The class was co-hosted by CUESA, Center for Urban Education about Sustainable Agriculture, who puts on the Ferry Building Farmer's Market, farm tours, and educational events and Urban Kitchen, a group that hosts affordable, single-purpose classes and workshops themed around the DIY Slow Food concept.
Here is what I learned:
The word shrub comes from a Persian word for a syrup with citrus and fruit in it, which is also the base of the word sherbet. Originally, shrubs did not have vinegar in them, but as they spread around the world they began to incorporate it. Why? Because Persia had citrus fruit and other countries did not. Citrus provides the acidity that helps preserve these syrups, and so does vinegar, which can be made from non-citrus fruits. So vinegar was a citrus substitute.
That explains why we see some recipes for shrub syrups with and some without vinegar. Blueberries, for example, need the extra acid; pineapple does not. I had always wondered about that. Mystery solved.
Furthermore there is a separate type of shrub related to the switchel. According to Colliau, the switchel dates back to Roman times. It was water mixed with vinegar and perhaps sugar that was used to hydrate the slaves. Wikipedia seems to pick up the trail of the switchel as it enters nascent America, where it was used similarly for hydration rather than as a preservative syrup.
Making Shrubs, Fast and Easy
They made it incredibly easy for us to make our own shrubs in this class. They put out a bunch of berries, stone fruits, herbs, and spices. We filled mason jars with our selection of them. Then we poured hot vinegar to fill the jars.
Done. Next we wait a week, giving the jar a little shake each day. Then we add sugar and stick it in the fridge -ready to drink!
I made a blueberry-raspberry-thyme shrub and a strawberry-pepper-coriander shrub. I CAN'T WAIT TO DRINK THEM!
Vinegar tip: Colliau says don't use distilled white vinegar, use wine/champagne or fruit vinegars. Be wary of apple cider vinegar as the flavor can be overpowering.