Quality Characteristics of Biscuits Produced From Cassava, Millet and Sweet Potato Composite Flour
The Objective of the Study
The objective of the study is to investigate the quality characteristics of snacks produced with cassava, millet and sweet potato composite flour.
Cassava (Manihot esculenta Crantz)
Cassava (Manihot esculenta Crantz), also referred to as yucca in Spanish, mandioca in Portuguese and tapioca in French, belongs to the Euphorbiaceae family (Burrell, 2003). It has been reported that the crop originated from South America and was domesticated between 5,000 and 7,000 years B.C. (Olsen and Schaal, 2001). The first import of cassava to Africa was by the Portuguese from Brazil in the 18th century, but now cassava is cultivated and consumed in many countries across Africa, Asia and South America (Nhassico et al., 2008; FAOSTAT, 2013). The crop has drought resistant root which offers low cost vegetative propagation with flexibility in harvesting time and seasons (Haggblade et al., 2012). Cassava can be cultivated throughout the year between latitude 30º N and 30º S, in different soil types except hydromorphic soil with excess water (Iyer et al., 2010). The stem grows to about 5 m long with each plant producing between 5 to 8 long tubers with firm, homogenous fibrous flesh covered with rough and brownish outer layer of about 1 mm thick. The root can be stored in the ground for over 2 years, and this serves as a means of food security to the farmer in West African countries such as Nigeria (Nhassico et al., 2008; Falade and Akingbala, 2010)
Cassava is a subsistence crop in Africa, and supplies about 200 – 500 calories per day (836.8 – 2092J) for households in the developing countries (Sánchez et al., 2006; Omodamiro et al., 2007). In the early years, cassava was neglected as food crops because of its low protein content (< 2%) and high cyanide content (120-1945 mg HCN equivalent/ kg) (Iglesias et al., 2002; Charles et al., 2005), but it is considered the fourth most energy rich food source due to the high (>70 %) carbohydrate content (Falade and Akingbala, 2010). The leaf of cassava plant is higher in protein (3 – 5%) and some macro nutrients, and therefore consumed as vegetable in some countries (Salcedo et al., 2010; Burns et al., 2012). However, the tuberous root is the major edible part of the crop. The root serves as a source of food security against famine because of its long storage ability in the ground prior to harvest (El-Sharkawy, 2004). The root can be processed into different food forms for human consumption, animal feed and as industrial raw material for paper, textiles and alcoholic drinks (Falade and Akingbala, 2010; Haggblade et al., 2012). In Thailand, cassava dry chips and pellets are the major export commodity (Falade and Akingbala, 2010), while in Nigeria, it is processed mainly into gari and fufu.
Utilization of cassava root in food is numerous, however, the potential in food and other industrial applications is limited by the rapid postharvest physiological deterioration, which reduces the shelf-life and degrades quality attributes (Sánchez et al., 2006). This physiological deterioration is attributed to its high moisture level (60 to 75%), and respiration rate which continues even after harvest (Salcedo et al., 2010), resulting in softening and decay of the root and thus rendering it unwholesome for human consumption. Other factors that can cause deterioration of cassava root include pests, disease, and mechanical damage such as cuts and bruises which occur during postharvest handling and processing (Falade and Akingbala, 2010; Iyer et al., 2010). The cut area exposes the root to vascular streaking and microbial attack, thereby accelerating deterioration and decay (Buschmann et al., 2000; Opara, 2009). Studies have shown that physiological changes start within 24 h after harvest with a blue black discoloration commonly appearing on the root after 72 h (Iyer et al., 2010; Zidenga et al., 2012). The colour change of the root is accompanied by fermentation and thereafter an offensive odour indicating complete rotting (Reilly et al., 2004). This rapid degradation of quality in fresh cassava roots is a major reason for the poor utilization, poor market quality, short root storage life and low processing yield (Reilly et al., 2004; Sánchez et al., 2006).
Converting cassava root to other food forms creates products with longer shelf-life, adds value to the root, and reduce postharvest loses (Falade and Akingbala, 2010). Furthermore, the application of novel postharvest handling, processing, packaging and storage techniques is of critical importance for successful large scale production and utilization of cassava roots and products. Successful application of these postharvest technologies will contribute towards maintaining product quality and safety as well as reducing incidence of postharvest losses, and thereby, improve food security (Opara, 2013).
Classification of Cassava Root
Cassava roots may be classified into sweet and bitter based on the level of cyanogenic glucoside in the tissue. The major cyanogenic glucosides found in cassava are linamarin and lotaustralin, which can be hydrolyzed into hydrogen cyanide (HCN) (Iglesias et al., 2002). Hydrogen cyanide is a toxic compound harmful to human health and could lead to death if consumed in excess (Nhassico et al., 2008; Burns et al., 2012). Bitter cultivars of cassava root have higher level of cyanide content (28 mg HCN/ kg) than the sweet type (8 mg HCN/ kg) dry weight bases (Chiwona‐Karltun et al., 2004; Charles et al., 2005). Sweet cassava root cultivars with lower cyanide content can be eaten fresh or boiled (Nhassico et al., 2008) while the bitter type with higher cyanide concentration require further processing to eliminate the toxins before consumption (McKey et al., 2010).
Symptoms of cyanide consumption include fast breathing, restlessness, dizziness, headache, nausea and vomiting. In chronic cases, symptoms could result in convulsion, low blood pressure, and loss of consciousness, lung injury and respiratory failure which could lead to death (Burns et al., 2012). It has also been reported that consumption of these cyanogens causes irreversible paralysis of the legs and stunted growth in children (Ernesto et al., 2002; Nhassico et al., 2008). Greater quantity of these glucosides are bio-synthesized in the leaves and are absorbed in the root but predominantly on the peels (Siritunga and Sayre, 2004; Cumbana et al., 2007). Total cyanide found in the fresh unpeeled root and the leaves range from 900 – 2000 ppm and 20 – 1860 ppm, respectively, depending on cultivar (Cardoso et al., 2005). However, during processing about 90% of the HCN is lost due to the linamarin breakdown and the residual cyanogen levels should be below the safe limit (10 ppm) recommended by the World Health Organization (WHO) for cassava flour (FAO/WHO, 2005). Removal of cyanogenic compound from the root during processing for production of cassava-based foods is one major approach to promoting safety in cassava consumption (Iglesias et al., 2002).
MATERIALS AND METHODS
Cassava (Manihot esculenta crantz) was purchased at the local market in Emure-ile in Owo Local Govt. Area, while millet (Pennisetum glaucum) and sweet potato (Ipomoea batatas) were purchased at the local market in Owo, Ondo State. Other materials used for the biscuit production such sugar, salt, baking powder, flavour etc. were also purchased in Owo local market. The equipment used for the biscuit production were all gotten from the processing laboratory of the Department of Food Science and Technology, the analysis was carried in the Food Chemistry Laboratory of Food Science and Technology, Rufus Giwa Polytechnic, Owo, Ondo State, Nigeria.
Production of cassava flour
The method used as described by Cardoso et al. (2005) with several modifications. The cassava roots was first washed in clean water to remove dirt from the roots, the cassava was then peeled in order to have access to the inner part, the cassava was cut into smaller pieces, washed in a clean water, then it was dried using cabinet drying machine, the drying process was conducted at 65°C for 48 hrs. Dried cassava chips were then ground and sieved using 500 µm sieve then stored for further analysis (Figure 1).
RESULTS AND DISCUSSION
Table 4.1: Proximate composition of biscuits from cassava, millets and sweet potato
CONCLUSION AND RECOMMENDATIONS
The chemical analysis of snacks made from composite flour of cassava, millet and sweet potato showed significant increase in protein and ash content, and this indicates a high nutritional value. The statistical analysis of the sensory evaluation of the composite flour was most preferred. This revealed cassava, millet and sweet potato flour can be incorporated for snacks production to improve its nutritional value and eating quality. This without skepticism will contribute to reducing the problem of protein-energy malnutrition. Use of composite flour for snacks making will add value to these local crops and reduce over dependence on wheat flour thereby saving the country’s foreign exchange earnings.
Based on the result of this research, it is therefore recommended that; cassava, millet and sweet potato flour blends can find useful application for snacks products for which composite flour of cassava, millet and sweet potato has been used. Products developed from a blend of cassava, millet and sweet potato flour can be very useful snacks product in respect to nutritional value. Popularizing the use of these flour blends for such products for which composite of cassava, millet and sweet potato flour is used, will go a along way to reduce the country’s dependency on the composite flour hereby saving scarce foreign exchange. Substituting up to 10% level of cassava, millet and sweet potato flour in product development will improve its nutritional value.
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