CHAPTER ONE

INTRODUCTION

1.1 Background

Proteins are the most abundant macromolecule found in cells and all parts of cells. The building blocks of proteins are amino acids. Proteins range in size from small peptides to huge biopolymers.

Proteins exhibit enormous diversity of biological functions and are the most important final product of the information transfer pathway (central dogma of molecular biology).  From the amino acid building block the organism is able to make a wide diversity of products such as enzymes, hormones, antibodies, transporters, growth factors, and myriads of other substances having distinct biological activities. (David and Michael, 2004).

Proteins provide the structure for pretty much every part of the body from cells, muscle, cartilage, organs etc. They also perform specific activities in different forms in our bodies such as enzymes, hormones, antibodies, growth and maintenance proteins. They can also be used as a source of energy in the absence of carbohydrates (the primary source of cellular energy) but they usually produce more toxic by-product when used for the generation of energy than carbohydrates. Proteins are made up of essential and non- essential amino acids building blocks.

The essential amino acids are to be gotten from the diet. Animals are a better source of proteins than plant and their products. Complete proteins are those which contain all 20 amino acids e.g. meat whereas the incomplete proteins are those which lack some of the amino acids e.g. corm and other cereals.

Corn  commonly  called  maize  is  a  herbaceous  cereal  widely  grown  for  food  and  livestock fodders .It  is  grown  in  different  agro-ecological  zones  alone or  together  with  other  crops.It  ranks  with  wheat  and  rice  as  the  chief  grain crop with  it been the  most cultivated grain crop in  2009 with  817 million tonnesharvested (fao.org) .Some  of  world’s  leading  producers  of  the  cereal  include; China, Brazil, United States of America, France, and Mexico.

In Cameroon, it is also one of the major grains cultivated. It is cultivated mainly in the western highland. The yield in this part of the country accounted for 60% of the national yield in 1990-1991(Conte and Fussilier, 1993). Bafoussamand  Bueaare part of the highest maize producing part ofthe country.

Corn  is  grown  in this  places  mainly  for  home  consumption, even  though  it is now  grown  more  and  more for   commercial  purposes due to increase in demand due to the development of industries using it as raw material(e.g. brasseries). The  variety  of  maize  planted  are  the  same and  the  methods  of  cultivation  mostly  traditional  but  different. The climatic conditions in these two areas arenot that different with about 1500-3000mm of rainfall annually.(George and Aliou, 1992)

The  plant usually  attain  a height  of  2m  and  is  composed  of a stalk on  which  grows  long leaves, male and  female  flowers. The mainstalk terminates in a staminate (male) inflorescence or tassel.The  tassel is  made  up  of  many  small flowers  called  spikelets,  and  each  spikelet  bears  three small anthers, which produce pollen grains, or  male  gametes.

The  pistillate (female) inflorescence which becomes  ear  is  a unique structure  with  up  to  1000  seeds  borne  on a hard core called the cob. The ear is enclosed in modified leaves called husks. The individual silk fibers that protrude from the tip of the ear are the elongated styles, each attached toan individual ovary. Pollen from the tassel is carried by wind and falls onto the silks, where it germinates and goes down through the silk until it reaches the ovary.

Each fertilizedovary grows and develops into a kernel.  The roots of the plant are superficial (do not exceed 50cm into the soil). Adventitious roots usually develop on nodes at the base of the stalk. The stalk is longand ithas a diameter of 5 to 6 cm. It is lignifiedwith asweet marrow. It also has large leaves (up to 10cm large and 1m long.). A stalk of the plant gives rise to 3 to 4 ears but only one of these ears usually attains its final development stage.The  way  the  grains  are arranged  depends  on  the  variety   to  which  the  plant  belongs (Plessis, 2003).

Corn consist mainly of starch, but also has some proteins, fat, fiber, minerals and vitamins. The proteins corn makes up 8-12% of the kernel weight. Corn proteins are classified according to their solubility with the most abundant being the alcohol-soluble form collectively called prolamins (e.g. zein).

The water soluble corn proteins are called albumins and it also soluble in dilute salt solutions; globulinswhich are soluble in dilute salt solutions. The albumin and globulins are considered to be thebiologically active form ofcorn proteins. The prolamins make up about 60% of the total protein in a corn kernel and are the storage form of the corn proteins. The glutelins are soluble in alkali.

1.2 Classification

Kingdom: Plantae

Division: Magnoliphyta

Class: Liliopsida

Order: Poales

Family: Poaceae

Genius: Zea

Species: mays

Scientific Name: Zeamays

Common Name: Corn or Maize

1.3 History And Origin Of Corn

For western civilization, the story of corn began in 1492 when Columbus’ men discovered this new grain in Cuba. It is thought that the grain was exported to Europe (where it was mainly a garden curiosity) by Columbus’ men rather than imported to the American continent like manyother grains. Corn then moved from a simple garden curiosity to a very important food crop and spread via Europe to Asia.

Although corn is indigenous to the western hemisphere, its exact birthplace is far less certain. Archeological evidence of corn’s early presence in the western hemisphere was identified from corn pollen grain considered to be 80,000 years old obtained from drill cores 200 feet below Mexico City. Another archeological study of the bat caves in New Mexico revealed corn cobs that were 5,600 years old by radio-carbon determination. Most historians believe corn was domesticated in the Tehuacan Valley of Mexico 3000-7000 years ago. The original wild form has long been extinct.

Evidence suggests that cultivated corn arose through natural crossings, perhaps first with gamagrass to yield teosinte and then possibly with back¬crossing of teosinte to primitive maize to produce modern races. There are numerous theories as to the ancestors of modern corn(Lance and Garren, 2002).

1.4 Varieties Of Corn

There are four main varieties of corn, they include;

Dent corn  or  ‘field’ corn (Zea  mays  indenata) which  may  be  white  or  yellow  and  it  kernel contains soft  or  hard  starch  which  becomes  indented  at  maturity. It  is  used  for  livestock  feeds, industrial  products  and  to  make  processed  food.

Flour  corn (Zea mays  amylacea) is  primarily  white  even though it  can be  grown  in  other  colours  like  blue. It  is  thought  to  be  the  oldest  variety  of  corn  grown  by  native  Americans. It is  used  in  baking  since  it’s  kernel  is  starch  filled  and  soft  thus  easy  to  grind.

Popcorn (Zea  mays  everta) is a type of flint corn which usually  has  a  soft  starchy  center  and  a  hard exterior shell. When  popcorn  is  heated  the  natural moisture  inside  the  kernel  turns  to  stream,  this  builds  enough  pressure  for  it  to  explode  exposing  it  white  starchy  mass. It  should  be  noted  that  all  types  of  corn  will  pop to  a  certain degree  but  will not  have  enough  starch  to  turn  inside  out  or  a  hard  outside  to  create enough   pressure  to  explode. It  is  one  of  the  oldest  form  of  corn .

Flint  corn also  known  as  indian  corn (Zea  mays indurata) is   used for  similar  purposes  as  dent  corn. It  is  distinguished  by  its  hard  outer  shell and  kernel  with  a  range  of  colours  from  white  to  red.

Sweet  corn (Zearugosa  or Zeasaccharata) is  primarily  eaten  on  the  cob  or  it  can  be  canned  or  frozen  for  future  use. It isused for feedor flour. It  is  extra  sweet  because  it  contains  more  natural  sugar  than  other (Field  corn  contains  4% of  sugar  while  at  the  same  stage  standard  sweet  corn  contains 10%  sugar).50%  of  the  sugar  can  be  converted  to  starch  24 hours  after  the  sweet  corn  is  picked,so  it  is  best  to  eat  it  fresh (Lance and Garren, 2002).

1.5 Cultivation And Pest:

Each grain is composed of a germ(embryo  and  cotyledon), albumen and the  pericarp which  is  a hard envelop which  protects  the  grain  from  fungi and  bacterial  invasion.

Corn  is  grown  in   different  climatic   zones (the equatorial  forest, the  savanna etc.) but  the   most  suitable  climatic  zone  is  the  savanna  with  800 to  1200mm  annual  rainfall and sunny  days which decreases parasitism. Corn needs temperatures between 10-19°C. The altitude should not be more than 1800 m. The  choice  of  the  variety  to  be  cultivated  depend  on  the  climate,  the soil, the zone of  cultivation, the  cultivation  technique  and  what  the  harvest  is  to be  used  for.

Corn  needs  about  450 to 600mm  of  water  per season, which  is  moistly  acquired  from  soil  moisture  reserves. About 15kg of grain is produced of each millimeterof water consumed.

The assimilation of elements such as nitrogen, phosphorus and potassium etc. reaches their peak   during  flowering.

The maize kernel consists of an endosperm,embryo, a pericarp and a tip cap.Theendospemcontains of the kernel’s starch and the embryo contains the part that gives rise to the next generation, while the pericarp and tip cap encloses the entire kernel.

Soil  tillage  is  the  foundation of  any  crop  production  system  and  is  the  biggest  cost  factor  in maize production. Soil tillage helps to change the soil’s structure and texture, hydraulic properties and stability to such an extent that plants willgrow and produce optimally. Soil tillage helps to improve soil structure, reduce the effect of wind and water erosion, weed control and the incorporation of residues.

Corn is attacked by several parasitic organisms and insect pest. This organism attack the root, stalk, and ear. The  most  important  attack  form  parasitic  organism  come  from  fungi  which  attack  the  crop  causing  rots, lesions on the  leaves  reducing  the crop’s yield. Two  important  viruses  also  attack  the  corn, they   are  stunt  and  the  maize  dwarf  mosaic. Corn  earworm  is  another  pest  that  has  greatly  reduced   the  corn  yield in recent  years .Weevils, rats  also  attack  and  destroy  this  crops during  drying and storage.

1.6 Uses Of Corn

The  importance of cereals grains  to  the  nutrition of  millions   of  people  around  the  world  is  widely  recognized but corn is also used for the as animal feed and for the manufacture of high fructose corn sweeteners.

Industrially it is used to produceethanol, as filler for plastic, as insulating material; produce adhesives and abrasives,pharmaceuticals,organic acid, explosives, chemicals, paint etc.

It is also used as a majorstudy plant in discipline like biochemistry, genetic and soil fertility(Lance and Garren, 2002).

1.7 Hazards

1.7.1 Pellagra

Corn or maize was highly welcomed into the farming system due to its high productivity. But soon enough a problem of malnutrition arose wherever maize was used as a staple food. This was new since the indigenous populations who first grew corn for food did not have this problem.

This was because they socked the maize in alkali-water made of lime and ash which liberates niacin whose lack leads to pellagra. Pellagra was also characterized by protein deficiency as a result of the lack of lysine and tryptophan. Alkali-water was also found to increase the availability of these amino acids.The indigene also consumed other sources of niacin and protein such as beans.

Pellagra was epidemic in the 19th century in southern US. These lead to theories which tried to explain the cause of pellagra. The first was the deficiency theory was suggested that it was cause by the deficiency of a molecule. The other was the germ theory which explained that pellagra was caused by a germ transmitted by stable flies.

Charles Davenport explained that people contracted pellagra if they were susceptible to it due to certain ‘constitutional inheritable’ traits of the affected individual. It was later show in 1932, that pellagra is associated to the deficiency of niacin. Pellagra is now rare due to the promotion of balanced diet and the development of high lysine maize. But it still exist today in areas with less food and in refugee camps where people survive on donated corn

1.7.2 Allergy

Corn contains a lipid transfer protein which is not destroyed by cooking. This protein is responsible for the allergy associated with corn consumption. It causes skin rashes, diarrhea, and mucous membrane irritation etc and in severe cases itmay leadto anaphylaxis.It is unclear how corn consumption leads to allergy and the number of people affected is not known.

1.8 Rationale

Research has being carried out to determine the chemical composition of maize and its nutritional value but little has being done in the field of water soluble protein extraction from corn. Most of the work done in the field of protein extraction from corn involves the extraction of the alcohol soluble protein in corn (zein), since it is commercially useful.

Very little or no experiment has been carried out to compare the water soluble content of corn from Bafoussam with that from Buea. Comparing the water soluble proteins in corn from these localities is important because the cereal is highly consumed in these areas and the water soluble protein quantity in corn somehow determines its protein quality since they contain lysine and tryptophan in contrast prolamins.

1.9.1 Objectives:

1.9.1.1Overall Objective

To  compare the  water  soluble  proteins  content  of  maize from  Bafoussam(west  region)  and  that  Buea (south-west  region), Cameroon.

1.9.1.2Specific Objectives

1. To determine the water-soluble protein content of corn from Bafoussam.
2. To determine the water-soluble protein content of corn from Buea.
3. To compare the water-soluble protein content of corn from Bafoussam with that from Buea.

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