Wholefood Cooking

Low Sugar Jam



I’m thinking jam. Tis the season with the berries and stone fruits harvesting.

We have become very accustomed to fruits available all the year round, but you will find they have nowhere near the same level of flavour. Fruits are fleeting, lasting only a few weeks, but there is a way to capture that moment — jam. But not jam as you might know it, but a spoonful of deliciousness that tastes like the fruit it is, with just enough sweetness to bring out it’s full flavour. A snapshot of the season in a jar. Now I am often asked can you make jam with something other than sugar, or less sugar and the answer is complex, and included below. So here it all is – as Wholefood Baking is currently out of print, I’ve put the recipe here for you. I promise you that once you know the hows, it’s very easy. But there are rules….

The only fruit to use is that which is ripe, preferably organic and in season. Fruits such as this are bursting with natural sweetness, colour with enormous complexity and luscious flavour. The jam (it’s a universal recipe) here relies less on sugar, and more so on technique to capture the true complexity and glory of fruit flavour — it is a snapshot of the fruit at its best and the season. Jams are very easy to make, and will store in the pantry for up to one year. On a cold winter’s day, when you take that batch of scones out of the oven, you will thank yourself for your stash of homemade jams and the colour and taste of summer will lift your spirits.

Technically, the object of preserving is to slow down the process of decay. Food spoils from the continued activity of natural enzymes in all fruits and vegetables and the continued work of microorganisms in the form of moulds, yeasts and bacteria present in the food and air.


Jam relies on sugar to saturate the natural moisture of the fruit and thus preserve it. I am often asked if something other than sugar can be used to make jam — the answer is complex. Many of the sugar-free jams you see are made with white grape juice concentrate, use pectin and have been processed in a boiling-water bath. Because there is not enough sucrose to saturate the fruit and preserve it (and this is true of many other non-sucrose based sweeteners, such as stevia, agave and brown rice syrup), the boiling-water bath is the preserving method. I prefer to use one of the semi-refined organic raw sugars (not rapadura, which is too low in sucrose and too strong in flavour)( I like to use the Billingtons Golden Castor Sugar)  in the smallest possible amount, this allows the glorious flavour of the fruit to shine through.  Most jam recipes call for equal quantities of sugar to fruit by weight. You need about 60–70 per cent sugar for good gelling to occur naturally (sugar, pectin, acidity). I find this way too much sugar and prefer a ratio of 20–40 per cent sugar to fruit, but this will vary with the fruit — tart fruit will require more, and sweet fruit will require less. Because the holy trinity of sugar, pectin and acid is disrupted, this will result in a softer ‘set’, which I happen to prefer.

Pectin is a carbohydrate that helps to ‘set’ jam. It is particularly concentrated in the skins and cores of fruit. The conversion of the pre-curser substances to pectin occurs naturally during ripening but can also be forced by long cooking, as in the traditional methods of making jam without added pectin. Fruits vary in how much pectin, or pectin pre-cursers, they contain. Pectin produces structure and a kind of stiffness in jam by forming a water-holding network within the crushed fruit. Before gelling starts, individual molecules of pectin are surrounded and isolated from each other by water molecules. If the surrounding solution is acidic enough, the pectin loses some of its attraction for these isolating water molecules. Sour fruit will normally provide enough acid to take care of this step. If the acid content of the fruit is low, lemon juice can be added to make the fruit mixture more acidic. Once the pectin has loosened its hold on the water molecules, something more attractive must pull the water away from the pectin — this is the role of sugar. With its water stripped away, pectin opens out into a structure that links readily with other pectin molecules to form a three- dimensional network — a gel.


Fruits with high natural pectin and acid content include:  blackberries + crab apples + cranberries + plums+ quinces+ sour apples

Fruits with low natural pectin and acid content include: apricots+ blueberries + figs+ grapes+ guava+ peaches+ pears+ prunes+ raspberries + rhubarb+ strawberries

Low-pectin fruits benefit from the addition of lemon, to boost the acidity and thus setting. Unripe fruit (sour) will also increase acidity. Jam is best made with a good percentage of fruit that is not overripe because as the fruit ripens, the pectin breaks down and you will not get a good set.


The right pot is critical to making low-sugar jam, I cannot stress this enough.  Mine is a traditional French copper preserving pan that is shallow and wide. It’s about 12 cm (41⁄2 inches) high, 36 cm (141⁄4 inches) across the base and 39 cm (151⁄2 inches) across the top, with a 10 litre (350 fl oz) capacity. The wide surface area encourages evaporation and reduction, thus cooking the jam quickly. It is extremely difficult to make jam in a deep pot with a small surface area — tall pans are a major cause of runny jam.

However, you can make smaller amounts in your average large domestic saucepan. You can use a simple stainless steel pan — just make sure it is not too deep. A wider and more shallow pan with less capacity (for example, a sauté pan with a 5 litre/ 175 fl oz capacity and a depth of 8 cm/31⁄4 inches) is better than a pot with a 10 litre/350 fl oz capacity, but a depth of 16–18 cm (61⁄4–7 inches), or even a frypan with a large shallow surface area. It will mean you can only make small amounts at a time — about 2 kg (4 lb 8 oz) of fruit, but your jam will be more successful. You can also use a 20–24 cm (8–91⁄2 inch) typical domestic saucepan, but keep the amount of fruit to 1 kg (2 lb 4 oz).

Never make jam in large quantities — another cause of runny jam — and never crowd your pan. How much fruit you use (the weight) will depend on the size of your pan — for mine, I use 4 kg (9 lb). A good guide is to only fill your pan two-thirds full of fruit.


Always use tempered jars that can withstand the temperatures involved in sterilising, jam-making and storage. Some jars manufactured for products such as coffee, peanut butter and mayonnaise are not tempered and do not have strong seals on the lids. Jars must not be cracked, chipped or damaged in any way, and lids must not be scratched or dented. Jars can be re-used, but lids are good for one use only.


Your jars, lids, ladles and funnels must all be sterilised. This is easy to do in an oven at 120°C (235°F/Gas 1⁄2) for 20 minutes. Jars and lids must be sterilised, dry and warm. Once sterilised, turn the oven off and leave in the warm oven until the jam is ready. Equipment can also be boiled for 12 minutes in a large saucepan of water, then dried in the oven at a low temperature.


Bottling technique is the other very important part of making low-sugar jams — the jam must be spooned with a sterilised ladle through a sterilised funnel into warm jars (as hot jam into cool or cold jars will cause the jars to break) as soon as it is ready. Make sure the sterilised jars are warm (from sterilising and then being kept warm in the oven) and sit them on a wooden surface or on towels (so they don’t crack when the hot jam is added). This process will ensure the jars seal properly and that the jam does not spoil.

After ladling the jam into the jars, make sure there is no spillage as this will hinder a seal being formed. Gently wipe any spillage, taking care not to touch the sterilised lip of the jar. Place the lids on, taking care to touch only the outside of the lids. Holding the jars with a damp cloth (for a good grip), turn the lids until firm.

Let the jars sit until fully cool — do not move them for 12 hours or you can disrupt the vacuum process. A concave dip in the middle of the lid indicates a vacuum seal. If there is no concave dip, store the jam in the fridge and use straight away.

Once opened and the seal is broken, the jam begins to deteriorate and must be kept in the fridge.


The beautiful photo at the top of this post is ©Cath Muscat and all copy is ©Jude Blereau and Murdoch Books, and taken from Wholefood Baking. Published by Murdoch Books, 2013.

My Universal Low Sugar Jam


4 kg (9 lb) fruit (weighed whole)
800 g (1 lb 12 oz) (20% ratio) to 1.6 kg (3 lb 8 oz) (40% ratio) semi refined raw sugar - I use the Billingtons Golden Castor Sugar
1 medium lemon, skin on, cut into 8 bits

Jam made from 4 kg (9 lb) fruit with 30 per cent sugar in a 10 litre (350 fl oz) jam pot (with the dimensions described ) will take about 1 hour from beginning to end. Using 1 kg (2 lb 4 oz) fruit in a smaller 20–24 cm (8–91⁄2 inch) saucepan will take about 45 minutes.

This is how I make jam, but you can equally cut the fruit up and macerate it with the sugar overnight — this will give you a quicker cooking time the day after. If doing so, stage 1 will happen very quickly.

The technique described here is not suitable for preserving jam made without sugar, or jams made with vegetables, fish or animal products as these products are too low in acid and need to be processed appropriately in a boiling-water bath to eliminate the risk of botulism.

You may be concerned that weighing fruits with stones in will ultimately end up weighing less (and thus ultimately will result in a higher ratio of sugar). I don’t worry about this, as I only start with 20% (800 g) and adjust it from there. The finished ratio of sugar will most often sit somewhere between 25 and 30%, no matter how your fruit started out.


Preheat the oven to 120°C (235°F/Gas 1⁄2).
Sterilise your jars and lids (opposite), place on a baking tray lined with a clean tea towel and keep warm in a low oven.
Wash the fruit (there is no need to dry it) and cut into smaller portions. Discard any stones (as in apricots, et cetera). As a general guide, leave blueberries and small strawberries whole, but chop larger strawberries; cut apricots and plums into halves or quarters; and cut figs into quarters or smaller segments. Place the fruit in your jam pot, together with the sugar and lemon and gently stir the sugar through.

Stage 1 

Place the pot over very low heat, allowing the sugar to dissolve — this takes about 15 minutes, or a bit longer, depending on the size of your pot.

Stage 2

Once the sugar is visibly starting to dissolve, increase the heat slightly until you see a gentle bubbling. Stir frequently. It is at this stage you taste and add sugar as needed. Continue to cook for 15 minutes (or longer if using a deeper pan) — the juices will have weeped out from the fruit, thus increasing the amount of liquid in the pot.

Stage 3

Increase the heat to very high and boil until a ‘set’ is achieved. As you are now cooking at a high boil, you need to stir frequently to check the feel of the jam and to make sure it isn’t

sticking to the base (wearing a long-sleeved shirt is good here). As the jam reduces, it will thicken. You may need to reduce the heat to a slower boil as the jam thickens but keep stirring frequently. This stage should take about 30 minutes, but the deeper the pot, the longer it will take. It should take about 10 minutes if using a small 1 kg amount.

Set is generally considered to occur when the jam reaches 105°C (221°F) for a 60% sugar jam. But this doesn’t hold for low-sugar jams, where the relationship between sugar, acid and pectin has been disrupted (neither does it hold at a higher altitude, where set point can be at considerably lower temperature). You need to rely on other techniques to judge when your jam is ready. I go by appearance and ‘feel’ and cook the jam until it is fairly thick. The bubbles also, become more volcanic and flat. Placing a small amount of jam on a saucer or dish and chilling it is another good method for checking the consistency: when cool, run your finger through the middle — you want to see a clear line of plate underneath. Any juices that flow into the line should look like lovely liquid jam, and not at all watery, and should have body.

If you are sterilising by boiling, about 30 minutes before your jam is ready, bring a large pan of water to the boil, or place in the oven as described on page 270. Sterilise your funnel and ladle by boiling for 12 minutes. While they are boiling, remove the jars and lids from the oven, keeping them on their trays. Remove the funnel and ladle from the boiling water and shake a little to remove the water, allowing the air to dry them off. As soon as the jam is ready, ladle the warm jam through the funnel, into the warm jars. Seal the lids tightly, then leave to sit until totally cool. There should be a concave dent in the middle of the lid; if there isn’t, store the jam in the fridge and use it straight away — never a hard thing to do.