EFFECT OF VARIETY AND PROCESSING METHODS ON THE PHYSICOCHEMICAL AND SENSORY PROPERTIES OF GARI IN THREE DISTRICTS OF THE BRONG AHAFO REGION

ABSTRACT
The effect of variety and processing methods on the physicochemical and sensory properties of gari in three districts of the Brong Ahafo region was studied. The study aimed at investigating the effect of cassava varieties and processing methods on the proximate, functional, physicochemical and sensory properties of gari. Gari was processed from Bankyehemaa, Ampong and Bensre cassava varieties. Each of the varieties was processed using both traditional and modern processing methods to obtain six gari samples. Physicochemical, proximate and functional analyses were conducted on all the six samples, after which sensory evaluation was carried out using a thirty member panel based on ratings on bases of colour, taste, aroma, texture and overall acceptability. The results showed that carbohydrate, protein and moisture content of gari from all the varieties were significantly different (P < 0.01). Bankyehemaa had the highest carbohydrate (90.31%) and protein (3.41%) contents. Processing methods did not have any significant impact (P > 0.01) in making variation among the functional properties of gari. The hydrocyanic acid level of the varieties was not significantly influenced (P > 0.01). However, the interaction of variety and processing methods influenced significantly differences among pH and hydrocyanic acid of gari. Traditionally processed gari had the least cyanide content as compared to gari obtained from modern processing method. Overall acceptability from sensory evaluation showed that Bankyehemaa gari samples processed through both methods were the most preferred, and the traditionally processed Bensre gari was the least preferred. From the results, it was concluded that variations in physicochemical properties were due to both genetic variation and processing methods. Traditionally processed gari is safer for consumption due to low hydrocyanic acid content.

CHAPTER ONE
1.0 INTRODUCTION
Cassava is a popular root crop widely cultivated in the tropical areas. It is scientifically known as Manihot esculenta which belongs to Euphobiaceae family. The plant is a woody shrub usually cultivated as perennial. The enlarged tuberous roots are highly perishable and can be stored only for a few days after harvest. The root provides a lot of carbohydrates to consumers. The crop is highly resistant to drought and has the ability to survive on poor soils. Variation in yield depends on cultivar, planting season, soil type and fertility of soil. Yields of improved varieties can reach 20-25 tonnes per hectare when cultivated under proper management practices. It is mainly cultivated for the roots but its leaves are also used as vegetables. The tuber contains 25 to 30% starch but poor in minerals, protein, vitamins (Ayankumbi et., al 1991). Both the leaves and roots are for human consumption and for feeding animals which are important source of carbohydrates, protein and minerals in the diet.

Cassava provides food security in Africa. More than two billion people living in Africa, Asia and Latin America will depend on roots and tubers such as cassava, yam and sweet potato for their nutrition and tax income by 2020 (Scott et al., 2000). Also, Food and Agriculture Organization Corporate Document Repository entitled “The World Cassava Economy” produced by Agriculture and Consumer Protection indicated that almost 70 % of the world cassava production is produced in Nigerian, Democratic Republic of Congo, Brazil, Thailand and Indonesia .The report added that more than 50 % of the present global production of cassava is cultivated in Africa of and about 70% of the region’s production is harvested in Nigeria, Democratic Republic of Congo and Tanzania.

According to Egesi et. al. (2006) Nigeria is the leading cassava producer worldwide which produces about 45 million metric tonnes and cassava transformation in Nigeria is the most advanced in Africa. Globally, Ghana is and the sixth highest cassava producer and the third in Africa, with about 70 percent of local farmers producing over 14 million metric tonnes every year. Production of cassava in Ghana increased from 14,270,000 metric tonnes in 2011 to 14,547,000 metric tonnes in 2012 and went up to 14, 990,000 metric tonnes in 2013(www.theafricareport.com/West-africa/ Ghana).

Recently there is an increasing demand for quality products processed from fresh cassava such as gari, flour, dough, starch and alcohol. This has enhanced the production of cassava because farmers have ready market for their produce. Generally, roots of cassava mature 6 -18 months depending on the cultivar. The crop is popular because of its use in producing food such as gari, fufu and kokonte. The root deteriorates quickly after harvesting and has to be processed within 24 hours after harvest (Hahn, 1998). Gari is a fermented product of fresh cassava tubers which is an important source of energy for consumers in Tropical Africa (Ihekoronye and Ngoddy, 1985). Gari is also widely consumed because it has a longer shelf life as compared to other products produced from fresh cassava. Its wide consumption is also attributed to the ease of preparation for eating. The popularity of gari in rural and urban communities is due to its ease and ready- to-eat-form (Flach, 1990).

A safety concern in the eating of cassava based products such as gari is due to the presence of cyanohydrins which breaks down to produce hydrogen cyanide (Ernesto et al., 2002; Bokanga, 1994). Some cassava varieties contain large quantities of cyanide which is toxic to human health and gives the tuber a bitter taste. Cassava varieties are classified as sweet or bitter based on the cyanide level.

Bitter varieties have high starch content and are usually used for industrial purposes. The sweet varieties are normally consumed as food. Gari processing methods vary from locality to locality and from processor to processor. However, the two most common methods are the traditional and modern methods. Both methods of processing bring about reduction in the cyanide content of the fresh cassava tubers. The traditional gari processing method reduces the cyanide content in gari through prolonged period of fermentation up to seven days which is a vital strategy for producing a safe product (Sanni, 2001).

According to Nweke et. al. (2002), gari processed by the traditional method contain varied amounts of cyanide because different processors tend to shorten fermentation period in order to meet the increasing market demand. The traditional method of processing gari is tedious and usually used to produce gari in small quantities, as compared to the modern method which is used to produce gari in commercial quantities. It is therefore important that the use of modern method should aim at reducing the period of fermentation and still eliminate cyanide so as to obtain gari quality and also produce quantities that would meet the ever increasing market demand for gari. Gari is produced from any available cassava variety. Since different cassava varieties differ in quality characteristics, the interactions between cassava variety and the method of processing may affect the physicochemical properties of the gari, and consequently the quality of the gari produced. Studies have shown that the major processes involved in gari processing (peeling, grating, fermentation, pressing and roasting) vigorously effect cyanide elimination, as well as other physicochemical properties of the product (gari).

Not much research have been done on the effect of cassava variety and gari processing methods on the physicochemical properties of gari. Therefore understanding the effect a particular cassava variety and processing methods have on the proximate functional and physicochemical properties of gari will greatly aid the production process of gari. In recent times, improved cassava varieties such as Ampong, Bankyehemaa, Sika bankye and Esam bankye have been introduced to farmers for cultivation within the Wenchi Municipality, Techiman Municipality and Techiman North District, all in the Brong Ahafo Region.

Most gari processors now use these new varieties alongside popular local varieties like Kentema, Bensre, Asuma, Ahenemma, Buoyam and others .The gari processors in the study area complain that even though the improved varieties are high yielding, they do not produce the best quality gari as compared to some of the local varieties. Some cassava growers have therefore threatened to stop the cultivation of these new varieties. This can be a threat to food security because the demand for cassava, and for that matter gari, would be high as a result of low production of cassava.

More often than not, most gari processors use a mix of both the local and improved varieties in processing gari. Since each variety has different physicochemical properties, there is the need to conduct a study into the physicochemical properties of selected local and improved cassava varieties commonly cultivated and used for gari processing in the study area so as to ascertain the claim by the processors. In addition, research on the methods of processing gari, and making appropriate recommendations with reference to a particular variety would be of great benefits especially to the people within the study area and the nation as a whole.

The study would provide a solution to the inability of gari processors to identify varieties which would produce gari of the best quality so that farmers would know which varieties to cultivate based on demand of the gari processors. It may also provide information for government, financial institutions and Non-Governmental Organizations (NGOs) who would be interested to support cassava farmers and gari processors in the study area.

1.1 OBJECTIVE
The main objective of this research was to determine the proximate, functional and physicochemical properties of selected local and improved cassava varieties using two different gari processing methods.

1.1.1 Specific Objectives
The specific objectives were to:

i. To investigate the effect of cassava varieties on the proximate composition and of gari.

ii. To investigate the effects of cassava varieties on the functional properties of gari.

iii. To investigate the effect of processing methods on the physicochemical properties of gari.

iv. To determine the interactive effect between cassava varieties and processing methods on the physicochemical properties of gari.

v. To determine the relationship among physicochemical properties and sensory attributes of gari.

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Item Type: Ghanaian Project Material  |  Attribute: 86 pages  |  Chapters: 1-5
Format: MS Word  |  Price: GH50  |  Delivery: Within 30Mins.
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