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ThesisItem Open Access Microbial quality assurance of curd during production and storage(Department of Veterinary Public Health, College of Veterinary and Animal Science, Mannuthy, 2005) Praseeda, R; KAU; Nanu, EIn the present investigation, a total of 180 freshly prepared curd samples belonging to 10 batches were collected on the day of production. Two samples from each batch were selected at random and examined on zero day and the remaining samples were stored under refrigeration and duplicate samples examined on day 3, 5, 7, 9, 12, 15, 18 and 21 of storage. A total of 80 curd samples belonging to four brands viz. A, B, C and D were also collected from retail outlets in and around Thrissur Corporation. All samples of curd were tested to evaluate the microbial quality by estimating the total viable count (TVC), coliform count (CC), faecal streptococcal count (FSC), psychrotrophic count (PC) and yeast and mould count (YMC). Isolation and identification of Escherichia coli, Staphylococcus aureus, Salmonellae, Pseudomonas aeruginosa and Bacillus species were also carried out. The organoleptic qualities of curd such as colour and appearance, flavour, body and texture and product acidity and physico-chemical parameters such as pH and titratable acidity were also assessed. Microbial quality assurance of curd during its production and critical control points of microbial contamination in the production line were also evaluated during the study. Paired‘t’ test of the data revealed that mean TVC of the samples increased at a highly significant (p<0.01) level from zero day to fifth day of storage, after which it decreased gradually. The mean CC of curd samples showed a gradual decreasing trend till the 12th day of storage. Coliforms were not detected in 90 per cent of the fresh curd samples. The mean FSC of curd samples also decreased significantly through out the storage period. On 18th and 21st day, 70 per cent of the samples did not reveal the presence of faecal streptococci. The mean PC decreased subsequently during storage till 12th day, after which it slightly increased. The mean YMC of fresh curd was 3.91 ± 0.11 log10cfu/g and it increased gradually from third day of storage compared to the count of the fresh sample. The count increased by 1.5log10cfu/g on the 12th day of storage and the increase was highly significant (p<0.01). A highly significant (p<0.01) and positive association was observed between the mean TVC and FSC on 21st day of storage. A significant (p<0.05) and negative association was observed between the mean TVC and PC on day nine of storage. A similar association was observed between mean CC and PC of samples on 12th day of storage and mean YMC and PC of samples on 15th day of storage. E. coli was not detected from any of the fresh and refrigerated samples of curd. Staphylococcus aureus was isolated from 35 per cent of fresh curd samples. On day 3, 5 and 7 of storage, 25, 20 and 10 per cent of the samples revealed the presence of the organism and all isolates were coagulase and TNase positive. None of the curd samples revealed the presence of Salmonellae and Pseudomonas aeruginosa. Bacillus species were present in 70 per cent of the fresh samples and 20 per cent each of the samples tested on day 15 and 18. Bacillus cereus was not detected in any of the curd samples and among the isolates, 55.4 and 25.67 per cent were B. subtilis and B. coagulans. The mean titratable acidity showed an increase till ninth day of storage and then decreased throughout the storage period. The pH of fresh curd samples decreased on storage and after 15th day, it increased gradually. Analysis revealed that flavour scores decreased during storage. Body and texture score remained almost the same throughout the storage period except a slight decrease on the third day. Colour and appearance score decreased significantly during the storage period and product acidity score also got reduced during storage. Of the 80 samples collected from the four brands, 42.5, 37.5 and 20 per cent had mean TVC at the level of 109, 108 and 107 cfu/g, respectively. Highly significant (p<0.01) difference was observed in mean CC of the samples of the different brands. Coliforms were not detected in the samples of brand B and 80 and 70 per cent samples of the brands C and D, respectively. A highly significant (p<0.01) difference was observed between the mean FSC count of samples from the four brands. Of the samples, 40 per cent did not reveal the presence of the organism and the count in 50 per cent samples from brand A was at the level of 103cfu/g. E. coli was not detected in the samples of brands B and D. The organism was isolated from 5 and 15 per cent of samples of brand A and C and the four isolates belonged to the serotype O157, O5, O148 and rough type. None of the samples from the four brands revealed the presence of Salmonellae. Pseudomonas aeruginosa was present in 2.5 per cent of the samples from the four brands. Staphylococcus aureus was detected in two of the curd samples, one (5%) each from brand A and C. Bacillus species was isolated from 62.5 per cent of the samples and among the isolates, 14.14 per cent was B. cereus. Analysis of variance test revealed a highly significant (p<0.01) difference in the mean titratable acidity and pH of the samples from the various brands. Organoleptic score analysed by Kruskal-Wallis test revealed that the product acidity score of the market curds varied significantly (p<0.01). Air samples collected from the various areas of curd production revealed highest bacterial count at the area of thermal treatment and lowest at the area of cream separation. The mean YMC was higher at the pasteurisation room. Hand washings of the personnel had the highest mean TVC and CC. E. coli was detected only in hand washings of personnel. Samples collected from the cream separator had the highest mean TVC and least in packaging material. Faecal streptococci were detected in all the samples tested and highest count was observed in the case of storage can. Samples from the double jacketed vat had the highest CC. Coliforms were not detected in the washings of the packaging material. Heat treated skim milk was free of coliforms and the mean FSC was significantly (p<0.05) lower than that of starter inoculated milk after one and six h of incubation. Yeast and moulds were not detected in heat treated skim milk, but present in starter inoculated one and six h milk samples. The mean pH of fresh curd samples was significantly (p<0.01) lower than that of heat treated skim milk. The starter culture was free of coliforms and faecal streptococci. The present study reflects the importance of quality assurance during every step of production and storage of curd to avoid early spoilage and to safeguard consumer health. Presence of pathogenic organisms in curd is of great public health significance as it is consumed as such paving way to food poisoning.ThesisItem Open Access Microbial quality assurance of milk in its production, processing and storage(Department of Veterinary Public Health, College of Veterinary and Animal Science, Mannuthy, 2005) Prejit; KAU; Nanu, EIn the present study 296 milk samples were collected from dairy farm, processing plant and retail shops and analysed for the microbial quality by estimating various microbial counts and assessing the presence of certain bacteria of public health importance. The microbial, physico-chemical and organoleptic qualities of pasteurized milk samples stored under refrigeration were evaluated. The critical points of bacterial contamination of milk at various stages of production, pasteurization, packaging and storage were also assessed during the investigation. Out of 60 samples of raw milk from individual animal, pooled milk and chilled milk analysed, 46.7 and 36.6 per cent samples were graded as very good and good based on BIS (IS 1977). However only 25 per cent samples were only considered satisfactory based on coliform count with none of the pooled milk samples meeting the standards. Pooled milk samples revealed maximum contamination with highly significant (p0.01) difference between mean TVC and CC and significant (p0.05) difference between mean PC and FSC of milk from individual animal. However mean E.coli count was more in individual animal milk sample when compared with pooled milk. The pooled milk sample was kept under chilled condition for 17 hours. The chilled milk had higher mean TVC, ECC and PC however the increase was not statistically significant. Pasteurization of milk was effective in reducing the microbial population of raw milk and there was highly significant (p0.01) reduction in TVC, CC, PC, FSC and YMC. From the sample of milk collected immediately after heating, after pasteurization and after packaging the mean TVC was high in packaged milk sample (4.76±0.15 log10 cfu/ml). Coliform was absent in cent percent of heated milk. However, 60 per cent of packaged milk had the organism with the mean count of 0.98±0.36 log10 cfu/ml. Only 40 per cent of packaged milk was graded satisfactory based on coliform standards prescribed by BIS (Indian Standards, 1992). E.coli could not be detected from milk collected after heating section and immediately after pasteurization. Maximum microbial contamination was seen in packaged milk. This indicates that contamination of milk occur in the storage tank or packaging section. Hence proper cleaning and sanitation of storage tank and packaging machine will reduce the microbial contamination to a considerable extent. The microbial analysis of the retail milk sample (56) of the brands A, B, C and D revealed that the samples of the brand B had highest mean TVC (5.91 ± 0.01 log10 cfu/ml) and FSC (1.52 ± 0.22 log10 cfu/ml). The highest mean coliform (3.08 ± 0.29 log10 cfu/ml), E. coli, (2.35 ± 0.38 log10 cfu/ml), psychrotrophic counts (5.68 ± 0.25 log10 cfu/ml) were seen in the samples of brand C. Brand A had highest mean YMC (1.21 ± 0.22 log10 cfu/ml). Only 23.2 and 26.8 per cent retail samples met the TVC and CC standards prescribed by BIS (IS-1992). However, 57.14 per cent of the samples of the brand A met the standard. On comparison of freshly packed milk obtained from dairy plant with the retail brands revealed that freshly packed milk sample had highly significant (p0.01) difference and lesser TVC, CC and PC in comparison with the brands B, C and D. Thus the microbial quality of retail milk available in the locality varied among different brands hence strict hygienic measures should be adopted to minimize microbial contamination. Pasteurized milk stored under refrigeration (4±1°C) showed an increase in TVC, CC, ECC, PC, FSC and YMC throughout the storage period. However, the initial growth rate of microorganism was slow due to sub lethal injury of microorganism during pasteurization and storage of milk under refrigerated condition. The increase in TVC, CC, ECC, PC, FSC and YMC between zero day and 12th day was 3.96, 1.76, 0.16, 3.76 and 2.37 log10 cfu/ml, respectively. The increase in the count of organism during storage may present the problem of shelf life deterioration of milk. The public health impact on the consumers was assessed by isolation and identification of E.coli, S. aureus and L. monocytogenes, the organisms of public health importance. Escherichia coli contamination of milk occurs through unhygienic handling of milk. The organism was detected in four samples (20 per cent) of the samples of raw pooled milk and was of serotypes 05 (2 samples), 0141 and 0172. Ten per cent of freshly packaged and refrigerated milk samples revealed the presence of the organism and all isolates were of serotypes 0148. A total of 38 E.coli isolates were obtained from retail milk samples. S. aureus was isolated from 60, 5, 12.5 per cent of the samples of raw, freshly pasteurized and retail milk, respectively. The organism was isolated from 5 per cent of the samples stored on sixth day and from 10 per cent samples stored on the eight day. L. monocytogenes was not isolated from milk samples. Sensory analysis of refrigerated milk samples showed an overall reduction in the score of colour and appearance, flavour, odour and body as the storage period increased. Development of off odour, salty or stale flavour and presence of clotted particles indicated the sensory spoilage and the maximum shelf life obtained was eight days. There was reduction in mean pH value throughout the storage period. All the samples showed positive to clot on boiling test on the day 12 of storage but the sample showed sensory unacceptability earlier. The various critical points of bacterial contamination of milk was evaluated by collecting samples of air, water, rinse samples from utensils, equipments, hand washing of milker/personnel in the processing line, strainer and packaging material and were subjected to estimation of various bacterial counts. The mean total viable count and yeast and mold count of air samples were found to increase after the milking process or processing. Among the water samples, coliform and E. coli was detected more in the samples obtained from dairy farm. High microbial count was recorded for milk pail, milkers hand washings and package machine wash indicating an important sources of contamination. Strict hygienic practices followed by health education will minimize the microbial contamination to a considerable extent.