Effect of Storage on Fructan and Fructooligosaccharide of Onion (Allium cepa L.)

The purpose of this study was a comparative examination of the fructan and fructooligosaccharide (FOS) content of different varieties of onions (Allium cepa L. cv. Sturon, Hysam, Durco, Grano de Oro, and Caribo) and the changes produced during their commercial storage. In fresh onions, the Grano de Oro variety presented a remarkably different behavior, showing low contents of total fructans and FOS and high levels of reducing sugars. In the other varieties, Sturon, Hysam, Durco, and Caribo, fructans were the main carbohydrates, the lowest polymerized FOS being the major oligomer. Storage period caused in these varieties important increased levels of free fructose attributed to fructan hydrolysis. Maleic hydrazide treatment had no significant effect in avoiding the hydrolysis of fructans during storage conditions for the Sturon variety. Varieties with >16% dry matter or 15% soluble solids contents could be stored for 6 months at 0 °C and 60−65% relative humidity. Keywords: Onion (Allium cepa L.); carbohydrates; fructans; fructooligosaccharides; storage