Extraction, characterisation, and enzymatic degradation of lemon peel pectins

The albedo of Spanish lemons (16.0% w/w of lemon fresh weight) was extracted to obtain a chelating agent soluble pectin fraction, a diluted sodium hydroxide soluble pectin fraction and a residue (4.2, 1.8, and 5.0% w/w of fresh albedo, respectively). These fractions represented 61.3, 12.4, and 10.4% of the galacturonic acid present in the albedo, respectively. Fractions were studied and their characteristics were compared with those of lemon albedo modified hairy regions (MHR) (1.4% w/w of fresh albedo), solubilised from the albedo after treatment by a technical enzyme preparation. All extracted pectins were rich in galacturonic acid, next to varying amounts of arabinose, galactose, and glucose residues, Based on molecular size, albedo-MHR consisted of at least five populations. From the rhamnose:galacturonic acid ratio (0.21-0.28), the high acetyl content, and the degradability by rhamnogalacturonase, it was concluded that the four major fractions represent rhamnogalacturonans having only small differences within their fine structure. The fifth fraction contained more galacturonic acid and was only degraded by polygalacturonase.