Doris and Jilly Cook » Kitchen chemistry

Salt+Meat=Love

dorisandjilly — Fri, 14 Jan 2011 19:07:08 +0000

It’s true. I’ve slipped down the slippery slope of food preservation: meat. With the encouragement of Mrs. Wheelbarrow and The Yummy Mummy, I’ve thrown my hat in for a year of charcuterie. It helps that it’s my kind of challenge: you can participate, or not, as the mood strikes. And since I always have a hankering for expensive cured meat products, this first challenge—duck prosciutto—seemed right up my alley.

Which is not to say that my first attempt turned out perfectly. The duck came out a hair too salty; I think I left it to hang too long; and it’s really, really fatty. Nevertheless, I think I’m hooked. Making duck prosciutto (and presumably lots of other preserved meat products) is really as simple as dousing a duck breast in salt overnight, then letting it hang for a week. When you touch it, your hands come away smelling like high-end tapas. While duck breasts are hardly cheap (I paid $12.95/pound for fresh ones at Reading Terminal), duck prosciutto isn’t exactly something you can find in just any neighborhood deli. I like the idea of making it myself, using duck from a butcher I trust. I especially like the idea of controlling what goes in the cure mix. (No nitrates for me, thanks.)

Since everyone participating in charcutepalooza is playing along from Michael Ruhlman’s Charcuterie, I’ll spare you the “recipe” (such as it is). I thought that, instead, you might want an explanation. I certainly did. How does this work, exactly? When people say salt acts as a preservative, exactly how does it do that?

Well. It turns out that salt curing works on a basic chemical principle. Systems seek equilibrium. The first step in most salt cures, including this one, is to submerge your meat in salt. If the font size in the diagram below represents concentration, and the dotted line represents the boundary between the meat and salt (on one level, skin; on another, cell membranes), the system might look something like this:

If the system had its druthers, all the different things in the system would distribute themselves equally, both inside and out of the meat. But, because of the boundary membranes, they can’t. Proteins, fats, and some bacteria are stuck inside, while water, salt, and other ions (potassium, calcium, etc.) have no trouble passing through. After about a day, your system might look something like this:

This is exactly what happens to a duck breast that’s been sitting in salt all night. Here’s mine, after its evening in brine:

Notice how flat it is? If you could touch it, you’d see that it’s already quite hard. It’s absorbed quite a bit of the salt from the outside, and eliminated some of its water. Although it seems counterintuitive, this is actually a kind of dehydration. The resulting combination of high salt levels and low water levels makes it difficult for dangerous bacteria to survive—making it safe for you to hang your meat for a week to develop further flavor.

Now, keep in mind that you can’t hang your duck breast just anywhere because the meat still contains other kinds of bacteria that you don’t want to encourage. Nor do you want random yeast taking hold. You want a spot between 50 and 60°F, and you need to wrap it up in something to keep it clean. I wrapped mine in muslin and hung them from the basement rafters:

And after a week, I had duck prosciutto. It’s like magic, except it’s not. It’s osmosis and dehydration. And even though it’s not perfect, it’s still pretty delicious.

So, how did yours turn out?

Ask the Goats: Canning Kimchi?

dorisandjilly — Mon, 03 Jan 2011 06:55:48 +0000

Ask the Goats is a semi-regular Monday feature in which we, the goats, attempt to answer your food preservation questions. Got a question? Drop us a line at dorisandjilly@gmail.com.

Q. I would like to can kimchi so that it can be preserved without refrigeration and for longer periods. Is this possible? You have no information on your site.—Robin A.

A. Alas, no. All sources I’ve seen say that while it’s safe to can sauerkraut and fully fermented cucumber pickles, it is not a good idea to can kimchi. Although I have yet to find an extended explanation, there seem to be two separate issues. First, there’s the practical problem that kimchi is generally too fragile to withstand the heat of a water-bath processor. Fresh kimchi is delicious; boiled kimchi, not so much. But putting aside the texture, there’s also the question of acidity. In fully fermented foods, like sauerkraut, the lactic acid produced by the bacteria is strong enough to bring the acidity below a pH of 4.6—the magic number necessary to make a food safe for water-bath canning. The shorter fermentation period in kimchis, however, is usually not strong enough to ensure such a high pH.

There’s one other thing to consider. If you’re eating fermented foods for their health-giving properties, keep in mind that canning will kill the good bacteria along with the bad. Killing bacteria is, after all, the point of water-bath processing.

And finally, yes, you really should refrigerate your kimchi. I just had to throw out a batch that I’d been storing in my 55°F basement. I had hoped that the temperature would be cold enough to inhibit the growth of molds, but such was not the case. The kimchi at the very bottom of the jar was still edible, but the rest of it had an off-taste from mold spores that had dissolved in the brine. Another jar of fully fermented pickled green tomatoes, on the other hand, had been more successful at fending off the molds. Presumably the higher acidity level had something to do with it. Chalk it up to lessons learned.

Ask the Goats: Leaking after Processing?

dorisandjilly — Mon, 18 Oct 2010 13:55:40 +0000

Ask the Goats is a weekly feature in which we attempt to answer your questions about growing, making, preserving, and eating food. Got a question for the goats? Drop us a line at dorisandjilly@gmail.com.

Q. Last week I canned a few quarts of crushed and whole tomatoes. I thought I had done everything correctly, including allowing proper headspace in my jars. However, after processing some of the jars leaked some of their juices while cooling. At first I was concerned, but it seemed that the jars had sealed properly so I cleaned them and put them away. I checked on the jars yesterday and found that the two quarts of crushed tomatoes had leakage signs. I tossed them out

So here’s where the question comes in… yesterday I canned 6 quarts of pickled peppers. I was especially careful with the headspace this time around. Again several of the jars had leakage while they were cooling (as evidenced by dried briney trickles down the sides of the jar). I know for sure all ended up sealing properly (as I was sitting in the adjoining room while they cooled and heard many plinking sounds!). Anyway… is a small amount of leakage normal after removing your jars from your canner? Should I be concerned about my peppers? Am I doing something incorrectly?—Lindsey Nicolescu

A: Ah, siphoning—the canner’s bane. The problem you’ve described is fairly typical, especially in pressure canning (see this earlier Ask the Goats on a related problem). Whether you’re water-bath canning or pressure canning, the cause is the same: a sudden change in temperature or pressure can cause trapped air in the jars to suddenly expand, forcing liquids out. In a pressure canner, you can reduce the chance of the problem by leaving the jars to cool in the canner, but obviously, this strategy won’t work in the water-bath. What you can do is turn off the heat and take off the lid when the processing time is done, then wait five minutes. This cools things down a bit and reduces the chance that you’ll get siphoning without overcooking the product too much. I had never noticed this before your question, but it’s actually the strategy recommended in many canning books, including the Ball Blue Book and Put ‘Em Up.

The main danger from siphoning is that it can interfere with your seal. If this is the case, refrigerate or reprocess them. Depending on their contents, you might even be able to add more liquid before trying again. If you do get a seal, the jars are safe, but you’ll want to eat them first, as they’ll be more prone to oxidation. Again, this isn’t a safety issue, but a quality issue.

As for preventing the problem in the first place: siphoning is much more likely to happen in liquid-y products (peaches in light syrup, pickled peppers, tomatoes in water, etc.) than in thick, gloppy canned goods (jams, chutneys, relishes). Be sure to remove air bubbles, and watch that headspace. Then cross your fingers, spin three times, and hum.

Ask the Goats: Why Ovens Don’t Count

dorisandjilly — Mon, 11 Oct 2010 19:30:24 +0000

Ask the Goats is a (mostly) weekly feature in which we, the goats, attempt to answer your food preservation questions. Got a question? Drop us a line at dorisandjilly@gmail.com.

Q. I made a beef stew in a 350°F oven. That’s hotter than a water bath, so why can’t I just can the stew as is? Why do I need a pressure canner?—anon (to me, anyway) via Kaela at Local Kitchen

A. This is a great question, just at that point where common sense bumps up against the laws of physics. We say, over and over again, that the heat of a water-bath canner is not sufficient to kill off the kinds of nasties (botulism, I’m looking at you) that can live in low-acid, anerobic environments (i.e., beef stew). But, obviously, a 350°F oven is much hotter than the 212°F of boiling water. So, what’s the problem?

The problem has to do with what’s inside the stew pot. When an oven thermometer reads 350°F, that means that the air temperature is 350°F. Your stew, on the other hand, is going to be hovering at its boiling point. This is a consequence of what’s called the Phase Change Law, which says (more or less), that a substance will maintain the temperature at which it changes phase until the phase change is complete. Water melts at 32°F, and it boils at 212°F. If you put a pot of boiling water in the oven, it’s not going to get above 212°F until all of the water has turned to steam. Then, and only then, can the temperature start increasing.

Now, in beef stew, you’ve got a liquid that, depending on what it has in it (water, wine, stock, etc.) is boiling probably somewhere between 190°F and 212°F. But you’ve also got solids that are probably at a lower temperature. Think of what happens when you put a large roast in the oven. You might cook it for hours, and it might still be at 150°F. All of which is to say that your beef stew is nowhere near 240°F.

But how does the pressure canner do it? Well, when I said that a substance that’s changing phase will maintain an even temperature, that’s not quite true. It will maintain an even temperature under conditions of constant volume and pressure. Crank up the pressure, and the temperature goes up. And hence, safe canning conditions for low acid foods.

Want more canning advice? Check out the liveblogging stream from the panel on canning, preserving, and foraging that I participated in with Marisa from Food in Jars, Hank from Hunter Angler Gardener Cook, and Sean from Punk Domestics at last weekend’s BlogHerFood conference in San Francisco. I had a blast, and I hope those in attendance found it as informative as I did entertaining.

Ask the Goats: Pinging Vegetable Stock

dorisandjilly — Mon, 27 Sep 2010 18:06:37 +0000

Ask the Goats is a weekly series in which we attempt to answer your questions about growing, making, eating, and preserving food. Got a question for the goats? Drop us a line at dorisandjilly@gmail.com.

Q. Hi. I am not new to canning. But something happened this year that has never happened before. I canned 16 quarts of vegetable soup. I used the water bath method and processed them for 1 hour. I checked the seals and they were good. One week later the lids started pinging. What went wrong? That was an awful lot of work to throw away. I am very disgusted. P.S. My salsa, peach preserves, strawberry jam are all sealed and delicious.—Mary

A. Alas, Mary, vegetable broth is a low-acid food, and therefore not safe for water-bath canning. For the purposes of canning, all foods are either high-acid or low-acid foods. The kinds of food-born pathogens that can live in a high-acid environment can be killed fairly easily with moderate heat, so you can process them in a boiling water bath. Low-acid foods, on the other hand, can harbor botulism spores that are not destroyed at 212°F. Low-acid foods must be processed in a steam pressure canner that can reach much higher temperatures (usually 240ºF).

Remember, only fruits (excluding tomatoes, figs, green mangoes, and white peaches) and certain kinds of fermented pickles are acidic enough for water-bath canning without adding acid. For everything else, you have to either acid—sometimes in substantial quantities—or use a pressure canner.

Pressure can vegetable stock just as you would chicken stock (for step-by-step directions, click here). The Ball Blue Book recommends 35 minutes for quarts at 10 pounds pressure. If you don’t have a pressure canner, you’ve got to freeze it.

In happier news, the winner of the Put ‘Em Up! giveaway is Amanda Nelson, who’s new to canning and expecting twins! I think your strategy to put up as many nibble-ables as possible is an excellent strategy.

Ask the Goats: Adjusting Processing Times

dorisandjilly — Mon, 20 Sep 2010 14:55:54 +0000

Ask the Goats is a weekly feature in which we, the goats, attempt to answer your questions about growing, making, eating, and preserving food. Got a question? Drop us a line at dorisandjilly@gmail.com.

Q: When you have a boiling-water bath recipe, how much do you adjust the processing time for different size jars? Most jam recipes have processing times for 1/2 pint jars, but what if I wanted to can pint size jars? Or vice versa? Sometimes I don’t have all the same size jar for one recipe and I don’t want to over or under process.–MP

A: Great question! When you’re processing the jars, you’re doing two things. First, you’re heating up the air inside the jars and thereby forcing some out. This creates a vacuum when the jars cools. In a good rolling boil, you can accomplish this in about 5 or 10 minutes, regardless of the size of the jars.

The variable processing time for different size jars has to do with the second function of heating up the jars: killing food-borne pathogens like yeasts, molds, and bacteria. The length of time to accomplish this depends on the size and contents of the jars. For some foods, like applesauce or grape juice, the processing time will be the same regardless of whether you’re making half-pints, pints, or quarts. In most cases, though, you have to add time—typically 5 or 10 minutes—for larger jars.

If you’re moving to smaller jars, you’ll definitely be safe using the recommended processing time, but—depending on what you’re making—you map run the risk of over-processing. This isn’t an issue for things that have already been cooked a long time, like ketchups, chutneys, and most sauces. Things get a little more dicey when texture matters, for instance, peaches and pickles.

So, to make a long story short: there is no rule of thumb for whether and/or how much time to add or subtract when switching between jar sizes. With jams, you should feel free to move between quarter-pint, half-pint, and pint jars. For everything else, you’ll want to check your recipe against a published canning reference. Both the Ball Blue Book and the National Center for Home Food Preservation are pretty good about listing different times for different sizes. And besides, it’s not such a bad idea to check their guidelines anytime you’re using a recipe you’ve found online.

Happy canning!

Salsa Verde Safe for the Water-Bath

dorisandjilly — Sat, 21 Aug 2010 02:13:25 +0000

For the August canjam, I made what I made almost exactly a year ago today: salsa verde. And because I am creature of habit, I’ll say pretty much what I said in last year’s post: there are shockingly few published instructions available for canning tomatillos. Most of these recipes treat tomatillos like tomatoes, adding acid, and they treat salsa verde like regular tomato salsa, adding onions. But here’s the thing. Being a stubborn goat, I don’t like either of these preparations. I like a salsa verde that’s pretty much tomatillos, water, and a jalapeno or poblano pepper or two.

So what is a goat to do? Turn to Twitter, of course. Last year, zoecancan was kind enough to point me to an incredibly helpful article in the peer-reviewed journal Plant Foods for Human Nutrition. Since it’s behind a paywall, I’ve reproduced the abstract below:

Three studies were conducted to evaluate the safety of tomatillos and products containing tomatillos canned by the water-bath processing method. In the first study, plain tomatillos were processed for 25, 37.5, 50 and 62.5 min. In the second study, five tomatillo/onion combinations were prepared while five tomatillo/green chile combinations were prepared in the third study. pH evaluations were conducted to determine safety in all studies using pH 4.2 as the cut-off value. No differences in the pH of plain tomatillos were detected due to processing time. All jars of plain tomatillos had pH values below 4.1. All combinations of tomatillos/onions and tomatillos/green chile containing more than 50% tomatillo had pH values below the 4.2 cut-off value. Results of the three studies indicate (1) acidification of plain tomatillos is probably unnecessary for canning by the water-bath processing method and (2) combinations of acidic tomatillos and low-acid onions or green chile must contain more than 50% tomatillos to have a pH low enough for safe water-bath processing.

So, based on this, I feel pretty comfortable saying that it’s safe to water-bath can this version of salsa verde, or in fact any version of salsa verde where the quantity of tomatillos (by weight) exceeds the combined weight of onions and/or peppers and herbs. The acid safety cut-off is a pH of 4.6, so at 4.1, this is plenty acidic (remember that a lower pH means higher acidity).

For the recipe, along with instructions for water-bath canning (for the scientific), pressure canning (for the conservative), or freezing (for the squeamish), click here. This time, 2 pounds made 4 half-pints. It scales up, so, if you’ve got a bushel full of tomatillos, knock yourself out!

Ask the Goats: Bad Seals in the Pressure Canner

dorisandjilly — Mon, 16 Aug 2010 13:05:42 +0000

A note from the goats: This blog used to have a weekly feature called “Ask the Goats.” At the time, most of our readers were people we knew in real life, and we quickly ran out of questions. Since then, our audience has grown, and we’re now getting a steady stream of questions on Twitter, in the comments, and via e-mail. We’d like to use this forum to share our answers with the rest of you, who are quite likely wondering about the same things. Keep the questions coming, and we’ll try to answer them on Mondays!

Q: I’ve just read your instructions [for canning chicken stock]. I’ve tried twice now to can a batch of stock in my pressure canner and most of the jars won’t seal. I removed air bubbles, left 1″ in the jar, and followed the other instructions. Any ideas why these jars won’t seal?—Jen

A: After Jen asked me this, we had a long e-mail discussion about the various options. She was indeed doing everything right, but we eventually settled on two things. First, her stock was fairly fatty. While this makes for delicious stock, it can make getting a good seal more difficult if fat gets trapped between the lids and the jar. But secondly, and more importantly, this was a case of opening the pressure cooker lid too soon.

But what, exactly, constitutes “too soon”? Most pressure canning instructions, including mine, tell you to wait about 10 minutes after letting the pressure drop of its own accord before opening the lid. Over time, though, I’ve found that this is too soon. A pressure canner full of chicken stock is very, very hot. Even when the pressure drops inside the canner, the temperature and pressure inside the jars is still quite high. The dramatic change in pressure from removing the lid (even after the indicator has fallen) can be enough to cause liquid to spurt or seep out of the jars. This not only causes you to lose some of your precious chicken stock, but it also interferes with the seal. So now, whenever I pressure can anything with a significant amount of clear liquid (beets, tomatoes, stock, etc.), I always wait at least an hour after the pressure drops before opening the lid. Ideally, I do this at night and just turn off the heat and go to bed. The next morning, I take off the lid, and viola! Everything seals.

Jen e-mailed me about a week later with an update. Success!

Home Canning FAQ

dorisandjilly — Wed, 09 Jun 2010 13:05:55 +0000

The best part of any food preservation class (besides the food) is always the discussion. Usually, I have quick answers for a fairly regular set of questions about food poisoning, the physics of pressure cookers, storage, and the differences between jams, preserves, conserves, and compotes. But recently, I’ve started to hear some new ones. This post is an attempt to round up some of the answers to both. Feel free to add more questions in the comments, or drop us a line.

Why is canned food shelf-stable?

When you can something, you’re doing two things. First, you’re killing bacteria, molds, and yeasts through the addition of heat. Second, by creating a seal, you’re preventing new bacteria from getting in.

What’s the difference between pressure canning and water-bath canning?

For the purposes of canning, all foods are either high-acid or low-acid foods. The kinds of food-born pathogens that can live in a high-acid environment can be killed fairly easily with moderate heat, so you can process them in a boiling water bath. Low-acid foods, on the other hand, can harbor botulism spores that are not destroyed at 212°F. Low-acid foods must be processed in a steam pressure canner than can reach much higher temperatures (usually 240ºF).

How do I know if a food is high or low acid?

All fruits except for figs and tomatoes are acidic enough to can in a water-bath canner. Figs and tomatoes can be safely canned this way with the addition of a small amount of lemon juice. Everything else—including vegetables, meats, fish, and mixtures of high acid and low acid foods (for instance, salsa)—either has to be pressure canned or made more acidic. The short answer to this question is to follow the recipe. The longer answer, recommended only for experienced canners, involves comparing fruit/vegetable/acid ratios and densities from trusted sources. Please be cautious when using internet canning recipes, and consider comparing unfamiliar instructions to published guidelines, such as those of the National Center for Home Food Preservation and those listed in the Ball Blue Book of Preserving.

What’s the processing time?

The term “processing time” refers to the amount of time that you either boil or pressure can your jars. The amount of time depends on the food—check your recipe. In a boiling water bath, you start timing when the water returns to a boil. In a pressure canner, you start timing when the canner reaches pressure.

I have a pressure cooker. Can I use it as a canner?

That depends. Small pressure cookers are not necessarily guaranteed to reach and maintain the appropriate temperatures necessary to kill botulism spores. Most pressure canners are 23 quarts or larger—large enough to hold 7 quart jars on a rack, or 14 jelly jars, stacked. If you’re not sure, contact the manufacturer. My attempt to explain the science of pressure cookers is here.

Do I have to sterilize the jars?

If the recipe calls for a processing time of more than 10 minutes, no. Otherwise, yes. In either case, manufacturers generally recommend that you pre-heat your jars to reduce the chance of breakage, particularly before processing in a water-bath canner.

Can I use a dishwasher to sterilize my jars? What about to process them?

If your dishwasher has a sterilization setting, you may use it to sterilize your jars. You may not, however, process your jars in the dishwasher. You need to use a boiling water bath or a steam pressure canner, as per the recipe.

If I have a low-acid food, but I just want to keep it for a few weeks, can I water-bath can it?

No. Food is either safe for water-bath canning, or not. If you do not have a pressure canner but have a food that needs to be pressure canned, you either need to refrigerate it or find some other way to preserve it.

How long will canned food keep once it’s opened?

Once the jars are opened, canned food is just like regular food, with similar keeping times. Something pickled might last months; a highly sweetened jam might last several weeks; and a tomato sauce might last only a few days.

Can I reduce the sugar or salt in a recipe? What about sugar substitutes?

YES. Contrary to what you may have heard, it is perfectly safe to reduce the sugar in a canning recipe so long as you are using an appropriate processing time. (The highly liability conscious company that sells Ball jars backs me up on this.) Sugar is a preservative, which means that food (particularly fruit) with sugar added will retain more of its original color, taste, and texture. It also means that the jars will keep longer once you’ve opened them. You may not get the texture you’re expecting if you reduce or substitute sugar—for instance, your jams might not set. But since sugar does not affect acidity, it doesn’t affect safety. Same thing with salt: the amount of salt in canning recipes is not enough to act as a preservative. It’s there for flavor. If you need to reduce your salt, just leave it out.

How will I know if a jar has gone bad?

A broken seal, a bulging lid, moving bubbles, mold, foam, bad smells, funky texture, and sliminess are all signs that you should not eat the contents of a jar.

Why do you store jars without their rings?

See previous question. If you’ve got an active bacterial population in your jar, they will produce various gasses. If the rings are removed, the pressure inside the jars can eventually build up to the point that the lid pops off. This is your signal, months later when you find the jar in the basement, to not eat it. If the ring is attached, the lid might not pop off. In rare cases, the jar might even explode. On a more mundane level, you should remove the rings because moisture trapped between the jar and the lid will cause them to rust.

How long can you store your jars?

That’s a good question. The USDA generally says 1 year. Many experienced canners will tell you that they fairly regularly keep their canned goods for longer than that, and just as many will tell you that food begins to lose its flavor much sooner (say, 6 months). Since the whole point of preserving foods is to hold you over until the next year’s harvest, shoot for a year.

Got more questions? Bring ‘em on!

February Can Jam: CARROTS!

dorisandjilly — Thu, 28 Jan 2010 13:58:31 +0000

(Photo from Chris Campbell’s Flickr photostream)

Attention all canjammers! The focus of the February Tigress Can Jam is CARROTS.

Got that?

Yes, carrots.

The Tigress and I made this choice with both excitement and trepidation. The excitement because vegetables are new territory for many water-bath canners; the trepidation because carrots are a low-acid food, and therefore come with certain rules. So. Let’s be clear. No matter what you find on the internets, you absolutely have to add acid to carrots to make them safe to can. In fact, a lot of acid. So much acid, in fact, that the Tigress and I strongly encourage you—nay, insist!—that you start off with a published recipe, and tweak from there. (If you have a home pH meter and/or are a master food preserver, you get a free pass.) Think pickles, relishes, and chutneys. Once you’ve found a recipe you like, feel free to tinker with the spices, the balance of salt and sugar, the exact combination of vegetables, etc. HOWEVER, be sure that you are not reducing the proportion of acid to the food.

Let’s give an entirely hypothetical (as in, don’t try this at home) example. Say you have a recipe that includes 5 cups of carrots, 2 cups of cauliflower, a handful of herbs, 1 T of salt, 1/4 c. of sugar, and 3 cups of vinegar. It would be fine to reduce the cauliflower to 1 cup and add 1 cup of peppers, throw in some mustard seeds, and add more sugar. It would not be OK, though, to just add a cup of peppers without adding more vinegar, because then you’ve lowered the acid content (that is, raised the pH).

Um, if this is at all confusing, that means you should stick with the recipe.

Have fun, be careful, and remember to post your fabulous creations between Sunday, February 14 and midnight, Friday, February 19.

Happy canjamming!