Molecular modifications in cereal and tuber starches induced by microwave treatment: A comprehensive analysis using asymmetric flow field-flow fractionation

Abstract

This study investigated the impact of microwave treatment (MWT) on the molecular structure of starches from cereal (normal and waxy rice, normal and waxy maize, and wheat) and tuber (potato and tapioca) sources using asymmetric flow field-flow fractionation (AF4) coupled with multi-angle light scattering and differential refractive index detectors. The starches were treated under the same conditions (7.5 W/g, 25 % moisture, 100 ◦C, 30 min). In addition to conventional parameters such as number- and weight-average molecular masses, radii, and dispersity, novel metrics, including mass-to-radius ratios, apparent density, and concentration profiles related to molecular mass, were employed to elucidate structural transformations. The results revealed that non- waxy cereal starches exhibited greater resistance to hydrolysis owing to higher structural compaction, whereas waxy cereals experienced homogenisation of molecular radii and apparent density. In contrast, tuber starches, particularly potato, underwent molecular aggregation, forming homogeneous structures with low dispersity and a high concentration of large particles. This study introduces a novel approach for evaluating and understanding the molecular structural modifications in starch induced by MWT and how the original matrix affects these modifications, providing valuable insights for future research and applications of this physical modification process