Defatting improves the hydrolysis of granular starch using a mixture of fungal amylolytic enzymes

Native and defatted starches (corn, wheat and rice) were hydrolyzed in the granular state (35 °C) for 24 h using a mixture of fungal α-amylase and glucoamylase. Changes in the morphology and properties of starch granules indicated that the defatting treatment affected the granular structure of the starch. The DE value for non-defatted granular starch was 53% for corn, 28% for wheat, and 7% for rice. The presence of distinct pores and cavities in corn could account for its high degree of hydrolysis while in wheat starch; pores exist on certain parts of the granule surface. When lipids were removed, the DE value significantly increased for corn showed (62%), wheat (41%), and rice (28%). Defatted starches exhibited lower swelling than non defatted starches, contributed to their greater susceptibility to enzymatic hydrolysis. The results showed that hydrolysis of these starches in the granular state could be increased by defatting the starch.

► Extent of hydrolysis increases significantly for defatted starch compared to native.
► DE value defatted starch increased 17% for corn, 46% for rice and 300% for wheat.
► Amylose content and swelling of hydrolyzed defatted starch decreased significantly.
► Defatting cause partial irreversible swelling and starch able to swell more.
► Defatted starch showed higher susceptibility to enzymatic hydrolysis compared to native.