ADVERSE EFFECT OF FERMENTED MILK CONSUMED BY NIGERIA

ABSTRACT 
The aim of this study was to identify the adverse effect of fermented milk consumed by nigeria by examining the antimicrobial properties of Lactic Acid Bacteria (LAB) isolated from fermented milk collected from Fagge, Kumbotso, Dala, Gwale, Tarauni and Ungogo LGA in Kano state. Traditional fermented milk in Nigeria are produced by spontaneous fermentation using traditional utensils. In this study, thirty homesteads from six LGA that produce and process fermented milk were selected and interviewed using semi- structured questionnaires. Kindirmo and Maishanuhave similar processing method whereby fermentation is achieved by accumulation of milk; mean while Wara is produced by allowing the milk to ferment naturally. The pH decreased logarithmically, nonlinearly over the fermentation period from 6.5 ± 0002 from first day of fermentation to 3.92±0.001 over 4 days.There was no significant difference (p<0.05) in the pH values between the three types of fermented milk preparations. Cell free supernatants (CFS) of 180 LAB isolated from traditional fermented milk were evaluated for antimicrobial activities against selected food borne pathogens; Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Candida albicans ATCC 14053, Bacillus cereus ATTC 10876 Geotrichumklebahnii(IKST F. Lab. isolate) Escherichia coli ATCC 25922 using the well diffusion method. Twenty LAB isolates that shown the highest inhibitory effects were selected for biochemical identification using API 50 CHL were identified as; Lactobacillus plantarum (53%), Lactobacillus rhamnosus(29%), Pediococcuspentosaceus(6 %), Lactobacillus paracaseissp.paracasei(6%) and Lactococcus lactic ssp. lactis (6%), of which Pediococuspentosaceus showed the most inhibitory effect on all the indicator strains and they have potential to produce bacteriocin Pediocin and the most inhibited indicator strain belonged to yeast Candidafamata. In addition to antimicrobial activities, the major organic acids in all three types of milk were found to be lactic acid 0.265±0.056 mg/L. However, the levels of volatile organic compounds in the naturally fermented samples varied from one sample to another but, butyric, acetic and propionic acid were found in trace amounts. Some of the volatile flavor compounds found in Kindirmo, Wara and Maishanu were acetic acid, 2,3 Butanediol and Lactic acid. 

CHAPTER 1: INTRODUCTION 
Fermented milk is one of the foods which are highly respected and form part of daily intake in Nigeria. There are different types of fermented milk in Nigeria which have different preparation methods. The diversity of such fermented milk products is derived from the heterogeneity of traditions found in the Nigeria, cultural preference, different geographical areas where they are produced, the staple and/or by-products used for fermentation. These types of milk are mostly prepared using natural ingredients without any addition of preservatives. 

Fermentation is a relatively efficient, low energy preservation process which increases the shelf life and decreases the need for refrigeration or other form of food preservation technology (Marshall, & Mejia, 2011). It is therefore a highly appropriate technique for use in developing countries and remote areas where access to sophisticated equipment is limited. 

Traditional fermentation is a form of food processing where microbes for example, lactic acid bacteria (LAB) are utilized (Cheluleet al., 2010). The technology of fermentation has been used for centuries as a form of food preservation technique for perishable food products (Hansen, 2002). Over the years, it became part of the cultural and traditional norm among the indigenous communities in most developing countries, especially in Africa. On this note, the people living in remote areas prefer fermented over unfermented milk due to improved flavor and texture that accompanies fermentation. In addition, these products are an important supplement to the local diet and provide vital elements for growth and good health. This popularity has made fermented foods one of the main dietary components of the developing world. 

Fermenting milk assist in the preservation of milk by generating lactic acid and other antimicrobials, production of flavor compounds (e.g. acetaldehyde and diacetyl) and other metabolites (e.g. extracellular polysaccharides) that confer consumer desired organoleptic properties to the product (Chelule, et al., 2010). Fermentation also improves the nutritional value of milk; it releases free amino acids and promotes synthesis of vitamins (Kailasapathy, 2008). Fermented milk contains special therapeutic or prophylactic properties against cancer and lactose intolerance (Mercenier, et al., 2002). Fermentation also, improves food safety through inhibition of pathogens (Adams & Mitchell, 2002) as well as removal of toxic compounds in food. These significant changes cause desirable biochemical effects resulting into development of new aroma, flavor, taste and texture thereby increasing the sensory quality, palatability and acceptability of the product. 

Statement of Problem 
Kindirmo, Masanza or Mabasiand Maishanuare common fermented milk products in the rural areas of the northern Nigeria. Like any other traditional fermented milk in the developed countries, these types of milk serve as substitutes for traditional vegetables, beans or meat supplementing nutrition for low income households and for women and children in rural area (Bille, et al., 2002). In addition, the fermentation is based on spontaneous process due to the growth of the micro flora naturally present in the raw material. Therefore, the quality of the fermentation end product dependents on the microbial load and spectrum present in the raw material. Since Kindirmo, Masanza or Mabasiand Maishanuare not prepared uniformly by the rural processors, they have fluctuating qualities due to natural fermentation, uncontrolled fermentation temperature and time. Failure of fermented milk to cause food poisoning in spite of uncontrolled fermentation environments suggests unique chemical properties in these products. Therefore, there is a need to examine the diversity of LAB, the antimicrobial content of the milk and to purify the most predominant LAB in traditional fermented milk from the northern parts of Nigeria. Previous antibacterial activity studies have been performed by isolating LAB from fermented products. However, LAB isolated from Nigeria traditionally fermented milk has not been intensively studied. 

Objectives of the Study 
The overall aim of the study was to identify the adverse effect of fermented milk consumed by nigeria by examining the antimicrobial properties of Lactic Acid Bacteria (LAB) isolated from fermented milk. 

The specific objectives of this research project were: 
1. To analyze the physicochemical properties (pH, viscosity and titratable acidity) for the three types traditional fermented milk in Nigeria. 

2. To isolate different types of lactic acid bacteria using selective media such as Rogosa for 

Lactobacillus spp. and M17 for Lactococcus spp. e.t.c. 

3. To identify starter culture strains to the species and sub-species level using biochemical and genetic identification methods (API 50 CHL and 16S rDNA). 

4. To screen the isolated strains for antimicrobial compounds with the ability to act as a natural competitive substance inhibiting other microorganisms that share the same niche; these include: hydrogen peroxide, organic acids, diacetyl and bacteriocins. 

5. To determine the concentration of different organic acids (lactic and acetic acids) using conversional method (titration) and chromatographic method (HPLC). 

1.5 Significance of the Study 
Fermented milk plays an important role in the diet of low income and the majority of people living in the rural areas in Nigeria. This research work provides a baseline data on the antimicrobial activities of Nigerian fermented milk products. It focuses on antimicrobial compounds profiling of different starter cultures from fermented milks produced in Nigeria which has not been reported previously. In addition, this research identified the types of micro flora in traditional fermented milk to the genus level. Once the identity of the milk fermenting micro flora is known it would be possible to optimize fermentation process through alteration and modification of starter cultures so as to improve the quality of fermented milk products for possible commercialization purpose. Furthermore, knowledge of the starter cultures metallic products would facilitate their ease of extraction and subsequent use in food industries as preservatives. Alternatively, the isolated LAB could be used as probiotics. Micro flora profiling is significant as it may unravel species’ diversity and concentrations in the fermented milk; it may shed light on the organisms’ ecological characteristics as they interact with the host and the environment at large. 

1.6 Limitation of the Study
Preferably, the study was to include all LGA in Kano state in Nigeria, but Nigeria is a very big country and there are many different cultural groups with different traditional foods and fermented milks. It would be an expensive, time consuming and labor intensive to screen all fermented milk products in Nigeria. DNA sequencing facilities are not available in Nigeria; genetic identification of the starter cultures was therefore done at Inqaba Biotech Laboratory in South Africa. During the screening and strains identification phases, a large number of isolates was obtained. Therefore, only isolates which showed outstanding results on different tests, in particular, the bacteriocengenic strains which showed protective characteristics were considered for identification on molecular diagnosis’ and other antimicrobial tests such as diacetyl, hydrogen peroxide and organic acids using conversional analytical techniques, since screening all isolates was going to be a very expensive and time consuming process.

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Item Type: Project Material  |  Attribute: 59 pages  |  Chapters: 1-5
Format: MS Word  |  Price: N3,000  |  Delivery: Within 30Mins.
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