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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.

The objective of this study was to investigate the level of microbial contamination of yoghurts sold in Enugu Urban.

Six different brands of bottle packaged yoghurt were brought from hawkers and beverage stores in Enugu Urban. Each sample was serially diluted using sterile distilled water as diluents (Prescolt et al 2002) and Iml of 10-3 sample was plated in duplicate using the pour plate method on MacConkey agar and nutrient agar media the plates were incubated at 370C for the 24hrs.

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.






Chemical Composition Of Milk

History of Yoghurt

Traditional Method of Yoghurt Production

Processing Of Yoghurt

Yoghurt Quality

Yoghurt Pasteurization

Yoghurt Preservation

Refrigeration of Yoghurt

Yoghurt Flavour

Quality Control of Yoghurt

Microbiological Analysis

Pathogenic Bacteria

Yoghurt Spoilage

Biochemical Analysis

Yoghurt pH


Materials And Methods

Sample Collection

Analysis Of Sample

Identification Of Isolates

Bacteria Identification

Biochemical Tests





Conclusion And Recommendation





        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.


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