Effect of phytic acid on the structure, properties and oil absorption of wheat flour

Abstract

With the different amount (0%, 0.25%, 0.5%, 1%, 1.5%, 2%) of phytic acid (PA) added, the changes of structure, properties and oil absorption characteristics of wheat flour (WF) were studied. First of all, the phosphorus content in flour increased after PA treatment, which proved that the modification was successful. SEM images showed there were aggregation in the WF modified by PA (PA-WF). The surface of starch showed gradually rough, but the shape of starch particles remained relatively intact. Moreover, XRD and FTIR patterns of all samples showed no significant difference. It was proved that the degree of structural modification of flour by PA was small in the non-gelatinizing system, and it mainly occurred in the non-crystalline region. In terms of properties, the thermal stability and hydrophilicity of PA-WF were improved because the phosphate groups of PA reacted with the hydroxyl groups on the starch to form more stable covalent bonds instead of the hydrogen bonds, and the phosphate groups were hydrophilic. Not only that, the peak viscosity of PA-WF-1.5% was higher than that of the control group, and the other PA-WF were the opposite. With the increase of phosphorus content, the peak viscosity were lower than that of the control group, suggesting that the system mainly consisted of crosslinked starch rather than esterified starch. In terms of oil absorption characteristics, the total oil absorption and surface oil distribution of PA-WF were decreased after frying, which proved that using PA to modify WF was beneficial to reduce oil absorption.