Abstract:
Sour orange (Citrus aurantium sp.) has not been explored sufficiently as a
potential source of pectin, and its peel as a waste from fruit juice industry
has been recently under investigation as a potential low-cost source of
pectin. In the present work, pectin was efficiently extracted in moderately
high yield from sour orange peels in acidic medium, which was not
explored for the same raw material before. Chemical confirmatory tests
were carried out to identify the characteristics of the isolated pectin. The
isolated pectin has mainly glycosides with gel-forming properties and free
from starch and non-reducing sugar. Qualitative tests were carried out to
study the solubility of pectin in hot/cold water and hot/cold alkali, and it
was found that the solubility of sour orange pectin is similar to that of
commercial citrus pectin. Equivalent weight, methoxyl content,
anhydrouronic acid content and degree of esterification were determined by
titrimetric methods. Low degree of esterification (<28.6%) made it evident
that the sour orange pectin is a low-methoxyl pectin. According to X-Ray
Diffraction (XRD) analysis, sour orange pectin was found to be amorphous
by nature. FTIR spectra of isolated pectin revealed the existence of
functional groups such as amide, alcohol, carbohydrate ring, unsaturated
ester, carboxylic acid, aliphatic amine and alkyl halide, and isolated sour
orange pectin was identified as amidated pectin.
