Effect of partial gelatinization and lipid addition on alpha-amylolysis ofbarley starch granules

The effect of partial gelatinization with and without lipid addition on the granular structure and on alpha-amylolysis of large barley starch granules was studied. The extent of hydrolysis was monitored by measuring the amoun t of soluble carbohydrates and the amount of total and free amylose and lip ids in the insoluble residue. Similarly to the alpha-amylolysis of native l arge barley starch granules, lipid-complexed amylose (LAM) appeared to be m ore resistant than free amylose and amylopectin. Partial gelatinization cha nged the hydrolysis pattern of large barley starch granules; the pinholes t ypical of alpha-amylase-treated large barley starch granules could not be s een. Lipid addition during partial gelatinization decreased the formation o f soluble carbohydrates during alpha-amylolysis. Also free amylose remained in the granule residues and mostly amylopectin hydrolyzed into soluble car bohydrates. These findings indicate that lysophospholipid (LPL) complexatio n with amylose occurred either during pretreatment or after hydrolysis, and free amylose was now part of otherwise complexed molecules instead of bein g separate molecules. Partial gelatinization caused the granules to swell s omewhat less during heating 2% starch-water suspensions up to 90 degrees C, and lipid addition prevented the swelling completely, alpha-Amylolysis cha nged the microstructure of heated suspensions. No typical twisting of the g ranules was seen, although the extent of swelling appeared to be similar to the reference starch. The granules with added LPL were partly fragmented a fter hydrolysis.