G.M. Rabiul Islam, A.K.M. Abdur Rahman-Un-Nasir
Pectin derived from citrus peel is both an excellent stabilizing agent and a high value functional food ingredient. Citrus macroptera and Citrus assamensis are endangered wild citrus species from northeast India. Although their peel is consumed locally as a vegetable and used for making pickles, no information is available on the quality characteristics of the pectin obtained from these fruits. Thus, the aim of this study was to isolate and characterize the pectin obtained from the peel of C. macroptera and C. assamensis in order to explore its potential industrial applications. Peels were acid digested and pectin was extracted with ethanol, methanol or isopropanol, and subsequently characterized. Pectin yield was highest with ethanol precipitation in both fruits. The equivalent weight (EW) of pectin extracted from C. macroptera and C. assamensis was 732.55±18.49 and 655.22±50.85, respectively, while methoxyl content, anhydrouronic acid content and degree of esterification (DE) were 1.62±0.24% and 1.36±0.25%, 33.28±1.36% and 34.74±1.56%, and 27.69±3.20% and 22.37±4.26%, respectively. Both fruits yielded low methoxyl pectin (LMP) (DE <50%) and Fourier transform infrared spectroscopy analysis revealed that pectin from both fruits has functional groups within the 1740–800 cm–1 spectral region. Pectin from both C. macroptera and C. assamensis can be used for manufacturing low sugar foods as LMPs can form gels with low amounts of sugar or even without sugar in the presence of divalent cations.