Investigating The Level Of Microbial Contamination Of Yoghurts Sold In Enugu Urban

Project and Seminar Material for Microbiology

Investigating The Level Of Microbial Contamination Of Yoghurts Sold In Enugu Urban


Abstract


The objective of this study was to investigate the level of microbial contamination of yoghurt sold in Enugu Urban. Six different brands of milk products were brought from hawkers and beverage stores in the city. The products were analyzed by microbiological analysis. The results showed that most of the samples analysed met the requirements compared to standard organization. The presence of Staphylococcus aureus and Escherichia coli in the samples may constitute a health hazard to consumers if mishandled. The high heterotrophic bacterial and coliform counts may be an indication of possible faecal contamination of the product by potentially pathogenic organisms even though they were isolated from less than three of the six brands examined.


Chapter One


1.0 Introduction

Yoghurt is a cultural diary product produced by lactic fermentation of milk (Hui, 1992). Yoghurt is produced by the controlled fermentation of milk by two species of bacteria; Lactobacillus bulgaricus and Strptococcus thermophilus.
These two species of bacteriae have now been established as the yoghurt starters.

Any sort of milk may be used to make yoghurt, but modern production is dominated by cow milk. It is the fermentation of the milk sugar (Lactose) into lactic acid that gives yoghurt its gel-like texture and characteristics tang (Davis, 1974).

Milk is often regarded as being nature’s most complete food. It earns this reputation by providing many of the nutrients which are essential for the growth of the human body. It is an excellent source of protein, vitamins, minerals particularly calcium and also some anti-bacterial substances such as lysozyme, ladoferin (transferin) and lactoperoxidases. In addition to the major constituent, milk contains a large amount of lactose sugar, phosphate, peptone and nitrogenbase enzyme (Clurance et al., 1963). Yoghurt has practically the same food value as the basic milk product (Ruud and Bert, 2004).

Fermented milk products such as yoghurt contain bacteria from the lactobacilli group. These bacteria occur naturally in the digestive tract and have a cleansing and healing effect. Therefore, the introduction of fermented products like yoghurt into the diet can help prevent certain pathogenic bacteria, which may cause illness. Many people suffer from a condition known as “LACTOSE INTOLERANCE”. This means that they are unable to digest the milk sugar (lactose). Such people can however, tolerate milk if it is fermented to produce foods such as yoghurt. During fermentation, lactic acid producing bacteria breakdown lactose and in doing so eliminate the cause of irritation (Ruud and Bert, 2004).

In countries where food borne illness are investigated and documented, the relative importance of pathogens like Staphylococcu aureus and Escherichia coli in yoghurt borne infection is well known (Obende, 1999). Diary foods are frequently contaminated with staphylococci and cases of staphylococcal contamination of milk and milk products like yoghurt have been recorded (Umoh et al., 1985). More than 50% of the strains of S. aureus are able to produce enterotoxin associated with food poisoning. The most important source of contamination by S. aureus is the human. (Payre and Wood, 1974).

The coli forms bacteria are also reported to be contaminants of yoghurt. The study of Obende, (1999) shows that 60% of yoghurt samples analyzed in Enugu Urban are contaminated with coli forms. The source of contamination of coli forms bacteria is through water used or through the workers or utensil used in processing (Gillies and Bodds, 1973).

Interestingly, most of the yoghurts are produced in little less than the cottage industries at homestead level under different brand names and are found in stalls, or more commonly hawked along the streets, motor parks and in the market. In view of this, the objective of this study was to investigate the level of microbial contamination of yoghurts sold in Enugu Urban.


Chapter Five


5.1 Discussion

The result obtained from the microbiological analysis showed that product were contaminated by microorganisms of public health concern the high heterotrophic bacterial and coliform counts may be a consequence of low level of hygiere maintained during the processing by some of the producers of the product.

The detection of escherichia coli, enterobacter sp, klebsiella sp, and Proteus sp is an indication of possible faecal contamination of the product by potentially pathogenic organisms even though they were isolated from less than three of the six brands examined.

It is not surprising that lactosacillus and streptococcus were isolated from virtually all the sample examined because they are the organisms used as starter cultures for the production of yoghurt.

Similar microorganisms were isolated from yoghurt a similar product by Uzeh et al (2006).

The isolation of staphylococcus aureus is also of public health importance because of its ability to cause a wide range of infections especially food –borne intoxication some of these organisms were also isolated by Olasupo et al (2002) from kanunzaki, a cereal based, non-alcoholic beverage Engel et al (1980), Olpala and Jideani(2006) noted that some of the sources of microorganisms that contaminate yoghurt are problem of plant sanitation, the filling operation or the container and also the workers.


5.2 Conclusion

The conclusion drawn from this research work is that yoghurt if produced under a good hygienic condition, the microbial load could be reduced to be within acceptable limits of standard organization.

It is evident from this study that most of the samples of yoghurt analysed met the requirements compared to standard. However, yoghurt samples containing relatively low counts of Staphylococcus aureus and Escherichia coli may constitute a health hazard to consumers if mishandled.


5.3 Recommendations

Yoghurt should be prepared in a good hygienic condition so as to reduce the microbial load. Also care should be taken during processing and storage of the yoghurt samples to prevent contamination with unwanted materials and microorganisms such as staphylococcus species, (e.g. staphylococcus aureus) and coliforms (e.g. Escherichia coli).


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