Bacteriological Guality of Bovine Milk in Small Hollder Dairy Farms in Debre Zeit, Hthiopia
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Date
2004-06
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Addis Ababauniversity
Abstract
The critical control points in milk handling, determination of bacterial load of milk at each
critical control points and farm water, isolation and identification of bacterial pathogens in
milk were determined from September 2003 to March 2004. A total of 178 raw milk samples
from various critical points, and 77 farm water samples were taken three times from 27 small
holder dairy farms of Adaa-Liben district dairy and dairy products producers and marketing
co-operative society. Pasteurized milk samples (n=100) were taken from Mama milk
processing plant. Specific gravity, alcohol and Californian mastitis tests were used as
screening tests, and total aerobic plate counts (TAPC) and coliform counts from milk and the
most probable number (MPN) of coliform counts from farm water were conducted. Isolation
and identification of the bacteria in the milk was conducted following standard methods.
The specific gravity values of milk from the dairy owner’s were in the range of 1.025 to
1.029. The normal range being 1.026 to 1.032 at 20 oC. Nine percent of the samples had
values below 1.026, an indication of some adultration with addition of water. All the milk
samples tested were alcohol test negative. Pooled milk was taken from 25 dairy farms and the
CMT results showed that 76 % of the total samples were CMT negative and the remaining 24
% were positive for CMT, indicating the presence of mastitis.
The mean total aerobic plate counts of raw milk samples analyzed were 2.10x105 (udder),
1.58x107 (bucket), 1.50x108 (storage container), and 5.67x109 cfu/ml upon arrival at
processing plant. The mean coliform counts were 4.84x103 (udder), 1.37x105 (bucket),
1.67x106 (storage container), and 1.26x107 cfu/ml upon arrival at processing plant. The
increment of the TAPC and coliform counts at each critical control points were observed
statistically significant (P < 0.001) for both counts. There was no significant variation
between milk collection centers and the interactions between milk collection centers and
critical control points for TAPC and coliform counts (P > 0.1). According to international
standards of raw milk quality both the TAPC and coliform counts have values above the
upper limits set. These include 10.4% of the raw milk samples from udder, 45.4% of raw milk
samples from milking bucket and 100% of raw milk samples from storage containers and
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upon arrival at processing plant for TAPC.and 37.7% of the raw milk samples from udder,
96.1% of raw milk samples from milking bucket and 100% of raw milk from storage
container and upon arrival at processing plant for coliform counts. Analysis of water samples
from the farms revealed that 54.6% were poor (non potable) quality.
Pasteurized milk in this study had TAPC and coliform counts ranging from 2.65x103 to
7.2x105 and 0 to 7.5x103 cfu/ml, respectively. Based on the international standards, 7% and
27% of pasteurized milk fall below the standards set for TAPC and coliform counts,
respectively.
In the course of this study the frequent bacterial pathogens isolated from raw milk samples
taken from the udder include: Staphylococcus aureus, Staphylococcus intermidus,
Staphylococcus epidermidus, Staphylococcus chromogenes, Streptococcus agalactae,
Streptococcus uberis, Streptococcus bovis, Corynebacterium bovis, Corynebacterium
ulcerans and Pseudomonas aeroginosa. Similarly, samples from milking bucket, storage
container and upon arrival at processing plant were additionally contaminated with bacterial
pathogens such as Micrococcus, Rhodococcus spp, Enterococcus fecalis, Bacillus spp,
Escherchia coli, Pseudomonas aeroginosa, Enterobacter aerogenes, Enterobacter
aglomerans, Klebsiella pneumonia and Citrobacter freundi. Streptococcus pyogenes and
Enterobacter aerogenes. Bacteria of public health significance isolated were Staphylococcus
aureus, Streptococcus agalactae, Corynebacterium ulcerans, Corynebacterium
haemolyticum, Streptococcus pyogenes and Escherichia. coli.
Bacterial pathogens such as Staphylococcus intermidus, Staphylococcus epidermidus,
Staphylococcus chromogenes, Streptococcus pyogenes Enterococcus faecium,
Corynebacterium haemolyticum, Corynebacterium ulcerans and Klebsiella oxytoca which are
normally eliminated by efficient pasteurization, were still present in the pasteurized milk
samples.
The present study showed that:
TAPC and coliform counts of raw milk were increased at all critical points from udder
to upon arrival at processing plant significantly. However, the counts decreased to
lower level after pasteurization.
Most probable number (MPN) of coliform counts from farm water samples showed
55.6% were of non-potable quality
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The number and types of isolated bacteria increased after the milk left the udder to
upon arrival at processing plant due to exogenous contamination sources.
The health of dairy herd, milking and storage conditions, unclean milk equipment,
frequent transferring of milk into different containers and sieves, contaminated water
were some of the basic determinants of milk quality. Furthermore, the milk was also
subjected to more contamination as it was transported long distances to the processing
plant under high ambient temperature and without cold chain facility and using
materials which were not airtight.
The high level of counts and isolate numbers and types found in the milk represent a poor
keeping quality and public health risk to the consumer and this suggests the need for
improved hygiene practice at all levels in the dairy.
Keywords: Milk, TAPC, Coliform counts, MPN, Raw, Pasteurized, Critical points, CMT
Description
Keywords
Milk, TAPC, Coliform counts, MPN, Raw, Pasteurized, Critical points, CMT