Study: Blueberry. 3.1.6 Blueberry Shrub Sorbet.
A couple of years ago, cocktails, in a ever-deepening quest to discover their roots,
recognized that only so much could be learned if they went back in time no further than pre-Prohibition days.
Deep in the historic cocktail strata, around the time of the early punches, was found the once-forgotten .
The shrub was once popular as an 18th Century solution to a common problem of American colonials: on a hot summer day in Northern Virginia, it would be nice to liven up one’s rum or brandy with something tart. But fresh citrus was seldom available, few tart fruits were in season locally, and refined acids existed almost exclusively in the labs of French tax collectors.
The answer they hit on — or at least George Washington did — was vinegar. A sweetened fruit vinegar, mixed with liquor, mimicked the unavailable citrus, and papered over the flaws of questionable rum.
Shrubs have been rediscovered, and can be found all over the menus of today’s post-speakeasies. (The Shrubbery at Chicago’s Owen & Engine is nice) A bad shrub can be easily made. A good shrub — tart, but not acetic — is a much greater challenge.
A good rhubarb shrub at Paper/Plates
The sorbet uses a classic preparation method, with only three ingredients (four if you add salt). The hint of balsamic lends it a deep flavor, reminiscent of an old-time shrub.
Here is how one makes sorbet:
Except, that does not work with blueberry. (Anybody want some icy blueberry jelly?)
The first attempt to make blueberry sorbet failed with a disappointing goo. An elegant syrup made from filtered and pureed fresh blueberry seemed an auspicious beginning. After a few hours of refrigeration, however, it realized that it preferred to be a jelly instead. The sorbet was going nowhere.
The problem was pectin.
Pectin is the magic polysaccharide responsible for transforming warm juice into silky jelly. A pinch of pectin can work miracles for a sorbet. (Read the list of ingredients of a good commercial sorbet; there, at the bottom, the odds are you’ll see “pectin.”)
But blueberry has more than a pinch. The U.S. Highbush Blueberry Council — yes, it insists that its “highbush” and highbush only — reports that blueberry typically holds 300 milligrams of pectin per half-cup. What’s more, the effects of blueberry’s pectin are unpredictable: the pectin content varies with time of the season (early and late-season blueberries are said to have more) and the pectin’s with the acidity of the mixture. Get the wrong blueberry, and blueberry syrup will become blueberry jelly on its own.
So let’s cop-out and use blueberry juice. The bet is that smart blueberry bottlers have solved the pectin problem in a way that our saucepan and blender have not.
Pure blueberry juice is available at most health food stores, marketed to the anti-oxidant-obsessed. The juice is bracing to the throat, only lightly sweet, with a powerful, almost overwhelming blueberry flavor. Like pure cranberry juice, a splash in lemonade or a mixed drink is refreshing, a straight shot a bit too powerful.
And it makes for a heck of a shrub.
The blueberry juice hunch turns out to be right. Balanced with a little balsamic vinegar, this sorbet, carefully made, keeps a nice texture.
Make a syrup. On very low heat, dissolve 1 cup sugar in 1 cup blueberry juice. Once integrated, add 2 tbsp. balsamic vinegar, and raise temperature. The vinegar will boil before the juice, allow it boil gently for 1 – 2 minutes, until the harsher components of the vinegar, but not juice, boils off. (When the acetic vinegar smell starts to fade, its time to stop.) Remove from heat and chill the syrup to near-freezing.
Integrate the syrup and freeze. Make sure the ice cream maker is extremely cold: if possible, place the entire ice cream maker in the freezer.
Mix 3/4 cup syrup and 1 cup chilled blueberry juice. If you trust your ice cream maker to be very cold, add a pinch of sea salt as a flavor enhancer. Churn according to manufacturer’s direction. Serve immediately, or allow to temper in freezer overnight.
1 + 1 cup 100% blueberry juice
1 cup sugar (granulated is fine; Demerara adds richness)
2 tbsp. balsamic vinegar (to taste)
pinch sea salt