Studies on some selected food-grade plant exudate gums in Ghana

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Gums are incorporated into food products to improve their quality and enhance their shelf life. Gums are recommended for use in food products based on their qualities. In Ghana, gums utilized by the food industry are imported though enormous potential for their exploitation exists. Therefore this study was conducted on gums from three tree species in Ghana namely Albizia, Cashew and Khaya. The properties of these gums were compared with those of commercial gum arabic obtained from Ghana to determine their suitability as food additives. The qualities studied include pH, sweffing power, solubility, water binding capacity, viscosity, emulsifying properties, percent moisture, ash and insoluble ash content, insoluble matter, variation of temperature with viscosity and stability of pH with time, of the gum exudates. Khaya gum (viscosity, 514 mPas at 2 %) and Albizia gum (viscosity, 2224 mPas at 2 %) were more viscous than Cashew gum (viscosity, 486 mPas at 10 %) and can therefore be used for thickening and bodying better than the latter. Cashew gum was, however, viscous than Acacia gum (viscosity, 203 mPas at 10 %). Like Acacia gum, all the three gums showed increase in viscosity with concentration and also increase in viscosity with decreasing shear rate, indicating that they are non-Newtonian solutions. Apart from Khaya gum which was found to be temperature stable and therefore did not show reduction in viscosity with increasing temperature, the other two gums just like Acacia gum showed this property. Albizia gum had the highest swelling power, making its viscosity break down relatively faster than the others. The water binding capacities (WBC) of Albizia and Khaya gums were significantly different from that of Cashew and Acacia gums (at p< 0.05). However, the WBC of Cashew and Acacia gums were not significantly different. Therefore the former can be used to inhibit ice crystallization and prevent staling in baked foods. Cashew gum can be used in bakery toppings to prevent the absorption of excess moisture by icing. Khaya gum was less acid stable but the acid stabilities of Cashew and Albizia gums compare favourably with that of Acacia gum. They can therefore perform better in acidic foods than the former. The emulsion stability (ES) value of Acacia gum was not significantly different from that of Cashew gum (at p< 0.05), but was significantly different from Khaya and Albizia gums. Therefore Cashew gum can stabilize emulsions better than Albizia and Khaya gums. Each of the gums has been found to possess some good qualities that make it a potential substitute in certain food products. Toxicological studies on the gums should, however be carried out.
A Thesis submitted to the Department of Biochemistry, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the degree of Master of Science in Food Science and Technology, 2001