I thought I'd post a few of the canning questions I've gotten from folks over the last several weeks, posed here or on Facebook or by email or in person. If you have more, leave them in the comments, and I'll post again with answers if I have them, and eventually I'll figure out how to put an FAQ page on this blog thing. So here goes . . .
Where can you find citric acid for canning tomatoes and tomato sauce?
Some health food stores carry it, as do some Indian groceries (where it may be labeled "lemon salt"). It's available online from Amazon, Kalustyans, and Leeners, among many other vendors. If all else fails, you can use lemon juice or Fruit Fresh, which is citric acid stepped on with ascorbic acid and anti-caking agents (see the quantities for lemon juice and Fruit Fresh in the recipes in the book).
Do you have to dry off the flat jar lids after they've been in the hot water and before you put them on the jars?
No. Just slap ’em on.
Can you forgo peeling the tomatoes for sauce and just blend them up, skins and seeds and all?
Sure. Just wash the tomatoes really well first (there are more bacteria on the surface of the tomatoes, obviously, though those will be killed during the long processing time in the canning pot).
Can you can pesto in a boiling water bath?
No. Pesto is not an acid food (it has a high pH), and so it's not safe to can it in a boiling water bath. Freeze it instead!
What are your favorite things to preserve?
Sour cherries, all-purpose tomato sauce, salsa verde, and grapefruit marmalade are some of my favorites. They're extra-fun to make and delicious and useful.
Are your recipes approved by the USDA?
No. As far as I know, the only recipes officially approved by the USDA are the ones published in its handbook and online at the National Center for Home Food Preservation. The USDA is not in the business of evaluating or testing recipes to be published by private companies; the agency has developed its own recipes, and those are the ones they officially stand behind. That said, all of the canning methods described in my book conform exactly to current USDA standards for processing: I don't advocate the so-called open kettle or inversion method, I ask you to sterilize jars in boiling water rather than in a dishwasher or oven, processing times are totally in line with the USDA's recommendations, and so on. Fruit preserves in my book are significantly lower in sugar than those made by standard recipes, but when fruit (which is high acid) is canned using reliable methods sugar is not necessary for preservation purposes. The canned pickles in my book were tested for pH levels at several stages in the process—before processing and several days or weeks later—and packing and processing times conform to those recommended by the feds (in addition, temperatures were checked during processing using the method required of commercial canners by the FDA). If you still have concerns about a recipe—mine or any other—you can always send it to your local extension agent to ask if it looks okay to him or her. And, as always, use your judgment when opening and using a canned food, whether it has sealed properly or not. If anything doesn't seem right to you, toss it!