MICROBIOLOGICAL SAFETY OF COMPLEMENTARY FOOD PRODUCE FROM ORANGE FLESHED SWEET POTATO (OFSP), AFRICAN YAM BEAN (AYB) AND PEARL MILLET.

MICROBIOLOGICAL SAFETY OF COMPLEMENTARY FOOD PRODUCE FROM ORANGE FLESHED SWEET POTATO (OFSP), AFRICAN YAM BEAN (AYB) AND PEARL MILLET.

This study is aimed at investigating the microbiological safety of complementary food produce made from orange flesh sweet potato, african yam bean, pearl millet.

CHAPTER ONE

1.0       INTRODUCTION

Complementary food are foods and liquids other than breast milk or infant formulas required during the second part of the first year of life for both nutritional and developmental reasons and also to enable transition from milk feeding to family food (koletzko et al, 2008).

As breastfeeding continues after six month, it is the time to introduce complementary food to meet all the growing child’s needs. Although exclusive breastfeeding provides the best start, after six month and as long as breastfeeding continue the child needs more vitamins, minerals, proteins and carbohydrates that are generally available from breast milk alone. Any non-breast milk foods or nutritive liquids that are given to young children during this period are defined as complementary foods. This is a very important time in every child’s life for health, growth and psychosocial development (Brown et al, 1998).

After six months of age, breast milk is not enough to meet the macro and micronutrient requirement of infants (Koletzko et al, 2008: Ijarotimi and keshinro, 2013). Infants also develop the ability to chew, hence begin showing interest for food other than milk, therefore the need to introduce the healthy complementary foods. According to Codex Alimantarius Commission CAC (2008), complimentary food should be of appropriate nutritional quality and energy to complement the nutrients obtained from breast milk for infants and family food for younger children.

A number of complementary foods have been developed in Africa, especially in Nigeria; most of these complementary foods are cereal-based (Amagloh et al, 2012). They are mostly formulated with maize as the major ingredient and complemented with soybeans, cowpea or groundnut. The legumes are added in an attempt to improve upon the fat and protein content of the food. However, over the years, the problem with malnutrition, especially micronutrient deficiencies of complementary foods (Bhandri et al,2001;Nestel et al,2003; Lutter et al,2008). Vitamin A and iron deficiency are amongst the world’s most prevalent nutritional problems (Lutter et al, 2008; Amagloh et al, 2012).

Sweet potato as a complementary food has been identified as a viable product both for supplementing the nutritional needs of the babies in developing countries while enhancing the utilisation of the crop. A number of studies by Ijarotimi and Ashipa (2006), Sanoussi et al.(2013) and Haque et al. (2013)  have been conducted in this wise. Some varieties have high amount of β –carotene which is a precursor of vitamin A (Picha and padda, 2009; burrietal, 2011) hence could be used to reduce vitamin A deficiency amongst children. Notwithstanding the high energy content of sweet potato and other micronutrient such as vitamin A, C, potassium , iron, and Zinc, it is low in protein and fat contents, hence the need to complement it with legumes and cereals when being used in complementary foods. Sweet potato in Nigeria is being promoted but there is limited diversified product from the crop, which could encourage its consumption. It is characterised by high moisture content hence high perish ability. The roots unlike other staples in Nigeria are sweet, and this has been a challenge in its acceptance especially when processed into already existing food forms. There is therefore the need to diversify orange fresh sweet potato (OFSP) into forms that are acceptable especially for children due to the high β-carotene (a Pro vitamin A) content of the roots and its sugar content, to reduce sugar added to complementary foods. This is because vitamin A deficiency is a public health problem in Nigeria with prevalence around 37.6% (Egbi, 2012).

The major drawback in the research work on a sweet potato-based complementary food including those by Ijarotimi and Ashipan (2006), Sanoussi et al (2013) was the viscous nature of the resultant complementary foods. But Amagloh et al. (2013) employed three processing methods which are (extrusion, roller drying and oven toasting) to resolve this drawback. The processes also improved the nutrient composition of the complementary foods. Germination and drying are among the simple and easily adaptable technologies for reduction of bulkiness (high viscosity) and increasing shelf life of cereal and legume based food formulations (Oluwamukomi et al, 2001).

Microbial load of a food is determined by the levels of micro organisms (measured in colony forming units per gram) in the food during production, packaging, storage and other handing as well as the type of food in question. However the incidence of diarrhoea among children fed with this type of complementary food has been reported (AHRTAG, 1990). High counts of indicator pathogenic organisms (e.g. Escherichia coli) and spoilage organisms (e.g. Bacillus cereus) were found in store non-fermented traditional Nigerian complementary foods (Rowland et al; 1978); while several contamination of Kenyan children’s food with Enterobacteriaceae and Staphylococcus aureus was reported by Van Steenbergen et al. (1983). Shelf life is the length of time that a commodity such as food may be stored without becoming unfit for use or consumption. It is the recommended maximum time for which products can be stored during which the defined quality of a specified proportion of the goods remain acceptable under expected conditions of distribution, storage and display (Gyesley, 1991). A food product within its shelf life should be safe to eat, keep its appearance, colour, texture and flavour and meet any nutritional claims provided on the label (New Zealand Food Safety Authority, 2005).

Micro organisms are found in different environment including our foods. These also includes raw foods and processed food, it is important to note that most processed food are not sterile, some still contain viable microbial cells and their spores. In the food industry, we always thrive to achieve what is known as commercial sterility. This implies that the food is not completely sterile, it may contain some viable microbial cells and their spores but not at a level that may be injurious to our health when such food is consumed. Furthermore, such food is expected to enjoy microbiological stability within a specific period of storage. Therefore under microbiological food quality control, we expect that processed food may contain viable microbial cells and their spores. However this should be within specified limit. Also some micro organisms are not expected to be found in some processed food. This is the needs for microbiological determination of complementary food. (Ogundele G.F, 2017)

All foods spoil with time but the rate differs from food to food. Factors that affect food quality include microbial (bacteria, yeast and mold) growth, non-microbial spoilage (rancidity, browning and loss of nutrients) and product related spoilage such as water activity, pH and oxygen availability (Fontana, 2008; Sivasankar, 2010). Water activity of a food is the ratio between the vapour pressure of the food itself, when in a completely undisturbed balance with the surrounding air media and the vapour pressure of distilled water under identical condition (U.S. Food and Drug Administration, 1984). Water activity of 0.80 means that the vapour pressure is 80% of that of pure water. It is the amount of water in a food that is available for microbial use and it helps to predicts microbial growth (Fontana, 2001). Water activity predicts food stability with respect to microbial growth rate of deteriorative reaction and physical properties of foods (texture and shelf life) (Ukegbu and Anyika, 2012). High values support microbial growth, therefore, moist food spoils faster than dry food. A food or solution’s pH is a measure of acidity or alkalinity using a numerical scale between 1 and 14. Low pH value shows acidity and it limits the growth of many micro organisms and vice versa (International Commission on Microbiological Standards for Foods, 1996). The pH limit for growth of any microorganism is 0.60 (Fontana, 2008).  Microbial load of a food is determined by the levels of microorganisms (measured in colony forming units per gram) in the food during production, packaging, storage and other handing as well as the type of food in question. The end of shelf life can be based on the quantity of microorganism present (NZFSA, 2005). Therefore, there is need to evaluate locally produced complementary foods to ascertain their microbiological quality.

Though a lot of work has been done on the effect of malting and drying on the production of complementary foods on the physical and chemical properties and microbiological quality of food formulated from other cereals and legumes (Ariahu et al; 1999, Sefa- Dedeh et al; 2001, Oluwamukomi et al, 2003; Obasi et al; 2009; Gernah et al, 2011). However, to further improve the nutrient composition of sweet potato based complementary food and to enhance the suitability of the sweet potato in the baby food industry, studies into the used of the orange fleshed sweet potato, which has higher β- carotene compare with the cream flesh. Moreover, African yam bean, which has been used as the protein and fat source in complementary food ha been reported to lack methionine and crysteine (Edema et al, 2005). These amino acids are abundant in cereal such as pearl millet. Therefore a blend of cereals such as pearl millet and African yam bean in the formulation of a complementary food may enhance the protein quality and nutritional composition of the complementary food.

Response surface methodology (RSM) will be used to investigate the effects of the best composition. RSM is a statistical technique that has been successfully studied in the development and optimization of the food products. RSM consists of a mathematical and statistical procedure that can be used to study the relationships between one or more dependent variables and interdependent variables. As an important subject in the statistical design of experiments, the Response Surface Methodology (RSM) is a collection of mathematical and statistical techniques useful for the modelling and analysis of problems in which a response of interest is influenced by several variables and the objective is to optimize this response (Montgomery 2005). Therefore the objective of this study is to formulate a complementary food from an orange fleshed sweet potato, pearl millet and African yam bean and the microbial levels will be studied to meet the nutritional requirement for babies (6-24months).

1.1       STATEMENT OF PROBLEM

Orange fleshed sweet potato is characterized by high moisture content, hence, high perish ability. The roots unlike other staple in Nigeria are sweet, and this has been a challenge in its acceptance especially when processed into already existing food forms.  There is thereof the needs to diversify orange fleshed sweet potato (OFSP) into form that are acceptable especially for children dude to the high beta- carotene ( a Pro vitamin A) content of the roots. This is because Vitamin A deficiency is a public health problem in Nigeria (Egbi, 2012).

Pearl millet also has limited uses in Nigeria compared with maize, despite its characteristic texture for porridge and nutritional advantages. It is used in additional to African yam beans in developing a complementary food has not yet been studied.

In addition, studied has been done to reduce the viscosity in orange fleshed sweet potato used in complementary foods through processing methods, however, there is limited information in the used of the OFSP variety which has been higher β- carotene studies.

1.2       JUSTIFICATION

Development of complementary foods from legumes, cereals and tubers will help diversify the uses of sweet potato and will provide an alternate healthy and nutritious for most infant in Nigeria. Due to its high vitamin A, it will help with effort to reduce vitamin A deficiency in Nigeria. The diversification and utilization of orange fleshed sweet potato will also help effort   to achieve food and nutrient security in Nigeria. An alternative use of millet will also be provided while the microbial level of complementary food blend with pearl millet and African Yam Beans will be known.

 1.3      AIMS AND OBJECTIVES

AIMS:

To develop and determine the microbiological safety of complementary food produce from orange fleshed sweet potato (OFSP), African Yam Bean (AYB) and pearl millet.

OBJECTIVES:

• Production of flours from orange-fleshed sweet potatoes, African yam bean and pearl millet.
• Determination of the microbial safety of OFSP, AYB and pearl millet using total plate count (TPC).
• Determination of fungi.
• Determination of coliform.
• Determination of total sugar and total starch.
• Determination of sensory evaluation of complementary food produced from the flour orange-fleshed sweet potatoes, African yam bean and pearl millet.