An insight into the multi-scale structures and pasting behaviors of starch following citric acid treatment

Using combined analytical techniques, this work discloses how citric acid (CA) treatment affects the pasting features of starch from a view of multi-scale structural evolutions. The treatment induced disruption events in starch multi-level structures and thus modulated the pasting behaviors. A structure-property relationship was proposed to rationalize CA effects on starch pasting properties. Specifically, CA disrupted starch structures from molecular scale to micron scale, eventually reducing pasting temperature and paste viscosities. Interestingly, unlike previous findings that acid hydrolysis normally reduces the breakdown viscosity, the CA here resulted in regulated breakdown viscosity (paste stability under shearing and heating) related to concurrent effects from granule surface corrosion and molecule degradation. Moreover, the molecule degradation of starch weakened its chain rearrangement tendency, allowing increased paste stability during cooling. Also, simply altering CA concentration effectively regulated starch structural and pasting features. Hence, compared to untreated counterpart, the CA-treated starch may serve as food agents with reduced paste viscosity, regulated paste stability under heating and increased paste stability during cooling.