Enzymatic extraction and characterization of pectin from kiwi and mandarin peels

In this study, pectin was extracted from the kiwifruit and mandarin peel by enzyme assisted extraction method. The physical and chemical properties of the obtained pectins were compared with the pectins extracted by the classical extraction method. Cellulase enzyme (Aspergillus niger) was used for the enzyme assisted pectin extraction method. Appropriate conditions were determined by the preliminary experiments for extraction process. The suitable conditions under pH 5.5 and 40°C were determined as 0.06 U/mL enzyme concentration and 240 min extraction time for 4 g of kiwi peel; 0.08 U/mL enzyme concentration and 300 min extraction time for 4 g of mandarin peel. Under these conditions, 6.72% pectin yield was obtained from the kiwifruit peel and 10.10% pectin yield was obtained from the mandarine peel. It was observed that pectins obtained by the enzyme assisted extraction had higher degree of esterification than pectins obtained by the classical method. In addition the pectin obtained by enzyme assisted extraction had higher equivalent weight and galacturonic acid content and higher solubility than the pectins obtained with classical extraction. FTIR spectra of examined pectins were found to be similar to the spectra of commercial and standart pectins. During pectin extraction simultaneously, 0.21 mg GAE/mL and 27 mg GAE/mL phenolic substances were extracted from kiwi and mandarin peels, and these extracts were found to have antioxidant capacities. The antioxidant capacities and total phenolic contents of pectins obtained by the enzyme assisted extraction method were higher than those obtained with the classical extraction method. The results showed that kiwifruit and mandarin peels could be used for pectin and phenolic material production by enzymatic extraction method and thus increase the value addition of fruit waste by utilizing them in an environmentally friendly way.