One can prepare jam using pectin or lemon juice. My next experiment was to see myself what is the difference. Strawberry jam seemed like a good one to try it on as I have made quite a few jars of it while using pectin.
First of all, some research:
http://www.dianasdesserts.com/index.cfm/fuseaction/bakingtips.Jams/Jams.cfm – to sump up pectin is necessary for thickening or gel formation while acid must be present in sufficient amounts for a gel to form. If natural acid is lacking, lemon juice or citrus fruit is added. Commercial pectin products contain organic acids, like fumaric acid.
https://www.theguardian.com/science/blog/2013/oct/03/science-magic-jam-making – You can add commercial pectin, which is extracted from the white inner skin (the pith or “albedo”) of citrus fruits or from apples. You can also buy special jam sugars with added pectin. As a rough guide, the juice of a whole lemon (30-40ml) will be needed for very low acid fruit, whereas half a lemon will be enough for medium acid fruit, and you won’t need any for the high acid fruits. In general, fruit with high pectin will also have high acidity and vice versa.
http://foodpreservation.about.com/od/Preserves/a/High-And-Low-Pectin-Fruit.htm – High Pectin Fruits: apples, citrus rinds, crab apples, cranberries, currants, gooseberries, plums, grapes, quinces; Low Pectin Fruits: apricots, blueberries, cherries, elderberries, peaches, pears, pineapple, raspberries, strawberries
For my experiment only using lemon juice for thickening the jam I used:
– 2 cups of strawberries
– 1,5 cups of sugar
– 1 tbsp of lemon juice
And set my bread machine for jam function.
Overall, I found that using lemon juice makes the jam more liquid, but again it might be due to the reason that strawberries are low pectin fruit. Thus, I would say that for strawberry jam you should add some pectin.