Without a carbohydrate called pectin, jam would just be sweet fruit juice and jelly beans would be colourful piles of sugary powder. Pectin is found in the cell walls of all plants, and is present in higher levels in certain fruit, such as apples and citrus fruits, with most pectin located under the peel. It is broken down as fruit ripens, leading to softer fruit. Pectin makes up 0.4% of a cherry’s weight, 1% of an apple’s, and 30% of citrus peel’s.
Jam making involves the stewing of fruit and sugar – at high temperatures, acid and pectin from the fruit react with each other, and the pectin makes everything stick together. Sugar increases this gelling ability. If the fruit is not acidic enough, then lemon juice can be added to the mix; if the fruits (such as berries) don’t contain enough pectin, this too can be added, in powder form, or in the form of a few apple peels (which can be removed before jarring). Once this mix reaches the setting point of 105°C (220°F), this chemical reaction is complete and the jam can be poured into sterilised jars and sealed.
Not a lot of shop-bought jam “measures up to home-made jam,” which “adds that touch of luxury to everyday eating.” It really is so easy to make, in any fruit combination you fancy, and it’s a great dinner party gift. In these times of convenience, receiving something home-made is as rare and unexpected as a tax rebate. And home-made always tastes sweeter.