Effect of frying on total oil adsorption of freeze-thawed and raw starches

The effect of frying on the total oil adsorption (TOA) of freeze-thawed corn starch (F-FC), wheat starch (F-FW), and tapioca starch (F-FT) was studied compared with their raw versions. Compared with fried raw corn starch (F–C), wheat starch (F–W), and tapioca starch (F-T), the TOA of corresponding fried freeze-thawed starches were significantly reduced by 8.47%, 10.64%, and 3.83%, respectively. After frying, as the amylose content increased by 1.24%, 0.65%, and 0.58%, the matrix oil adsorption (MOA), which is closely related to the amylose content, also increased slightly by 0.32%, 0.20%, and 0.72%. However, the increase in MOA has little impact on the reduction of TOA. The Fourier-transform infrared spectroscopy results indicated a reduction in the lipophilic groups of freeze-thawed starches upon frying, which could increase the oleophobicity of starches. The specific surface areas of F-FC, F-FW, and F-FT were reduced by 16.13 m2/kg, 33.57 m2/kg, and 8.17 m2/kg, respectively, which would reduce TOA. Therefore, the freeze-thawed starches adsorbed less total oil than raw starches after frying. X-ray diffraction results showed that all the samples were still A-type, but the crystallinity of freeze-thawed starches decreased by 1.47%, 2.80%, and 0.73% after frying.