IONIC GELATION OF LOW-ESTERIFICATION DEGREE PECTINS FROM IMMATURE THINNED APPLES

Abstract

Fruit thinning is a regular practice in apple (Malus x domestica Borkh.) orchards to increase fruit size and to promote blooming. This practice generates immature, small (10 to 40 mm diameter) fruits, which are occasionally used as cattle feed. The use of thinned apples for pectin extraction could increase orchards profitability and promote development of new transformation processes. Pectin is a polysaccharide located on the cell wall of plant tissues. Commercial pectins are extracted from different plant sources and have been mainly used in the food industry. The present research aimed to extract pectin from thinned Golden Delicious (GD) and RedChief Delicious (RChD) immature fruits and determine the effect of de-esterification on pectin gelling properties. Pectin was extracted using a controlled acid hydrolysis. Extraction yields were 12 and 11 % (w/w) for GD and RChD, respectively. De-esterified pectins were obtained by alkaline hydrolysis and showed an esterification degree of 35 and 42 % for GD and RChD, respectively. Using a polysaccharide concentration of 2 % (w/v), both de-esterified pectins formed ionic gels induced by calcium, which presented an elasticity of 147 and 90 Pa for GD and RChD, respectively. In short, thinned GD and RChD immature fruits are a source of pectin with yield and properties similar to commercially available pectins.