Effect of date syrup on physicochemical, pasting, textural, rheological and morphological properties of sweet potato starch

The effect of date syrup on sweet potato starch was investigated at 20°Brix and three starch and date syrup ratios (1:1, 1:2 and 1:3). Native and date syrup added sweet potato starches were evaluated for physicochemical, pasting, textural, rheological and morphological characteristics. With increase in ratio of date syrup in sweet potato starch water binding capacity and paste clarity decreased whereas oil binding capacity, sedimentation value and swelling power increased. At all the starch-date syrup ratios lower peak and final viscosities were observed as compared to the native starch. Texture profile results indicated that the hardness and springiness increased up to 1:2 ratio and then decreased. The rheological properties showed higher values of storage modulus than loss modulus and exhibited weak gel behaviour for all the starch gels. The decreased value of loss tangent (tan δ) showed that sample with date syrup was more elastic in nature. Scanning electron microscopy analysis revealed that addition of date syrup altered the starch morphology. Increase in syrup ratio resulted in aggregation of starch granules and slight patches of syrup were also seen on starch granules. This study suggested that date syrup find many practical applications in starch based industries as it is natural sweetener with many nutrients.