Effect of Palm Oil Addition at Different Stages of the Manufacturing Process on the Quality Characteristics of Garri
Objective of the Study
The objective of this project study is to examine the effect of palm oil addition at different stage of the manufacturing process on the quality characteristics of garri.
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 (Opara, 1999; 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 (Opara, 1999; Opara, 2009; Buschmann et al., 2000). 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).
Economic Importance of Cassava
Annual global production of cassava is estimated to be over 238,000 tonnes, with Africa contributing about 54 %, followed by Asia and South America. Cassava root produces excellent flour quality and therefore has been promoted as composite flour for use in the food industries (Shittu et al., 2008). Cassava flour is also highly recommended in the diet of celiac patients with strict adherence to gluten-free food products (Briani et al., 2008; Niewinski, 2008). Celiac disease is an autoimmune complex that affects the bowel after the ingestion of gluten containing grains or cereals such as wheat and rye (Briani et al., 2008).
In view of enhancing cassava productivity to promote economic development, the global mandate on cassava research was given to the International Centre for Tropical Agriculture (CIAT) in Colombia while the International Institute for Tropical Agriculture (IITA) in Nigeria obtained the regional mandate on cassava research (El-Sharkawy, 2007). However, due to widespread consumer preference for maize, cassava cultivation in South Africa is low compared to other African countries like Nigeria, Ghana, Angola, Tanzania, Uganda and Malawi. Cassava production in South Africa is limited to small scale farmers close to Mozambican border, with annual production between 8 and 15 t/ha (Mabasa, 2007) compared to 54,000 tonnes productions in Nigeria (FAO, 2013).
MATERIALS AND METHODS
The cassava (Manihot esculenta crantz) tubers used for this study were obtained from a local farm in Emure-ile, Owo while crude palm oil was purchased from a local store in Owo, Ondo State. The processing of garri was done in the Processing Laboratory of Food Science and Technology, Rufus Giwa Polytechnic, Owo.
Preparation of Garri Samples
Freshly harvested cassava roots were processed into garri following the procedure reported by James et al. (2012), with modification. The tubers were peeled using stainless steel knife to expose the fleshy white part which was washed with clean water and further grated into a mash using local cassava grating machine. The mash was weighed and divided into 3 equal portions. The first portion was thoroughly mixed with 35cl crude palm oil, placed in a hessian and allowed to ferment for 72 hours. This was followed by dewatering using hydraulic press and later garified (toasted) into yellow garri, this portion was coded PBF (Palm oil Before Fermenting).
The second portion was placed in a hessian bag with no palm oil was added, fermented for 72 hours after which it was dewatered using hydraulic press. It was sieved and garified with the addition of palm oil, into yellow garri, this portion coded FWNP (Fermented With No Palm oil Addition).
RESULTS AND DISCUSSION
Table 4.1: Chemical Composition of White and Yellow Garri Samples.
CONCLUSION AND RECOMMENDATIONS
The study revealed the proximate, energy value, functional and chemical properties of white and yellow garri. Yellow garri 2 has the best nutritional properties, it was has the highest protein, ash, fat and fibre content, yellow garri 1 was recorded to have the best outcome next to yellow garri 2. This is due to addition of palm oil which increases their nutritional qualities. Both samples (yellow garri 1 and 2) were also recorded to have the same least moisture content indicating prolong storage stability of the samples. There was no significant difference in the carbohydrate content of the garri samples. White garri have the least energy value while yellow garri 2 have the highest value followed by yellow garri 1. The TTA of the garri samples were below 1%, however yellow garri 2 have the highest TTA followed by yellow garri 1 and white garri. White garri sample sensory was evaluated to have the best outcomes in all sensory parameters.
Further studies on the effect of palm oil on the microbial qualities of yellow garri at different stages is recommended, also I recommend the consumption of yellow garri due to its nutritional qualities compared to white garri.
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