Microbial Contamination Of Yoghurt
An in-depth assessment of the microbial contamination of selected yoghurt sold in Onitsha Market was conducted in this study using standard microbiological procedures. The study also evaluated the physical parameters of the yoghurt brands at the time of purchase. The results demonstrated that the pH values of the yoghurt samples ranged from 4.29 to 4.56, while their temperature readings were between 8°C and 17°C. The mean total count of the samples on Brain Heart Infusion (BHI) and De Mann Rogosa Sharpe (MRS) agar media ranged from 2.0×10^7 to 6.0×10^8 cfu/ml and 1.0×10^8 to 5.4×10^8 cfu/ml, respectively.
The yoghurt isolates were identified as Streptococcus and Lactobacillus species. These isolates exhibited resistance to commonly used antibiotics and inhibited the growth of Staphylococcus aureus and Pseudomonas aeruginosa from clinical samples. Additionally, no viable growth of the isolates was observed in simulated gastric fluid with a pH of 1.5 to 2.5. A slight decrease in the viable count of Lactobacillus spp. from 4.0×10^7 to 3.0×10^7 cfu/ml and Streptococcus spp. from 3.0×10^8 to 2.0×10^8 cfu/ml was observed in bile with a pH of 8.28 to 8.30. The isolates were recovered from faecal samples two weeks after ingestion, with mean counts ranging from no growth to 5.8×10^8 cfu/ml on MRS agar media.
The findings of this study indicated poor microbiological standards of commercial yoghurts sold in Onitsha Market at the time of this research. Despite this, the isolates were found to exhibit some probiotic potentials, and no pathogens were isolated from the samples. It is recommended that strains of microorganisms capable of delivering full probiotic benefits to consumers be utilized in commercial yoghurt production. This result highlights the necessity for improved hygienic measures in the processing, storage, and distribution of these products to prevent public health challenges.
ABSTRACT
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
1.2 STATEMENT OF PROBLEM
1.4 AIMS AND OBJECTIVES
1.5 SIGNIFICANCE OF STUDY
1.5 LIMITATION OF THE STUDY
1.6 RESEARCH QUESTION
1.7 DEFINITION OF TERMS
CHAPTER TWO
2.0 LITERATURE REVIEW
2.1 CONCEPTUAL REVIEW
2.2 YOGHURT CULTURE BACTERIA
2.3 YOGHURT
2.4 HEALTH BENEFITS OF YOGHURT
2.5 YOGHURT APPEARANCE
2.6 FERMENTED MILK PRODUCTS
2.7 MILK FERMENTATION AND BIOCHEMICAL CHANGES
CHAPTER THREE
3.0 MATERIALS AND METHODS
3.1 MATERIALS
3.2 METHODOLOGY
3.2.1 STUDY AREA
3.2.2 SAMPLE COLLECTION
3.3 MICROBIOLOGICAL ANALYSIS
3.3.1. PREPARATION OF MATERIALS
3.3.2. PREPARATION OF SERIAL DILUTIONS
3.3.3. ENUMERATION OF TOTAL AEROBIC BACTERIA (TEB)
3.3.4. ENUMERATION OF COLIFORM BACTERIA
3.3.5. ENUMERATION OF YEAST AND MOULDS
3.4. ISOLATION AND IDENTIFICATION OF MICROORGANISMS
3.4.1. GRAM REACTION
3.5. BIOCHEMICAL TEST
3.5.1. CATALASE TEST
3.5.2. INDOLE TEST
3.5.3. OXIDASE TEST
3.5.4. MOTILITY TEST
3.5.5. COAGULASE TEST
3.5.6. CITRATE UTILIZATION TEST
3.5.7. METHYL RED TEST
3.5.8. VOGES PROSKAUER
3.5.9. CARBOHYDRATE FERMENTATION TEST
3.6 DATA ANALYSIS
CHAPTER FOUR
4.0 RESULTS AND DISCUSSION
4.1 RESULTS
4.2 DISCUSSION
CHAPTER FIVE
5.0 SUMMARY AND CONCLUSION
5.1 SUMMARY
5.2 CONCLUSION
REFERENCES
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