Introduction
Onions (Allium cepa) belong to the Allium family, the same family as garlic, leeks, chives, scallions and shallots.Onion is one of the oldest vegetables and can be found in a large number of food recipes  spanning almost the totality of the world’s cultures, being the second most important horticultural crop after tomatoes. They are commonly used to flavor dips, salads, soups, spreads, stir-fry and other dishes.
Onion and other Allium vegetables are characterized by their rich content of thiosulfinates, sulfides, sulfoxides, and other odoriferous sulfur compounds. The cysteine sulfoxides are primarily …