Production and Evaluation of Biscuit From African Yam Bean, Sorghum and Wheat Flour Blends
Objectives of the Study
The aim of this study is to produce flour from African yam bean, sorghum and wheat; to examine the proximate properties of the flour produced from African yam bean, sorghum and wheat and lastly, to analyze the microbial composition and sensory properties of the biscuits produced from the flour blends.
African yam bean (AYB) (Sphenostylis stenocarpa)
African yam bean is known and called different names by different tribes in Nigeria, some of the names are Azama, Ijiriji, Azam, and Uzaaki in Igbo; Girigiri in Hausa; Akpaka in Delta and Nsama in Ibibio. Other names are Okpodudu, Ahaja, Nzamiri, Odudu and Sese in Igala. In some parts of Ghana, it is called Kulege or Kutreku. African yam bean belong to the family: Fabaceae (alt. Leguminosae) subfamily: Faboideae tribe: Phaseoleae subtribe: Phaseolinae., also placed in: Papilionaceae. It is also called yam pea in English and it is usually cultivated in the following African regions Northeast Tropical Africa: Chad; Ethiopia East Tropical Africa: Kenya; Tanzania; Uganda, West-Central Tropical Africa: Burundi; Central Africa Republic; Zaire West Tropical Africa: Cote D’Ivoire; Ghana; Guinea; Mali; Niger; Nigeria; Togo South Tropical Africa: Angola; Malawi; Zambia; Zimbabwe (USDA, 2007).
African yam bean is grown both for its edible seeds and its tubers (Klu et al., 2001). The seeds are mostly used in some regions. It is a vigorous vine which twines and climbs to heights of about 3m and requires staking, with its prolific spattering of large flowers which may be pink, purple, or greenish with white, making it an attractive ornamental (NAS, 2009). The slightly woody pod which contains 20 to 30 seeds is up to 30cm long and mature within 170 days (Klu et al., 2001). The seeds of African yam bean vary in sizes and shapes. The seed coat has a range of colors from pale white to black with spotted or mottled grey, cream and brown in between. In Nigeria, it is grown mostly in the northern part where it is grown mainly for its seed (Alozie et al., 2009).
Distribution of African Yam Beans
Sphenostylis stenocarpa is native to tropical west and central Africa and is cultivated in southern and eastern Africa (Klu et al., 2001). Both wild and cultivated types now occur in tropical Africa as far south as Zimbabwe, throughout West Africa from Guinea to southern Nigeria. It thrives on deep, loose sandy and loamy soils with good organic content and good drainage. It grows better in regions where annual rainfalls range between 800-1400mm and where temperatures are between 19-27°C (Klu et al., 2001). The plant flowers after 90days and the pods mature in 140 to 210days. The tubers are ready to harvest 150 to 240days after sowing. Cultivation conditions for African Yam Beans.
African yam bean Processing Methods Used
Roasting is a traditional processing technique, it has the capacity to develop attractive flavours in foods so treated. It also induces important functional properties, attributes that should be compatible with nutritional value (Bressani, 2003).
Fermentation is one of the oldest and cheapest traditional processing methods used in the home and industries to improve the nutritional quality of food and reduces anti nutrient and toxic substances like phytic acid, polyphenols and oxalic acids, Hydrogen cyanide, raffinose and stachyose among others to improve food use (Mahungu et al., 2007). It is the metabolic process in which carbohydrates are oxidized with the release of energy. During fermentation, the microbial enzymes converts storage nutrient in foods to readily utilizable form (Rajalakshimi and Ramakrishanan, 2007). Fermentation begins when a food rich in simple sugars, yeast, and water are combined and left at room temperature. During the first stage, the yeast cells multiply, using the sugars for energy, and produce small amounts of alcohol (Byrd-Bredbenner et al., 2007). Many foods which are inedible are made edible in their unfermented form and this is brought about by the extensive hydrolysis of the indigestible components and the removal of anti-nutritional factors by the micro-organisms.
Reasons for Fermentation
Some reasons why fermentation of legumes is used in the preparation of foods are:
- Legumes often contain substances that are undesirable, such as the trypsin, phytates among others. The treatments of the beans (soaking or heating) in preparation for fermentation or the enzymes produced by the microorganisms remove or destroy these factors.
- Moist products spoil readily, however after fermentation some products will keep without refrigeration for extended periods of time. This is especially true of the fermented products that are high in salt.
- All the legume fermentations involve the action of proteolytic and lipolytic enzymes with the result that the final products are more digestible.
- Almost invariably the final product has a changed flavor more acceptable to the consumer.
- In many instances the microorganisms increase nutrients such as vitamins, including riboflavin and vitamin B12 in some of the bacterial fermentations.
- Finally, fermentation may reduce energy requirements. Thus, a short cooking may be the major energy input required while the microorganisms do the rest of the work by using energy from the substrate.
Source: Hesseltine and Wang (2000).
In addition, fermentation equally extends shelf life and level of safety (Hesseltine and Wang, 2000). It increases essential amino acids like methionine, improved palatability, increase non protein nitrogen (Reddy and Salunkhe, 2000). Proteolytic acid and amylolytic enzymes from micro-organism in fermentation process enhance digestibility and nutritional quality (Murato et al., 2007). It equally enhances flavour, aroma, texture, keeping quality and improves nutritive values (Eka, 2000). Fermented corn, cowpea and African yam bean are known to have higher nitrogen balance than its unfermented counterparts (Eka, 2000).
Processing of African yam bean and its effect
Most legumes are not fit for consumption in their raw state except they undergo some processing operations. Processing is done to improve the quality and functionality of foods, for increased bioavailability of nutrients and reduction of undesirable compounds such as toxins and non-nutritional compounds. African yam bean is one of such legumes that requires careful and appropriate processing for consumer palatability and safety. This is because pulses are generally high in compounds that alter normal metabolic processes. Over the years, the bean has been pre-processed and processed using different methods. Such methods includes: germination, roasting, fermentation, soaking as well as cooking or boiling.
Germination in food processing is a process where seeds are steeped or soaked for a period of time and then sprouted at the early stage of development of seeds to plant. Some authors have reported that germination results in improved flavour, nutritional composition, amino acid content and reduction of non-nutritional compounds in many legumes (Rumiyati et al., 2012). In addition to this, germination results in breakdown of complex carbohydrates in legumes into simple sugars through the action of endogenous enzymes thereby enhancing digestibility (Nkhata et al., 2018). It was reported that germination of AYB resulted in improved protein quality and enhanced the bioavailability and digestibility of other nutrients with a marked decrease in non-nutritional compounds like oxalate, phytic acid, trypsin inhibitors amongst others (Nwosu, 2013). Germination also improved the antioxidant content of AYB, for instance, it has been demonstrated from literature that the antioxidant content and free radical scavenging activity of the bean improved significantly after germination (Uchegbu, 2015). Hence, germinated AYB meal is said to be a good dietary inclusion for individuals with complications from oxidative stress, hyperlipidemia, and diabetes.
Roasting has also been used in the processing of AYB and was reported to have increased the minerals composition such as calcium, potassium, phosphorus, magnesium, etc of the bean as well as resulting in great decrease in non-nutritional compounds (Ndidi et al., 2014). Uchegbu (2015) stated that roasting improved the phosphorus content of the bean, while tannin content was non-detectable, although this was attributed to the removal of the seed coat that resulted from roasting. This method has been described as a viable method of preparing AYB snacks which are mostly consumed with palm kernel in the eastern part of Nigeria (Uchegbu, 2015).
MATERIALS AND METHODS
Source of Materials
African yam bean, Sorghum and wheat were bought from a local market in Owo, Ondo State Nigeria, and other ingredients used for this study were purchased at Ikoko market Owo. This research work was carried out in Department of Food Science and Technology, Rufus Giwa Polytechnic Owo, Ondo State, Nigeria.
Method of Flours Preparation
Preparation of African yam bean flour
The African yam bean flour was prepared according to the method described by Ihekoronye and Ngoddy (2005) as shown in Figure I. During preparation, two kilograms of African yam bean seeds which were free from dirt and other foreign particles such as stones, sticks and leaves were weighed, cleaned and soaked in tap water for 8 hours. Thereafter, the seeds were drained, dehulled manually, boiled (100oC, 30min) and dried in cabinet dryer (65oC, 6hr). During drying, the dehulled seeds were stirred at intervals of 30 minutes to ensure uniform drying. The dried seeds were milled (attrition mill) and sieved to obtain cooked lima bean flour. The African yam bean flour obtained was finally packaged in an air tight container which was later subjected for further analysis.
RESULTS AND DISCUSSION
Table 4.1: Proximate composition of biscuit from African yam bean, sorghum and wheat flour
CONCLUSION AND RECOMMENDATION
The production of biscuit from African yam bean, sorghum and wheat flour prove to be successful, the nutritional content of the biscuit indicate that the blends of legumes flour (African yam bean) and cereal flour (sorghum and wheat) can help control malnutrition among young and adult, from the result ASW1 has less moisture content, and higher fat, protein, CHO content making it more nutritious compared to sample ASW2, ASW3 and ASW4 respectively, this indicate that the production of biscuit from African yam bean, sorghum wheat flour up to 40% AYB, 30% Sorghum and 30% wheat is of great source and can last longer due to it’s low moisture content. The sensory attributes of the four samples shows the ASW4 has higher acceptance compared to other samples.
Based on the finding above, it is therefore recommended that food producing industries should consider the use of legumes flour such as African yam bean, soybean and others in the production of biscuits because it will enhance the nutritional content of the biscuit and can help control protein malnutrition.
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