doi:10.5455/vetworld.2013.400-404 Microbiological evaluation of yoghurt products in Qena city, Egypt

Aim: To examined Large and small scale yoghurts for presence of microorganisms of sanitary importance. Materials and Methods: A total of 100 random samples from various dairy shops, street vendors and supermarkets located in Qena city were collected within 2008 - 2010. Results: The recorded results show that (92%) and (70%) of the examined small and large scale yoghurt samples had 4 3 Psychrotrophic count with an average of 3.9 x 10 and 6.8 x10 respectively. It was found that Enterococci were detected in 4 3 (58%) and (40%) with an average count of 1.72 x10 and 2.0 x 10 for the examined small and large scale yoghourt samples. S. 3 2 aureus were detected in (72%) and (36%) with an average of 8.5 x 10 and 9.41 x10 for both small and large scale yoghurt 4 samples. Regarding yeast and moulds they were found in (94%) and (40%) with an average counts of 1.4 x 10 for small scale 2 and 3.9 x 10 of large scale yoghurt samples. Most probable number (MPN) technique showed that [(38), (20)], [(35), (17)] and [(30), (6)] out of the total examined small and large scale yoghurt samples were contaminated with coliform, Fecal coliform and E. coli respectively. The incidence of E. coli biotype I and II for examined small scale yoghurt samples were (63.4%) and (36.6%), while for the examined large scale yoghurt samples were (16.7) and (83.3) respectively.


Introduction
Coliforms are routinely used as indicator to the quality of the milk and milk products as some members Yoghurt is the most popular type of fermented of coliforms are responsible for the development of milk in Egypt.The nutritive value of yoghurt is objectionable taints in milk and its products rendering attributed to the fat content, sugar and casein.
them of inferior quality or even unmarketable [3].Therefore, yoghurt is recommended for sick and Escherichia coli (E.coli) frequently contaminate convalescent people.It is also inhibit the bacterial flora food and it is a good indicator of fecal pollution [5].Its of intestine which may lead to constipation, presence in milk products indicates presence of other autointoxication and colitis, as well as, it helps in the enteropathogenic microorganisms which constitute a absorption of calcium and phosphorus [1].public health hazard [5].

Psychrotrophic bacteria are ubiquitous bacteria
Staphylococcus aureus (S. aureus) in food article that are able to grow at refrigerated temperature, and is an index of its contamination from personnel sharing their natural habitats are soil, water and animal.Some in production and handling.Moreover, Enterotoxigenic of psychrotrophs affect the quality of dairy products S. aureus strains may find opportunity to grow and through their production of enzymes, in particular multiply in the food leading to food poisoning among lipase and proteases which are heat stable leading to consumers [6].decrease the keeping quality of milk products.Some Presence of yeasts and moulds in milk and dairy members of Psychrotrophic bacteria have been products are undesirable even when found in few implicated as a causal agent of food poisoning [2].numbers as they resulting in objectionable changes that Enterococci may have a distinctive role as render the products of inferior quality [7].indicators of poor factory sanitation owing to their This study aimed to evaluate the microbiological relatively high resistance to drying, detergents, as well quality of small and large scale yoghurt in Qena city as to freezing temperature.Moreover, these organisms which may be contaminated with microorganisms of are also implicated in food poisoning outbreaks [3].Several investigators have reported the occurrence of sanitary importance that gaining access to product Enterococci in dairy products [4].
from various sources during production, handling, distribution, and may be implicated in food poisoning.by [22].Lower count was recorded by [23].Whereas, • Confirmed test for E. coli count [11]: 2 • Identification of E. coli recovered from the examined the Enterococci count was ranged from 1.0 x 10 to 1.5 4 3 samples using [8]: x 10 with an average count of 2.0 x 10 /g for large scale 4. Enumeration and isolation of S. aureus [12]: yoghurt samples.Higher counts were obtained by [18, • Morphological characters for all isolate by staining 20,24].Lower counts were recorded by [22,25].
The existence of Enterococci in yoghurt is an indication 5. Total yeast and mould counts [16].
of neglected sanitary control measures during Discussion production.Moreover, Enterococci count is considered It is clearly evident from Table-1, that (92%) and more reliable than the coliforms count as an index of (70%) of the examined small and large scale yoghurt sanitary quality of yoghurt as they are able to survive samples were contaminated with psychrotrophs with a the unfavorable microenvironment as the low pH value 3 5 of yoghurt.count/g was ranged from 1.7 x 10 to 3.0 x 10 with an 4 It is clear from the finding in Table-1, that (72%) average count of 3.9 x 10 /g for small scale yoghurt and (36%) of the examined small and large scale samples.Higher counts were obtained by [17].While, yoghurt samples were contaminated with S. aureus large scale yoghurt samples had counts ranged from 4.0 with an average of 8.5 x 10 /g for small scale yoghurt x 10 to 6.0 x 10 with an average count of 6.8 x 10 /g. 2 samples and an average of 9.4 x 10 /g for large scale Higher counts were obtained by [18,19].Lower count yoghurt samples.In case of the examined small scale was recorded by [20].yoghurt samples, higher counts were obtained by [27].The high incidence and counts of psychrotrophic Lower counts were recorded by [17].While incase of bacteria detected in small scale yoghurt could be the examined large scale yoghurt samples, higher attributed to the absence of heat treatment, carelessness According to the limits proposed by Egyptian infections or in symptomatic carriers that come in standards [26], we found that (76%) and (40%) of the contact with food [29].
examined small and large scale yoghurt samples failed Concerning yeasts and moulds it was found in to comply with the limits, (Table -4).Whereas (98%) and (40%) of the examined small and large scale according to the limits proposed by Food standards yoghurt samples with count/g was ranged from 2.5 x [32], we found that (62%) and (26%) of the examined 2 5 4 10 to 1.4 x 10 with an average of 1.4 x 10 /g for small small and large scale yoghurt samples, respectively scale yoghurt samples.Higher counts were obtained by failed to comply with the limits, (Table -5).[28].Lower counts were recorded by [30].While, large Presence of coliforms in such high incidence in scale yoghurt samples had counts ranged from 1.00 x small scale yoghurt samples declare neglect sanitary 2 3 2 10 to 1.40 x 10 with an average of 3.9 x 10 /g (Table measures reflecting the using of poor quality raw milk, 1).Higher counts were obtained by [20,27,28].Lower insufficient preheating process, also presence of other counts were recorded by [30].enteric pathogens.Moreover, coliforms as an indicator According to the limits proposed by the Egyptian of post processing contamination in yoghurt standards [26], we found that (98%) and (40%) of the manufacture has been established and recommended examined small and large scale yoghurt samples, by public health authorities worldwide [33].Such rate respectively failed to comply with the limits (Table - 4).
of contamination of the examined large scale yoghurt Yoghurt by nature is a high acid product, therefore it samples is indicative of post processing contamination may be considered as a highly selective environmental as these organisms unable to survive the heat treatment favoring the growth of yeasts and moulds as spoilage applied during yoghurt manufacture.microorganisms, as well as, their presence in yoghurt is These data were surprising when one considered being indicative of poor sanitary practices.
what was stated by [34] that yoghurt wasn't a good medium for coliforms as the number of coliforms Concerning the coliforms results in Table-2, introduced by inoculation decreased rapidly and indicated that (38) and ( 20) samples out of the th couldn't be isolated after the 4 day due to the combined examined small and large scale yoghurt samples, effect of lactic acid and peroxides produced by starter of a strategy to enhance producing of save and high culture.On contrary, [35] proved the aciduric tendency quality dairy products. of coliforms and found that pH 4.5 or 5 are quite standards [26] and Food standards [32], we found that enterococci in dairy foods.Indian Journal of Microbiology, all recorded samples were failed to comply with the 48, (3): 317-325.limits, (Tables 4 & 5).

5.
Singh, P. and Prakash, A. ( 2008) Isolation of Escherichia The variation between the obtained data and the obtained by [23].undertake safety measures to avoid potential threats Rome, Italy.and apply educational programs for dairy products 12. AOAC "Association of Official Analytical Chemists" (2000) th Official methods of analysis of AOAC international.17 Ed., producers about the risk of the contamination of this William Horwitz (ed.), Gaithersburg, Maryland, USA.product, how to prevent or at least reduce this 13.Koneman, E., Washington Winn, Jr., Allen, S., Janda, W., pathogens from the yoghurt and how to apply strict 10. Deibel, R. H. and Hartman, P. A. (1984) The Enterococci, 405.In Compendium of methods for the microbiological Conclusion nd examination of foods, 2 Ed., Speck, M.L. (ed.).American Public Health Assoociation, Washington, D.C, USA.In light of the above, yoghurt samples obtained 11.FAO "Food and Agriculture Organization "(1992) Manual of from Qena city markets constitute a high risk hazard to food quality control.4. Rev. 1 Microbiological analysis.consumers.The finding of the study warrant the need to Food and Agriculture Organization of the United Nations.

Table - 1
. Statistical analytical results of microbiological examination of the examined yoghurt samples

Table - 2
. Frequency distribution of positive yoghurt samples of Coliforms, Fecal coliforms & E coli based on their MPN The recorded by [25, 27].According to the limits proposed highest frequency distribution of coliforms in small by the Egyptian standards [26], we found that (72%) scale yoghurt samples was (36.8%) and lied in the [20,28]were obtained by[20,28].Lower counts were respectively were contaminated with coliforms.

Table - 3
. Frequency distribution of E. coli biotypes recovered from the examined yoghurt samples

Type of yoghurt sample No. of samples examined No. of isolated E. coli E. coli biotype I E. coli biotype II
Table-4.Summarized results of microbiological examination of yoghurt samples in compared with the Egyptian standards (Egyptian Organization for Standardization and Quality Control "EOSQC, [26])

Table - 5
. Summarized Results of microbiological examination of yoghurt samples compared with the Food Standards[32] Ed., Speck, M.L. (ed.).American Public Health Assoociation, respectively.Higher result for E. coli biotype I was Washington, D.C, USA.
th Standards Methods for Examination of Dairy Products.17Byinspection of Table-3, we found that the