Jam/Jelly/Preserve recipes are infuriatingly robotic. "Use one package of this specific pectin-product, exactly this much fruit, precisely this much sugar, no more and no less of this much lemon juice. If you don't, Doom Will Befall You!" One is expected to be a Good Little Housewife and just follow the instructions. No getting creative! It's not allowed!
Fortunately, over the years, I have found various bits and pieces of information that provide clues to the desperately needed "why" to the Rules. I don't know that I'd consider my sources authoritative, but at least it's something to go on when creating new recipes.
So. Step one, juice the melon. This turned out to be a lot harder than I'd remembered. Chop it open, scoop out the seeds, cut off the rind, puree. So far so good. But for beautiful clear jelly, a pale yellow like stained glass, I need juice, not puree. I poured the glop into coffee filters to let it drain. The glop holds onto juice fiercely; the liquid stopped dripping out and the puree was still sopping wet. Wrap-and-squeeze is really tricky because the more moisture remains, the easier it is to just burst the wet paper filter, and this stuff was super-wet. In retrospect, putting it all into one big cheesecloth bag, then putting that in a cotton bag, then pressing out the juice, would probably have been faster.
Anyway, in the end, I had about 4 1/2 cups of juice (1.3 liters). The watermelon jelly recipe I was using as a starting point called for six cups. I ended up scrapping it and going back to first principles, which I've actually never done before.
So: four cups (because that seemed a reasonable goal for "juice for one melon") into the pot. Heat it up. Add one package of Sure-Jell dry pectin. Attach thermometer, and stir in four cups of sugar. Bring to a boil. Boiling point: 215°F. The sugar raises the boiling point of the liquid, but that's not high enough. It takes 220°F (or so I've read) to trigger the reaction that causes the pectin to set. That, and sufficient acid. More on that later.
Adding sugar: 4.5 cups. 5 cups. Eeek! Sudden surge of foamy hot syrup pours over the edge! Heat off! Towels! Wiping! Belatedly throw in 1/2 teaspoon of butter for anti-foam effect. Return to boil, carefully, stirring all the while. Argh! 219°F. Fine. Add another 1/2 cup of sugar. Aaand there! 220°F, maybe even 221.
Now it's time to check the pH. Jellies and other water-bath canning foods have three forms of defense against being spoiled by bacteria and fungi. First is that high concentration of sugar. Sugar is very hygroscopic: it pulls water toward it. Most bacteria landing on the jelly (or hiding out in it) will be instantly mummified.
For those micro-organisms that can resist being dehydrated, there's the heat. Pasteurization occurs at about 160°F. Milk, for example, is heated to that point, because that kills off the majority of Bad Things that can contaminate food. Jelly, being a liquid, and being heated to 220°, is completely pasteurized, and pouring it into the jars sterilizes them as well. Sealing the jars keeps new bacteria and fungi from invading our jelly, so until it's opened, it's safe.
Except for one particularly insidious evil little germ: Clostridium botulinum. The bacteria itself is not very dangerous, in that you can't normally "catch" a case of botulism. Rather, the bacteria, if it can have a little grow-and-reproduce party on something a human wants to eat, poops out a remarkably nasty neurotoxin. The neurotoxin itself, fortunately, will break down if heated to 85°C (185°F). Less fortunately, botulism spores won't. They can survive temperatures up to 250°F, so boiling doesn't kill them.
Fortunately, they only grow under fairly specific conditions. Canning does give them the low-oxygen environment they like. What they don't like is the acidity. Most fruit is fairly acidic, and botulism spores don't grow if the pH is below 4.3. This is why if you want to home-can meat or vegetables, you need a pressure cooker; a pressure cooker can get the temperature past 250° and kill botulism in foods that aren't acidic enough.
The tricky bit is that "acidic" doesn't automatically mean "sour." A ripe peach is deliciously sweet, but it's still acidic enough to safely water-bath can. The sour of the unripe peach is still in there, it's just masked by the sweet. But are melons acidic enough to safely water-bath can?
According to my litmus strip test, yes. The litmus paper I happened to have on hand wasn't ideal for this, because it's designed to read from 4 to 7. It doesn't really give me a precise read on how far between "4" and "5" something is, because those two values are pretty close in color. But the casaba jelly in the pot looked like a solid "4" to me. I added 3 tablespoons of lemon juice (pH 2.0–2.6) just in case. Note that a pH value of 2 means lemon juice is 100 times more acidic than something with a pH value of 4.
By the the way, the county extension office (aka the government) says to use bottled lemon juice because it has a standardized acid level. While this is true, it turns out that fresh lemon juice (excluding Meyer lemons) is all but guaranteed to be significantly more acidic than the bottled juice.1,2
Finally, there's the fourth safety factor for canned goods: you. If you pull a jar off the shelf and the lid isn't sealed, if it looks funny or smells weird or tastes odd, congratulations! Your built-in bio-assay analysis tools have functioned as designed: what you're holding may no longer be "food." Throw it out.
So, my casaba melon jelly recipe isn't Officially Certified by, well, I'm not sure exactly who would have to do what before Sure-Jell or Ball or whomever would be able to put in in their recipe books, but personally, I have at least as much confidence in the safety and reliability of my casaba jelly as I do anything else I've home-canned.
By the way, this stuff tastes amazing. The fresh casaba is quite watery; the flavor is delicate, and the melon itself is a pale green-white. In jelly form, it's an intense fruity punch, and a lovely golden color.
Although I do provide more specific instructions here than most jelly recipes offer, this is still not a first-time jelly-maker's recipe. You should at least have the instructions from the box of pectin at hand to explain some of the details of "processing" that I've omitted.
Casaba Melon Jelly
- 4 cups casaba melon juice (juice from one melon)
- 5 1/2 cups sugar
- 1 package powdered pectin (Sure-Jell or similar)
- 3 tbsp lemon juice (fresh or bottled)
Remove seeds and rind from melon, puree, then strain. Wrapping the puree in layers of cheesecloth and letting the juice drip out for a few hours, then gently squeezing to wring out the remaining juice is one method.
Heat lids and jars in a simmering water bath. (You should NOT boil them. Boiling can damage the seals on the lids. The water should be around 150–180° F to soften the lid seals and prevent thermal shock from shattering the jars.)
Put juice in a large sauce pan and bring to a boil. Add pectin, stirring until dissolved. Add butter (foam control). Add sugar, stir until dissolved. Bring to a full boil for about five minutes. A "full rolling boil" will probably get you a countertop full of foam, butter not withstanding, so it's much less messy to bring it just to a boil and keep stirring it to keep the foam down. The goal is to get the mixture to 220ºF.
Turn down heat to hold at a simmer, skim foam. (Foam can go in a jar as well for foamed jelly.)
Pour jelly into pre-heated jars. Fill to about 5mm (1/4 inch) from top. Screw on lids. Process for 5 minutes in a water-bath canner.
Makes 4 pints (aka 8 half-pint jars, or 16 4oz jars)
Note: if you didn't get 4 cups of juice from the melon, you can add up to 1/4 cup of water to make up the difference. More than that means you should probably get another melon.