Thursday, July 6, 2017

Fresh versus dried fruits

The other day a friend of Pairteas asked me why certain fruits—blueberries, kiwis, and apricots in particular—go better with oolongs when dried than when fresh.

The first point to make is that the chemicals in oolongs for the most part activate the warm to hot receptors. Consequently foods that activate the cool/cold receptors, such as blueberries and apricots, will cause the flavors of most oolongs to disappear.

The second point is that drying, whether of fruit or tea leaves, changes their chemistry. When they are fresh, fruits and tea leaves are still alive, so they respond to drying by making defense chemicals in response to the stress. 

For example, fresh ginger has two chemicals, zingerone and gingerol, that are slightly different in flavor. Zingerone activates the cold receptor (TRPA1) and gingerol activates the hot receptor (TRPV1). As ginger dries, these chemicals disappear or, to be more exact, are transformed into shogaols that collectively activate TRPA1. For those of you who were at our WTE about green tea way back in 2015, you might remember how a tiny bit of dried ginger dampened the bitterness of the tea and brought out its herbaceous qualities.

Apricots have compounds that hit the cold receptors, so can kill the flavor of an oolong.  As apricots dry phenyl ethyl alcohols and linalool oxides oxides appear—they hit the warm/hot receptors and make oolong happy.

As for blueberries, don't know what happens in them specifically. Fresh blueberries hit the cool/cold receptors, as does blueberry jam—the berries don't have a chance to make an abundance of stress chemicals before they are cooked and their enzymes denatured. My guess is that drying makes them create a panoply of chemicals similar to those in apricots.

And as for kiwis—will have to do some experiments once I get settled in my new home...

...and please do experiments yourselves to see what happens. Would love to hear from you!

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