Sulfur is found widely in the natural world. It is familiar to us as a yellow mineral used for manufacturing, shipped around the country by rail in tanker cars. It is also a highly active chemical, found in whole families of organic molecules. It is present in many foods, notably eggs and the cabbage family of vegetables. Sulfur is also found in many flavoring ingredients where its pungent flavor is beneficial.
The onion family is used in most of the world's cuisines, bringing a distinctive sharpness and sweetness to raw or cooked dishes. The onion family's famous ability to bring tears to a cook's eyes results from the same sulfur compounds that give the desirable flavors. Fresh onions are a vegetable, not a seasoning, but dried onions are available in powder and granulated forms for use as a seasoning.
Garlic is part of the same family as onions, with less water, more sugars and similarly pungent sulfur compounds. Like onions, garlic imparts a distinctive savoriness to foods, providing a versatile background flavor that is valued in most of the world's cuisines. Garlic can be cultivated in almost any climate, with cold weather producing a more pungent bulb. Like onions, garlic is dehydrated and ground for use as a seasoning ingredient.
The sulfur compounds in mustard are activated when the seeds are ground up and mixed with a liquid ingredient such as water or vinegar. A pinch of dry mustard powder placed on the tongue will seem flavorless for the first few seconds, until it is activated by the saliva. At that point, it will become very hot indeed. Commercial mustards minimize the heat in varying degrees with other flavorings. The sulfur compounds in mustard are strong enough to be used in chemical weapons, such as the "mustard gas" that killed so many in World War I.
Spices and Other Flavorings
A number of other spices and herbs derive their flavor and aroma from sulfur compounds, such as horseradish and wasabi. Both are part of the same family as mustard. Nigella seed, widely used in Indian and Middle Eastern cooking, has a sulfur-like flavor reminiscent of both onions and garlic, with a hint of egg. Beans are another family of foods that are high in sulfur, and some are used as flavorings. Fenugreek is a type of small bean that's ground as a spice in Indian cooking. Carob, a popular chocolate substitute, is also a bean and is high in sulfur compounds.