DEVELOPMENT OF PECTINS IN SUNFLOWER STALKS AND HEADS

Abstract

The development of water- and oxalate-soluble pectins in the maturing stalks and heads of four sunflower cultivars was investigated. Largest changes in the distribution and characteristics of pectins occurred after physiological maturity and a killing frost. In the interval from flowering to the normal harvest date, oxalate-soluble head pectins increased from an average of 5.5% to about 20.0% of the dry, threshed head weight. Pectins extracted into water and oxalate solutions from stalks and heads in this interval contained up to 85% galacturonic acid and 2.7–10.9% methoxyl content. Stalk pectins and water-soluble head pectins produced extremely weak gels at every stage of development. Gel powers of oxalate-soluble head pectins from early cultivars increased with maturity and exceeded that of a commercial low methoxyl pectin at harvest. However, gel power remained low for oxalate-soluble head pectins from late cultivars at all stages.