Preparation and characterization of crystalline complexes between amylose and C18 fatty acids

- V-amylose complexes of C18 fatty acids were prepared in aqueous batch mode.
- Complex yield could reach >70% by thermal control of reaction.
- Linolenic acid (C18:3) was more effective in complex formation than linoleic acid.

Inclusion complexes were prepared by using high amylose maize starch and C18 fatty acids including stearic, oleic, linoleic, and α-linolenic acids, under reaction conditions varied in temperature (50, 70, and 90 °C), pH (5, 6, 7, and 8), and reaction time (3, 6, 24, and 48 h). Among the four C18 fatty acids tested, stearic acid was most effective and linoleic acid was least effective in the complex formation. The reaction at 90 °C for 24 h provided the maximum recovery (about 75%) in the complex formation using stearic and oleic acids. Linolenic acid, however, could reach its maximum recovery (>70%) when reacted for a shorter period (6 h, 90 °C). Under DSC analyses, the polymorphs formed by linolenic acid appeared more uniform compared to those by other FAs. All the complexes exhibited V type crystalline structures under X-ray diffraction analyses, consisting of type I and type II polymorphs in DSC thermograms when recovered from the reaction mixtures.