Some jam recipes don’t require more than 300g of added sugar per kilo of fruit. I tried one with plums, tasted the result and thought about the potential benefits of such a recipe with regards to sugar intake, food miles and food self-provisioning.

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Experimenting with the recipe

On the lookout for fruit to make jam for family and friends on a Saturday morning in South-West France, I found ‘plums for jam’ crates on a farmers’ market stall. The greengrocer told me that they were very ripe. Indeed, the plums were quite sweet.

The five kilos of Reine Claude plums I bought on 14 September in Arcachon on the South-West coast of France. The plums were coming from the Lot et Garonne district. Photo 14 September.

We started up a conversation. I said I wouldn’t use as much sugar as usual to make the jam. He replied: “300 grams per kilo maximum”. I was surprised. When the fruit is particularly sweet, I add 600 to 700 grams of sugar per kilo of fruit rather than my usual 750 to 800.

“300 grams per kilo? That’s very little”, I said.

“Oh yes, that’s the way we do it. It’s an old recipe from my grandmother. You add the sugar and you cook the jam for three hours on a very gentle heat. Two and a half hours to three hours. It will keep for years.”

I didn’t know jam could be cooked for such a long time. I was determined to try it out.

I had brought my large jam pan from Aurillac, so I had my tools. I realised I couldn’t use the pan, as it was incompatible with the induction cooking hob, but found another way. I made several batches using a smaller one I found in the house. It was even better, as I was able to test several recipes and compare the results.

The tools I used. From left to right: a jar filling cup, a second hand jar, a scale, a fruit juicer for the lemon, a spoon to stir the jam, a dented knife to split the plums, a ladle to fill the jars, a board to split the lemon, the house’s pan, various cups for convenient handling of fruit and sugar.

I made three batches of jam. I used two kilos of fruit for the greengrocer’s recipe and two kilos for my usual recipe (adding 600g of sugar and cooking the jam on a high heat for about ten minutes).  The remaining kilo enabled me to address another question, that of the lemon juice. I thought people didn’t add lemon juice in the olden days, because lemons were not that common and their role in contributing to making the jam set was possibly unknown. I decided not to add lemon juice to the one kilo batch. Then I could compare jam made with and without lemon juice.

Here is the process I went through.

After quickly rinsing the plums in cold water, I split them in two with the dented knife, an efficient way of cutting the skin, to make stone removal easier.

I added the 300g sugar per kilo to the net fruit weight…

… and the juice of half a lemon per kilo of fruit. I put the pan on the heat without delay.

I prepared the second batch (left), one kilo with 300g added sugar and without lemon juice while the first one was cooking. After two hours on the hob on a low heat, a lot of water had evaporated from the lightly simmering first batch, now of a brownish gold colour.

Two hours and a half. This is how long it took for the batch with lemon juice to get to the right level of thickness, comparable to what I obtain with my usual plum jam recipe. Surprisingly enough, it took less long to cook the second batch. I can see two explanations: first, adding lemon adds liquid, which has to evaporate. Second, and more importantly I think, evaporation is a function of volume and surface. With a smaller volume in the one kilo batch without lemon juice, the water evaporated faster because the surface area to volume ratio was higher. There is a lesson here for jam makers who want to cook their jam as quickly as possible: use wide pans.

In terms of texture, the two batches were very similar, thick but not set, like my usual plum jam. Taste-wise, the acidity brought by the lemon juice was noticeable, but the difference was small. What stood out was how concentrated the taste of plum was in both cases.

The third batch, made with 600g of added sugar per kilo, unsurprisingly tasted sweeter, probably too sweet for people who have come into the habit of eating less sugar. The first two batches were the winners, with a sweet and pleasant taste very different from the runny and too acidic low-sugar plum jams I had tried in the past.

What can be learnt from the experiment?

Taste, sugar intake, food miles and self-provisioning

I would argue that there is a case for revisiting our home-made jam recipes for fruit that do not need a lot of added sugar, such as plums, to make a classic jam, a sweet one that keeps for years.

Cooking for two to three hours over a low heat enables to obtain the expected outcome: evaporation allows for the concentration of the sugars naturally present in the fruit and ensures both sweetness and long conservation. The result? A great jam with an intense taste compared to what is available in the trade. Still too sweet for someone with a low-sugar diet I would say, but great.

With regards to food miles, less added sugar and no lemon juice means less quantities of food products transported over long distances. If on top of this the fruit is produced locally, for instance in the jam maker’s own garden, it starts to make a real difference. An incentive for garden owners to plant more fruit trees and develop food self-provisioning? Another advantage of this recipe is that the jam keeps for years, which means that people can stock up during productive years.

I would like to test this low-sugar/long-cooking recipe with apples, pears, apricots, peaches… I remember a jar of apple jam I was given which had probably been prepared with this kind of recipe. It was delicious, with slightly candied morsels. It was obvious it had been cooked for a long time. I am glad I met this greengrocer. His grandmother’s recipe may substantially influence the way I make some of my jams in the future, as much for environmental reasons as for gastronomical ones.