Physico-chemical Properties of Phosphoryl Chloride Cross-linked Wheat Starch

Chemical methods are the most common routes for modification of starch. In this study, cross-linked wheat starch was produced using phosphoryl chloride as a cross-linking agent and its physico-chemical properties were studied. The crosslinked starch had a cross-linking degree of 3.86 x 10-5. In SEM micrographs, some blister- like spots were observed on the cross-linked starch granules. The results also showed that the water solubility, water absorption, and intrinsic viscosity (determined by U-tube) of the cross-linked starch were reduced compared to native starch. The crystalline pattern and the degree of crystallinity (as determined by wide angle X-ray diffractometer) of native and cross-linked starches were similar. Determination of the thermal properties of the samples using differential scanning calorimetry (DSC) revealed that the gelatinization peak temperature and the gelatinization enthalpy of the cross-linked starch increased compared to those of native starch. Determination of the pasting properties of the cross-linked starch using rapid visco-analyzer (RVA) showed that it had lower peak, breakdown, and final viscosities compared to those of native starch. Moreover, the cross-linked wheat starch showed more stable peak viscosity during heating. The results of this study suggest that the cross-linked wheat starch has the potential use in food production systems such as production of jam, baby food, soups, and salad dressing in which the increase in viscosity as a result of elevating temperature is not desirable, anymore.