Fourier transform infrared (FTIR) spectroscopy is a fast analytical technique being successfully used in depicting the chemical characteristics of foods. The objective of this research was to use FTIR to characterize the fractionation behavior of coconut testa flour (CTF) under sequential extraction using three different solvents. In this study, CTF obtained from five Sri Lankan coconut cultivars namely; Gon Thembili, Ran Thembili, San Raman Tall, Tall x Tall and commercial hybrid were subjected to sequential extraction using hexane, ethyl acetate (EtOAc) and methanol (MeOH). FTIR spectral data were acquired within the range of 4,000–500 cm-1 adopting the KBr pallet method. The contours of the FTIR spectra obtained for both hexane and EtOAc extracts were roughly similar, except for few regions. The presence of lipid molecules in these two extracts was confirmed by a dominant absorption peak due to ester linkage of triacylglycerols. Spectra of EtOAc extracts were nevertheless found to differ from those of hexane extracts by the presence of phenolic constituents since most of them contained additional peaks at ~3460 cm-1 and ~1635 cm-1. The spectral pattern of MeOH extracts differed significantly from those of the previous two sets of spectra due to drastic differences happened in the chemical composition. The occurrence of stretching vibrations of hydroxyl groups indicated the strong presence of carbohydrates and phenolic constituents in MeOH extracts. Existence of small amounts of proteins and lipids in this extract tended to give low-intense signal in the spectra. The distinctive differences of spectra of MeOH extracts from those of the other two extracts has been confirmed by principle component analysis (PCA), which exhibited 97% and 2% variance along principle component 1 and principal component 2, making up 98% of total variance. In conclusion, FTIR evaluation of various solvent extracts were helpful in identifying the changes in bimolecular distribution during sequential extraction of CTF. In addition, PCA has proven to be quite successful in discriminating the differences of both solvent extracts and cultivars.
Citation: Gunarathne R, Marikkar N, Mendis E, Yalegama C, Jayasinghe L, Ulpathakumbura S. 2022. Mid-IR Spectral Characterization and Chemometric Evaluation of Different Solvent Extracts of Coconut Testa Flour. J Food Chem Nanotechnol 8(3): 69-75.