Changes in swelling and rheological properties of corn starches after acid-methanol degradation

Abstract Corn starches were acid treated in methanol containing 0.36% HCl for different durations to investigate the swelling, molecular and rheological characteristics of acid-methanol-treated (AMT) starches during gelatinization. The molecular size of starches were ranged from 736 × 10 3 to 6.9 × 10 3 , 675 × 10 3 to 4.2 × 10 3 and 410 × 10 3 to 2.8 × 10 3 anhydrous glucose unit (AGU) for waxy corn, normal corn and Hylon V starch, respectively. AMT caused increasing in close packing concentration (C*) and granular collapse, as well as decreasing in the maximum value of storage modulus (G′ max ) of starch. Effect of AMT on waxy corn starch was more profound than on normal corn and Hylon V starches. AMT waxy corn starch showed undetectable G′ max when molecular size was lower than 678 × 10 3 . AMT Hylon V starches with molecular size lower than 62.3 × 10 3 AGU showed dramatically increasing in G′ max -decrement value. Results reveal that AMT enhances the discrepancy in molecular swelling and pasting characteristics of starch granules.