So here is my plan. Instead of buying sugar free artificially sweetened jam or reduced sugar jelly made with extra water and thickeners, I want to take really good full-of-fruit preserves, heat it up and add my own water and thickener. I was thinking of using potato starch. Any thoughts?

Update My goal is to reduce sugar consumption without buying artificially sweetened preserves or expensive commercially diluted preparations. My thought was to buy some really good preserves and do the dilution myself. I tried it with corn starch but it didn't thicken.

  • 1
    I don't understand your question (which is about thickening jam), because in your explanation, you suggest thickening fruit preserves. Why do you want to thicken fruit preserves? Isn't it already pretty thick...jam-like?
    – moscafj
    Mar 15, 2016 at 16:43
  • I also don't understand what you are trying to make here. Are you looking for something shelf-stable, or a perishable food? Is your goal to have as high as fruit content as possible, and if yes, why are you considering diluting the preserves? Or what is it you are trying to achieve?
    – rumtscho
    Mar 15, 2016 at 16:54
  • 1
    I suspect that they're trying to reduce the sugar in existing preserves by thinning it, but they want to maintain a jam-like consistency.
    – Joe
    Mar 15, 2016 at 17:31
  • @Joe, that is what i am trying to achieve
    – bracha
    Mar 15, 2016 at 18:22
  • 1
    It's nice that you came back to clarify! The edit function does not make it necessary to delete everything, it's better to keep the old information in, because many other people won't have seen it. Just add the new stuff, or improve the old so that it still makes sense for somebody who sees the whole thing for the first time. I combined your two versions as an example.
    – rumtscho
    Mar 15, 2016 at 18:42

2 Answers 2


OK, to clear up some things here. The first thing: whatever you do, you will not have a shelf-stable product you can keep in the pantry. If you want to make that, you will have to follow a known-safe recipe with sufficient acid and sufficient sugar and proper canning procedures. It will still have lots of sugar though.

Let's assume that you don't need something shelf-stable, just a fruit preparation with little sugar in it. The expensive commercial "low sugar" jams are not diluted at all. They simply contain much more fruit than the others. So there is no way you can replicate them by starting with high sugar commercial jam.

So your options are:

  1. Cook jam from scratch to the consistency you want. High-sugar recipes are shelf stable, mid-sugar ones need refrigeration once opened, low-sugar ones only hold for a few days in the fridge. Here you have to use the thickener suggested in your recipe.

  2. Don't make jam from the fruit. If you want very little sugar and have to give up the convenience of preserving the whole thing, just use fresh fruit puree.

  3. Eat commercial low-sugar jam with something else. OK, you can in principle cook a water-based pudding (that's what starch+water makes) and add the jam, but it is probably tastier to add it to pudding made with milk, or to yoghurt.

You cannot really reprocess commercial jam well. It is thickened with pectin, which cannot be re-thickened after heating. It is also sensitive to the amount of sugar and acid, so adding more pectin and water will probably produce something weird. And in the end, if you find some thickener which produces a texture you like, the product will neither be as shelf stable as proper jam, nor as sweet as proper jam, which for most people would not be worth the effort. If you really want to try, pectin should be the thickener to go.


I would suggest you use Agar as your thickener. Finding the right proportion will take some experimenting, as too much will create a jell-o like consistency.

Food grade agar can be purchased online or in an Asian grocery store.

Potato starch would probably give it a consistency more like a sauce & would make it taste & feel starchy.

Note that I do agree with the comments made previously; I'm not sure why you need a thickener to begin with, but if you do, I'd suggest agar.

  • Agar doesn't work as well wtih acidic foods : "Agar does not hydrate well in acidic liquids, making gelling difficult. To get around this issue, first hydrate the agar in a neutral liquid and then add it to the acidic liquid." ; "The gelling ability of agar is affected by the acidity or alkalinity of the ingredients it is mixed with. More acidic foods, such as citrus fruits, kiwi and strawberries, may require higher amounts of agar."
    – Joe
    Mar 15, 2016 at 19:02
  • Yeah, I've done it before with a pineapple based 'energy gel'. Joe is right, if you decide to go this route, it may take more than the packages recommended amounts.
    – renesis
    Mar 15, 2016 at 19:50

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