Microbial Contamination of Yogurt

Microbial Contamination of Yogurt – Microbiology Projects

CHAPTER ONE

1.0 INTRODUCTION

Yogurt 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 is produced commercially at home. (Willey et al., 2008). In its commercial production, nonfat or low-fat milk is pasteurized cooled to 43°c, and is 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 sugar and lactose into lactic acid. This process gives yogurt its texture. The associative growth of the two organisms results in acid production at a rate greater than that produced by them individually. Yogurt is generally made from a standardized mixture containing whole milk, partially defatted milk, condensed skim milk cream, and nonfat dry milk. Alternatively, milk may be partly concentrated by the removal of 15- 20% water in a vacuum pan or by heating. While the microorganisms fermenting milk confer on it certain health benefits inadequately pasteurized milk may contain microorganisms 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 immunosuppressed and prone to bacterial and fungi infection. (Boor,2001).

Health complications associated with the 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 are resistant to conventional antibiotics. Thus, can confer antibiotic resistance to the infected host while providing no alternative drug (Gould, 1994). Heat-treated yogurt does not contain lactic acid bacteria as these are killed during post-fermentation. Yogurt manufacturing companies mainly market “heat treat” yogurt to prolong its 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 yogurt sold in Enugu.

CHAPTER ONE

1.1 INTRODUCTION

Yogurt 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 is 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 is 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 yogurt its texture. The associative growth of the two organisms results in acid production at a rate greater than that produced by them individually.

Yogurt is generally made from a standardized mixture containing whole milk, partially defatted milk, condensed skim milk cream, and nonfat dry milk. Alternatively, milk may be partly concentrated by the removal of 15- 20% water in a vacuum pan or by heating. While the microorganisms fermenting milk confer on it certain health benefits inadequately pasteurized milk may contain microorganisms 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).

1.2 Statement of the Problem

Health complications associated with the 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 are resistant to conventional antibiotics. Thus, can confer antibiotic resistance to the infected host while providing no alternative drug (Gould, 1994). Heat-treated yogurt does not contain lactic acid bacteria as these are killed during post-fermentation. Yogurt manufacturing companies mainly market “heat treat” yogurt to prolong its 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 yogurt sold in Enugu.

1.3 Objectives of the Study

The main objective of this study is to assess the microbial contamination of yogurt. Specific objectives include;

i. To determine the level of the microbial content of yogurt

ii. To know the nutritional value of yogurt.

1.4 Significance of the Study

The study shall elucidate the impact of eCommerce on the performance of businesses to provide a comparative analysis with the traditional buying and selling practice. This study will be of immense benefit to other researchers who intend to know more about this study and can also be used by non-researchers to build more on their research work. This study contributes to knowledge and could serve as a guide for another study.

References

Agu, K., Archibong, E., Anekwe, D., Ago, C., Okafor, A., Awah, N. (2014). Assessment of bacteria present in yogurt sold on Awka Metropolis. Scholars Journal of Applied Medical Sciences, 2: 3071–3075.

Akkaya, L., Birdane, Y. O., Oguz, H., Cemek, M. (2006). Occurrence of aflatoxin M1 in yogurt samples from Afyonkarahisar, Turkey. Bulletin of the Veterinary Institute in Pulawy, 50: 517.

Aliasghari, F., Javadi, M., Homayouni Rad, H., Izadi, A. (2016). Application of laxative foods in prevention and treatment of constipation. MOJ Food Processing and Technology, 2: 00045.

Asghari-Jafarabadi Rad, M., Rafraf, M., Nabavi, S., Somi, M.H., Homayouni-Rad, A., Asghari-Jafarabadi, M. (2014). The effect of probiotic and conventional yogurt consumption on anthropometric parameters in individuals with non-alcoholic fatty liver disease. Journal of Babol University of Medical Sciences, 16: 55–62.

Bbosa, G. S., Kitya, D., Odda, J., Ogwal-Okeng, J. (2013). Aflatoxins metabolism, effects on epigenetic mechanisms, and their role in carcinogenesis. Health, 5: 14.

Beheshtipour, H., Mortazavian, A. M., Haratian, P., Darani, K. K. (2012). Effects of Chlorella Vulgaris and Arthrospira platensis addition on the viability of probiotic bacteria in yogurt and its biochemical properties. European Food Research and Technology, 235: 719–728.

Bonyadi, M., Mojarrad Khangah, S., Qanbarov, K. Q., Gojezadeh, M., Dalili Oskuee, R. (2011). Determination of the number of lactic acid bacteria and yeasts in the combination of traditional yogurts of villages of East-Azerbaijan province. Medical Laboratory Journal, 5: 62–65.