Physio-chemical properties of sugar syrup produced from two varieties of yam (Dioscorea dumetorum and Dioscorea alata) using exogenous enzymes

Abstract

Physio-chemical properties of sugar syrup produced from two varieties of yam (Dioscorea dumetorum and Dioscorea alata) using exogenous enzymes were studied. Starch and flour samples of two yam varieties (Dioscorea dumetorum and Dioscorea alata) were converted into sugar syrup by enzyme hydrolysis using exogenous enzymes. The sprouted and unsprouted tubers were processed into dried starch by washing, peeling, and milling; stirring, settling for about 6 hours; the supernatant was decanted and the sediment which contained the starch was filtered with muslin cloth and oven-dried at 70oC for 30minutes to produce the dry starch. The sprouted and unsprouted tubers were also processed into fine flour by drying, milling and sieving with a 0.8 mm sieve. Alpha and Beta amylase enzymes were used in the syrup production. Physiochemical analysis was carried out on the syrup and results obtained were subjected to statistical analysis using analysis of variance (One-way ANOVA). The results obtained show that the pH values ranged from 4.45 to 5.65 while the moisture content values ranged from 67.42 to 72.25%; the dextrose equivalent results for the samples were 26.68, 26.47, 29.64, 27.13, 29.56, 26.34, 30.15 and 24.79% for the un-sprouted Dioscorea dumentorum flour (UD), sprouted Dioscorea dumetorum flour (SD), un-sprouted Dioscorea alata flour (UA), sprouted Dioscorea alata flour (SA), un-sprouted Dioscorea dumetorum starch (UDS), sprouted Dioscorea dumetorum starch (SDS), un-sprouted Dioscorea alata starch (UAS) and sprouted Dioscorea alata starch (SAS) respectively. This indicates that sample UAS had the highest level of hydrolysis. For the sugar syrups; sample SD had the highest viscosity value (950.05cp) while sample UA had the lowest value (835.10cp). The specific gravity of the sugar syrup samples ranged from 1.16 to 1.29 with sample SDS having the highest value and sample UD having the lowest value. Result from the analysis on sugar concentration (disaccharides) showed that the highest maltose concentration was recorded in sample SDS (57.27%) and the lowest was obtained in sample UA (51.65%). The glucose concentration of the sugar syrup samples ranged from 1.55 to 2.05%; sample SA recorded the lowest value of 1.55% while UAS recorded the highest value of 2.05%. The maltotriose, raffinose and starchyose concentrations of the sugar syrup samples ranged from 7.39 to 7.76%, 0.12 to 023% and 0.93 to 1.15% respectively. Results of this work suggest that sugar syrup can be made from underutilized yam species.