Molecular encapsulation of ascorbyl palmitate in preformed V-type starch and amylose

Abstract

In the present study, we introduce a simple method to prepare inclusion complexes by "inserting" guest molecules into preformed "empty" V-type amylose helices. Ascorbyl palmitate (AscP) was used as a model guest material to investigate the effect of solvent environment, complexation temperature, annealing and guest concentration on inclusion complex formation. High complexation temperature was not necessary for encapsulating guest molecules in amylose helices, avoiding thermal degradation of guest compounds. This method would also avoid the wasting of guest materials because uncomplexed guest can be reused. It was found in the study that intermediate ethanol and acetone concentrations (generally 40-60%, v/v) at room temperature were appropriate for the complexation between V-amylose and AscP. Annealing, i.e. heat treatment in ethanol solutions at elevated temperatures (45-70 °C), was able to significantly increase the crystallinity of V-amylose and V-starch to as high as 65% and facilitate greater complexation evidenced from higher enthalpies, probably due to more regularly arranged helical cavities in larger crystalline phase. The complexation between V-amylose and AscP was also found to be enhanced with AscP concentration, while the dissociation temperature experienced a slight decrease.

Keywords: Amylose; Ascorbyl palmitate; Bioactive; Inclusion complex; Molecular encapsulation; Starch.