Formation and crystallization of amylose-monoglyceride complex in a starchmatrix

The formation of amylose-lipid complexes in a gelatinized potato starch mat rix was investigated using potato starch and glycerol monopalmitin. These c omplexes exist in two forms, with the amounts of each of the forms being de pendent on the temperatures and durations of the pre-treatments. Differential scanning calorimetry (DSC) was used to analyze transition temp eratures and melting enthalpies, and thereby determine the amount of the co mplexes in the samples. X-ray diffraction analysis was used to investigate their crystallinity. In measurements with DSC, form I started to melt at 88.5 degrees C, and for m II at 112.9 degrees C. When complex form II was preheated at 100 or 110 d egrees C, its melting point rose to 116.3 and 1 19.7 degrees C, respectivel y, because of an annealing effect. The same phenomenon occurred with comple x form I: when preheated at 90 degrees C, its melting point rose to 96.8 de grees C. The crystal formation of form II appeared to be slower when treate d at 110 degrees C than at 100 degrees C. Their maximum melting enthalpies were reached after about 24 h and 4 h of preheating, respectively. In X-ray diffraction analyses, form II showed a V-pattern, but form I did not. This indicates that form LI is more crystalline than form I. It was possible to transform form I into form II when it was heat treated, because form I was then partially or totally melted. As a comparison, the charged substance cetyltrimethylammonium bromide creat ed complex form I with amylose in the starch matrix, but not form II. (C) 2 000 Elsevier Science Ltd. All rights reserved.