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Verjuice
Verjuice, or the juice of green fruits, is an acid liquor expressed from crab-apples, sour grapes, and unripe gooseberries, and used in sauces or ragouts as a substitute for lemon-juice; indeed, for some dishes experienced cooks prefer verjuice to lemon-acid. To prepare it from unripe grapes, gather the grapes while they are transparent, and extract the juice from them by a wine or cider press, or by pressing them in a cloth. Filter it repeatedly till it is clear. Bottle it, and expose it to the sun, uncorked, for six or seven days. The liquor will ferment, and the bottles must be filled up every morning. To preserve it, an ounce of salt should be added to each pint of juice, and it should be kept in well-closed bottles. Gooseberry verjuice is much used in France. It is sweetened and coloured, and sold as "Syrup de Groseilles." It is made just like grape verjuice. When crab-apples are made use of for this purpose, they must be gathered fully ripe, then piled in a heap, and left for a few days to sweat before the juice is expressed from them. All decayed apples must, of course, be discarded. As verjuice is very liable to undergo decomposition, the vessels in which it is to be preserved should be sulphured before it is put into them. To do this, introduce into the jars a burning match that has been dipped in melted sulphur, fill the bottles while they are full of the smoke, and cork instantly and very securely.
The entry describes a genuine and still-current ingredient, but the preservation method belongs to a period before anyone measured what was actually going into the bottle. Read it for what verjuice is; buy bottled verjus or use a current recipe if you want to cook with it.
- The sulphur match is the problemBurning a sulphur-dipped match inside a jar generates sulphur dioxide, which is still used in winemaking — but as measured potassium metabisulphite, dosed in parts per million against a known volume. A burning match gives no control at all over the residue, and sulphites at uncontrolled levels are a real hazard to asthmatics and sulphite-sensitive people. The fumes themselves are a respiratory irritant in a domestic kitchen.
- A week of open fermentation in the sunLeaving uncorked bottles of raw fruit juice outdoors for six or seven days is an invitation to whatever yeasts, acetic bacteria and moulds are in the air. The entry treats this as the way the liquor "worked"; it also means the finished product is a lottery, and the instruction to top the bottles up each morning appears to be aimed at keeping air off the surface.
- Salt as the only measured preservativeAn ounce of salt to the pint is roughly 28 g to a 570 ml imperial pint, close to a 5 per cent brine. That is a real preservative load, and it also means the verjuice is emphatically salty — nothing like the neutral acid the recipe implies when it offers it as a stand-in for lemon juice.
- Crab-apples left to sweatPiling ripe crab-apples in a heap for several days to soften them before pressing is the standard old cidermaker's step, and it does raise the juice yield. It also runs the fruit through a warm, uncontrolled mould-friendly stage; the recipe's own instruction to discard decayed apples is doing a great deal of work.
- "Syrup de Groseilles"Cassell's glosses this as gooseberry, and gooseberry verjuice was certainly made. In modern French, though, groseille on its own means redcurrant, and sirop de groseille is a redcurrant cordial; gooseberry is groseille à maquereau. Do not read the two as interchangeable.
- What verjuice tastes likePressed unripe grape juice runs around pH 2.5 to 3 — sharply acidic but softer and less perfumed than lemon, with a faint green-grape sweetness. That may be part of the appeal in delicate sauces, where citrus oil and fragrance would dominate, though the entry itself gives no reason for the preference. Commercial verjus is sold unfermented and is generally labelled to be refrigerated after opening.
The name is simply French vert jus, green juice, and it was one of the two great souring agents of the medieval and early modern European kitchen, sitting alongside vinegar in every large household's stores. Sour green grapes were the classic source in wine country; in England and northern France, where grapes ripened badly or not at all, crab-apples and unripe gooseberries did the same work, and crab-apple verjuice is often said to have remained a farmhouse staple into the eighteenth century. Its long decline is usually traced to the spread of cheap imported lemons, which offered the same acidity with a fragrance verjuice lacks — which is exactly the trade-off Cassell's is arguing about when it says some cooks still preferred the older liquor. The entry sits in "The Principles of Cookery" rather than among the recipes. It has returned to commercial production in the last few decades, chiefly from Australian and Californian vineyards thinning unripe fruit.