Drying methods used in starch isolation change properties of C-type chestnut (Castanea mollissima) starches

• Drying methods using in starch isolation impact properties of chestnut starches.
• Ethanol drying had the least impact on structure of chestnut starches.
• Freeze drying can disrupt the long- and short-range order of chestnut starches.
• Freeze-dried starch had higher digestibility than oven- and ethanol-dried starches.
• Ethanol drying was a preferred method used in starch isolation.

The effect of different drying methods used in starch isolation on structural and functional properties of Chinese chestnut starches was investigated. Freeze-dried (FD) starch granules exhibited some scratches and pores on their surface, which were not observed for ethanol-dried (ED) and oven-dried (OD) starch granules. ED starch showed the highest relative crystallinity and short-range molecular order of double helices, followed by OD starch, and FD starch showed the lowest values. These results indicated that freeze drying disrupted the ordered structure of starch granules. At 92.5 °C, OD starch exhibited the highest swelling power, whereas FD starch showed the lowest swelling power. ED starch showed higher gelatinization temperatures and enthalpy changes than OD and FD starches, indicating that ED starch contained higher amount of crystallites than did OD and FD starches. FD and OD starches were hydrolyzed more greatly by alpha-amylase and amyloglucosidase compared with ED starch. Our results showed that freeze-drying disrupted the ordered structure of chestnut starch and it is not preferred for starch isolation.