How Is Fruit preserved?


Preservation allows fruit to last much longer than its normal life. Fruit preserves include jam, jelly, conserve, compote, marmalade, and fruit butter. Though all preserves are very similar, the consistency and preservation process differ for each type.

Jam – crushed or chopped fruit spread, 47 parts weight fruit to 55 parts sugar

Jelly – smooth spread without pieces of fruit, strained for clear consistency, >55% fruit juice

Conserve – jam made from a mixture of fruits

Compote – fresh or dried fruit slowly cooked in syrup

Marmalade – soft jelly with pieces of fruit rind, more sour than normal jelly

Fruit butter – fruit cooked slowly to achieve a dense texture

Most preserves contain just four simple ingredients.

Fruit, the main ingredient, provides the flavor for the delicious jelly.


Sugar bonds with the water in the fruit and dehydrates the living cells. The dry environment prevents the growth of bacteria that causes fruit to spoil. Thicker jellies have more sugar and less water, which lengthens their shelf life.

The dehydration process is known as hydrolysis. At high temperatures, the sucrose reacts with water and breaks down into glucose and fructose.

Sucrose + Water -> Glucose + Sucrose

C12H22O11 + H2O -> C6H12O6 + C6H12O6


Notice that both products have the same empirical formula, but different structures, making them different sugars.

Moreover, pectin holds the jelly together. In the presence of acid and heat, this carbohydrate becomes a gel. The gel thickens the mixture, producing a jelly that properly sets when cooled. Furthermore, the rind of citrus fruit contains pectin, so most marmalades do not require additional pectin.

Lastly, acid aids the gelling process of the pectin. Additionally, it creates an acidic environment, which slows the growth of bacteria. The ideal pH of jelly is between 2.8 and 3.5.

Most fruit is preserved thermally. Heat kills bacteria and inactivates enzymes in the fruit that cause browning and softening. After it has been cooked, the mixture is transferred to clean containers and sealed. Popular in factories, canning protects the preserves in airtight containers, but glass mason jars and ramekins work perfectly for homemade jelly.


Ripe diced strawberries and sugar go into the pot.


Strain the lemon juice to avoid seeds in the jam.


The rind of the lemon provides enough pectin for the mixture to thicken.


Bring to a boil and mash the strawberries.


After 5 to 8 minutes of boiling, test the jam for doneness.  Drip the jam onto a frozen spoon, let cool, and run your finger through it.  If it leaves a clean line, the jam is ready!


Transfer to mason jars or adorable ramekins.



Strawberry Jam

2 ½ cups strawberries, diced

1 lemon

¼ cup sugar

A pinch of salt

Freeze 2 to 3 metal spoons.

Combine the fruit and sugar in a pot. Squeeze in the lemon juice and add the rind. Place over medium heat and mash the fruit to desired texture.

Bring the mixture to a boil and stir frequently.

After 5 minutes of boiling, check doneness by dripping the jam on the frozen spoon. Let cool for a couple of seconds and then run finger through jam. The jam is done when finger leaves a clear line.

Check for sweetness and add more sugar or lemon if necessary.

Remove from heat and spoon into a glass jar. Discard the lemon rind. Seal and refrigerate for up to 3 weeks.


Serious Eats

The Kitchn


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