With growers telling us the British strawberry season may run into December, it makes sense to turn some of the fruit into jam...or should I say conserve, since that is what you will see on most labels these days.

Traditionally, a conserve refers to a mixture of fruits; however, it now implies a certain cachet humble “jam” lacks. Of course, most of us won’t make our own, because the supermarket shelves are stacked with it, so why bother? Well, one good reason is you know what goes into it.

What is in commercially made strawberry jam? While our grandmothers’ recipes suggest roughly half fruit and half sugar, commercial jams only have to contain 350g per kilo by law, ie, 35g per 100g. Some, particularly those reduced in sugar, contain water, sweeteners, glucose syrups and preservatives.

However, there are a number of high-quality jams, such as Duchy Original, Wilkin & Sons, Frank Cooper’s and Bonne Maman, with a high ratio of fruit – between 50g and 60g per 100g.

Isn't strawberry jam difficult to make at home? It can be, because strawberries are notoriously low in the natural setting agent pectin, which is why commercial jams add more. Christine Huddleston makes a strawberry and rose petal jam with whole fruit and fresh lemon juice, which supplies the pectin; however, she says she sometimes needs to add a little extra. “A brilliant way to solve the problem is to substitute a quarter of the fruit with cranberries, which are full of pectin,” she says. “The jam will be a little sharper, but lovely.”

Otherwise, these are her tips: “Put the whole strawberries in a pan with a little water, and simmer until they are soft. Old-fashioned preserving pans are best because they help evaporation. Slightly crush the berries with a potato masher for a nicer texture. For 6kg of strawberries use 6.5kg of sugar, and about 80ml of lemon juice (this might still be a soft set, so use jam sugar, which has pectin in it, and reduce the lemon juice to 30ml). Bring to the boil for about 2-3 minutes; that’s all.

Do the wrinkle test: put a spoonful on a plate that has been in the freezer, then put it into the fridge for a couple of minutes. Run your finger through it and if it wrinkles it will set. If it doesn’t, boil it a little longer, and if necessary add more sugar. If it is too sweet, add more lemon. A pinch of cinnamon can help, too. When you are happy, briefly rest the jam in the pan with the lid on before stirring and potting into sterilised jars. This helps to stop the fruit floating to the top.”

Where to buy: Strawberry and rose petals conserve, £3.30, Mrs Huddleston’s (01296 712005; www.mrshuddleston.com). Strawberry jam, Forman & Field, £3.50 (www.formanandfield.com).

Readers’ queries

Where can I order interesting savoury tarts for picnics?

The Metfield Bakery has a wide selection, from Cromer crab and samphire to goat’s cheese, wilted spinach and garlic. Prices start from £5.90 for two individual tarts to £30 for 10-12 people (01362 695340; www.metfieldbakery.com ).

If you have a food query, e-mail food.detective@thetimes.co.uk

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