Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: thedoc on 15/08/2012 13:27:51

Title: What makes jam set, or not?
Post by: thedoc on 15/08/2012 13:27:51

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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Title: Re: What makes jam set, or not?
Post by: RD on 14/07/2012 14:57:36

Quote from: thedoc on 14/07/2012 14:30:02

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

peaches are not acidic, like say raspberries (http://www.cooks.com/rec/view/0,1923,144183-255194,00.html), so need extra acid ...

Quote

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

Quote

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