EFFECT OF DRYING METHODS ON THE NUTRIENT AND PHYTOCHEMICAL PROPERTIES OF SOME CULTIVATED AND WILD LEAFY VEGETABLES.

ABSTRACT

The aim of this study was to determine the nutrient and phytochemical composition of fresh, sun and shade dried okra, bitter, scent, G. latifolium and roselle  leaves.  The vegetables  were purchased  from two markets.  Okra, bitter, scent  and G.latifolium leaves were purchased from Nsukka and roselle leaves were bought from Jos market. All the vegetables were washed, weighed and divided into two equal parts. Each part was sun, or shade dried, pulverized, packed and stored. The fresh samples for each of the vegetables served as control. The fresh, sun and shade dried samples of all the vegetables were separately analyzed for various nutrient and phytochemicals on dry weight  basis  using  standard  assay  techniques.  Data  generated  were  statistically analyzed. The means were separated and compared. All the fresh samples had high moisture   values(Okra   leaf;   62.22%,   bitter   leaf;   62.32%,   scent   leaf;   62.46%, G.latifolium; 61.44% and roselle leaf; 85.53%) . The moisture content of the sun and the shade dried samples differed (P<0.05). The exception was that of roselle whose sun  and  shade  dried  values  were  comparable  (6.36  and  6.38%)  (P>0.05).  Fresh samples of all the vegetables had lower protein. The processed okra, bitter, scent and roselle leaves had comparable values (P>0.05). Moisture lost due to drying increased nutrient density of the vegetables, especially the roselle leaves. The phytochemicals (Tannins,  phytate,  saponins  and flavonoid)  of the fresh samples  were higher than those of the sun and the shade dried samples. This showed that fresh vegetables are better sources of phytochemicals as against the sun and the shade dried samples. The shade dried samples had lower tannins except for  the bitter leaf and the sundried samples  had lower phytate  except the G.  latifolium.  The sun and the shade dried samples had comparable saponins and flavonoids content (P<0.05). As judged by the results, domestic food processing techniques improved the nutrient content of these vegetables and decreased some of the food toxicants and antinutrients.

CHAPTER ONE

1.0   INTRODUCTION

Man must eat to survive for the continuity of the human race. The foods for human  consumption  are of both plant and animal  origin.  Cereals,  legumes,  roots, tubers, suckers, oils, nuts, fruits and vegetables are plant foods. Meat, milk, eggs and oils  are  animal  products.  Both  plant  and  animal  foods  contain  nutrients.  Oxford Medical Dictionary (2003) defines nutrients as substances that must be consumed as part of the diet to provide  energy,  protein  for growth  or  substances  that  regulate growth  or energy  production.  Carbohydrate,  proteins,  fats,  vitamins,  minerals  and water are the existing six nutrients.

It is known that too much or too little of these nutrients have adverse effects on health. The source of these nutrients equally determines how healthy  one is. A typical example is in the case of fats. Animal fat contains about  40-60% of fat as saturated fatty acids. Plant oils contain mostly unsaturated fatty acids ranging from 73 to 94% of total fat (Wardlaw  & Kessel, 2002). Plant oil  is the most beneficial  to health. Current studies showed that plant nutrients are not inferior to animal nutrients as  it  was  earlier  thought.  In  addition,  plants  contain  other  non-nutritive  dietary components    that    are   beneficial    to    health.    These    components    are   called phytochemicals.   “Phyto”   because   they   are  only   found   in  plant   based   foods (Pamplona-Roger,   2005).   The   present   study      concentrated   on   nutrient   and phytochemical levels of five cultivated and wild vegetables.

Vegetables are generally herbaceous (non-woody) plants that are cultivated in farms,  collected  from  forest  trees,  market  and  home  gardens  as  well  as  kitchen gardens for home use. Usually, all the botanical parts of the plants (leaves, buds or flowers,  calyxes,  fruits,  stalk,  roots  are consumed)  (Pamplona-Roger,  2005).  This study laid emphasis on green leafy vegetables.

History shows that vegetables were used for a number of purposes. Many in the past consumed these vegetables without knowing all they contain. Scent leaf was used and is still being used to stop diarrhoea. How and what stops diarrhoea in scent leaf  is  still  a  puzzle  to  many.  The  foods  our  ancestors  consumed  consisted  of carbohydrates, starchy vegetables, leafy vegetables and little or no animal products. There were not much occurrences of various chronic diseases such as morbid obesity, cancer, heart and renal failure three to four decades ago as they are now. The juvenile and paediatric cases of these diseases are on the increase. The cause of their increase

is due to migration/changes in lifestyle and food habits (Ene-Obong, 2008). The very sharp shift from traditional diets as well as the advent of exotic diseases appears to suggest a serious warning. These warnings call for urgent increases in consumption of preventive and curative substances inherent in plant based food, especially vegetables.

Chemically,  green  leafy  vegetables  are  composed  of  water;  90  to  95%, minerals   e.g.   phosphorus,   potassium,   calcium,   iron,   vitamins,   fibre,   proteins, chlorophyll and most recently discovered- phytochemicals (Pamplona-Roger, 2005). Indigenous traditional foods are on the verge of extinction. The younger generation is ignorant of them as such; consume less of these vegetables (Ene-Obong, 2008). As most of these traditional foods are on the verge of extinction, so are the vegetables, condiments and spices used in their preparation. Some of the wild forest vegetables might have been used by a particular community in the past. Based on these serious observations associated with less consumption of indigenous foods and increases in many  chronic  ailments,  it  is  imperative  to  study  the  nutrient  and  phytochemical potentials of some cultivated and wild vegetables.

1.1      Statement of problem

The increase in the consumption of western diets and neglect of our traditional foods has precipitated a corresponding increase in ill-health due to diet related non- communicable diseases. These diseases are of various forms; cancer, kidney and liver diseases,  diabetes  and  many  more.  Prevention  of  these  diseases  based  on  new incidences  of  these  diseases  is  imperative.  This  is  because  these  diseases  are  of increasing  public  health  concern.  Extensive  studies  are  ongoing  to  address  these public health threats both for the cure of already existing cases and prevention of new cases. One hopes that the results of these studies will provide baseline information as to their causes and treatment.

However, some of the information based on the results of recent studies point to the type of foods consumed by people. Currently, nutrients from plant based foods have promising  solution (Ene-Obong,  2008). Vegetable  based foods  are advocated because of their high content of non-nutritive dietary components that are safer and more   beneficial   to  man.  Some   of  these   vegetables   contain  antioxidants   and phytochemicals.  Sadly,  in Nigeria,  little  attention  is  paid to fruits and vegetables. Statistics  from World  Bank (1991)  showed  that  at  the National  level, an average household expenditure on household staples was highest on fish (N140.84) followed by meat products  (N81.54).  The least weekly expenditure  was on fruits  (N13.12) followed by weekly expenditure on green leafy vegetables (N20.88).

Vegetables are the most affordable dietary sources of vitamins, trace elements and other bioactive compounds that offer the only practical and sustainable way to ensure that micronutrients are supplied through the diet (Odo, 2007). It is imperative to  study  more  vegetables  for  their  nutrient  and  photochemical   potentials.  The investigation of these vegetables would be of immense benefit to the society.

1.2      Objective of the study

The general  objective  of the study were to determine  the effect  of  drying methods on the nutrient and phytochemical  properties of some cultivated  and wild leafy vegetables.

The specific objectives of the study are to;

a.   determine nutrient, and phytochemical content of these vegetables

b.   sun, shade dry and pulverize these vegetables to determine the nutrient content of their flours.

c.   determine the nutrient and phytochemical potentials of these vegetables on dry weight basis.

1.3      Significance of the study

The results of this study would be a promising and useful tool to home makers on  the  increasing  need  to produce  both  cultivated  and  wild  forest  vegetable  and consume them, especially the children and younger adults. Increase consumption of these vegetables might be the solution to the cases of micronutrient deficiencies world wide and some chronic and deadly diseases such as cancers and other diseases and their complications, particularly in developing countries, Nigeria inclusive.

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