Acidity Level of Fruit in Jam and Jelly Preparation

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- Martha, why is the acidity of fruit important in making jam?

- The fruit contains natural components that influence the end product of the jam or jelly that you are making.

One of these is the acidity in the fruit.

Acid helps to extract the pectin from the fruit during the cooking process.

This helps to form a gel.

That will not take place unless the fruit is fairly acidic.

Acidity varies from fruit to fruit, and from some extent to the variety of a particular fruit.

For example, two different varieties of apples may have a different acidity.

Acidity is also lower in fruit that is past its prime or over-ripe.

- Martha, why do some recipes call for the addition of lemon juice?

- For fruits that are lower in acid, there needs to be some way of putting additional acid in.

This is often in the form of lemon juice.

It's frequently added with apricot or peach jam.

- Can you clarify?

Should I be using fresh lemon juice or bottled lemon juice?

- That's a very interesting question, in that, as you know, for canning tomatoes, we always say use bottled lemon juice because the acidity is consistent.

However, the recipes that come from the pectin manufacturers frequently will say use fresh lemon juice because it has a better flavor than the canned lemon juice.

In addition to lemon juice for acid, sometimes vinegar is added, as when you are making mint jelly.

Long cooking jams that are made without any added pectin frequently combine fruit flavors, taking a fruit that is naturally high in pectin, such as the apple, combining it with pear for a nice pear apple jam.

The two fruits complement each other to make a better set for your jam.

- Martha, which fruits are high in acid?

- The ones which tend to be higher in acid include things like your citrus fruits, as I mentioned the applies.

This is a quince.

It looks a little bit like a pear.

But it's a famous old-fashioned fruit.

Grapes are very high in pectin.

Regular plums, kiwi, pomegranate.

- Which fruits are low in acid?

- Well, that's when you get into some of your berries, your pears.

Figs are very low in acid.

They may even require longer processing time because of that.

Peaches and apricots, yes.

When you are using your fresh fruit, use research-tested recipes to determine if you need additional acid, and the amount that you need for a good jell.

We wish you lots of success in making your jams and jellies.