Learn how to make jam successfully – form a gel with enough acid.

Making jam successfully requires 3 basic components; pectin, sugar, and acid. Since I have already covered pectin and sugar previously, today we tackle acidity.

Why Does Jam Need Acid?

Much like sugar, acid has a couple of different roles in jam making.

Brightness and flavor: Have you ever added a splash of vinegar to French fries or a bowl of tasteless soup? Squeezed lemon over poached fish? Piled chopped, fresh tomatoes on a plate of pasta? If so, you have enhanced the flavor of a mild food (potatoes, white fish, pasta) by adding a bit of acid. Adding acid to jam works the same way. Adding a little lemon juice increases the fruit flavor of your jam.

Gel: Peter Yarrow, Noel Paul Stookey, and Mary Travers were (are) all fantastic singers separately. But when they formed a trio, Peter, Paul, and Mary created magic. We get the same – albeit less musical – harmony when we combine pectin, sugar, and acid. All three are needed to form a perfect jam gel. Sugar slurps up the water, while acid acts as a matchmaker between pectin molecules, allowing it to set up correctly. Some fruits have enough natural acid so they don’t need any added to the mixture. Other fruits always need added acid.

Which Fruits are Naturally High in Acid?

In addition to the following, all under-ripe fruits have more acid than their ripe or over-ripe counterparts.

• Cranberries
• Most citrus fruits
• Quince
• Rhubarb
• Pineapple
• Kiwi

Which Fruits are Naturally Low in Acid?

In addition to the following, all over-ripe fruits are lower in acid than their under-ripe or ripe counterparts.

• Sweet cherries
• Apricots
• Peaches
• Pears
• Figs
• Plums
• Nectarines

Which Fruits are in Between?

• Apples
• Most berries
• Mangoes
• Guavas
• Sweet oranges

How to Add Acid to Jam

When making jam, use a combination of some under-ripe fruit along with your ripe and over-ripe fruit.

If you are making jam from a low acid fruit, like peaches, be sure to add lemon juice or citric acid. Usually we add about 1 Tablespoon of lemon juice to each pound of fruit used in the batch. You can also use 1/8 teaspoon of powdered citric acid if you prefer – citric acid can usually be found at the health food store.

You could also use lime juice instead of lemon juice. However, lime juice adds flavor instead of enhancing flavor. I like to use lime juice when making mango jam or sweet cherry jam, as I enjoy the lime-fruit flavor combination. I would never use lime juice with peaches though, as it would overpower the delicate peach flavor.

What About Quick Cooking Recipes?

If you make quick cooking jams, you may notice that your recipe doesn’t call for added acid, even if you are making a low acid fruit jam. This is because commercial pectin often adds acid to the pectin itself, thus eliminating that step for you.

Jam Making Basics Series

Check out these other posts in this series

Jam Making Basics – What is Pectin?

Jam Making Basics – The Role of Sugar