1.1 Introduction
Yoghurt is a fermented dairy product obtained from the lactic acid fermentation of milk. It is one of the most popular fermented milk products in the world and produced commercially at home (Willey et al., 2008). In its commercial production, non fat or low fat milk is pasteurized cooled to 43°c and are inoculated with known cultures of microorganisms referred to as starter cultures. The starter cultures may be a pure culture of a particular species of Lactobacillus or a mixed culture of Streptococcus thermophilus and Lactobacillus bulgaricus in a 1:1 ratio.
The coccus which is the Streptococcus thermophilus grows faster than the Rod which is the Lactobacillus bulgaricus and is primarily responsible for acid production while the rod adds flavor and aroma. The growth of these Microorganisms causes the transformation of milk’s sugar, lactose into lactic acid. This process gives yoghurt it’s texture. The associative growth of the two organisms results in acid production at a rate greater than that produced by them individually.
As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Limitation of the study and Definition of technical terms.
1.2 Background of Study
Yoghurt is the most popular fermented dairy product over the world, and its taste and aroma differ from other acidified products in that, the aromatic substances include small quantities of acetic acid and acetaldehyde. Yoghurt is generally made from a standardized mixture containing whole milk, partially defatted milk, condensed skim milk cream and non fat dry milk. Alternatively milk may be partly concentrated by removal of 15- 20% water in a vacuum pan or by heating. While the microorganisms fermenting milk confers on it certain health benefits inadequate pasteurized milk may contain microorganism of special importance to man (Boor and Murphy, 2002).
In which its presence or absence in milk may reflect success or failure of good manufacturing practice (GMP) or cause infection when consumed together with food. This is of economic significance in Africa where the HIV/AIDS and cancer scourge has left the public who consume milk products immune suppressed and prone to bacterial and fungi infection (Boor, 2001).
Yogurts are regarded as ready to drink foods commonly taken for energy production and for health, all over the world, especially in Nigeria (Alli et al., 2010). This product blend is rich in protein and improves healthy living (Cueva and Aryana, 2008). It is important however to evaluate the microbial gravity of some milk products sold in Nigeria. This research aims at Investigating the Level of Microbial Contamination of Yoghurts Sold in Owerri Municipal.
1.3 Statement of Problems
Investigation revealed that the challenge of yogurt production in Nigeria is characterized by inadequate housing facility, lack of bacteriological free water (potable); poor waste management, lack of adequate environmental sanitation in areas of high population density and people with low income.
Also, the Agencies in charge of enforcing good environmental sanitation laws are not usually available to caution or prosecute offenders. This regulatory negligence results in the nonchalant attitude of these industries in disposing of their waste adequately.
1.4 Aim and Objectives of Study
The aim of the study is to investigate the Level of Microbial Contamination of Yoghurts Sold in Owerri Municipal. In achieving this aim, the following specific objectives were laid out as follows:
- To determine whether microbial isolates are pathogenic; and
- To isolate and characterize microorganisms that may be present in the yogurt samples.
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