Starch was extracted (isolated) from cocoyam with the aid of water solution of oxalic acid and ammonium oxalate in 8 samples of ratios, 1:3, 1:1, 3:1, 2:3, 2:1, 1:2 and 0:0 respectively. The physiochemical properties were investigated in order to unveil its characteristics and unravel the potentials for industrial applications of the cocoyam starch. The physiochemical properties investigated includes; Amylose and Amylopectin contents, water binding capacity, particle size distribution, swelling power and solubility. The results obtained showed that swelling power and solubility of the starch were temperature dependent. The solubility was found to increase with temperature increase as the cocoyam starch showed highest solubility within the 70-90°C temperature range. The swelling power was found fluctuating between the temperatures of 25-90°C. The swelling power starch sample isolated with blending ratios of 2:1 and 1:2 were temperature dependent. The Amylose content ranges from 3.06 to 31.21%.

The degradation rate of Volatile Fatty Acids (VFAs) produced predominantly in the acidogenesis stage is a key process parameter to be optimised to ensure a successful Anaerobic digestion (AD). Thermodynamically, the oxidation of the VFAs are energetically unfavourable, and as such external energy source apart from the energy derived from the hydrolysis of Adenosine Triphosphate (ATP) is needed for the initial activation of the VFAs, initial growth of the methanogens in AD process and improved degradation rate of the VFAs. Thus, this research investigated the influence of polyphosphate hydrolysis on the degradation rate of the VFAs at high concentration. Sodium-propionate, Sodium-butyrate and Sodium-acetate salts were added at the start of experiments in order to increase the concentration of the VFAs. The polyphosphate salts used were; Na-hexametaphosphate, Na-tripolyphosphate and potassium pyrophosphate. The control experiment was polyphosphate free and three process parameters (degradation rate, cumulative biogas production and specific methane content) of anaerobic digestion were investigated. The experiments were carried out at a mesophilic temperature of 37.5˚C for 41 days. The results of the investigation showed that the treated reactors with the polyphosphate salt solution in low concentration performed better than the reactors with high concentration of the polyphosphate salts solution. All the treated reactors with poly-P salts performed better than reactor Nr-9 (control experiment), but reactor Nr-1 was outstanding with an improved degradation rate of 47%, cumulative biogas production of 21% and specific methane content of 23%.

Abstract. Starch was extracted (isolated) from cocoyam with the aid of water solution of oxalic acid and ammonium oxalate in 8 samples of ratios, 1:3, 1:1, 3:1, 2:3, 2:1, 1:2 and 0:0 respectively. The physiochemical properties were investigated in order to unveil its characteristics and unravel the potentials for industrial applications of the cocoyam starch. The physiochemical properties investigated includes; Amylose and Amylopectin contents, water binding capacity, particle size distribution, swelling power and solubility. The results obtained showed that swelling power and solubility of the starch were temperature dependent. The solubility was found to increase with temperature increase as the cocoyam starch showed highest solubility within the 70-90°C temperature range. The swelling power was found fluctuating between the temperatures of 25-90°C. The swelling power starch sample isolated with blending ratios of 2:1 and 1:2 were temperature dependent. The Amylose content ranges from 3.06 to 31.21%.