PRODUCTION OF GLUCOSE SYRUP FROM YAM STARCH USING ASPERGILUS NIGER
Abstract
This study investigated the production of glucose syrup from yam (Dioscorea spp.) starch through acid and alkaline hydrolysis, with comparative evaluation of yield, quality, and physicochemical properties. Yam tubers were sourced locally, starch extracted via wet milling, gelatinization, and sedimentation, then divided for hydrolysis using dilute hydrochloric acid or sodium hydroxide under controlled conditions. Aspergillus niger was incorporated to enhance enzymatic breakdown during fermentation. The resulting syrups were analyzed for pH, total soluble solids (°Brix), glucose concentration (DNS assay), viscosity, color, and yield. Alkaline hydrolysis yielded superior results, achieving 84.3% conversion efficiency and 7.9 mg/mL glucose concentration, compared to 78.5% yield and 6.2 mg/mL for acid hydrolysis. Alkaline-treated syrup exhibited clearer golden-yellow color, lower viscosity, higher °Brix (62.7), and pH 8.2, while acid hydrolysis produced darker syrup (pH 3.8) due to by-product formation (e.g., hydroxymethylfurfural). Microscopic examination confirmed A. niger's active role in amylolytic activity. Yam starch proved a viable, underutilized alternative to maize/cassava, promoting agricultural diversification in tropical regions. Alkaline hydrolysis, augmented by fungal enzymes, offers a cost-effective, sustainable method with minimal corrosion and impurities, suitable for food, beverage, and biotechnological applications. Recommendations include industrial adoption of alkaline processes and further optimization for scalability.
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