Characterization of hydroxypropylated-distarch phosphate barley starch and its impact on rheological and sensory properties of soup.

Barley starch was dual modified by hydroxypropylation using 8% and 12% propylene oxide, separately, based on starch weight (dry basis) followed by cross-linking through addition of 1% mixture of sodium trimetaphosphate (STMP) and sodium tripolyphosphate (STPP) to form 8HPCL and 12HPCL E1442 (hydroxypropylated-distarch phosphate) barley starches, respectively. These modified starches were incorporated at 5% and 8% levels in soups. Functional characteristics of starches like swelling power, solubility and water retention capacity greatly improved after dual modifications. Paste clarity increased fivefold in case of 12HPCL (starch prepared using 12% propylene oxide and 1% mixture of STMP and STPP) modified barley starch. Higher level of hydroxypropylation also declined the retrogradation process in starches. All soups demonstrated thixotropic behaviour with flow behaviour indices less than one. Soup [S-(8HPCL)] made with addition of 8% (8HPCL) barley starch demonstrated highest linear viscoelastic region (LVR), yield stress (τ) and complex viscosity (Ƞ). Lowest value of tan δ (0.09) was also observed for S-(8HPCL) soup, suggesting its higher consistency. Native barley starch when added to soup at a level of 5% was the least acceptable in terms of sensory characteristics.