ASSESSMENT OF NUTRITIONAL AND PHYSICAL CHARACTERISTICS OF MAIZE (Zea Mays) STORED IN METALLIC SILOS

ABSTRACT

The magnitude of deterioration of maize (Zea Mays) in storage and storage losses recorded globally is worrisome especially in the developing countries. However, with the evolution of metallic silos, there has been tremendous reduction in the storage losses. In the storage of maize (Zea Mays L.) in metallic silos especially for long period, certain degenerating changes do occur, due to the interaction between the stored maize and the immediate environment. These degenerating changes over time are expected to affect the Nutritional (NP) and Physical (PY) characteristics of the grain. The main objective of study is to evaluates the quality attribute of maize stored in metallic silos for a period of eight months, with a view to assess the extent of deterioration of some NP and PY characteristics, with duration of storage, based on the location of the grain in the bulk and size of the metallic silos. The values obtained were compared to the control, which is the values of the parameters of the stored maize determined using standard methods, before the inception of the storage. The temperature and relative humidity of the immediate environment were also recorded within the period. A randomized block design of 13 quality attributes, 9 sample location and 3 replicates making a total of 351 samples were used. The evaluation of data obtained was done using statistical package for social sciences (SPSS 20) for windows evaluation version to determine levels of significance and trend of deterioration for all values obtained, using Multiple Analysis of Variance (MANOVA) and Duncan’s multivariate test. The NP properties evaluated include percentage Ash content AC, Crude Fiber CF, Protein CP, Carbohydrate content CHO, Fats FC, and Energy EV. The PY characteristics evaluated also include, percentage Moisture content MC (wb), Insect Damaged grains ID, Foreign Matters FM, Hectolitre weight HC, Mould infested grains M, and Germinability/viability V. The result of this

CHAPTER ONE

1.0   INTRODUCTION

1.1  Background to the study

Maize (Zea mays) is the most popular cereal crop planted and stored in Nigeria, International Institute for Tropical Agriculture, (IITA, 2009). It constitutes a staple food in South America, South Africa and Sub Saharan Africa (SSA) and accounts for more than 50% of Agribusiness in these regions, Food and Agricultural Organization (FAO, 1995). As important dietary component, it provides a substantial amount of nutrients which includes vitamins, minerals, protein and carbohydrates for human and animal consumption especially in developing countries of the world, due to its ability to be consumed directly and be processed into a wide range of products (IITA, 2009).

It can be stored in a wide range of grain storage structures all over the world, depending on available resources, intended use of the grains, climate, storage duration, capacity, available technology and culture, but are stored in commercial quantity in metallic silos (FAO, 2009).

As a hygroscopic and biological active material, the interaction of Maize (Zea mays) with the immediate environment during storage is ongoing.   In bulk storage of maize in metallic silos, especially for long period, certain degenerating changes are expected to occur due to this interaction, that will affect the physical and nutritional characteristics but the extent of deterioration of this is yet to be ascertained. The extent of this deterioration or how successful storage of Maize in a metallic Silos in any geo- ecological zone will be, is dependent on the Grain storage factors such as physical, biological, and climatic. This is because climate among others plays major role in the storability of agricultural produce (Alabi, 2001). Climatic variables known to influence storability of maize in metallic silos include temperature, humidity, rainfall or precipitation, solar radiation and wind. However, with proper monitoring and control of these variables, enormous storage losses associated with maize storage can be minimized.

The characteristic/ behaviour of the structural material used for the construction of any silos, in respect to solar radiation and thermal conductivity are also important factors towards successful storage. However, it is known that daily variation of ambient temperature determines the temperature gradient across the wall of the silos, the head space and inside the grain mass. Higher temperature will invariably result to more moisture condensation on the silo walls (Alabadan, 2005).   Humidity as a variable also affects the physiological response of stored grain and organism/pest in the storage bin. Wind speed and direction, size of ventilation openings also plays an important role in the thermal state / regime and stability of metallic silos temperatures (Ileleji, 2010).

The rainfall pattern in any geo-ecological zone no doubt plays an important role in the thermal stability of a metallic silos, especially during the rainey seasons since rainfall affects relative humidity of the ambient air directly, and considering high thermal conductivity characteristics of metallic silos. If a metallic silo is porous, it will be even worse because moisture will the transmitted into the silo directly and as well as the grain mass.

Minna, Niger state is located in the Guinea Savannah climate zone of Nigeria, the average daily temperature range throughout the year from available records is between 18 – 390C, the highest temperature record between February and April, while the lowest were record between November to January. Variation in diurnal temperatures can be as high as 16.50C during hot dry seasons. Yearly variation in temperatures between the harmattan season and the hot season is about 200C.   The average annual rainfall is about 1250mm and most of it falls between April and October. The dry season varies between 120 to 140 days in a year. The average solar radiation received on a typical day ranges between 21y / hr at sunrise (05.00hrs – 06.00hrs) and 601y / hr in the afternoon (between 12.00 and 14.00hrs). The average sunshine in a day is 9hours. Mean daily relative humidity ranges between 29 % in January to about 85% in August (Alabi, 2001).

The above climatic variables will encourage moisture migration and condensation as far as storage of grains in metallic silos is concerned, but prolonged dry season observed will also ensure that grains are kept dry and at safe moisture content level.

1.2       Statement of Problem

Maize storage in Nigeria dates back to the pre-historic time, but is often associated with high storage losses which is estimated between 25% to 43%, yearly according to (Oyebanji, 1996; Adejumo and Raji,2007; Ahmed,2009). This is due to inefficient and ineffective traditional storage structures, and practices used by farmers. These situation and conditions further makes it difficult for individuals, farmers groups and food industries to achieve the ever growing quest from for high quality stored agricultural produce all year round, especially grains.

Amidst increasing global demand for high quality stored agricultural produce, people who engage in maize storage activities in Nigeria and other developing countries, still pay less attention to the Nutritional and Physical degenerating changes that takes place in the stored grains, provided they are not physically spoilt. Many of these changes can be counterproductive as it may actually harm the consumers and lowers the actual quality of these grains at long run, especially with longer periods of storage. Thus, the absence of grain grading standards in Nigeria has not helped matters.

Since metallic silos store grains in large quantity, and have proved to be efficient in reducing the enormous storage losses recorded with the traditional system of grain storage, the ability to harness or enhance its huge economic potential, through research information on storage duration in relation to quality makes this study a worthy research.

1.4        Aims and Objectives of the study

The main aim of this study is how to reduce enormous storage losses associated with maize storage in metallic silos.

The objectives are to

i.          To evaluate the Nutritional and Physical attributes of maize stored in metallic silos based on location of the grain in the bulk and duration of storage.

ii.         To assess the above properties in respect to size of the metallic silos used.

iii.        To evaluate the effect of size of metallic silos, location of grain in the bulk, and size of metallic silos on the grain germinability/viability.

1.3    Justification of the Study

Maize grain accounts for about 15 to 56% of total daily calories in diets of about 25 developing countries particularly in Africa and South America (Vasal, 2000). With its additional demand by industries, there is no doubt that it is an essential commodity. Research has shown and demonstrated that the best qualities of maize are the ones from the present harvest irrespective of the intended use (FAO, 1995), but maize storage is inevitable due to the susceptibility of manmade or natural emergencies which can disrupt or lower penultimate harvest. Since maize is the most planted and stored cereal crop in Nigeria, and it is stored in commercial quantity in Nigeria and all over the world in metallic silos. Information on the degenerating changes that takes place in the stored maize within

the Allowable Storage Time (A S T), in metallic silos, is very important, as it will provide proper /

optimum usage, and enhance the economics of maize storage and food security in general.

1.5       The Scope and Limitation of the Study

The scope of this work is to evaluate the Nutritional and Physical characteristics of maize stored in metallic silos located in Minna Niger State, Nigeria for a storage period of eight months. The Nutritional characteristics evaluated are namely, Ash content, Carbohydrate content, crude Fiber, Fats content, and crude Protein. The physical characteristics evaluated in course of this research work includes, percentage Moisture content (wet basis, wb), MC, Hectoliter weight, HC, percentage Foreign matter, FM, percentage Broken grains, BK, percentage Insect damaged ,ID, percentage Mould infested grains ,M, and Germinability/Viability ,V.   However, the temperature and relative humidity and temperature of the head space of the silo bin was also monitored and recorded within the period of the research work.

At the end of the studies, the data generated will be analyzed using statistical methods. The result will be evaluated to a logical conclusion and recommendations will be made based on the result.

1.6 Contribution of study to literature

This research work is expected to provide basic information on how the quality attributes of maize stored in metallic silos are affected over storage period. It will also provide specific information on the Nutritional and Physical characteristics, and the integrity of the stored maize if used as seed,

This information would be invaluable to people who engage in maize storage in metallic silos, as a business or responsibility, in Guinea Savannah climate of Nigeria. It will also enable them to plan

and program their storage activities depending on the dynamics of deterioration and intended use, in order to maintain quality and to make economic gains.

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