Michigan State University Extension
Preserving Food Safely - 01600551
Use reliable recipes with detailed instructions. Recipes that come with liquid or powdered pectin products are reliable as are the recipes in the recipe section of this database.
FOLLOW INSTRUCTIONS CAREFULLY. If the recipe says to "boil hard for one minute," use a clock.
MEASURE THE INGREDIENTS CAREFULLY. Remember -- fruit, pectin, acid and sugar have to be present in the right amounts for jelly or jam to "set up."
NEVER CUT DOWN ON THE AMOUNT OF SUGAR. It takes a lot of sugar for a gel to be formed. If you use less, you'll wind up with syrup.
NEVER DOUBLE A RECIPE. If a double batch of jelly or jam is cooked for the usual time, it will be undercooked; thejelly or jam will be soft and runny. If boiled longer, it will have a caramelized flavor and dark color.