MICROBIAL SUCCESSION DURING FERMENTATION OF SOME CEREALS

Abstract

Microbial succession of some fermented cereals was carried out using standard microbiological methods. The results revealed higher bacterial count from sample fermented in plastic container A (6.4 to 1.44 x 10⁵ cfu/ml), B (6.1 x 10⁴cfu/ml to 1.22 x 10⁵ cfu/ml), C (3.9 x 10⁴cfu/ml to 1.03 x 10⁵cfu/ml), Samples fermented with earthen pot, showed lower bacterial count with sample D (2.7 x 10⁴cfu/ml to 9.2 x10⁴cfu/ml), E (3.3 x 10⁴cfu/ml to 1.15 x 10⁵cfu/ml) and F (4.2 x 10⁴cfu/ml  to  9.0 x 10⁴cfu/ml ). The total fungal count results revealed higher fungal count from samples fermented with plastic container with sample A (0.4 x 10³cfu/ml to 1.7 x 10⁴cfu/ml), B (0.4 x 10³cfu/ml x 10³cfu/ml to 1.9x 10⁴cfu/ml), while C (0.2 x 10³cfu/ml x 10³cfu/ml  to  1.6 x 10⁴cfu/ml ). The results of samples fermented with earthen pot, showed lower bacterial count with sample D (0.2 x 10³cfu/ml to 1.0 x 10⁴cfu/ml), E (0.1 x 10³cfu/ml to 1.4 x 10⁴cfu/ml) and F (0.4 x 10³cfu/ml to 1.8 x 10⁴cfu/ml). The study revealed microorganism associated with progressive fermentation of cereals at day one in plastic container to include Bacillus, Streptococcus sp and Staphylococcus sp for day 1 and 2, while day 3 showed Streptococcus sp, Lactobacillus sp and Leuconostoc sp. Earthen pot revealed the presence of Lactobacillus sp and E. coli for day 1, day 2 had Lactobacillus sp and Micrococcus sp, while day 3 had Lactobacillus sp respectively. Fungal included Penicillin sp for day plastic.  Day two include Bacillus sp, Streptococcus sp, Staphylococcus sp, Lactobacillus sp and Micrococcus sp while fungal were Penicillin sp and Apergillus sp, while day three recorded bacterial isolated to include Streptococcus sp, Leuconostoc sp, Lactobacillus sp and Lactobacillus sp as bacterial and fungal as Candida sp. Streptococcus sp and  Lactobacillus sp recorded the highest frequency distribution 3(23.1%) each, Bacillus  sp and Staphylococcus sp recorded 2(15.4%), while E. coli, Leuconostoc sp and Micrococcus sp recorded the least frequency occurrence 1(7.7%) each respectively. Penicillium sp recorded the highest frequency distribution 4(44.5%), followed by Candida sp recorded 3(33.3%), while Aspergillus sp recorded the least frequency occurrence 2 (22.2%) each respectively. Therefore this study significantly shows that prolonged fermentation is good since it inhibits the growth of pathogenic bacteria leaving behind only the lactic acid bacteria (LAB) which are beneficial to the body due to their activities as probiotic, thereby increasing the nutritional content of the fermented food, reducing the toxicity of the food, forces  digestion and palatability of the food.

CHAPTER ONE

1.0    INTRODUCTION

Fermentation of cereal based foods is a common practice in Africa for food preservation. It is a technology that is simple; home based and has fed millions of people. Currently, a variety of fermented foods are produced from cereals at house hold and semi industrial scale. These foods are used as weaning food for infants and children (Lei and Jacobsen, 2004; Kalui et al., 2008) and also for adults. A wide range of cereal-based fermented foods and related processes is a testimony to cultural diversity and to the ability of humans to find ways to produce foods in different contexts. The beneficial effects are the preservation of foods and the increase in their organoleptic characteristics because of the production of lactic acid and other metabolites synthesized by lactic acid bacteria (Guyot, 2012).

Cereals which include maize (Zea mays), Sorghum (Sorghum bicolor), millet (Peninsetum americanum) and acha etc are used in the production of gruels which is used as complementary food for babies and serves as breakfast for adults. Functional foods are defined as foods that, in addition to their basic nutrients, contain biologically active components, in adequate amounts, that can have a positive impact on the health of the consumer. These foods generally contain health promoting components beyond traditional nutrients (Berner and O′Donnell, 1998).

Recently, people have realized that fermented foods have a role beyond provision of energy and body maintenance. Scientific investigation has shifted to research on the fermentation benefits (Kalui et al., 2010). Investigation has revealed that fermentation processes have been discovered to produce active substances (Grajek et al., 2005), flavor enhancing compounds, important enzymes and amino acids. Some fermentation microorganisms are known to produce anti–microbial substances which lead to safe and long shelf life of food products (Corgan et al., 2007; Kalui et al., 2009; Kalui et al., 2008; Parvez et al., 2006; Steinkraus, 2000). Useful microorganisms which have health benefits are associated with fermentation. Predominant among these organisms are Lactic acid bacteria (LAB) which produce lactic acid during fermentation (Holzapfel and Schilinger, 2002; Shah, 2007).

These organisms are generally regarded as safe (GRAS). Human’s need for natural health enhancing foods is a reason for research development in functional and traditional foods. Many workers have undertaken research into the probiotic potency of many traditional fermented foods (Grajek et al., 2005, Reid, 2008; Vasiljevic and Shah, 2007). These foods contain phytochemical compounds called bioactive substances that prevent the initiation, promotion and development of allergies and diseases, rather promote the nutritional and health benefits of the food products (Sanders, 2003; Pisulewski and Kostogrys, 2003; Pervez et al., 2006; Lei et al., 2008; Vasiljevic and Shah, 2007).

Cereals are considered major component of human food in Africa including Nigeria. Nutritionalists have given more concerned and attention to cereal based foods from maize, sorghum and millet sources. These cereals have high content of soluble non-starch polysaccharides such as beta glucan which has a health promoting role. Clinical and epidemiological studies indicating that beta glucan from barley or oat based products control cardiovascular disease in humans as reported by Beck et al. (2010), Shimzu et al. (2008); Karmally et al. (2005) and Keogh et al. (2003).

Duchonova et al. (2013) suggested that the multiple beneficial effects and health benefits of cereal can be exploited in different ways hence design of novel cereal foods or ingredients can be targeted at a specific population. Furthermore, cereals are good fermentable substrates for the growth of probiotic microorganisms (Kochova et al., 2011 and Kedia et al., 2007; Charalampopoulos et al., 2009). Cereals can be used as sources of non- digestible carbohydrates. This selectively stimulates the growth of colonic lactobacilli and bifidobacteria which act as probiotics (Charalampopoulos et al., 2002; Chavan and Kadam, 2009; Duchonova and Sturdik, 2010).

Growth of lactic acid bacteria (LAB) in cereal based fermentation has led to a variety of cereal-based fermented foods like burukutu, pito, ogi etc. Hence incorporating human-derived probiotic strains in cereal substrates under control conditions would produce essential health benefits. There is thus increasing awareness among consumers (users) about the health benefit and pharmacological properties of diets with high fibre content. Cereal-based fermented food products contain bioactive ingredients like dietary and functional fibres. Prolong lactic acid fermentation of cereal products is the cheapest method of safely preserving weaning food, the contamination of which is a major cause of disease and associated malnutrition (FAO/WHO, 1997).

During the fermentation process, a change of naturally occurring microorganisms resulted in a population dominated by lactic acid bacteria during prolong fermentation process (Steinkraus et al., 2003; Hounhouigan et al., 2003; Johansson et al., 2005). In order to demonstrate the role of these organisms in the fermented products, it is essential to quantify the predominating groups of organisms and to investigate thermodynamics of the overall community. In addition, the final quality as well as the storage of the product strongly relies on the way the fermentation was carried out. Studies have shown that phenotypic identification of fermentative microflora is time-consuming and often problematic due to ambiguous biochemical or physiological traits (Hugas et al., 2003; Sierra et al., 2005). Therefore, the aim of this research work is to assess the microbial changes associated with fermented cereal based foods at different stages of the fermentation, in order to promote health issues.

Aim and objectives of the Study

The aim of this study is to investigate the microbial succession during cereals fermentation using earthen pot and plastic bowel. Therefore, the objective of this study is to:

       i.  Identify and characterize naturally occurring microorganisms in fermented cereals using earthen pot and plastic bowel.

     ii.  To investigate the microorganisms associated with the spontaneous fermentation of the cereals samples both in earthen pot and plastic bowel.

  iii.   To assess the occurrence of microbial changes during fermentation of cereals samples both in earthen pot and plastic bowel.

  iv.            To predict a quality control measures on microbial changes during fermented cereals samples in earthen pot and plastic bowel.

1.2     Significant of the Study

This study will be of significant to food nutritionist as it will highlight some micro organism (lactic acid bacteria) present in the fermentation of cereals at different stages, as these bacterial act as probiotics which its presence in a fermented food leads to the preservation of the food samples. The study will be of emerge benefits to food industries in the process of preserving their food product with the use of these naturally occurring lactic acid bacteria (LAB) obtained from the fermentation of cereals which are cheap and could be easily obtained from cereals food products.

General public consuming cereals grains will also benefited from this work, since it will educate the public on the need for the consumption of prolonged fermented cereals food which contain lactic acid bacteria (probiotics), which has the potential and capability of preserving the cereals food products as well as increasing of the nutritional and health benefits of the food. More specially, this study will also add to the already existing literature on the microbiological changes on fermentation of some cereals grain.

1.3     Scope and Limitation of the Study

The scope of this study is to isolate, identified and characterized microorganisms (bacteria and fungi) associated with different stages of fermentation of cereals grain. Individual organisms’ isolated and microbial loads at different stages of the fermentation are to be considered. This study is limited only to bacteria and fungi as well as their colony count obtained from different stages of the fermentation of the cereals such as maize (Zea mays), Sorghum (Sorghum bicolor), millet (Peninsetum americanum) due to time factor and also due to the financial constraint as all the financial burden involved in the research work are solely on the research student.

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