Optimization of Enzymatic Modification of Steviosides by Alpha-amylases
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Abstract:
In order to improve taste quality, enzymatic modification of stevia by grafting glucose was investigated using soluble starch as glucose donor. The hydrolysis was catalyzed by acid-resistant mesophilic α-amylase, whose trade name is Taka-diastase, that was screened from three different α-amylases. Using stevioside conversion rate as an indicator, the enzymatic processes were optimized and the optimum conditions obtained were donor starch concentration 100 g/L, substrate ratio 1:10 (m/m), reaction temperature 60 ℃, and enzyme concentration 1.50 U/mL. The conversion rate of the modified stevioside was determined as 42.5% by high performance liquid chromatography (HPLC). The organoleptic evaluation results showed that the enzymatic modification improved the taste quality of stevia significantly. The sweetness became mild and soft, and a slight bitter taste still remains at high concentration, but disappears at low concentration. Desirable taste quality with significantly reduced production cost could be achieved by enzymatic modification of stevia.
