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.

SUGAR, PECTIN AND ACID

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.

PICK THE RIGHT POT

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.