Optimisation of procedures for conversion of cassava flour into glucose syrups by plant enzymes

Abstract

Six plant sources (rice, millet, sorghum, maize malts, sweet potato and kudeme) were evaluated for a-amylase, β-amylase, amyloglucosidase, limit dextrinase and β-glucanase activity, and potential for use in production of glucose syrups from cassava flour. The objective was to identify the plant sources with the highest potential for each enzyme; optimize enzyme development in the plant sources identified; and to develop mathematical models for the controlled hydrolysis of cassava flour using these crude plant enzymes. Sweet potatoes gave the highest β-amylase activity whilst rice malt showed the highest activity for a-amylase,amyloglucosidase and limit dextrinase. Millet malts gave the highest level of β-glucanase activity. Optimisation of sweet potatoes, rice and millet malts for increased enzyme activity showed that, the pink-skinned sweet potato varieties -Okumkom and Faara - gave optimum β-amylase activity. For rice malts the optimum malting period varied between 9-13 days depending on the enzyme in question. Rice variety l"OX3108 was the most promising choice for optimum development of all four amylolytic enzymes. Application of gibberellic acid and non-matting conditions of malting most effectively stimulated the production of amyloglucosidase and limit dextrinase respectively, but suppressed a-amylase activity. The malting period for optimum development of β-glucanase in millet malts was 11 days. The mathematical models developed were used to establish optimum conditions for a one step dextrinisation process leading to a DE of 15-20, and a saccharification process for the attainment of a DE of 45-47. Other polynomial-based mathematical models were developed. for the production of maltodextrins and glucose syrups richer in specific hydrolytic products. Overall, the findings of this study demonstrate the potential to replace expensive imported sugar syrups with Ghanaian equivalents prepared from cassava flour and plant derived enzymes