Physicochemical, morphological and thermal properties of oxidized starches from Lima bean (Phaseolus lunatus)
Mary Oluwaseun Okekunle, Kayode O. Adebowale, Bamidele I. Olu-Owolabi, Alf Lamprecht
Abstract
Modification have been proven to improve and help overcome the limitations in the functional properties of native starch. Starches extracted from three Lima bean (Phaseolus lunatus) varieties were subjected to oxidation for physicochemical, pasting, morphological and thermal properties evaluation. Oxidized starches presented high moisture, low-fat, decreased swelling power and increased solubility compared to native starches. The particle size range of native and oxidized starches was 18.21-43.18µm and 19.18-48.82µm respectively, but no marked differences in the FTIR spectra. Peak viscosity of native starches was in the following order: Brown Lima bean starch > Red Lima bean starch > White Lima bean starch, but oxidation resulted in increased peak viscosity of starches. Oxidized starches revealed pores with slight grooves (using a scanning electron microscope), but native starches presented smooth surfaces without pores. To and ΔH reduced significantly in oxidized starches. X-ray diffractogram illustrated typical ‘C’ pattern characteristic of pulse starches. X-ray pattern of native and oxidized starches differed insignificantly. Overall, oxidation improved the physicochemical and thermal properties of Lima bean starch and potentially suitable for industrial application.