Alas, people (including us) aren't eating jams and jellies as fast as we can make them, so we have to make things that we can eat in bulk this year.
Well, we just got back from my high school reunion in Walla Walla, which means we drove across the state, with plenty of chance to hit various roadside fruit stands. We've got 4 lbs of cherries, about 30lbs of peaches, and I'm not sure how many pounds of mangoes and apricots ready for canning.
Big surprise: I found exactly one suggestion for canning mangoes on the web. But peaches? Oh, everybody's got an opinion there. And they're all a little different. Cold pack vs. hot pack. Light vs. medium syrup (and for those that bother to define “light,” there's little agreement on how light “light” really is). Proper method of preventing browning (salt&vinegar, lemon juice, FruitFresh, or ascorbic acid (I'll just note that FruitFresh™ is nothing but a very expensive way to buy powdered ascorbic acid, AKA “Vitamin C”).
Most recipes state that it's very important to get all the bubbles out. None of them say why. Many of them also state that one must put the peach halves cut side down. Note that this is directly contradictory to getting bubbles out, since it creates a dome trap for air. Why face them rounded side up? Again, nobody actually gives a reason.
This is actually endemic across the web. My Pinochle Rules are almost unique among rules for games of any kind because I actually explain why I have selected one common variant over another. “Play it this way because the game is better. For this specific reason.” How I wish more people would take the time to do that, whether it's for telling me to use a sea sponge for faux painting, using an up-spiral bit for routing out wood, using CVS instead of Fink for installing Postfix (oh, Lord! how I wish people posting instructions on installing and configuring Unix software would do that!!), or any of dozens of other “Hey, let me tell you what to do” web sites, books, and instructional videos.
My mom, I think, nailed the “cut side down” issue the instant I mentioned it to her. “It's prettier.” Yes, by all means, let's tell home canners to make the canning process more difficult, make it harder to get bubbles out (I still don't know why that's important for sure), because we don't want them disappointed by how ugly the cans that they'll be tucking away in a dark place in the pantry will look.
The whole “no air” thing is also almost certainly a purely esthetic issue, anyway. Exposed to the oxygen in the trapped air, the peach will oxidize and turn brown. Doesn't hurt a thing, won't change the flavor, but it'll look funny. That Would Be Bad. I could solve that problem by just tossing a little chip of dry ice into the jar before processing.
Then there's the syrup. It's not a preservative; that's done via the heat-treating. The sugar/water bath is for keeping the fruit firm, hydrated, and colorful. I learned this from one site that (hooray!) bothered to explain one of the “why's”: “Sugar is added to improve flavor, help stabilize color, and retain the shape of the fruit.” I'll make a guess on the “how.” Although (according to some of the recipes), you can pack the peaches in just plain water, if you do that, they'll absorb extra water and get a bit mushy. The sugar water is hygroscopic; it will try to pull water out of the peaches, keeping them from waterlogging (“retain shape”). It will also almost certainly sweeten them a little bit (“improve flavor”). Finally, it cuts the exposure of the fruit to the oxygen in the air (“stabilize color”).
By the most strict interpretation, a “simple syrup” is equal amounts (by volume) of sucrose dissolved in water. This is what some recipes call a “medium” or “heavy” syrup. The recommended syrup for peaches falles between 1:3 and 1:1.
In a textbook case of “parrotting back without a clue”, one recipe tells me this: “...make your syrup by combining 2-1/4 cups of sugar with 5-1/2 cups of water. If you like your syrup a little heavier use 3-1/4 cups of sugar with only 5 cups of water. We use about 1-1/2 batches of syrup for every 7 quarts of peaches.” Now, 7 quarts is “one canner load,” that is, a standard water-bath canning pot will hold 7 quart jars. Other than that, check out the preposterous measures! 2.25 cups of sugar and 5.5 cups of water make enough syrup for 0.6 canners' worth of jars? Did it never occur to these people to adjust the amounts to make, oh, if not “one jar's worth” of syrup, at least some more easily measured amount? Most of the recipes at least had somebody smart enough to say “2 cups sugar to 4 cups water” or the like somewhere along the way!
Well, we here at the Royal Botanical Gardens and Herbarium of the Dutchy of Grand Fenwich (you can find us on the web at http://rbg.grandfenwick.net of course) are not the fools that apparently the vast expanses of home canning mavens would be. Our preliminary research shows that there would appear to be some consensus that 2.5 lbs of peaches will fill one quart jar, and will require roughly 1.5 cups of syrup to cover.
Step one is to go metric. Dealing with cups, quarts, pints, pounds, and fluid ounces is madness, utter madness. A one cup measure is 480 cubic centimeters, or almost 0.5 liters. If you really care about precision, let it be slightly mounded up. My liquid measures already have metric markings, and my scale does grams as easily as pounds. A “one quart” jar holds more than that to the brim. It also holds a bit more than a liter, so there's no reason not to declare it a “one liter” jar as well.
How many liter jars will I need for the load of peaches we have? I haven't actually weighted them yet, but each liter jar will take about 1.2kg of raw peaches, and will need about 400ml of light (1:2) syrup. Based on actual tests here in the RBG&H processing plant (the kitchen), I know that 150ml of granulated sucrose dissolved in 300ml of water will create 400ml of syrup. So now I (and apparently I alone in the World, or at least the Web) know the amounts per jar, not per some-arbitrary-fractional-amount-unrelated-to-other-amounts of the ingredients needed.
Oh, but then things took an Alton-esque turn. I decided to see if anybody had actually published the formula for solving (volume of sucrose) + (volume of water) = (volume of syrup). It's not linear. If you want 400ml of 1:2 syrup, you need 300ml water, as mentioned above. If you want a 1:1 syrup, then you need to mix 258ml of sugar with 258ml of water. If you want a 1.5:1 syrup (which was right at the limits of saturation for sucrose in water), then you're looking at 360ml sugar and 240ml water. Since my initial experiements had been to just the three data points listed, I wasn't sure I wanted to try to solve the formula from that. First, check the web. Well, no sign of the answer there yet, so I'll probably make another batch of simple syrups and fill in some more datapoints. But I did discover this amazingly detailed, scientific discussion of simple syrup and invert syrup at Baker's Exchange.
I consulted with the Herbarium's Head Gardner and Resident Physician (that is to say, Eric), and he felt there was no disadvantage to using an invert syrup instead of a simple syrup. Sucrose is promptly converted to fructose and glucose in the body anyway; converted fast enough that a sucrose “sugar rush” is not appreciably slower than a glucose one. On the other hand, an invert syrup won't crystallize. Blammo! In one fell swoop, I can now never worry about my jams & jellies crystallizing again. Woot! Also, since invert syrup is more hygroscopic than simple syrup (and tastes sweeter!), we can use an even lower ratio than 1:2 and still maintain the same “retain shape” and “improve flavor” properties of the simple syrup.
Or so go my current theories. My dad told me a saying that I love to pieces: “In theory, there's no difference between theory and practice, but in practice, there is.” We'll try canning peaches face up and face down, with hot pack and cold pack methods, and with both simple and invert syrups, and see what works how for whom when. I strongly suspect, however, that by this time next year, there will be a new web page on the Herbarium web site: “Methods and Myths for Home-Canning Peaches.”