Modified waxy wheat starch compared to modified waxy corn starch

Waxy wheat starch (WWS) and waxy corn starch (WCS) were cross-linked in an aqueous slurry at c. 37% starch solids with 0.013 to 0050% phosphoryl chloride (starch basis) at pH 11.5 for 60 min in the presence of c. 2.1% sodium sulphate (starch basis). Increasing levels of phosphoryl chloride caused a steady decline in the final paste consistency of cross-linked WWS, but that of WCS proceeded through an optimum. Starch paste consistency was the resistance to stirring measured in a pasting instrument. WWS cross-linked at a low level gave a higher final paste consistency compared with cross-linked WCS. WWS and WCS were hydroxypropylated (HP) to low (c. 2.0%) and medium (c, 4.0%) levels by reaction with propylene oxide at pH 11.5 and 45 degrees C. and the HP starches were then cross-linked with 0.008 to 0.018% phosphoryl chloride. Again, cross-linked HP-WWS gave pasting curves with higher consistency at 6.25% starch solids compared with HP-WCS. WWS and its modified forms yielded pastes of lower clarity than those from WCS, but the pastes from HP/ cross-linked WWS had better freeze-thaw stability. Cross-linking with phosphoryl chloride (0.025%) followed by acetylation with acetic anhydride (8.0%) yielded modified waxy wheat and waxy corn starches with similar paste consistencies, but a force-distance instrument indicated that the modified WCS was significantly stringier than the modified WWS. (C) 2000 Academic Press.