 180c and 140c, respectively. The activation of LPS can
prolong the shelf life of milk ranging from 6 to 12 hours without deterioration. The study showed
that LPS increased the shelf life of milk significantly at all temperatures. This study revealed that
application of LPS had no significant impact on the nutritional composition of milk. In
conclusion, activation of the LPS potentially decreases the microbial load and prolongs the shelf
life of raw cow milk up to 6-12 hours based on the storage temperatures. Further studies should
be done in different parts of the country under the specific temperatures especially in the high
milk-shed areas of the country particularly by rural smallholder dairy farmers for practical usage
of the system.
Description
A thesis submitted to College of Veterinary Medicine and Agriculture, Addis Ababa
University in partial fulfillment of the requirement
Veterinary Microbiology
requirements for the Degree of Master of Science in
Keywords
Lactoperoxidase system, antimicrobial effect, microbial load