What's Happening

• Garlic is cherished because it's rich in highly reactive sulfur compounds, which interact with oxygen in the atmosphere to create its distinctive pungent, savory flavor and aroma. Those chemically lively compounds are also the cause of oddly green garlic. Natural enzymes in the garlic interact with atmospheric oxygen and the sulfur compounds in the garlic to create a pigment closely related to chlorophyll -- an effect that's accentuated by the oven's gentle, diffused heat. A mixture of onions and garlic creates a slightly different pigment, shading more to the blue portion of the color spectrum.

Minimizing the Effect

• The green tinge is found primarily in older garlic, which accumulates a higher concentration of sulfur compounds as it ages and becomes slightly drier. You can minimize the risk of color change, if you find it unappetizing, by using the freshest available garlic or -- if appropriate -- sauteing it instead at a higher temperature. If gentle heat is better for your dish, simply allow more time to cook your garlic. As with chlorophyll, the garlic's verdant hue will fade to a dull khaki over time, for a much more food-friendly color. In even longer cooking, the garlic's own sugars will gently caramelize and lend the garlic an eye-appealing golden-brown tone.