Are fruit jams good for your health?

by Jennifer Bowden / 14 September, 2017

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Jams are about 65% sugar; in other words, each tablespoon contains about two teaspoons of sugar.

QUESTION: I recently made plum jam and guava jelly and am making a jelly using albany grapes. What nutritional value do these preserves have?

ANSWER: In centuries past, jams, jellies and fruit preserves were seen as a great way to store food. But are these high-sugar spreads still a good option in an era of ultra-processed foods and epidemic obesity?

Most harvested fruit has a short life and a relatively short season, so clever homemakers without refrigerated storage found ways to preserve surpluses, thereby creating an off-season source of delicious spreads.

The fruit in jams, jellies and preserves is conserved through boiling and the addition of a significant amount of sugar – typically in a 1:1 weight ratio. Boiling reduces the fruit’s water content and destroys potentially damaging micro-organisms, and the sugar binds to the water in the fruit, reducing the amount available for the growth of bugs.

In a roundabout way, we can thank Napoleon Bonaparte for the advent of canned (and jarred) foods. The British blockade of France during the Napoleonic Wars of the 19th century purportedly led French inventor Nicolas Appert to develop a process of preserving food through heating it in sealed jars. Food is placed in jars and heated to a temperature that destroys potentially destructive microbes. During heating, air is driven out of the jar, and as the food cools, a vacuum seal forms, preventing air and harmful bugs from getting back into the jar.

So why the historical rundown on jam preparation and canning? Well, it highlights two important nutritional points about jam: sugar and heat.

To meet official labelling requirements of jam, a preserve must be high in sugar. In fact, the Australia and New Zealand Food Standards Code requires that jams, by definition, contain no less than 650g of water-soluble solids (sugar is the major water-soluble solid in jam) per kilogram of product. And if it is sold as a specific fruit jam – for example, strawberry – it must contain no less than 400g of the specific fruit per kilogram.

So jams are about 65% sugar; in other words, every tablespoon contains about two teaspoons of sugar. In contrast, fresh fruit, such as berries, is about 10% sugar.

What’s more, preparation processes that involve high heat can cause nutrient losses, particularly to heat-sensitive vitamins such as vitamin C. As a result of these losses and the added sugar, one tablespoon of berry jam (weighing 15.6g) offers a mere 0.5mg of vitamin C, whereas a large strawberry (12g) has 5.5mg.

Historically, fruit jams and preserves have provided a useful and important source of energy and minor nutrients throughout the year. However, in this era of over-abundant food, much of which is processed and contains too few nutrients and too much sugar, the importance of jam in our diets has changed.

Although jam has some nutrients, the amounts are negligible compared with an equivalent weight of fresh or tinned fruit. What’s more, the quantity of added sugar makes jam more of a treat or occasional food. Fortunately, there are lower-sugar fruit preserves on the market (they can’t technically be called “jams”) and ways to make homemade jams with less sugar. So enjoy homemade jams and preserves, but if you’re looking for a good source of nutrients, eat whole fruit instead.

This article was first published in the August 5, 2017 issue of the New Zealand Listener.

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