EFFECT OF CORN WET-MILLING CONDITIONS (SULFUR-DIOXIDE, LACTIC-ACID, AND STEEPING TEMPERATURE) ON STARCH FUNCTIONALITY

Starch functional characteristics varied with wet-milled corn steeping temperature and concentrations of lactic acid and sulfur dioxide. Sta rch was laboratory-wet-milled from Golden Harvest 2572, a medium-hard yellow dent corn hybrid. Batch steeping levels of temperature (43 and 57 degrees C), lactic acid concentration (0.2 and 1.5%, v/v), and sulf ur dioxide concentration (0.05 and 0.30%, v/v) were assigned in a 2(3) factorial experiment. Starch milled from corn steeped with 1,5% lacti c acid at 57 degrees C had reduced Brabender Viscoamylograph pasting, shear thinning, and set-back viscosities. These starches also had incr eased water solubility as measured by high-performance size-exclusion chromatography. Solubilized in 90% methyl sulfoxide, starch from corn steeped at 57 degrees C with 1.5% lactic acid or 0.30% sulfur dioxide (SO2) had lowered resistance to shear as evident in formation of small er molecular sized polymers. Higher differential scanning calorimetry endotherm peak start, onset, and peak maximum temperatures were observ ed for starch obtained from corn steeped at 57 degrees C or with 0.2% lactic acid. Endotherms were also narrower for steeping at 57 degrees C than at 43 degrees C. When viewed by scanning electron microscopy, m ore surface irregularities were present on starch granules from corn s teeped at 57 degrees C and 1.5% lactic acid than those from corn steep ed at 43 degrees C or 0.2% lactic acid.