MVSc

In the present investigation a total of 180 raw milk samples, consisted of 108 individual milk samples obtained from farmers belonging to three co- operative societies (S1, S2 and S3) and 72 pooled milk samples from the three societies were collected and evaluated the microbial quality. The samples were also tested to detect the presence of Escherichia coli, Staphylococcus aureus and Yersinia. The isolated Escherichia coli cultures were confirmed using Polymerase Chain Reaction (PCR) technique. The pooled milk samples obtained from the societies were also tested to detect the adulterants and preservatives added in the milk. During the investigation the factors contributing the bacterial contamination of milk from various sources were also evaluated to identify the critical control points.
Statistical analysis of the data revealed highly significant difference (P<0.01) in microbial counts of individual samples of the three sources. The overall mean total viable count, coliform count, Escherichia coli count, faecal streptococcal count and yeast and mould count was 6.01 ± 0.07, 4.44 ± 0.07, 0.86 ± 0.11, 3.14 ± 0.10 and 2.09 ± 0.12 log10 cfu/ml, respectively. Samples of S2 had the highest mean count on the basis of total viable count, coliform count, Escherichia coli count and faecal streptococcal count. Milk samples from S2 revealed maximum contamination. Escherichia coli was not detected in 63.89 per cent of individual samples. Analysis of the data revealed significant (P<0.05) and positive correlation between total viable count and faecal streptococcal count and also between total viable count and coliform count. A similar correlation was observed between coliform count with faecal streptococcal count.
Microbial analysis of milk samples collected from six farmers of S1 revealed that samples from F1 had highest mean total viable count (6.29 ± 0.15 log10 cfu/ml) and the lowest count was observed in samples of F5 (5.58 ± 0.37 log10 cfu/ml). Highest mean coliform count (4.77 ± 0.19 log10 cfu/ml) and yeast and mould count (2.74 ± 0.25 log10 cfu/ml) were seen in the samples of F3, whereas lowest coliform count (3.52 ± 0.77 log10 cfu/ml) and yeast and mould count (1.75 ±0.56 log10 cfu/ml) was observed in the samples of F2 and F5, respectively. Samples obtained from F6 did not revealed the presence of Escherichia coli, but the count was highest in the samples of F5 (1.50 ±0.49 log10 cfu/ml). The highest (3.97 ± 0.09 log10 cfu/ml) and lowest (1.80 ± 0.59 log10 cfu/ml) faecal streptococcal count was observed in the samples of F6 and F5, respectively. Critical difference test of the data revealed that none of the bacterial association was significant in the samples of S1.
Microbial analysis of individual milk samples collected from the farmers of S2 revealed that samples from F2 had highest mean total viable count (7.08 ± 0.20 log10 cfu/ml) and coliform count (5.33 ± 0.15 log10 cfu/ml) and the samples from F5 showed lowest values for the above two counts. Similarly, the bacterial counts, viz., faecal streptococcal count (4.10 ± 0.18 log10 cfu/ml) and yeast and mould count (2.99 ± 0.24 log10 cfu/ml) were highest in the samples of F3. Lowest values for faecal streptococcal count (3.12 ± 0.31 log10 cfu/ml) and yeast and mould count (0.96 ± 0.61 log10 cfu/ml) were in the samples of F4 and F6, respectively. Samples obtained from F2 did not revealed the presence of Escherichia coli, but the count was highest in the samples of F6 (2.23 ± 0.49 log10 cfu/ml). Analysis of the data of the samples obtained from S2 revealed that significant (P<0.05) and positive correlation between total viable count and faecal streptococcal count and also between total viable count and coliform count. A similar correlation was observed between coliform count with faecal streptococcal count and yeast and mould count.
Analysis of variance test of the data of the samples belonging to the farmers of S3 revealed highly significant (P<0.01) difference between the mean total viable count and coliform count. The samples of F2 had lowest total viable count (4.85 ± 0.18 log­10 cfu/ml), but the highest count was in the samples of F6 (6.66 ± 0.38 log­10 cfu/ml). The samples belonging to F4 had the highest mean coliform count (4.96 ± 0.17 log10 cfu/ml) while the lowest count was observed in samples of F1 (3.74 ± 0.13 log10 cfu/ml). The highest mean Escherichia coli count (0.80 ± 0.51 log10 cfu/ml) was seen in the samples belonging to F1 and F5. The samples belonging to F2, F4 and F6 had the mean count of 0.33 ± 0.33 log10 cfu/ml. The highest mean faecal streptococcal count (3.66 ± 0.14log10 cfu/ml) was seen in the samples of F4. The samples of F3 had the lowest mean count (2.13 ± 0.68 log10 cfu/ml). The samples belonging to F3 had the highest mean yeast and mould count (2.77 ± 0.11 log10 cfu/ml) and the lowest mean count was observed (1.41 ± 0.64 log10 cfu/ml) in the samples from F1. A significant (P<0.05) and positive correlation was observed only between the total viable count and coliform count of the samples of S3.
Analysis of variance test of the data revealed highly significant (P<0.01) difference in the bacterial count of the 72 pooled milk samples obtained from the three sources. The overall mean total viable count, coliform count, Escherichia coli count, faecal streptococcal count and yeast and mould count was 6.19 ± 0.09, 4.65 ± 0.09, 1.27 ± 0.16, 3.50 ± 0.06 and 2.37± 0.11 log10 cfu/ml, respectively. Escherichia coli was not detected in 50.00 per cent of pooled samples. Samples of S2 had the highest mean count based on total viable count, coliform Count and Faecal Streptococcal Count. Escherichia coli count and yeast and mould count showed highest values in the samples of S3. Significant (P<0.05) and positive correlation was observed only between total viable count and coliform Count of the pooled milk samples.
Escherichia coli was isolated from 36.11 per cent individual samples and 50.00 per cent of pooled milk samples. Fifteen isolates from individual samples and eighteen isolates from pooled milk samples were serotyped. The serotypes obtained were O12, O29, O60, O68, O75, O79, O96, O107, O116, O131, O160 and O172. Twelve isolates each from individual samples were untypable and rough. Among the pooled samples three isolates were untypable and fifteen isolates were rough. Congo red binding property was shown by nine and sixteen serotyped isolates obtained from individual and pooled milk samples, respectively.
Staphylococcus aureus was isolated from 40.74 per cent of individual and 34.72 per cent of pooled milk samples. Yersinia was isolated from 22.22 per cent of individual samples and 29.17 per cent of pooled milk samples. From the individual samples, five isolates of Yersinia enterocolitica was obtained. Yersinia frederiksenii, Yersinia intermedia, Yersinia aldovae and Yersinia kristensenii was isolated from ten, five, two and 1 of the individual milk samples. Yersinia pseudotuberculosis was obtained from one of the individual sample. From the pooled milk samples, three isolates each of Yersinia kristensenii and Yersinia aldovae was obtained. Yersinia intermedia and Yersinia frederiksenii was isolated from eight and six samples, respectively. Yersinia enterocolitica was obtained from one of the sample.
Grading of individual milk samples based on total viable count as per the standards prescribed by Indian Standards (1977) revealed that 34.26 per cent samples were graded as good. The per cent of samples graded as fair was 32.41. Only 15.74 per cent samples was graded as very good, whereas 17.59 per cent was graded as poor. The highest (40.28) per cent of pooled milk samples was graded under the category fair, while 9.72, 31.94 and 18.06 per cent samples were graded as very good, good and poor, respectively.
The various critical control points of microbial contamination of milk was evaluated by collecting samples of air, water, hand wash of the milker or milk handler and utensil wash and subjecting to estimation of the bacterial load. Hand wash was found to be a major source of contamination. The highest microbial count in the samples of water, utensil wash and hand wash was observed in the samples obtained from S2. The higher mean microbial count in the milk samples of S2 might be attributed to the contamination from these sources.
Adulterants (starch and cane sugar) and preservatives (carbonates, formaldehyde and boric acid) were not detected in any of the 72 pooled milk samples examined.
The Escherichia coli isolates obtained from raw milk were confirmed by Polymerase Chain Reaction (PCR) and the analysis of the electrophoresed gel under UV transilluminator revealed the presence of a 366 bp band in 93.33 per cent isolates.