PHYSICAL, CHEMICAL, MICROBIAL PROPERTIES OF OGI (PAP) MADE FROM MALTED SORGHUM AND SORGHUM GRAIN

PHYSICAL, CHEMICAL, MICROBIAL PROPERTIES OF OGI (PAP) MADE FROM MALTED SORGHUM AND SORGHUM GRAIN

LITERATURE REVIEW

Introduction

In the sub-Saharan Africa, most of the breakfast meals for both adults and young kids are prepared using cereals, legumes roots, cassava and potatoes. Ogi is one of the popular porridges that are widely used in the West Africa nations. It is one of the cheap and popular weaning foods in most of the countries in West Africa. There are a variety of methods that is used to prepare Ogi. Ogi is primarily prepared from maize, sorghum or millet. Cereals form a big proportion of the food taken. Cereals have approximately 12-14% water, 65-75% carbohydrates, 2% lipids and a protein content of about 7-12%. Cereals in their natural forms have several other nutrients such as vitamins and minerals but these are not biologically available. Their constant use may cause anaemia, malnutrition and other dietary diseases. Gelatinized Ogi is commonly refereed to as pap and in mostly used as the weaning food for infants and also as adult breakfast meal. There are different traditional names given to these semi solid foods such as Eko, Agidi, Akamu among others. Semi solid food made from sorghum is usually referred to as Ogi-baba. The viscosity of the final semi solid food produced depends upon the water that was used during the preparations process. Ogi is one of the staple food for infants in African countries such as Nigeria (Nago et al.,1998). In Nigeria and other parts of Africa 90% of the infants are introduced to complementary foods to supplement the mother milk after the age of 6 months (Faber, 2001). In addition to infant weaning, Ogi is also consumed by adults and also used by an infant mother to stimulate the production of milk. The use of semi solid food such as Ogi for nursing the sick has been encouraged by the doctors as it is light in the stomach and easily digested. Children are mostly feed with mashed adult food which is bulky and absorbs a lot of water. These foods are also bulky and they inhibit a chid ability to feed on more nutritive food contents. There is therefore the need to develop nutritionally balanced diet that has enough calories, is less bulky and can be digested by the infants. During the stage where the infant is feed with complimentary foods, the kid is vulnerable to malnutrition and he must be provided with semi solid foods that provide the requisite nutrients for the fast growing infant.Complimentary food must be prepared so that they are drinkable, are less bulky and free from bacterial contamination (FAO/WHO, 1998). The food must also be of the right quantity to satisfy the infant at one feeding. Ogi is mostly prepared using traditional fermenting and malting technologies which are simple but don’t guarantee quality and lack of contaminations as well as lack the appropriate nutritive value (Marero et al., 1989). It is one of the first complimentary foods that are used during the weaning process. The main reasons for fermenting these grains is to convert starch contents in the cereals such that it does not require dilution. The fermenting process also removes the pathogens. According to brown et al.(1998), Ogi provides about 20-26 Kcal/ kg per day to an infant who has an average density of 0.26 Kcal/ kg.

Sorghum properties

Sorghum bicolour is one of the important serial in the world. Sorghum comes from the genus sorghum and the family is Poaceae (Gramineae), there are four subspecies, these are: grain sorghum, grass sorghum such as hay and pasture, sweet sorghum such as guinea corn and boom corn such as brooms and brushes (Kimber, 2000). Grain sorghums are classified as sorghum bicolour with some ranging from white, red and brown. Sorghum is the fifth most important cereal after rice, wheat, maize and barley.

The grain produce protein and energy requirement for millions of people around the world. Most of the poor people in Africa rely on sorghum as a source of food (Elkhier and Hamid, 2008). The diversity of sorghum makes it an important food crop as it can tolerate both hot and dry conditions. Sorghum is also used in the brewing industry for the production of both alcoholic and non alcoholic beverages.

Sorghum has high starch gelatinisation temperatures that are higher than the temperature range for endogenous amylases. During the processing of sorghum, there is poor degradation of β-glucans and poor hydrolysis during mashing results to the formation slow worth filtration. This results to the reduction in extraction efficiency and the formation of haze.

Nutritional value

Sorghum has many nutritive values: starch is one of the major carbohydrates that are found in sorghum. It is comprised of amylopectin and amylase. The former is a branched polymer chain of glucose while the later comprises of a polymer with a straight chain.

The average values of carbohydrate ranges from 56-73%. Amylopectin forms 70-80 % of the total starch contents with the remaining percent be amylase. The starch content is greatly affected by the genetic and environmental factors. The starch found in sorghum is harder to digest as compared to that found in maize. The gelatinization process for isolated sorghum starch is the same as that of ground starch.

The protein content of sorghum is also greatly affected by genetic and environmental factors as well as the agro-climatic conditions. The main proteins to be found in the sorghum are albumin, globulin polamin and glutelin . There is a wide variety of essential amino acids in sorghum proteins; Lysine amount is 71-212 Mg per gram of nitrogen. The essential amino acids found in sorghum are shown in the table below

 

Amino Acid

Composition (mg/g)

Isoleucine

245

Leuccine

823

Lysine

126

Methionine

87

Cysteine

94

Phenylalanine

306

Tyrosine

167

Threonine

189

Tryptophan

63

Valine

313

CHEMICAL SCORE

37

 

Preparation effects on the physical, chemical and microbial

The methods of preparations vary from community to community. Various researchers have also come up with different methods of preparing Ogi. One of the methods entails soaking the cereals in water for a period of 3- 5 days. This water is changed every day until froth forms on top and an alcoholic smell is produced. These methods have been shown to produce Brevibacterial spp. There is also another method which involves the use of hot water and soaking the grains for a period of 24 hours. The other method entails cooking for 10 minutes and then steeping at ambient temperature. Researcher have found out that the actual processing of grains to produce Ogi results to the loss of about 40% of the total proteins but the digestibility of the proteins is increased by 20% and while about 50% of the macro and micro nutrients are lost (Nago et al., 1998).

The production process results to serious alterations in the physical, biological and chemical process of the resulting pap. The final viscosity of the Ogi is greatly affected by the temperature and the egression of polysaccharides. Prolonged steeping always results to carbohydrates loss and spoilage. The processing conditions may also introduce a vast number of bacterial. The use of hot water increases the softening rate and also the effects of aflatoxins but this Ogi will not raise while be cooked.

Sorghum has high nutritional value and fermentation process alters this value. However, there are some benefits of the fermenting process. The fermentation process results to the breaking down of complex substance to digestible nutrients (Omemua et al., 2007). Various researchers have found out that there are many microbiological and nutritional changes during the fermentations process. The researcher shows this process results to production of lactic acid bacterium lactobacillus plantarum, aerobic bacteria Corynebacterium and aerobacter. There is also the production of yeasts such as: Candida mycoderma, rhodotorula and sacchyaro-myces cervisiae. During the process, molds such as penicillium, aspergillus, fusarium and cephalo-sporuim are also present in the fermentation process. Lactobacillus plantarum is the most predominant micro organism and is responsible for the fermentation process and lactic acid production. Other microorganisms such as Corynebacterium and Candida mycoderma affect the flavor of the Ogi (Odunfa, 1985).

Microbial fermentation has some profound advantages and hence its preference in the production of Ogi. It is used in food preservation, reduction in volume of food materials, taste and appearance improvements, reductions in cooking and food preparations period, production of safe foods and increase in some nutrients (Afoakwa, et al., 2007)

Microbial properties of Ogi

The microbial content of Ogi has also been found to be affected by the preparations methods and the ingredients used. The preparation of Ogi requires the use of substance such as water and other ingredients which may be contaminated. Poor sanitary conditions have been found to affect the food and water where Ogi production is prevalent. The main organism that has been isolated from Ogi preparations substance and equipments are aspergillus flavus, Fusarium oxysporium, Candida Albicans, Saccharomyces Cerevisiae, Escherichia Coli. Lactobacillus plantarum. Pseudomonas Aeruginosa. and Staphylococcus aureus. Researchers have found out that the non enteric bacteria were found in all the study samples that were screened while the enteric bacterial developed at the later stages of the fermentations process. The researcher also showed that poor handling of the fermented Ogi also re-contaminated with the enteric bacteria. It has been found out the main contamination sites were water, medium for soaking, the grinding mill and the contamination that results during storage and transportation.

 

Studies done by Shephard et al. (2002) established that there are toxins associated with cancer such as mycotoxins. High levels of Fumonism have been reported due to use of supernatant from Ogi as the solvent for removing active ingredients from the traditional herbal plants. There is also the development of Aflatoxins during the storage process and this can cause problems to the young kids. Poor hygiene during the preparation of Ogi also results to contamination and infections by diseases such as cholera. During the storage of Ogi, fungi contaminations often occurs and moulds grow and produce Mycotoxins and certain yeast produce infections and allergies (Odunfa and Oyewole, 1998)

Studies carried out to show the interrelationship between micro-organism found in Ogi and the nutrition reveal that some of the micro-organism used in fermentations result in addition of the nutritive value of Ogi. Studies show that there is an increase in the lysine content during fermentation (Odunfa et al.,1994)

Physical properties of Ogi

The textural quality of Ogi depends upon the cereal type, milling technique, fermentations process, the size of the grains, and the steeping method used. The particle size in Ogi is of paramount importance as it influences: mixing, the starch consistency, heating rate, mass transfer and rheology. The acceptable particle size is <125 µm is ideal. Other tests carried out document the textural qualities of sorghum porridges and Ogi as well as the rheological properties. Studies have also shown that the swelling of Ogi is greatly influence by the fermentation property. Adeyemi (1983) found out that during the processing of sorghum to Ogi, there is a considerable reduction in the viscosity of the fermentation samples.

The stability and gelling tendency of Ogi are greatly affected by the fermentation process. Increase in the fermenting period to over four days result to poor stability, gelling tendency among other problems.

The process of Ogi fortification influences the rheological properties of Ogi. The addition, some materials may increase the viscosity or decrease it. Okra seeds added to the Ogi show a minimization of starch stability values while Ogi blended with roasted okra seed resulted in high viscosities. Fortified Ogi has a low sensory texture as compared to the unfortified one. The texture and viscosities have an imperative role as this determines its acceptance among the local community. For example, the textural value of Agindi which is made from Ogi greatly influences its acceptance among the local communities. The textural values are usually described as firm, consistent and smooth gritty appearance. The fermentation processes play an important role in the textural properties of Ogi.

Nutritional and chemical properties of Ogi

During the processing of sorghum to make Ogi, there is a great loss in the nutritive value. There are some vitamins such as pathogenic acids, folic acid, riboflavin, niacin and thiamine. Other lost elements are fiber, proteins, calcium, iron and phosphorous. Processing steps such as steeping, milling and sieving result to great reduction in nutrient content (Aminigo and Akingbala, 2004). Most of the nutrients found in the testa and germ of the seed are lost during processing as these are removed. Akobundu and Hoskins (1982) also found out that processing of Ogi using sorghum reduces the protein utilizations and other biological values. One of the common practices during the making of Ogi is the discarding of steeping water during processing. This reduces the minerals and other nutrients found in Ogi. It is recommended less water should be used during serving so as to minimize loses. The processing techniques have a great impact on the components of Ogi. Traditional processing has been shown to lose more nutrients as opposed to the modern experimental milling methods. During the dehydration of the Ogi using a drum or tray drying, most of the heat sensitive nutrients such as lysine are lost. The key drawback in the use of Ogi for infant and adult staple food is the low nutritive value. There are a lot of attempts to fortify Ogi with nutritive additives such as proteins( Osungbaro et al., 2000) this has resulted in the blending of Ogi with soya and maize so as to improve the lysine content. Ogi has also been prepared to incorporate theuraptic properties so as to control diarrhea among the infants. According to Sanni et al. (2001), most of the traditional infant meals need fortifications and blending with other food so as to improve their nutritive values. The process of fortifications may also be done to improve tastes. Some of the added components are fried beans, sugar, milk, fruits and berry seeds to make it sour and on a laboratory scale, vanilla can be added. This ingredient sweetens the porridge as well as increase the nutritive value of this porridge. Most of the researchers link the high rate of kwashiorkor occurrence in young infants to the consumption of Ogi (Akanbi et al., 2003). This researcher proposes the addition of fortification ingredients such as melon, cowpea, soy bean and other animal sources (Sanni et al., 2001 & Nnam, 2000). A comparative research has also shown that Ogi made from maize’s more nutritious as compared to that made from sorghum.

 

 

 

 

 

 

References

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