FRUCTANS IN ONION BULBS IN RELATION TO STORAGE LIFE

Abstract

A 3-yr study with eight different onion cultivars, Allium cepa, was conducted to determine the association of water-soluble carbohydrates (WSC) with the storability of the bulbs. Onion bulbs were harvested in the fall of 1983, 1984 and 1985, and sample bulbs were analyzed for WSC. Water-soluble carbohydrates of onion bulbs consisted of a series of oligofructans, the maximum degree of polymerization (DP) being between 10 and 15, in addition to fructose, glucose and sucrose. Fructan concentration of onion bulbs harvested in 1985 decreased during storage. Onion cultivars with a short storage life, such as Buffalo, contained a relatively high moisture content, a high concentration of monosaccharides and a low concentration of fructans at harvest. These criteria may be used as an indicator for identifying onion cultivars with a very short storage life but not for the prediction of storability of onions with medium to long storage life.Key words: Onion, Allium cepa, storage, carbohydrate, fructan, HPLC, molecular size