[thedoc (OP)]

I make jam at home, and the recipes I use are always very specific about the amount of sugar and fruit to be combined with the pectin.

While attempting to make jam a few weeks ago, I was short 1/2 a cup of fruit, but decided to go for it anyways.

Unfortunately, it never set, and is more of a peach sauce than a jam. Why is this?
Asked by Molly C


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[RD]

Unfortunately, it never set, and is more of a peach sauce than a jam. Why is this?

peaches are not acidic, like say raspberries, so need extra acid ...

Acid in fruit is required to form the gel. In some jam recipes additional acid is required for a proper set. Lemon juice is an example of an added acid.

http://www.kraftcanada.com/en/cooking-tips/tipstechniques/jammaking/roleofpectinandacid.aspx

PEACH JAM WITH PECTIN   
4 c. (960 mL) peeled peaches
3 to 4 tsp. (15-20 mL) liquid artificial sweetener
1 tbsp. (15 mL) unsweetened lemon juice
1/2 tsp. (2.5 mL) ascorbic acid
1 3/4 oz. (21 g) pkg. powdered fruit pectin

http://www.cooks.com/rec/view/0,1723,157165-239195,00.html