ABSTRACT
This study was conducted to determine the effects of different traditional cooking methods on the nature of starch in some Nigerian starchy staples. The staples used were yam (Dioscorea spp), cocoyam (Colocasia esculenta spp), cassava (Manihot esculenta crantz),and plantain (Musa paradisiaca spp). Yam and plantain were cooked into boiled and roasted forms. Cocoyam was prepared as cocoyam chips, while cassava was used to produce cassava dough, tapioca, and cassava foo foo and gari paste. The proximate composition, total starch and resistant starch were done using the approved methods. However, soluble starch was obtained by difference. Determination of carbohydrate digestion was achieved using Spectophometric procedure. The moisture content ranged from 21.04 % in roasted white yam to 41.00%% in gari paste. The protein content of the staples was low; ranged from 0.55g/100g in cassava foo foo to 2.25g/100g in cassava dough. The fat, ash, and crude fibre contents were also low. The boiled hybrid plantain ranked highest (3.01g) in fat, while roasted local plantain had highest ash (4.20g) and crude fibre (3.30g) values. Roasted white yam (Dioscorea spp) had highest carbohydrate 73.25g. Loss of moisture caused increases in nutrient density. Processing caused significant differences (P<0.05) in different forms of some the foods .For example the protein content of roasted white yam was 4.29g/100g and this was significantly different (P<0.05) from both the raw (2.33g/100g) and the boiled (2.72g/100g) samples, respectively). However, in cocoyam (Colocasia esculenta) varieties (esculenta var. esculenta,esculenta var. antiquorum (small corm) and esculenta var. antiquorum (large corm)), processing caused no significant difference (P>0.05) in all the proximate parameters except for esculenta var. antiquorum (large corm) where the crude fibre content of cocoyam chips (3.08g) was significantly different (P<0.05) from raw (0.6g).Total starch content of the carbohydrates ranged from 20.36g/00g in raw local plantain to 50.95/100g in boiled water yam. The resistant starch content of the carbohydrates ranged from 9.25g/100g in cassava dough to 32.15g/100g in boiled water yam. The resistant starch content of carbohydrates was affected by heat. Processing increased the resistant starch, solubility and digestibility of the carbohydrates. For example, the local plantain had resistant starch of 20.65g/100g and 23.05g/100g for boiled and roasted samples as against the raw 10.35g/100g. The roasted water yam had more resistant starch than the roasted white yam
(22.85g vs 20.15g). The solubility of raw cassava was 14.82g and the processed samples had 33.30g/100g, 34.00g/100g, and 19.50g/100g for cassava dough tapioca, cassava foo foo, and gari paste, respectively. Digestibility of the carbohydrate foods increased from 27.17% in raw white yam to 71.92% in boiled white yam. Digestibility correlates positively and closely with the total starch content of the foods (r=0.9545; p<0.05), while the resistant starch content of the carbohydrates correlates positively but poorly with digestibility (r=0.6184; p=0.0017). The result of multiple regression analysis showed that moisture, protein, fat, ash and total carbohydrate as well as total and resistant starch of the foods influenced digestibility. Thus digestibility of a food depends on the interplay of many factors However, in conditions that require less energy dense foods (diabetes and obesity) emphasis should be on the processing method with highest amount of resistant starch.
1.1 Introduction
CHAPTER ONE
Food has been of utmost importance to human being since his creation on earth. The type of food we eat is a universal key factor that affects, as much as it defines the health of the people hence, the saying “you are what you eat.” This statement suggests that our health to a large extent is under our control. We can abuse our bodies by what we eat, drink or smoke (Ene – Obong, 2001), Food is very essential for long life and longevity (Joan and Mike, 2002) hence, Abraham Maslow, a renowned psychologist, classified food as one of basic human needs.
Food comprises of the six classes of nutrients – carbohydrates, proteins, fats and oils, vitamins, minerals and water. Carbohydrate (tubers, roots, cereals etc) is one of the four major classes of bimolecules and plays several important roles in the body (Gibney et al., 2002). Carbohydrates are diverse molecules that can be classified by the molecular size (degree of polymerization). The physico- chemical properties of carbohydrate and the fate within the body are also influenced by their monosaccharide composition and type of linkages between them.
Carbohydrates and other countless organic compounds originate from green plants. When carbohydrate is metabolized, energy is released but for the synthesis of carbohydrate a source of energy is required. This energy is obtained from the sunlight and dissolved by chlorophyll. It is used to build carbohydrate molecules from carbon dioxide and water. In the course of their formation, some of the simpler units needed to build these carbohydrates take part in various side reactions, by combining with other elements such as nitrogen phosphate and sulphur to form lipids and proteins (Benjamin and Abraham, 1962). Therefore, carbohydrates are compounds containing carbon, hydrogen, and oxygen (Gordom and Kessel, 2002), classified carbohydrate as simple and complex carbohydrates. Carbohydrates are also classified as sugars, oligosaccharides and polysaccharides.
The sugars consist of monosaccharide (for example glucose, fructose and galactose) and the disaccharides, which consist of the sucrose, lactose and maltose. These sugars are absorbed unchanged or with minimal digestion. The oligosaccharides contain 3-9 sugar units. They are not digested by the human enzyme but may be fermented by micro organisms in the
lower intestine to produce some gasses and short chain fatty acids (SCFAs). They include the raffinose, starchyose and fructo-oligosaccharides. The polysaccharides consist of non- starch polysaccharides (example cellulose, hemicellulose and pectin). These contain more than nine sugar units, and the starch. The starches are the amylose, amylopectin and modified starches. Starch that occurs abundantly in grains, cereals, tubers and fruits is the greatest source of carbohydrate for man. It consists of straight or branched chain of hundreds of glucose molecules connected together. Starches are rather long (Cataldo et al., 2001). Starches consist of two types of molecules, a linear or non-branched polymer of glucose (amylose) and a branched polymer of glucose (amylopectin), and modified starches. Some are digestible others are not Starches can be classified as rapidly digested starch (RDS) – these can be converted to glucose within twenty minutes of enzyme action. The slowly digestible starch (SDS) – they are found in cereals and retrograded starch, their digestion is slow but complete. The third class is the resistant starch (RS) –these are potentially resistant to digestion in the small intestine. Resistant starch can be further classified as physically inaccessible starch (RS1), resistant starch granules (RS2) and Retrograded starch (RS3). Most starches contain glucose linked by alpha or beta bonds. Human digestive enzyme can only digest carbohydrate linked by alpha bonds (for example maltose).
The primary function of food is to supply the body with energy, material for growth and repair and electrolytes. These roles are adequately performed when there is proper processing method and adequate nutrition. Adequate nutrition is one key to developing and maintaining an optimal state of health. Poor diet and sedentary life style are known as risk factors for life threatening chronic diseases like heart conditions, diabetes, obesity and some forms of cancer (Cataldo et al., 2001). Good health is ensured by eating judicious variety of foods and an adequate diet must provide all the nutrients require for energy, body building, maintenance and regulation of body process.
Sometimes, our foods are consumed raw, that is, in their natural forms without undergoing any form of processing (e.g. fruits like oranges, guava, banana and vegetable like cabbage, tomatoes, carrot, mangoes etc). Plant foods (starchy foods) are the most important dietary sources for meeting the nutritional needs of the population in Nigeria. However, these root crops are not easily digested in their natural state and are often
processed before they are eaten. Processing improves their digestibility, promotes palatability and improves their keeping quality as well as making the roots safer to eat. The processing methods conventionally used include, soaking in water, fermentation, sun drying etc. The heat used during cooking can be dry heat as in baking in an oven or over an open fire, or wet heat as when boiling, steaming or frying. Heat helps to sterilizer the food by killing harmful bacteria and other microorganisms, and it increases the availability of nutrients. Proteins are denatured by heat. In this form proteolytic enzymes more easily digest them; cellulose cell walls that cannot be broken down by monogastric animals like man are broken down, and some anti-nutritional factors such as enzyme inhibitors are inactivated (FAO, 1990). It has also been observed that heat treatment can result in transformation of starch lipid complex that can resist digestion.. Therefore, heat treatment can result in chemical modification, and fragmentation of the starch. The modification is mainly dependent upon the temperature, time, moisture content and pH involved.
Starches may be hydrolyzed to sugars (Gordom and Kessel, 2002). The percentage loss will depend partly on the cooking temperature and on whether the food is prepared by boiling, baking or roasting. Baking losses may appear deceptively low if expressed on a fresh weight basis, due to the concentration of nutrients by loss of water (FAO, 1990). It has also been observed that at low moisture levels, inter molecular rupture of alpha 1-4 linkages in starch produces oligosaccharides and more high molecular weight fragments containing 1-6 anhydroglucose units that are able to react with water, thus forming malto dextrin or with hydroxyl group in starch and other polysaccharides to form new structures (transglucosidation). Such new linkages are not degradable with amylolytic enzyme and present an irreversible chemical modification (Siljestrorne et al., 1986). Recent studies also noted that at high moisture levels, so called resistant starch may be formed probably by a retrogration process with the formation of strong intermolecular hydrogen bonds in the amylase function and a concomitant decrease in solubility. It is also documented that high moisture and temperature processing favour increase in the total dietary fibre.
The first step in processing any root crop is usually peeling. This may remove nutrients if it is not done carefully. Nutrients may be lost during cooking in two ways. First, by degradation: this can occur by destruction or by other chemical changes such as, oxidation and secondly by leaching into the cooking medium. Vitamins are susceptible to both
processes. For example vitamin C, the most thermo labile vitamin, is easily bleached into the cooking water or canning syrup. Boiling may result in a 20-30 percent loss of vitamin C from unpeeled roots and tubers. If peeled before boiling the loss may be much higher, up to 40 percent. However, minerals are affected only by leaching. Free amino acids could also be leached or may react with sugars to form complexes (FAO, 1990). Retaining the skin to minimize leaching and to protect the nutrients can reduce cooking losses.
1.2 Statement of Problems
The choice of what to eat is a problem to most Nigerians. Determining the appropriate amount of food to match energy needs over a long period is a problem to all. Furthermore, the diabetics and weight watchers have a problem of choice especially when it comes to carbohydrate foods. They eliminate virtually all the foods (Gerald, 1990), thus limiting food choices that lead to malnutrition and the attendant problems. This is so because in Nigeria there is limited amount of reliable data on the carbohydrate composition of common foodstuffs especially in their processed forms. Most of the available data are limited to the carbohydrate content of raw foods obtained by difference. This often leads some people to eat merely to satisfy hunger, while others eat to reflect their status in the society. In both cases ignorance plays a major role. People adopt food habit similar to those of the surrounding environment. Therefore, food habit in most individuals is deeply grained during childhood and remains resistant to change (Joan and Mike, 2002; Dickerson and Lee, 2001). Thus, food choices are often based on ignorance, misconception, superstitions and traditional/cultural unscientific beliefs.
As a result of misinformation especially in diabetics, malnutrition is becoming increasingly common. People either do not get enough or get too much of the nutrients (Population Bureau, 1986). Thus, diets for diabetics need not be inappropriately restricted in carbohydrate. The deficiency or excess of nutrients manifest as signs of malnutrition. In addition, the local staples are considered too sufficient in energy; hence some people starve for fear of getting too fat. This results in consequences like under weight, anaemia and marasmus which are common among Nigerians. However, people who indulge in excessive consumption of starchy foods are prone to disorders like obesity in which there is excessive
accumulation of body fat. The consequences of obesity are numerous; hence, Harrison
(1979), noted that life expectancy is reduced by 10 years for every 0.5kg over weight.
All these nutritional stresses resulting from processing and improper consumption of the local staples are implicated in short life span in Nigeria. Therefore, it is important to realize that lifestyle, environmental factor in addition to nutrition influence health and well – being, but nutrition is a major modifiable factor in promoting health, preventing and treating diseases and improving the quality of life.
1.3 Objectives of the study
General objective:
The general objective of this study was to determine the effects of different traditional cooking methods on the nature of starch in some Nigerian starchy staples.
Specific objectives: The specific objectives of the study were:
• to determine the proximate composition of the foods in their raw ,cooked, and processed forms.
• to determine the digestibility of the staples in their raw, cooked and other processed forms.
• to determine the amount of starch resistant to enzymatic degradation because of the various methods of cooking.
1.4 Significance of the study
There is inadequate information on the dietary composition of local foods in their processed forms. The data on the composition of the cooked local staples is necessary because starchy foods form the staple food for many societies. Starchy foods are the major energy yielding foods required by all. Even in disease conditions such as obesity and diabetes, energy is still necessary. The result of this work would help fill some gaps in Nigerian food composition table value for processed and cooked local foods. The results of this investigation would be a reference material for new investigators.
It would assist the Dieticians and Nutritionist when handling those with physiological challenged conditions such as diabetes. It would assist them to know the most suitable method to derive maximum energy from foods or reduce its utilization.
The knowledge and information gained from this study would assist people with diabetes to increase their food choices. This would prevent complications caused by diabetes mellitus. Apart from people with diabetes, the obese who requires weight loss would utilize the knowledge when selecting weight reducing diets as well as for those that need a desirable body weight.
The study would enable the public to appreciate different food choices and food processing methods that are available. The result of this work would spur new researchers to carry out detailed studies with other local foods, especially in their processed and cooked forms to determine their roles in preventing and controlling diseases.
This material content is developed to serve as a GUIDE for students to conduct academic research
THE EFFECTS OF DIFFERENT TRADITIONAL COOKING METHODS ON THE NATURE OFSTARCH IN SOME NIGERIAN STARCHY STAPLES
Project 4Topics Support Team Are Always (24/7) Online To Help You With Your Project
Chat Us on WhatsApp » 09132600555
DO YOU NEED CLARIFICATION? CALL OUR HELP DESK:
09132600555 (Country Code: +234)
YOU CAN REACH OUR SUPPORT TEAM VIA MAIL: [email protected]
09132600555 (Country Code: +234)