So why should you bother to spend an entire day over a hot stove waiting as the fruit slowly turns into mush? Jam is cheap and it can seem silly to can your own jams and sauces when you can buy it for $2 at the store. Well I do it mostly for the following reason: it’s the only way you can control how much sugar goes into your food.
Of course, jams are supposed to be sweet, in fact every recipe I read in my canning book asked for at least 500-700g of sugar (that’s 2-3 cups of sugar.) Yes, dear sir, that’s the as much as you would add in a cake. This goes for jams we buy in the stores as well, Smucker’s Strawberry Jam’s Nutrition Facts has 12g of sugar for every 20g (one teaspoon) of jam. In other words, 60% of the jam is sugar.