Evaluation of the Quality Attributes of Garri Produced From Three Cultivars of Cassava
Objective of the Study
The research work focuses on the evaluation of the quality attributes of garri produced from three cultivars of cassava.
Origin and General Overview of Cassava (Manihot esculenta Crantz)
Cassava (Manihot esculenta Crantz) is a root and tuber crop that has been identified important food, especially in Africa. In areas where cassava is a main staple, people have developed ways for its processing into storable products such as tapioca, starch, dough and gari. It plays a major role in efforts to alleviate the African food crisis because of its efficient production of food, year-round availability and tolerance to extreme stress conditions (Hehn, 2007). Cassava has some inherent characteristics which makes it attractive, especially to the smallholder farmers in Ghana (Bokanga, 2002). Cassava is the third most important food in the tropics, after rice and maize. Its importance derives from the fact that its starchy, tuberous roots are a valuable source of cheap calories, especially in developing countries where calorie deficiency and malnutrition are widespread. Cassava alone provides the major source of dietary calories for about 500 million people, many of them in Africa (Yeoh et al., 2008). Of all the tropical root crops, cassava is the most widely distributed and cultivated root crop in different parts of Africa (Onwueme, 2001).
It is particularly important in those areas where food supply is constantly threatened by environmental constraints such as drought and pest outbreaks, because of its ability to grow under conditions considered as suboptimal for the majority of food crops. It can be harvested any time from 6 to 24 months after planting and can be left in the ground as a food reserve for household food security in times of famine, drought and war. Currently, cassava is the largest source of carbohydrates for human food in the world, and it has a high growth rate under optimal conditions and the tuberous roots as well as the leaves are used as human food, animal feed and industrial products (Mann et al., 2007). Cassava roots contain high energy and high levels of some vitamins, minerals and dietary fiber, and contain no trypsin inhibitor, but create a problem due to presence of cyanide which is removed by postharvest treatments and cooking (Prathibha et al., 2005).
Cassava roots and leaves which constitute 50% and 6% of the mature plant, respectively, are the nutritionally valuable parts of the plant (Tewe and Lutaladio, 2004). The edible starchy flesh comprises some 80% to 90% total weight of the root with water forming the major components. The water content of cassava ranges from 60.3% to 87.1%, moisture content for cassava flour varies from 9.2% to 12.3% and 11% to 16.5% (Padonou et al., 2010). Water is an important parameter in the storage of cassava flour; very high levels greater than 12% allow for microbial growth and thus low levels are favorable and give relatively longer shelf life (Padonou et al., 2010). Cassava contains about 1-2% protein which makes it a predominantly starchy food. The protein content is low at 1% to 3% on a dry matter basis and between 0.4 and 1.5 g/100 g fresh weight (Bradbury et al., 2008). In contrast, maize and sorghum have about 10 g protein/100 g fresh weights (Montagnac et al., 2009). As human food, it has been criticized for its low- and poor-quality protein content, but the plant produces more weight of carbohydrate per unit area than other staple food crop under comparable agro-climatic conditions.
Cassava is an energy dense food and therefore ranked high for its calorific value of 250×103 cal/ ha/day as compared to 176×103 for rice, 110×103 for wheat, 200×103 for maize, and 114×103 for sorghum (Okigbo, 2009). The root is a physiological energy reserve with high carbohydrate content, which ranges from 32% to 35% on a FW basis, and from 80% to 90% on a dry matter basis (Montagnac et al., 2009). Raw cassava root has more carbohydrate than potatoes and less carbohydrate than wheat, rice, yellow corn, and sorghum on a 100 g basis (Montagnac et al., 2009). The lipid content in cassava roots ranges from 0.1% to 0.3% on a fresh weight basis, it ranges 0.1% to 0.4% and 0.65% on a dry weight basis (Charles et al., 2009). This content is relatively low compared to maize and sorghum, but higher than potato and comparable to rice. The lipids are either non-polar (45%) or contain different types of glycolipids (52%). The glycolipids are mainly galactose diglyceride. The predominant fatty acids are palmitate and oleate (Hudson and Ogunsua, 2004).
Cyanide is the most toxic factor restricting the consumption of cassava roots and leaves. There are three different forms of cyanogens present in cassava root and leaves, these are linamarin, acetonehydrin (lotaustralin) and free HCN. The linamarin and lotaustralin undergo a sequential enzymatic breakdown and the final form is toxic free cyanide. The total of these three forms is called Cyanogenic potential. Cyanogenic glycosides are effective defense agents against generalist herbivores including humans (Gleadow and Woodrow, 2002). Cassava leaves have a cyanide content ranging from 53 to 1,300 mg/kg of DW (Siritunga et al., 2003) and cassava root parenchyma has a range of 10 to 500 mg/kg dry matter, both of these are much higher than what is recommended (Arguedas and Cooke., 2002). Bitter cassava varieties, have cyanide levels higher than the FAO/ WHO (2001) recommendations, < 10 mg/kg dry matter, to prevent acute toxicity in humans. Several health disorders and diseases have been reported in cassava eating populations. Consumption of 50 to 100 mg of cyanide has been associated with acute poisoning and has been reported to be lethal in adults (Yeoh and Suna, 2001). The consumption of lower cyanide amounts are not lethal but long term intake could cause severe health problems such as tropical neuropathy, glucose intolerance, and, when combined with low iodine intake, goiter and cretinism (Delange et al., 2004).
MATERIALS AND METHODS
Freshly harvested cassava roots of three cultivars were obtained from a staff farm at Rufus Giwa Polytechnic, Owo, Ondo State.
The cassava root (10kg) of each cultivars was peeled manually with stainless steel kitchen knife. The peeled roots were washed and grated. The grated meal was then packed into hessian bag and allowed to ferment for 72 hours. The fermented pulp was dewatered using the screw press. The pressed cake was broken into pieces with hand and sieved with a wire mesh screen. The sieved pulp was toasted inside a wide shallow cast iron pot and stirred constantly over a low fire until well dried.
RESULT AND DISCUSSION
Table 4.1: Root characteristics/chemical composition of different cultivars of cassava
CONCLUSION AND RECOMMENDATIONS
This study shows that the garri yield from TMS 30572 (an improved cultivar) was 80% and 24% higher than the quality recovered from Anteota and Agbeloba cultivars respectively. However, Anteota cultivar had an improvement of 17.6% garri yield over its Agbeloba local cultivar. Although Agbeloba cultivar has the least swelling capacity, its low total hydrogen cyanide value is highly desirable. The results obtained in this study equally show that the potential exists for selecting cassava cultivars that are suitable for specific products among the existing cassava cultivars grown in each locality in Nigeria. The variability in the percent of garri cyanide content of the cassava pulp from the cultivars and their corresponding garri samples, swelling index and bulk density are clearly useful for the plant breeders that may select cultivars based on certain desirable quality characteristics.
On the basis of low cyanide level, Agbeloba could be selected for processing and utilization in products that require less processing time while the Anteota and TMS 30572 cultivars are well suited for garri production judging from the quantity and quality of garri produced from both.
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