I was recently asked how to measure the pectin content in fruit. It's not the sort of question I'm called on to answer very often these days, but it just so happens that I was asked it many years ago.
The occasion was a radio quiz when the headquarters of the 4YA and 4ZA radio stations were situated in Tay St, now long absorbed into the SIT campus and remembered only by us "mature" Southlanders.
I knew the answer to the question thanks to a very young Alison Holst, who had imparted this information in her first cookbook, which I still own and still refer to from time to time.
If you need to measure the pectin content of any fruit, just cook a small quantity, then place a teaspoon of the resulting cooled liquid in a jar with two tablespoons of methylated spirits then gently shake.
After a while, a clot will form. The bigger the clot, the higher the pectin, and the higher the pectin, the better the set of the jam or jelly.
Strawberries, on their own or as part of a jam mix, as in today's recipe, are low in pectin and need a helping hand to set when made into jams or conserves; hence the addition of tartaric acid.
Lemon juice will add acidity, but to be honest, I never get satisfactory strawberry jam without tartaric acid (a natural product derived from certain plants). There are other setting agents on the market, including pectin-infused sugar, but for economy and sheer convenience, tartaric acid gets my vote.
Occasionally I have made my own pectin by simmering very green, immature apples and then straining off the juice and freezing it in small containers. I add it to berry jams and jellies.
My cherry berry jam came about because of Christmas Day leftovers.
The strawberries and blueberries together weighed 800 grams, and I made up the extra 200g with stoned cherries. The resulting jam has great colour and flavour - and it set beautifully.
Today's recipe is ideal for those who grow strawberries and have small quantities on hand. As long as the assorted fruit weighs about 1kg, the recipe will serve you well.
CHERRY BERRY JAM (makes 5-6 small jars)
1kg mixed berries
Juice of 1 lemon
6 cups sugar
1 tsp tartaric acid
Method: Place the berries and lemon juice in a large pan.
Crush the berries lightly to produce a little juice.
Bring to the boil slowly, stirring from time to time.
Add the sugar, stir and bring back to the boil.
Cook for 5-7 minutes, then add the tartaric acid.
Continue to cook for a further 5 minutes.
Remove from the heat and add a small knob of butter to disperse any scum.
Spoon the jam into jars and seal with cellophane covers. Store in a cool, dark place.
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