Effect of gamma irradiation and temperature on fructans (fructo-oligosaccharides) of stored onion bulbs Allium cepa L

The effects of gamma irradiation doses and temperatures on fructo-oligosaccharides of onion bulbs after six months storage were investigated. Bulbs were ionized at doses of 0.15 and 0.30 kGy, and kept at 4, 10 and 20 °C during 24 weeks. The concentrations of glucose, fructose, sucrose and other fructo-oligosaccharides were then determined. Fructans content decreased with degree of polymerization (DP), and glucose, fructose and sucrose constituted major proportions of total carbohydrates, averaging 28%, 24% and 10%, respectively. Trisaccharides averaged 12%, while tetra-saccharides averaged 10% of total carbohydrates. High polymerized fructo-oligosaccharides averaged 13% for DP 5–8 and 5% for DP up to 12 U. After six months, glucose, fructose and sucrose of control and both irradiated bulbs decreased slightly but not significantly, while temperature and irradiation significantly influenced fruco-oligosaccharides of bulbs.