It will break the gel if you do that. It has to be hot to go into the jars.
Strawberry does that unless you let it sit for about 5 min. then stir, and put into the jars and process.

To re-process you'll have to open all the jars, re-heat the jam and re-bottle in clean hot jars with new lids.

The separation is happening because the berries are not fully saturated with the sugar syrup and they're lighter, so they float.

As Linda Lou implied when she mentioned breaking the gel, there is a risk that the re-cooked jam will not set again.

Carol

Most recipients of homemade jam do not care if it is not perfect; they are just pleased to have something tasty and handmade. You could tell them to stir it after opening, if someone should ask.

Next time you make strawberry jam heat the berries and sugar, cover and let sit overnight then finish processing the next day. They will have more time to absorb the syrup and usually will not have floaters. I use this technique for all my fruit jams - all types of berries, cherries, figs, peaches, etc. where there are bits of fruit. Those fruits that break down easily or have been pureed or went through a food mill do not seem to have the floating fruit problem so I just process the normal way.

Hope this helps.

Nancy

Suzie - If you have a food processor, next time try running half your fruit thru to a fine cut and the other half to a chunkier cut. I do that regularly to help with the "floating fruit" problem.
I used to do the overnight in the fridge but got to the point where I didn't want to reheat and wait until the next day. This is still a very viable alternative however with those fruits that have a lot of air in the fruit tissue (and strawberries are one of the worst).
Jim in So Calif