Processing operations affect starch hydrolysis, digestibility, absorption and glycaemic index (GI) of food. Although some studies have reported on the effect of boiling, frying, roasting and baking on glycaemic index of traditional staples. There is limited information on the contribution of drying, fermentation, boiling and steaming on starch bioavailability and glycaemic index. This research work aimed at determining the effect of fermentation, steaming, boiling and drying on starch bioavailability and predicted GI of some cassava-based traditional foods consumed in Ghana. The total starch, amylose, amylopectin, dietary fibre and predicted glycaemic index of the intermediate and finished products were determined according to standard protocols. This research has revealed the predicted GI of cassava (47.75%), ampesi (77.30%), akyeke (79.05%), cooked kokonte with sun dried flour (40.20%) and cooked kokonte with solar dried flour (61.11%). The dietary fibre content of Capevars bankye flour was found to be 1.631% and 1.214% for sun and solar drying processes respectively. The analysis established that steaming and boiling increase GI of foods, fermentation has no significant influence on predicted GI of fermented steamed products, and drying has no substantial effect on predicted GI of cassava flour. However, staples or products prepared from solar dried cassava flour would have higher predicted GIs than those of sun dried cassava flour. This work has also provided evidence in support of the fact that starch, amylose, amylopectin and dietary fibre content of a food affect the glycaemic index of the food.

1.1 Background
Cassava utilization and cassava-based traditional foods consumption in Ghana is on the increase. However, there are growing concerns about its effect on the health of consumers and diabetic patients due to the high carbohydrate content (Oppong-Apane, 2013). This has necessitated research into processing methods and glycaemic index of cassava-based traditional staples.

Most traditional foods are processed in one form or the other prior to consumption or storage and cassava-based traditional staples are not an exception. This processing activity enhances the eating characteristics, sensory and organoleptic properties, toxic removal, preservation, marketing and distribution of the food. It also increases food consistency, diversity, shelf-life and value addition (FAO, 2011). Processing of cassava involves methods such as cleaning, size reduction, drying, fermentation, cooking methods, heat treatment (pasteurization and sterilization) and many others (FAO, 2011; Granfeldt et al., 2000) which improves its palatability, and reduces cyanogen concentration and its toxicity (FAO and IFAD, 2005).

Studies have shown that these processing methods play a significant role in starch digestibility, nutrient metabolism and absorption, as well as the glycaemic index of the food. Further research has revealed that, there is greater variation in digestion, metabolism and absorption of food (carbohydrate) which emanates from the source of the carbohydrate, its composition and the processing methods, the foods go through during preparation or formulation (Granfeldt et al., 2000; Omoregie and Osagie, 2008). The glycaemic index (GI) of foods is the measure of the rate of absorption of carbohydrate into the blood after consumption of a meal and is significantly affected by the processing operations (Omoregie and Osagie, 2008). This is because these operations are suggested to cause cell wall disruption, depolymerization, retrogradation, gelatinization and hydrolysis of the carbohydrate to facilitate enzymatic reaction or digestion, for the release of glucose into the blood after consumption or eating (Bahado-Singh et al., 2011; Chung et al., 2008).

A study conducted by Granfeldt et al. (2000) on oat and barley flakes revealed that minimal processing operation like size reduction (product thickness) had no significant influence on GI. A research by Bahado-singh et al. (2011) on sweet potato cultivars, established a substantial impact of roasting, baking, frying and boiling on the GI of these cultivars. A cohort study carried-out on the glycaemic indices of fufuo, kenkey, banku and tuo-zaafi also indicated that the differences in GIs of the foods may be due to different processing methods that were used in their preparations (Eli-Cophie et al., 2017) but did not account for the extent of the impact of the individual unit operations resulting in the overall GI of the foods. Therefore, the effects of individual unit operations need to be evaluated separately to actually ascertain the contribution of each operation towards GI reduction or increment.

1.2 Research problem
Many processed and traditional foods go through succession of processing operations which may affect their digestibility and glycaemic index. A lot of works have looked at the effect of some of these operations on starch digestibility and GI. However, very limited information is reported on the contribution of drying, fermentation, boiling and steaming on GI of cassava-based traditional foods.

1.3 Justification
This work would establish and document the effect of fermentation, steaming, boiling and drying on the GI of some cassava-based traditional foods, which will contribute to scientific knowledge and effectively enable the use of glycemic index in conjunction with other dietary recommendations for proper treatment, management and prevention of diseases. Moreover, the GI data of local foods such as akyeke, ampesi and kokonte considered under this research would assist consumers in making informed food choices.

1.4 Main objective
The principal objective of this research is to determine the influence of processing methods on the glycaemic index of cassava-based traditional foods in Ghana.

1.4.1 Specific objectives
To determine total starch, amylose, amylopectin and dietary fiber content of fresh cassava, ampesi, akyeke and kokonte samples

To determine predicted glycaemic index of fresh cassava, ampesi, akyeke and kokonte samples using in-vitro assay

To determine the effects of fermentation, boiling, steaming and drying on the glycaemic index of intermediate and final products

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Item Type: Ghanaian Postgraduate Material  |  Attribute: 64 pages  |  Chapters: 1-5
Format: MS Word  |  Price: GH50  |  Delivery: Within 30Mins.


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