Important: Safety Warning
This page describes home-canning methods from before the causes of botulism were understood. Canning low-acid foods without a pressure canner, as described here, can allow the growth of Clostridium botulinum, whose toxin is among the deadliest known. Follow current USDA home-canning guidelines instead.
This information has been left in for historical purposes but should not be acted upon.
Home › Cold Drinks › Easy Grape Juice
Easy Grape Juice
Pick over the grapes, taking out all imperfect or unripe ones. Into each quart preserving jar, put a half cupful of sugar and a cupful of grapes; fill the jar with briskly boiling water. Put on the rubber rings and screw tops on the jars, and store in a cool place. A jar or two can be made at a time whenever you have a few grapes. Ready for use in a few weeks.
This is open-kettle canning at its most casual, and the failure points are worth naming precisely, because the recipe looks harmless.
- Nothing in the jar is ever heated throughNothing in the jar is reliably heated through -- Raw grapes and dry sugar are covered with boiling water, which drops in temperature against cold fruit, cold glass and cold sugar. The contents may not reach or hold a pasteurising temperature, so yeasts and mould spores on the skins can survive.
- The seal is guessworkThe seal is unreliable -- A vacuum forms only if the headspace is genuinely hot when the lid goes on. Here the headspace may be too cool for a dependable vacuum, so the closure can hold air, and a jar that appears sealed can be harbouring active fermentation or surface mould weeks later.
- Diluted juice is not reliably high-acidWhole grapes are acidic, but a cup of grapes plus half a cup of sugar in a quart of water is mostly water. Acidity is spread thin, and mould growing on the surface consumes acid and raises pH locally, which is the recognised route by which a fruit product stops protecting itself.
- "A cool place" is not coldA cellar shelf might sit anywhere from about 45F to 70F. Several weeks at those temperatures is an invitation to alcoholic fermentation, and a fermenting sealed jar builds pressure.
- The hardware no longer existsRubber rings and one-piece zinc screw tops were replaced decades ago by two-piece lids with a bonded sealing compound, which are designed to vent during heat processing. Old rings perished, and the method assumed a closure that behaved differently from anything sold now.
- What the recipe was aiming atThe intent — a light, sweetened grape drink made a jar at a time from odd handfuls of fruit — is entirely reasonable. Use a current tested recipe for grape juice, whether a boiling-water-bath process or simply a refrigerated batch made and drunk within a few days.
Unfermented grape juice as a household staple is a comparatively recent thing: before reliable heat processing it turned to wine on its own. The commercial version is generally traced to Thomas Bramwell Welch, a Methodist dentist in New Jersey, who in 1869 applied Pasteur's heating method to Concord grapes to produce a communion wine substitute for temperance congregations; his son built the business that made bottled grape juice ordinary. Recipes like this one sit downstream of that, in the era when grapes could be kept without fermenting but the reason the heating mattered was not necessarily understood. The appeal was that it needed no boiling kettle on the stove for hours, no straining, no jelly bag, just a jar filled and set aside, which is exactly the shortcut that made it unsafe.