Sour Grapes: An Under-Appreciated Ancient Ingredient

Do you have a case of sour grapes? That may not a bad thing—as long as we’re talking about the fruit, and not a dose of social media-induced envy or FOMO. Bright green, shockingly tart, unripe grapes are a very interesting and very healthy ingredient, a substitute for lemon juice or lemon slices in savory dishes, and the basis of inspiring condiments like verjuice (from French verjus —”green juice”), the bracingly sour liquid pressed from green grapes, as well as cooked syrups, whose shelf lives are longer.

Photography by Marie Viljoen.

I first became aware of sour grapes’ potential—and history—when I saw them one June at Balady, a halal supermarket in the Brooklyn neighborhood of Bay Ridge, where interesting produce shows up regularly: fresh grape and mallow leaves, unripe almonds, green, unshelled chickpeas. I pounced on them, taking home one conservative bunch. This happy encounter led to much experimentation, and to real satisfaction at dinner time.

Unripe grapes as an ingredient are not new. Before lemons (native to Asia) became commonplace around the Mediterranean and Europe (where fragrantly thick-skinned but juice-less citrons had arrived in Greco-Roman times), Greeks used sour grape juice as medicine—Aristophanes mentions it in Plutus (circa 408BCE).

The juice of unripe grapes is in fact antimicrobial (as well as stunningly high in antioxidants). This I learned after a failed attempt at making a sour grape vinegar one summer in Cape Town where the green bunches were dripping from fences in Constantia, an old wine-producing area. Instead of the anticipated fizzing activity that usually begins after a few days, the mixture just sat there, sulking. Nothing happened. I did some research. Their antibacterial properties presumably worked against the beneficial microbes needed for fermentation to occur (this recalcitrance changes as sugar builds up in riper grapes).

The Romans (whose food was basically Greek in technique then) deployed defrutum, a syrupy reduction of ripe juice, liberally, and it’s likely that the juice of astringent grapes was appealing as a souring agent, too (although finding reliable citations that wade accurately through the murk of Latin translation is challenging). But by the Middle Ages, certainly, verjuice was a commonplace, if summer-centric ingredient. (Interestingly, it could also be made with the puckering juice of crabapples or other tart fruit, like gooseberries—sourness has always been sought-after.)

Fresh, raw verjuice does not last long without refrigeration, or without preservatives like citric acid or sulphites. It oxidizes quickly, fading rapidly from a vivid green to sepia. Commercial versions are available (if one hunts diligently for them) and usually contain sulfites for preservation, and resemble white wine in color, thanks to clarification. Just-pressed verjuice will usually turn muddy-green while you are working, but it tastes vividly fresh.

Around the Mediterranean and Middle East, traditional condiments based on sour grape juice include some salt or sugar, and are cooked—and sometimes reduced, like pomegranate molasses, or the Roman defrutum—to concentrate their flavor and to extend their shelf life: Persian ab-ghooreh, Turkish koruk suyu or koruk ekşisi, and Lebanese hosrom (the word is Arabic) are just some examples of these treatments around the theme of sour grape juice.

In any grape-growing region sour grapes are not hard to find. In vineyards where grapes are cultivated for wine or for the table, bunches of unripe fruit are typically thinned about six weeks before harvest, to send more of the vine’s energy into the remaining grapes. In clever cultures they are valued, and sold. If you live Stateside and have friends with a vine? Beg.

And they grow wild: I have collected plush bunches of diminutive green grapes from feral vines on fences and trees in Constantia, Cape Town, and from an old farm’s dilapidated sheds in upstate New York. Depending on just how young they are, their seeds may have not yet matured to pebble-like hardness, which makes deploying the green berries whole in the juices around a roasting chicken or in a gentle fish stew less problematic than you might imagine. Crushing them is easy via a food mill, but there are other ways to extract their juice, too, like spinning them in a food processor. (While the latter method is quicker, it tends to break up some seeds, which add a tannic note to the later juice.)

In Brooklyn, I have been lucky to collect unripe Concord grapes from a friend’s backyard vine and from a local community garden whose owner is a friend of foragers. Their seeds were hard even in the unripe grapes and I used them all for verjuice and molasses.

The grapes sold by Middle Eastern stores (brick and mortar, or online) tend to be much plumper than Concords or wild grapes and they yield more than twice their amount of juice. They are often seedless, too, making crushing and cooking them even easier. (Unripe grapes from Kalamala Persian Grocery are $7.99/pound, in season early summer.)

I use sour grapes in four ways:

Roasted

Whole, they caramelize and concentrate in dry heat: Either pread out with splash of oil on a sheetpan and then tossed into a goat cheese-forward salad (with some sweetness like dried apricots added, to balance their sour surprise), or alongside vegetables like steamed carrots, parsnips or wedges of cabbage, or with fatty meats like lamb ribs (handily sourced from the same halal supermarkets that sell the grapes in summer).

Braised and Stewed

In moist heat green grapes melt lusciously: In firm fish (think monkfish) stews with fennel and saffron, in a beef shortrib braise with summer herbs, in slow casseroles with rich cuts like duck, or in the pan juices surrounding a plump chicken. The sour berries are pops of flavor, mellowed by cream or oil, and blending beautifully into cooking juices.

Verjuice

Crushed, pressed and strained, raw, pure verjuice lasts about two weeks in the fridge, and is used as you would lemon juice. It is also a very refreshing drink, with a pinch of salt added and diluted with sparkling water. Remember those antioxidants!

Verjuice Molasses

With the addition of sugar and a steady reduction, the verjuice forms a thick, intense syrup, as versatile as pomegranate molasses.

Verjuice Method

A food processor or a hand-cranked foodmill works well for crushing. Bear in mind that, if crushed, any existing seeds will add more tannin to the result. Food processors damage more seeds than a foodmill, but using a pastry blade damages fewer seeds, if there are any; if the grapes are seedless, chop away! For bottling, avoid using metal lids, as the verjuice is corrosive.

I find that 5 cups of store-bought unripe seedless table grapes yield about 2 ½ cups verjuice. Unripe Concord grapes will yield about half this amount.

• 5 cups (about 1 ¼ lbs) unripe but plump unripe grapes

De-stem each grape, then wash and dry them. Place them into the bowl of a food processor. Pulse until the grapes are coarsely crushed. Transfer the pulp to a cheesecloth-lined sieve placed over a bowl. Press the grapes with a wide wooden spoon to extract as much juice as you can. Pick up the corners of the cloth, twist to compress the pulp, and squeeze out as much juice as possible. Pour the yielded juice into a clean bottle, seal, and refrigerate. Return the crushed grapes to the sieve over the bowl and allow any remaining juice to drip out overnight, then bottle.

Verjuice Molasses

This reduction of verjuice is delicious. Expect an amber color when it is done. For storage, avoid metal lids as the acid content is high and the lid will corrode over time. If the reduction is cooked too long it will caramelize and become rigid. Watch its consistency carefully after an hour – it should be like pourable syrup.

• 5 cups verjuice (from about 10 cups/2 ½ lbs unripe table grapes)
• 1 cup sugar

Combine the verjuice and sugar in a non-reactive pot. Bring the verjuice to a boil over high heat then reduce the heat to maintain a vigorous simmer until the liquid has reduced by three quarters. Allow to cool, and pour into a sterilized bottle. Seal.

For more of Marie’s recipes, see:

• Herb Cheese: Make Your Own Boursin-Inspired Labneh
• Let the Sun Shine In: Cattail Pollen in the Kitchen
• Summer Solstice Elderflowers (in Cape Town)