Effect of UV Light on Drying Herbs
Answered by: Richard Alan Miller
Question from: Pyay Thu
Posted on: July 01, 2007

Does UV light has effects on herbs in terms of color, flavor and their properties if I am using sunlight to dry?

Of course various spectrums of light affect different plants quite differently, that’s what we have light zones and habitat. Short UV is often referred to as "Halogen series," as the spectrum given off is more toward normal lighting than light bulbs and indoor lighting facilities.

Longer UV may burn some of the plants, those wanting more northern exposure and shade. You can notice this with the edges of leaves beginning to brown and die. When I worked Lunar Base Alpha One (Boeing, 1970), I was the Physicist in charge of light. I had to simulate unfiltered light, directly from the sun. This meant I also dealt with wavelengths much longer than UV.

Longer UV can also hurt most field crops, and is why they are mostly grown at sea level.. The actual wavelengths are shorter at this altitude, as most of the longer UV is filtered out. This is why growing plants at higher altitudes (16,000+ ft) will often mutate the crop into something else.

So, responding to your question of color, flavors, and other qualities, it will vary on individual crops. Most herbs and spices are mints (square-stemmed, Labiatae Family), and as such will loose their volatile oils (mint) to light and temperature. This is why spearmint, peppermint, and basil are grown at sea level.

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