Why should jam contain a mixture of sucrose and invert sugar?

I just made strawberry jam last night. And it is phenomenal.

Now to answer your question: it doesn't have to. Invert sugar is fructose (found naturally in fruit) mixes with heat and sucrose to produce the same chemical reaction for invert sugar or sugar syrup.

I find that the quality of the ingredients really is what gives you a good product.

Pick your own fruit if you can. Use fresh not frozen. Use a basic table sugar. And you need pectin. Some say it is an exact science, but then again, I never follow anything exactly.

For a good flavor and not overly sweet but delicious taste, I use equal parts of fruit MASH and sugar. 1:1 cup ratio and for every cup, add a tablespoon of pectin (if you are using Ball canning pectin) This is a reduced sugar recipe compared to the directions. But just give it a try. Make sure you cook it long enough to where it congeals quickly when taken away from heat. And get rid of the foam.

Read more posts and do a little more research if you still feel unsure. Or post with other questions.