Thesis Abstract

Abstract
Yoghurt is a popular dairy product consumed worldwide due to its taste, nutritional value, and health benefits. However, the presence of microbial contamination in yoghurt poses a significant risk to consumer health. This research project aimed to investigate the microbial contamination of yoghurt and identify the types of microorganisms involved in the contamination process. The study involved the collection of yoghurt samples from various sources, including commercial brands and homemade preparations. Microbiological analysis was conducted using standard methods to assess the microbial load and diversity in the samples. The results revealed the presence of various microorganisms, including bacteria, yeast, and molds, in the yoghurt samples. Further characterization of the isolated microorganisms was performed using molecular techniques such as polymerase chain reaction (PCR) and sequencing. This analysis provided insights into the specific species and strains of bacteria and fungi present in the contaminated yoghurt samples. The findings indicated that the microbial contamination of yoghurt was primarily due to poor hygiene practices during production and storage. In addition to identifying the types of microorganisms present in the yoghurt samples, the study also evaluated the antimicrobial susceptibility of the isolated strains. Antibiotic susceptibility testing was carried out to determine the effectiveness of common antimicrobial agents against the contaminating microorganisms. The results highlighted the presence of multidrug-resistant strains in some yoghurt samples, posing a serious public health concern. Overall, this research project shed light on the microbial contamination of yoghurt and emphasized the importance of quality control measures in dairy production. The findings underscored the need for strict adherence to good manufacturing practices and hygiene protocols to prevent microbial contamination and ensure the safety of yoghurt products. The study also highlighted the potential risks associated with consuming contaminated yoghurt, including foodborne illnesses and antibiotic resistance. In conclusion, the microbial contamination of yoghurt is a critical issue that requires continuous monitoring and intervention to safeguard consumer health. By understanding the sources and types of microorganisms involved in yoghurt contamination, producers can implement effective control strategies to minimize the risk of contamination and maintain the quality and safety of yoghurt products.

Thesis Overview

1.0   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 andLactobacillus bulgaricus in a 1: 1 ratio. The coccus which is theStreptococcus thermophilus grows faster than the Rod which is theLactobacillus 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.

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).

Health complications associated with consumption of inadequately pasteurized milk products include serious infections that are hard, to treat with antibiotics. This becomes clinically significant if organisms isolated from an assessed sample is resistant to conventional antibiotics. Thus, can confer antibiotic resistance to the infected host while providing no alternative drug (Gould, 1994). Heat treated yoghurt do not contain lactic acid bacteria as these are killed during post fermentation. Yoghurt manufacturing companies mainly market “heat treat” yoghurt to prolong it’s shelf life (Hove et al, 1999). It is important however to evaluate the microbial gravity of some milk products sold in Nigeria. This project work aims at assessing the antimicrobial susceptibility pattern of microorganisms present in yoghurt sold in Enugu.