Physicochemical properties of starches and proteins in alkali-treated mungbean and cassava starch granules

• Selective leaching of amylose from the amorphous phase in mungbean and cassava starch granules was reported.
• Alkali treatment reduced amylose and granule-bound starch synthases in starch granules but did not affect crystallinity and pasting properties of starch granules.
• Cooking starch under alkaline conditions fragmented starch molecules into lower molecular weights.

This study explored the influences of envelope integrity of cooked starch granules on physicochemical and thermophysical properties of mungbean and cassava starches. Alkali treatment was used to selectively leach amylose from the amorphous region of both starches and partially fragmented starch molecules into lower-molecular-weight polymers. It was found that despite the loss of 40% of the original content of amylose, both mungbean and cassava starches retained similar crystallinities, gelatinization temperature ranges, and pasting profiles compared to the native starches. However, the loss of granule-bound starch synthases during alkali treatment and subsequent alkali cooking in excess water played significant roles in determining granular disintegration. The alterations in envelope integrity due to the negative charge repulsion among polymers within the envelope of swollen granules, and the fragmentation of starch molecules, were responsible for the alterations in thermophysical properties of mungbean and cassava starches cooked under alkaline conditions.