An effect of intragranular components of wheat starch on filtration rate of its enzymatic hydrolysates

Comparison of saccharification degrees and filtration rates of enzymatic hydrolysates of different wheat starch samples provided evidence that intragranular lipids more strongly retard enzymatic degradation of wheat starch and filtration of its digests than proteins and pentosans. Two wheat starch preparations with different content of intragranular lipids, proteins and pentosans were selectively de-fatted, de-proteinized or deprived of pentosans, liquefied with TERMAMYL 120L S alpha-amylase and further saccharified with AMG E glucoamylase. All hydrolysates were analyzed for the degree of saccharification and filtration rate. Enthalpy and temperature of dissociation of amylose-lipid complexes present in wheat starch and its hydrolysates were examined by using differential scanning calorimetry (DSC). Both starch preparations and samples of solid residues after filtration of their alpha-amylase digests were subjected to X-ray analysis to characterize amylose-lipid complexes in more detail. Our studies revealed that intragranular lipids included in amylose-lipid complexes, particularly in their crystalline polymorph, were the main factor responsible for reduced yield of wheat starch conversion and relatively low filtration rates of its enzymatic digests. De-fatting of both wheat starch preparations significantly reduced the number of amylose-lipid complexes, and provided higher degree of starch hydrolysis and better filtration properties of glucose syrups than extraction of intragranular proteins.