Jove wanted more canning specifics so I will share what I know about jelly as a first installment in Canning 101.
Yesterday, I cooked two batches of plums, adding no water, until they were translucent pulp, transferred pulp to a jelly bag, which in my case is really just a piece of fine mesh gauze, and hung it until all the juice had dripped. You can buy ready made devices and bags for this, but I would rather buy nice knives, All-Clad cookware, or dishes with my kitchen money.
What is important to remember is that if you want crystal clear jelly, don't be tempted to squeeze the bag or even manipulate it much. Sure, you waste a little juice, but if you want Blue Ribbon jelly don't do it! Once the juice is ready you may store it until later (up to 6 months in the freezer or a couple of days in the refrigerator) or begin jelly making immediately.
Before you start cooking the juice, assemble everything you need:
- More jars than you think you need because sometimes you miscalculate. Adding a cold jar to boiling water is dangerous and not sterilizing it is scary.
- The lids and rings or the tops, gaskets, and clamps
- A canning funnel. I prefer stainless steel everything, especially if doing acidic foods.
- A ladle, again, stainless steel.
- A spoon. At the risk of sounding like a broken record, stainless steel is preferred.
- A candy thermometer (only until you hear and see the correct temperature)
- A pot for cooking the juice. Choose a wide bottom stainless steel. You're right, I am a broken record.
- A wire rack or wooden cutting board to drain jars and cool the finished product.
Next measure your juice. Never be tempted to cook over 4 cups at a time unless you have an enormous shallow pot and a commercial stove. Experience speaks here!! Four cups of juice does not look like much in a big pot, but once sugar and heat are added the concoction expands. Plus, difficulty maintaining even heat throughout the pot without stirring adds further chaos to an overfilled pot.
Start heating the juice. When it simmers for about 5 minutes, skim off any frothy stuff that forms, then add the appropriate amount of sugar for the fruit. Start with amounts suggested in the Ball Blue Book or The Joy of Cooking. You can adjust to suit your taste or the ripeness of your fruit. Today, I used 3/4 cup sugar for every cup of juice. We like tart jelly and most of these plums were completely ripe.
Once the sugar is added stir using your stainless steel spoon until all the sugar is melted. Then raise the temperature and boil. Resist the temptation to stir now. It is fine to occasionally run the spoon around the bottom of the pan, but don't overdo it. Insert your thermometer, if you are using one. Don't leave the room! Again, experience speaks. You really only need to be making jelly when you are making jelly. Now is not the time for multi-tasking.
Watch and listen to the pot boiling as you watch your thermometer and you will only need a thermometer once. At first the juice/sugar mixture will expand until it looks as if it will erupt out of the pot. The surface will be covered with tiny bubbles (the second picture) and you will hear a faint and fast plip plip plip plip. As the mix is getting close to the gel stage (which is around 220 by the thermometer), the juice appears to shrink back into itself and the sound changes to a deeper, larger bubbled sound. Remove your jars and tools. Drain them on the rack. Insert your lids or gaskets in the hot (not boiling) water. When the juice takes on a thicker consistency and the bubbles make a slower gbluup, gbluup, gbluup, remove the pot from the fire. The jelly will quickly settle. Skim off any foam (lighter colored scummy stuff), then pour or ladle into jars. Apply the lids.
Many people don't use a hot water bath for hot pack jellies, but it makes me feel better to make sure I am not creating a petri dish in my pantry. Once the jars come to a boil and remain there 5 minutes, remove the pot from the fire and then set the jars out on the rack to cool. Listen for the pop of the jar sealing or watch for the tongue to droop.
You now should have Blue Ribbon worthy jelly.