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Pineapple and Strawberry Jam
4 level cups (2 lbs.) CRUSHED AND CHOPPED Fruit ½ bottle (scant 1/2 cup) CERTO Crush well about 1 qt. ripe berries. Put pineapple through food cutter, or chop very fine.
Measure 2 level cups of each into large kettle. Proceed as below.
This is one entry from a Certo booklet, and it deliberately stops short: the sugar and the boiling method live in the general directions the page refers to as "proceed as below." That missing half is what you need to supply.
- The instruction that matters mostCerto is liquid pectin, added after the boil, not before. The standard short-boil method is: combine measured fruit and sugar, bring to a full rolling boil, boil hard one minute, take off the heat, stir in the pectin, then skim and stir for about five minutes before filling so the fruit does not float.
- The sugar is not on this pageA four-cup fruit measure in these booklets normally took 7 to 7½ cups of sugar. Do not guess low: with liquid pectin the sugar is part of the gelling chemistry, and cutting it gives syrup rather than jam. Follow the ratio printed in a current pectin insert.
- How much Certo"½ bottle (scant ½ cup)" implies the old glass bottle of about 8 oz, half of it being roughly 4 oz. Liquid pectin now comes as a 6-oz carton holding two 3-oz foil pouches, so one pouch is noticeably less than the half bottle intended here. Measure by the pouch and match it to a current recipe rather than splitting it by eye.
- Food cutterA hand-cranked meat and vegetable grinder clamped to the table. A few pulses in a food processor does the same job, but stop while the pineapple still has texture; puree makes a cloudy, dense jam.
- PineappleWell-drained canned crushed pineapple works and is far more consistent than fresh. The bromelain in fresh pineapple that ruins gelatin desserts is not a problem here, since the enzyme is destroyed in the boil, but fresh fruit varies in acidity and many pineapple jam recipes add a tablespoon or two of lemon juice for that reason.
- StrawberriesA quart of berries crushed well yields roughly the two cups called for. Crush rather than blend, and use fully ripe fruit for flavour but not overripe, which is low in its own acid.
- SealingThe original booklets finished with a layer of melted paraffin poured over jam in tumblers. That method is no longer considered a sound seal. Fill clean half-pint jars, leave ¼ inch headspace, and process in a boiling-water bath as a current canning guide directs, or refrigerate and eat within a few weeks.
- YieldA full-boil batch on this scale makes roughly eight cups of jam, which is where the booklets' figure of ten or eleven of their small glasses comes from; that is considerably more than the same fruit would give by long boiling.
Certo was the brand that made short-boil jam a household routine. Liquid pectin extracted from apple pomace and citrus peel was commercialised in the United States in the early twentieth century, and the manufacturer's promotional recipe booklets, of which this is one, existed to teach cooks a method that ran against everything they knew: instead of boiling fruit and sugar down for half an hour or more until it sheeted off a spoon, you boiled for one minute and added pectin at the end. The selling points were fresh colour and flavour, a predictable set without a saucer test, and a markedly larger yield from the same fruit, since almost nothing boiled away. The pairing here is characteristic of the genre too. Strawberries are a fleeting local crop with plenty of natural acid, pineapple arrived year-round in cans from Hawaii, and combining them stretched a short season into something that could be made any month of the year.