| Maltose syrup has been widely applied in food industry, chemical industry, hygienical products and medical industry because of its low sweetness, good crystalline-resistance and high stability. It is one of the important products in starch sugar industry. However, starch particle possesses a semi-crystalline structure that consists of a loose amorphous region in the inner part and a firm crystalline region in the outer part. Enzymes could not easily enter into the inner regions of starch particles, resulting in a low reactive efficiency. Therefore, for the traditional producing technology of maltose syrup using starch as raw material, it is necessary to expand and gelatinize starch particles by heating starch milk and destroy crystalline structure of starch before hydrolyzation and saccharification.In this thesis, cassava and maize starch were mechanically activated with a customized stirring-type ball mill. The activated starches with different milling time were used as raw materials and fungal-a-amylase was used as the saccharification reagent. Then the effects of the mechanical activation on the saccharification, saccharifying kinetics and preparation technology of maltose syrups were investigated. The experiment results showed:(1) For cassava starch, the DE values of saccharification are 46.64% and 64.41% for non-activated starch and activated starch (with an activation time of 60 min), respectively. For maize starch, the DE values of saccharification are 43.81% and 61.33% for non-activated starch and activated starch (with an activation time of 60 min), respectively. It can be seen that the enzymolysis reactivity of starch was dramatically enhanced after the processing of mechanical activation. The reason is that the compact outer crystalline structure of starch particle was destroyed through the treatment of mechanical activation, which caused the breakage of starch molecular chain, the reduce of viscosity and finally the decrease of diffusion resistance of amylase. Other factors, such as gelatinization temperature, reaction time, substrate concentration and fungal-α-amylase amount, also have influences on the enzymolysis reaction. However, their effects are greatly related with the activation time. But the dependence weakens with the increase of activation time.(2) The kinetics study showed that action mechanism of fungal-α-amylase on both the saccharification of mechanically activated starch and the saccharification of non-activated starch follows the so-called Michaelis-Menten equation. For non-activated cassava starch, the Km and Vmax are 1.651 mg·mL-1 and 0.145 mg·mL-1·min-1, respectively; while for the activated one, the Km and Vmax are 9.086 mg·mL-1 and 0.761 mg·mL-1·min-1, respectively. For non-activated maize starch, the Km and Vmaxare 0.639 mg-mL-1 and 0.086 mg·mL-1·min-1, respectively; while for the activated one, they are 1.335 mg-mL-1 and 0.171 mg·mL-1·min-1, respectively. It can be seen that the reaction rate of activated starch is larger than that of non-activated starch. The results indicated that the mechanical activation processing could destroy the crystal structure and enhance the enzymolysis reactivity of starch obviously.(3) The study on preparation technology of maltose syrup showed that when the reaction temperature was 50℃, substrate concentration was 30 mg-mL-1, fungal-a-amylase amount was 4U, pH was 5.5 and the reaction time was 15 hours, the content of maltose in the produced syrup are 49.55% and 47.77% in the case of raw material of activated cassava starch (with an activation time of 30 min) and activated maize starch (with an activation time 60min), respectively. Under the same reaction conditions, however, the content of maltose in the produced syrup are only 37.34% and 41.59% in the case of raw material of non-activated cassava starch and non-activated maize starch, respectively. The result clearly indicated that the mechanical activation processing could favor the preparation of maltose syrup from starch even without gelatinization. |
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