The average home cook chops an onion just before using it, but those who cut onions in advance—whether for home or industrial cooking—have long noticed a peculiar occurrence: Waiting a while to use onions after cutting them often results in their developing a bitter taste that was not previously present when they were freshly cut.
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“For a long time, the only studied sulfur compounds of onion were the lachrymatory factor and thiosulfinates that are associated with its typical pungency and biting taste,” Kubec tells Food Quality & Safety. “Allithiolanes, on the other hand, are a group of sulfur-rich heterocyclic species with considerably higher molecular weight. Thus, allithiolanes do not affect significantly the smell of onion (they possess only a faint odor), but they have a striking impact on its taste.”
The formation of allitholanes, Kubec explains, is entirely spontaneous, triggered immediately when the onion bulb is cut or otherwise damaged.
In what may be frustrating for those in the food production industry who work with onions and hope to be able to avert the development of allithiolanes in cut and stored onions, Kubec says there is not an obvious industrial application to the study at present.
“I do not expect any immediate impact of our discovery on the food production industry,” he says. “At the moment, we only made the very first step by the identification of the bitter principles. In the near future, we will focus on the evaluation of biological properties of allithiolanes. It may turn out that although these species taste awfully bitter, they can also exhibit significant health-promoting activity.”