Abstract:

In order to overcome the difficulty of the original polarizing microscope-based method in monitoring the gelatinization of starch,a new method to dynamically monitor the gelatinization process,namely the integral optical density-based method,is proposed. In this method,the gradual disappearance of the birefringence light of starch granules under polarized light is taken into consideration,and the digital image analysis technique is used to analyze the integral optical density of the acquired real-time digital image of the gelatinization,thus obtaining the gelatinization degree. Then,the proposed method is compared with three traditional methods for gelatinization degree detection. The results show that ( 1) the gelatinization degree detected by the proposed method is the highest due to the response of the method to partial gelatinized starch; ( 2) there is a quantitative relationship between the disappearance of starch crystal structure detected by the proposed method and the thermal change detected by DSC during
the gelatinization; ( 3) there are not only difference but also correlation between the gelatinization degrees detected by the proposed method and by the DSC; and ( 4) the real-time date obtained by the proposed method well reflect the real state of starch during the gelatinization.

Key words: starch, gelatinization, dynamic monitoring, birefringence, integral optical density, digital image analysis technique