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The Science of Pectin

By David Joachim and Andrew Schloss
From Fine Cooking #136, pp. 34-35

Pectin, a fiber that’s naturally abundant in such fruits as cranberries and quince, is the secret to beautifully gelled jams and jellies. Here’s a closer look at how it works and how to guarantee success when making fruit preserves at home.

What is pectin?
Pectin is the glue of the plant world. Consisting of long chains of polysaccharide molecules that bond together to form a gummy paste, pectin helps hold together the walls of plant cells, much as mortar holds up the bricks in a house. The pectin content in fruits varies depending on the type of fruit and the fruit’s ripeness.

You can also buy liquid or powdered pectin, which is made by extracting pectin from fruits. This commercial pectin can be used to thicken preserves made with low-pectin fruits, such as strawberries or peaches, or to make jellies from thin fruit juices. Food manufacturers use commercial pectin to make gummy candies and to improve the mouth-feel of low-fat yogurts and baked goods.

Are there different types of pectin?
Yes. There are two main types of commercial pectin on the market: HM (high methoxyl) and LM (low methoxyl). HM pectin is the most widely available, even though it isn’t always labeled as such. More often, you’ll see labels for the two subsets of HM pectin: rapid set and slow set.

Rapid-set pectin works best when you want to suspend solid ingredients within a jelly, while slow set works best for clear jellies made from clarified fruit juices such as grape juice. Pull out the LM pectin when you want to make low-sugar and no-sugar jams and jellies or to make no-cook freezer preserves. LM pectin is often labeled “light” or for “low sugar or no sugar recipes.”

How does pectin thicken preserves?
It depends on the type of commercial pectin you use. The pectin molecules in raw, uncut fruit have an alkaline negative charge, which causes them to repel each other and to bond with water. When fruit is chopped and cooked to make preserves, acids in the fruit are released. This acid neutralizes some of the negative charges, allowing the pectin molecules to repel each other less. In the case of preserves thickened with HM pectin, added sugar attracts water molecules, bringing the pectin chains closer together to form a loose, fluid matrix. As the mixture cools, it gels into a firmer mesh-like network that cradles and supports the liquid and dissolved sugar. To most of us, that firmed-up network is called jelly, but in chemistry, it’s called a sugar-acid-pectin gel because sugar and acid are required to bond and gel the molecules in HM pectin.

When you use LM pectin, sugar and acid don’t bind the pectin molecules together. Calcium does, which is why chemists call that type of gel a calcium gel. LM pectin packages often come with a pack of calcium powder that is added separately from the pectin to activate the gel.

What can go wrong with pectin-thickened preserves?
Using commercial pectin to thicken fruit preserves is pretty straightforward. You chop, mash, purée, or juice the fruit, add your pectin and other ingredients, and bring the mixture to a boil. Let it cool, and the mixture gels. But if you don’t have the ratios of acid, sugar, or calcium and pectin exactly right, your preserves may be thinner or thicker than you like. Because pectin cooks pretty quickly and won’t thicken if reheated, these problems usually can’t be fixed, but knowing what may have happened will help you avoid missteps the next time.

Preserves are too stiff. Usually, this happens when you use too much commercial pectin for the type of fruit you’re cooking. Different fruits contain different amounts of natural pectin, so you’ll need to add different amounts of commercial pectin to achieve the right consistency. For example, strawberries require two times more pectin to form a gel than tart apples, such as Granny Smiths. Some high-pectin fruits, like cranberries, may not need any added pectin at all.

Also, cooking preserves at too high a temperature or for too long at a low temperature can boil away too much water, which throws off the ratio of pectin to liquid and overthickens the mixture.

Preserves are too runny. There are several reasons this can happen:

  • Too little acid. Low-acid fruits, such as peaches and pears, usually require a little added citrus juice to gel properly when using HM pectin.
  • Too little pectin. Low-pectin fruits, like apricots, often require some added pectin to gel properly.
  • Too little sugar. If using HM pectin without enough sugar, the sugar-acid-pectin matrix can be too loose to hold the liquid.
  • Wrong type of pectin. Low-sugar preserves made with HM pectin will not form a supportive matrix. But you can make sugary preserves with LM pectin as long as calcium is present to activate the gel.
  • Undercooking. With HM pectin, the sugar-acid-pectin matrix has to boil for a full minute in order to set; if it doesn’t, a gel won’t form.
  • Overcooking. Boiling preserves beyond the gel point (longer than a few minutes) or uneven heat distribution from lack of stirring or a pot that’s too small can all cause pectin to break down.

Preserves are lumpy.  This happens when pectin isn’t evenly dispersed in the mixture, either because the powdered pectin isn’t fully dissolved before it’s heated with the fruit or because the preserves aren’t stirred adequately during cooking. To prevent lumpy preserves, you can use a blender to rapidly mix the pectin into the liquid before heating the mixture, or you can mix powdered pectin with other soluble powders like sugar before whisking them into the liquid ingredients.

Preserves are weepy. Preserves that leak water as they cool or during storage contain too much acid, which can make a pectin gel unstable.

High- vs. low-pectin fruit
Pectin levels peak as fruits ripen and become plump and firm. But in overripe fruit, the pectin begins to break down, and the fruit becomes very soft and eventually rots. Use ripe fruit to get the most pectin from it.

If you’re preserving a low-pectin fruit or fruit juice, a general rule is to add 4 tsp. powdered pectin or 2 Tbs. liquid pectin to gel 2 cups of liquid or finely chopped fruit. Keep in mind that fruit naturally high in pectin tends to be acidic as well, which helps the fruit gel on its own when cooked.

High Pectin Low Pectin
• Chile peppers
• Citrus peels (not flesh)
• Concord grapes
• Cranberries
• Currants
• Gooseberries
• Quince
• Sour plums
• Tart apples
• Tomatillos
• Tomatoes
• Apricots
• Blueberries
• Cherries
• Citrus flesh (not peels)
• Figs
• Melons
• Peaches/nectarines
• Pineapples
• Raspberries
• Rhubarb
• Strawberries
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  • laenen | 12/15/2019

    Is there a high quality pectin that someone would recommend?

  • Leapy | 10/23/2019

    No, a compote is simply the stewed puree of a fruit, apple, apricot, rhubarb, pear, plum, pineapple, etc etc with sugar added to taste.
    A compote is not a jam, or a jelly, so you are not trying to set it.
    A compote is a perfect way to preserve all types of fruit for later use. It is generally kept in sealed sterilised jars.
    No added pectin required!

  • Ak512 | 04/30/2018

    hi, so if i want to make a pineapple compote (juice from pineapple and pieces of pineapple with little sugar ) do i use a LM pectin?

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