Going to the grocery store, it could be challenging to decipher between buying jam or jelly. They both look the same, start with the letter ‘J’, and taste similar. So, what exactly sets them apart? Add chutney, preserves, conserves, and marmalades to the mix and your brain also starts to feel like an unidentifiable spreadable semi-solid. Here is what distinguishes them:
- Jam – pureed/mashed/chopped fruit + sugar
- Jelly – fruit juice + sugar
- Conserve – multiple fruit with added nuts and/or raisins + sugar
- Marmalade – fruit particles/peels suspended within a see-through gel
- Preserve – whole fruit preserved with sugar
- Chutney – fruit, vinegar, sugar, and spices that can either be made smooth or chunky and spicy or sweet
Now that we know the nomenclature of spreads, you could guess that the first two ingredients of this jam are pureed peaches and sugar. To bring this together, the final ingredient used was lemon juice. But, what happens between the time this liquid solution becomes a spread? This is a result achieved by the gelation of starch. The starch that thickens jam comes from within the cell walls of fruit (more specifically the middle lamellae). This substance is called pectin. There are two kinds of pectin, low methoxyl (LM) and high methoxyl (HM). LM pectin is characterized by having a degree of esterification (DE) less than 50%. HM pectin is characterized by having a DE of greater than 50%. The higher the DE, the greater the proportion of carboxyl groups present are esterified with methanol. I’m assuming that in this case while making jam we are manipulating the HM pectin because we use acid (lemon juice) and sucrose (table sugar) which activates HM pectin. LM pectin is activated with the addition of Ca++. The sugar prevents pectin from dissolving in water, which allows the starches to come together and thicken. The lemon juice, or acid, also aids in bringing the polysaccharides (pectins) together. So, as it would be expected, a decrease in water activity by the addition of sugar and acid and increase of polymer to polymer interactions result in the formation of a gel network.
Fun fact #7: Fruits that have a very high amount of pectin include apples and citrus fruit.
3-Ingredient Peach Jam
- 5 peaches (makes about 3 cups pureed)
- 1 1/2 cup sugar
- juice of 1 lemon
Add peaches, lemon juice, and sugar into a deep pan. Dissolve sugar and bring to a boil for about five minutes. Continue to cook for about 15 – 25 minutes, removing any white foam that may form on top. It is ready to be put into cleaned mason jars when it passes the spoon test. To perform the spoon test place a spoon in the jam, and watch how it falls off the spoon. If it comes off in a sheet, it is ready. If it drips off the spoon, continue to cook. Keep refrigerated for up to a week.