ASSESSMENT OF MICROBIAL QUALITY, ADULTERANTS AND PRESERVATIVES IN PASTEURIZED MILK
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Date
2008
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College of Veterinary and Animal Sciences, Mannuthy.
Abstract
In the present study 200 pasteurized milk samples were collected from the
retail shops of Thrissur and Palakkad districts. From Thrissur district, 20 samples
each were collected from five brands viz., A, B, C, D and E, and an equal number
of samples were obtained from the brands F, G, H, 1 and J of Palakkad district.
All the samples were analyzed for the microbial quality by estimating various
bacterial counts and yeast and mould count and also assessed the presence of
certain pathogenic and spoilage bacteria. The milk samples were also tested to
detect the presence of adulterants viz., starch and cane sugar and preservatives
like carbonates and formaldehyde.
The study revealed that the samples belonging to Thrissur district had an
overall mean total viable count, coliform count, Escherichia coli count,
psychrotrophic count, faecal streptococcal count and yeast and mould count of
5.08 ± 0.05, 2.89 ± 0.09, 0.53 ± 0.11, 5.30 ± 0.01, 3.40 ± 0.14 and 1.89 ± 0.08
logio cfu/ml, respectively. The corresponding count in the samples of Palakkad
district was 5.24 ± 0.04, 3.01 ± 0.20, 0.78 ± 0.12, 4.99 ± 0.05, 3.20 ± 0.07 and
2.03 ± 0.09 logio cfu/ml. According to the total viable count limit prescribed by
BIS (1992) 50 per cent samples from brand E were graded as satisfactory and the
samples from all other brands were graded as unsatisfactory. The highest mean
total viable count was seen in the samples of brand A (5.39 ± 0.04 logio cfu/ml).
Of the samples collected from Thrissur district, the lowest count (4.51 ± 0.08
logic cfu/ml) was recorded from the samples of brand E. The samples collected
from 1 brand of Palakkad district had the highest mean total viable count (5.35 ±
0.05 logic cfu/ml) and the lowest count (5.19 ± 0.09 logic cfu/ml) was observed in
the samples of brand G.
Ot the 100 samples collected from Thrissur district, the samples
belonging to brand A had the highest mean colifonri count (3.40 ±0.17 logic
cfu/ml). An equal number of samples collected from Palakkad district revealed
that the highest mean count (4.39 ± 0.02 logio cfu/rnl) was observed in the
samples belonging to brand I. According to the bacterial count limit prescribed by
BIS (1992) 70 per cent of the samples from brand H were graded as satisfactory
and the samples belonging to all other brands were graded as unsatisfactory. The
overall mean coliform count of the samples belonging to various brands from
Thrissur and Palakkad districts were at the level of two and three logio cfu/ml,
respectively. The samples belonging to brand E of Thrissur and brand H of
Palakkad had the lowest mean count.
The samples collected from brand A of Thrissur district had the highest
mean Escherichia coli count (0.92 ± 0.31 logio cfu/ml) and the lowest count (0.10
±0.10 logic cfu/ml) was observed in the samples belonging to the brand E.
Among the samples collected from Palakkad district, the highest mean count
(1.54 ±0.11 logic cfu/ml) was observed in the samples of the brand I and the
lowest count (0.43 ± 0.23 logic cfu/ml) was seen in the samples belonging to the
brand H.
The highest mean psychrotrophic count (5.39 ± 0.02 logic cfu/ml) was
seen in the samples belonging to brand C of Thrissur district and the lowest count
(5.29 ± 0.05 logic cfu/ml) was observed in the samples of the brand B. Among
the samples from Palakkad district, the highest mean count (5.43 ± 0.01 logic
cfu/ml) was seen in the samples of the brand 1 and the lowest count (4.63 ±0.10
logic cfu/ml) was observed in the samples of the brand ff.
Of the samples collected from Thrissur district, the lowest mean faecal
streptococcal count (2.95 ±0.17 logic cfu/ml) was seen in samples belonging to
brand C and the highest count (3.78 ±0.16 logic cfu/ml) was observed in the
samples of the brand B. Among the samples belonging to various brands of
Palakkad district, the lowest mean count (2.88 ±0.12 logic cfu/ml) was seen in
samples of the brand G and the highest count (3.51 ± 0.21 logic cfu/ml) was
observed in the samples of the brand 1.
Among the samples collected from the five brands of Thrissur district, the
highest mean yeast and mould count (2.46 ±0.17 log lo cfu/ml) was seen in the
samples of the brand A and the lowest count (1.35 ± 0.08 log lo cfu/ml) was
observed in the samples of the brand E. Of the samples belonging to the five
brands of Palakkad, the highest mean count was seen in the samples of the brand
J (2.40 ± 0.24 logio cfu/ml) and the lowest count was observed in the samples of
the brand F (1.66 ± 0.09 logio cfu/ml).
A highly significant (P<0.01) difference was noticed among the mean
total viable count, coliform count, faecal streptoccal count and yeast and mould
count of various brands of pasteurized milk from Thrissur district. Similarly a
highly significant (P<0.01) difference was noticed among the mean coliform
count, Escherichia coli count and psychrotrophic count of the samples belong to
the five brands of pasteurized milk from Palakkad district.
Escherichia coli was isolated from 10 per cent of the samples belonging
to Thrissur and the isolates consisted of serotype of 04 (1), rough strains (2) and
untypable strains (7). The organism was isolated from 11 per cent of the samples
collected from Palakkad. One of the isolates was serotyped as 04 and three
isolates were serotyped as O60. One isolate fell in the class rough and six isolates
were untypable. Two isolates each from Thrissur and Palakkad districts revealed
Congo red binding charecteristics.
Staphylococcus aiireus could not isolate from the samples obtained from
Thrissur and Palakkad districts.
Pseudomonas organism was isolated from four and six per cent of the
samples from Thrissur and Palakkad. The isolates were identified as
Pseudomonas aeniginosa, Pseudomonas flourescens, Pseudomonas cepacia and
Pseudomonas putida.
Bacillus cereus was isolated from three samples obtained from Thrissur
district and two samples belonging to Palakkad district.
None of the samples from Thrissur and Palakkad districts revealed the
presence of the adulterants like starch and cane sugar and preservative like
bicarbonates. But formaldehyde was detected from 19 per cent of the samples
from Thrissur and 47 per cent of the samples from Palakkad.
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