The method is based on the initial treatment of the samples
with dilute nitric acid to extract pectin according to the
procedure by Aravantinos-Zafiris and Oreopoulou (1992),
followed by treatment with aqueous ethanol (determination
of total sugars) and successive treatment with protease
(to remove proteins), extraction with NaOH (hemicelluloses)
and treatment with H2SO4 (cellulose, lignin and
ash). The method also allows for the determination of proteins
and pectins in the citrus peels. Four samples from
each material (orange and lemon peels) were analysed.