FRUIT AND VEGETABLES: FRUIT PRESERVES
Diagram
Three preserves from fruit, sugar and pectin
Jam
Crushed or chopped whole fruit, cooked with sugar. The fruit pulp stays in the jar, so jam is opaque and spoonable.
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Jelly
Strained fruit juice only, cooked with sugar. No pulp, so jelly is clear and firm.
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Marmalade
Citrus fruit with peel shreds, cooked with sugar. The peel gives a bitter note and a chewy texture.
Figure 1: Jam uses crushed fruit, jelly uses strained juice, and marmalade uses citrus with peel. Drawn in our own style from Barrett, Somogyi and Ramaswamy, Processing Fruits, chapter 6 on fruit preserves and jams, and Chenoweth, How to Preserve Food, sections on jams, jelly making, and conserves and marmalades. Note: the Chenoweth source is from 1945, so the modern Barrett chapter is the main source here.
Introduction
Jam, jelly and marmalade are all fruit preserves in jars, and all three are made from fruit, sugar and pectin, but they use different parts of the fruit. Jam uses crushed or chopped whole fruit, so the pulp stays in the jar. Jelly uses strained fruit juice only, so no pulp is left and the preserve is clear. Marmalade uses citrus fruit with peel shreds, so the peel gives a bitter note and a chewy texture. The fruit part used is the difference, and it decides the look, the texture and the taste.
Barrett, Somogyi and Ramaswamy give a chapter to fruit preserves and jams, and Chenoweth gives separate sections to jams, jelly making, and conserves and marmalades. This article follows those two books, with the modern Barrett chapter as the main source.
Quick comparison
Table 1: Jam compared with jelly and marmalade
| Aspect | Jam | Jelly | Marmalade |
|---|---|---|---|
| Fruit part used | Crushed or chopped whole fruit | Strained fruit juice only | Citrus fruit with peel shreds |
| Pulp | Pulp stays in the jar | No pulp | Pulp and peel shreds stay in the jar |
| Look | Opaque, with visible fruit | Clear and transparent | Translucent, with visible peel shreds |
| Texture | Soft, spoonable, spreads with fruit pieces | Firm, smooth, holds its shape and cuts cleanly | Soft set with chewy peel pieces |
| Fruit used | Many fruits: strawberry, apricot, plum, raspberry | Fruits with clear juice: grape, apple, currant | Citrus fruits: orange, lemon, grapefruit |
| Sugar and pectin | Sugar and pectin set the fruit pulp | Sugar and pectin set the juice | Sugar and pectin set the fruit and peel |
| Acid | Acid from the fruit helps the set | Acid from the juice helps the set | Acid from the citrus helps the set |
| Flavour | Sweet, with the full flavour of the fruit | Sweet, with a clean juice flavour | Sweet and bitter, from the peel |
| Preparation | Fruit is crushed or chopped, then cooked with sugar | Juice is strained from cooked fruit, then cooked with sugar | Citrus is sliced, peel is shredded, then cooked with sugar |
| Use | Spread on bread, filling for cakes and pastries | Spread on bread, glaze for pastries and meats | Spread on bread and toast, served with meat and cheese |
Scientific explanation
Definition
Jam is a preserve made from crushed or chopped whole fruit cooked with sugar, so the fruit pulp stays in the jar and the preserve is opaque. Jelly is a preserve made from strained fruit juice cooked with sugar, so no pulp is left and the preserve is clear and firm. Marmalade is a preserve made from citrus fruit cooked with sugar, with peel shreds in the jar, so the preserve is translucent with visible peel and has a bitter note from the peel.
Working principle
All three set because pectin, sugar and acid form a network that traps water and fruit. In jam, the network holds the crushed fruit pulp, so the preserve is soft and spoonable. In jelly, the network holds only juice, so the preserve is clear and firm and cuts cleanly. In marmalade, the network holds citrus pulp and peel shreds, and the peel, which is rich in pectin, helps the set while its bitter oils give the flavour. Cooking drives off water, concentrates the sugar, and lets the pectin set as the preserve cools.
Apparatus
The books used here name no laboratory apparatus for telling the two apart, so no apparatus list is given.
Measurement procedure
The books used here name no single standard laboratory procedure for telling the three apart. The distinction is made from the fruit part used and from the look of the finished preserve: pulp means jam, clear juice means jelly, and citrus peel shreds mean marmalade. The setting point is judged in making by the sheet test and by temperature, as the preserving books describe, but the books give no worked calculation with numbers for this comparison, so none is given.
Factors affecting readings
Fruit ripeness changes the natural pectin and acid in the fruit. Sugar level and acidity decide whether the pectin sets. Cooking time changes the texture: too short and the preserve does not set, too long and it darkens and the flavour dulls. Peel thickness changes the texture of marmalade.
Formulas and calculations
The books used here give no formula for this comparison, so no formula or worked calculation is given.
Industrial applications
- Jam is used as a spread on bread and as a filling for cakes and pastries.
- Jelly is used as a spread and as a glaze for pastries and meats.
- Marmalade is used as a spread on toast and served with meat and cheese.
- Jam is used in yoghurt, desserts and sauces.
- Jelly is used where a clear, firm set is wanted, as in a glaze.
Advantages and limitations
- Jam: advantage: keeps the whole fruit, with its full flavour and texture. Limitation: opaque, so it cannot give a clear glaze.
- Jelly: advantage: clear and firm, so it cuts cleanly and glazes well. Limitation: loses the pulp and some of the fruit character.
- Marmalade: advantage: the peel gives a bitter note and a chewy texture that jam and jelly do not have. Limitation: the bitter peel is not to every taste, and it suits citrus fruit only.
FAQ
What is the difference between jam and jelly?
Jam uses crushed whole fruit, so the pulp stays in the jar, while jelly uses strained juice only, so it is clear.
Is marmalade a kind of jam?
It is a citrus preserve with peel shreds, so it is like a jam, but the peel and the bitter note make it its own kind.
Why is jelly clear?
Because it is made from strained juice with no pulp, so light passes through the set preserve.
Can any fruit make jelly?
No. The fruit must give a clear juice with enough pectin and acid to set, as grape, apple and currant do.
