358 Monitoring the crystallization of amylose-lipid complexes during maize starch melting using temperature resolved synchrotron X-ray diffraction.

A. Buleon (1), P. Le Bail (1), H. Bizot (1), and M. Ollivon (2). (1) Institut National de la Recherche Agronomique, BP 71627, Nantes France; (2) Université Paris Sud, 92296 Chatenay-Malabry, France.

Properties of starchy food products and related materials are intimately related to the crystallization of amylose and its complexation with lipids (Vh structural type). From the two endotherms observed by calorimetry upon heating lipid containing cereal starches in excess water, the first has been attributed to gelatinization of the native crystalline structure, while the second is usually assigned to the melting of the crystalline complex. In cereal starches, the intra-granular lipids have proved to form inclusion complexes with amylose as demonstrated by solid state NMR, but may also crystallize with thermal treatments. Using temperature resolved WAXS diffractometry implemented on a synchrotron radiation source with a heat flux detecting sample cell, we have monitored the crystallization of amylose-lipid complexes during heating of maize starch. Depending on the water content, Vh crystalline patterns appear before or after the completion of gelatinization. Two mechanisms are considered to act concurrently involving either de novo crystallization of released amylose and lipids or the build up of crystallites from amorphous complexes.