Spectroscopic techniques for elucidation of structural changes in temperate cowpea cultivars under germination: A useful tool for quality determination and industrial application

Abstract

The present study investigated the molecular changes induced by germination in cowpea cultivars by spectroscopic techniques. The ATR FT-IR, Intrinsic fluorescence, and UV spectroscopic techniques revealed that germination shows alteration in cowpea cultivars. The ATR-FTIR showed slight differences in band intensities corresponding to carbohydrates, lipids, and protein regions at 700 to 4000 cm-1 wavenumbers. Starch order structure understanding their functionality showed a reduction of short-range ordered structures in Black cowpea flour and long ordered starch fraction in White cowpea flour under germination. The study quantified the degree of ordered starch and their alteration in amorphous/crystallinity nature concerning germination and cowpea cultivars. The secondary structures revealed a reduction of β-sheets and α-helix content, representing decreased ordered protein structures and their shifting into random coils and turn structures. The germinated flours showed decreased fluorescence intensities with the shift from 347 to 348, reflecting the redshifts due to decreased concentrations of fluorescent compounds during germination in cowpea flour. UV spectrum revealed a similar spectrum with an increase in absorption of cowpea flour under germination. The electrophoresis showed variations in the intensities of high (25 to 225 kDa) and low (19 to 10 kDa) molecular weight proteins in germinated cowpea cultivars than the native one. Overall, this study demonstrated the potential of ATR-FTIR, fluorescence and UV-based spectroscopy as non-destructive techniques to assess the alteration of pulses at the molecular level and structural changes under the germination process.

Keywords

• Cowpea
• Fluorescence
• Germination
• Protein Structure
• Spectroscopy