Raman and Fourier transform infrared spectroscopy application to the Puno and Titicaca cvs. of quinoa seed microstructure and perisperm characterization

Abstract

The aim of this study was to investigate the quinoa fruit and seed microstructure, as well as to determine the qualitative composition of quinoa whole seed spatial localisation of food reserves in cultivars Puno and Titicaca using two complementary spectroscopic techniques (Fourier Transform infrared and Raman). The analyses of the seeds also included measurements of the crude proteins and starch contents. The experiment was carried out during the 2016 growing season in rain-fed conditions in the north of Serbia. The analysis of the scores of the principal components based on the Raman spectra revealed two groups in both seed parts (cotyledons and perisperm). The analysis of the loadings highlighted the spectrum region that contributed to the differentiation, e.g. the band at 472 cm(-1) was related to the amylopectin content in the perisperm region. As for the cotyledons, the spectral range from 1100 to 1650 cm(-1) was responsible for genotype differences and it included both the most important bands derived from Amide I, II and quinoa protein with globoid crystals composed of phytin. IR analysis, similar to the analyses of the crude proteins and starch contents in the seeds, failed to reveal any differences in biochemical composition between two analyzed genotypes.