Curious Cook

Peeling fresh fava beans with ease (and soda)

A few weeks ago Evan Kleiman of KCRW's Good Food tweeted me a question from one of her listeners: why did the cooking water for a batch of garden green beans turn pink? Not knowing for sure, I guessed that the color came from early stages of the browning discoloration that develops when many fruits and vegetables are cut or damaged. Mushrooms are especially prone to this, and I've noticed that they turn pink before getting more frankly brown.

Shortly after replying to Evan I happened to pull out a half-dozen fava bean plants from my garden, and I harvested pounds of green pods, old and young. I enjoyed the tender ones whole, tossed in a hot pan with a little oil and salt. They're deliciously different from ordinary green beans, with a flavor that's both meaty and flowery, even perfumed. The older pods I pulled open to collect the beans in their tough seedcoats.  I blanched a batch of these beans in boiling water to soften the skins and speed the tedious peeling. And I noticed that the blanching water became pink, especially under incandescent light (below).

This reminded me of how quinces and pears can turn pink and even red when they're slowly poached. They do so because they contain compounds called proanthocyanidins, molecules that don't participate in the usual fruit browning, but that fragment during cooking into anthocyanins, the pigments that color most red fruits and vegetables.

So I checked, and it turns out that the skins of most legume seeds, favas included, are rich in the same proanthocyanidins.

New theory! Colorless proanthocyanidins in bean seedcoats release fragments into the cooking water, and these are what turn the water pink.

I thought I could test the theory by cooking some skins by themselves and adding either citric acid or alkaline baking soda to the cooking water. Anthocyanin pigments are sensitive to pH. Acid usually shades them toward the red, alkali toward the blue. So if the fava seed coats are indeed releasing anthocyanins into the cooking water, I should be able to change the water's color.

Well, the color test didn't turn out the way I expected. The acid cooking water was the same pale pink as the neutral water, and it was the alkaline water that turned a deep, winey red (right). I still haven't figured that out. 

But I noticed something else that was easy to figure out, and much more useful than any color change. Whenever I cooked fava beans in alkaline water, more than half of them popped their skins in the pot, no hand-peeling needed! And the rest were easy to peel with a gentle squeeze at one end.

Here's a batch of alkaline-blanched favas fresh out of the pot, before any hand-peeling.

The skin-busting effect of alkaline cooking water makes good sense. Acidity maintains the structure of plant cell walls, and alkalinity breaks it down. That's why beans take forever to soften if you try to cook them in a tomato sauce. So soda in the blanching water weakens the fava seed coats enough that many of them rupture on their own in a couple of minutes at the boil, and the remainder easily break between finger and thumb.

Using soda seems such an obvious idea in retrospect that I'm surprised it's not already standard practice. Many recipes for dried favas do call for baking soda to soften their skins and speed the cooking. There must be other cooks out there who've been blanching fresh favas with soda. I'm now one of them.

So: to ease fava peeling, add about a tablespoon of baking soda to a quart of vigorously boiling water, and throw in the beans. Fish them out as they pop their skins so they don't pick up the soda soapiness, and drop them in a bowl of cold water to rinse. After two or three minutes, scoop the remainder into another bowl of water to cool them down. Peel them by gently squeezing on the thick end of the bean, if necessary nicking the thin end with your fingernails.

And check out the color of the cooking water before it disappears down the drain. It's a sign of the chemical defenses concentrated in the seed coats, and their likely nutritional value for us. That's the next challenge: making fava skins delicious enough to keep and eat with pleasure.

 

Sugar from the garden

While browsing among the vegetable starts at a nursery in Santa Cruz last year, I came across a flat of sugar beets. I'd never tasted sugar beets before. They're a special variety of Beta vulgaris bred for sugar production, with none of the colorful pigments of vegetable beets that would further complicate the manufacture of pristine white crystals. So I bought some seedlings and planted them. They grew well through nearly a year of benign neglect. Last month I dug them up and tried them out.

The beets I grew were irregular in shape and size, the largest weighing in at about a kilogram, or over 2 pounds trimmed of leaves and small roots. Both raw and roasted they had a mild beet flavor and were very sweet indeed. I used my refractometer, a handy instrument that measures the concentration of dissolved materials in liquids, to get a rough idea of the sugar levels in their juice. Most of the sugar beets ran between 15% and 18% dissolved solids, while store-bought red and chioggia beets were closer to 5%.

I was especially curious to see what a home version of beet sugar would be like. Refined white table sugar is manufactured from beets and from sugarcane by extracting the juices from the raw materials, evaporating off their water, and separating the sucrose sugars from everything else, including a host of other plant chemicals and byproducts of the evaporation process. That separation process involves the use of mineral lime, carbon dioxide, charcoal made from various materials (sometimes animal bone), and centrifuges.

Not for the casual sugar-maker! Instead I figured on making an unrefined sugar, a beet version of the delicious palm and cane jaggeries that come from Asia, or the cane panela (piloncillo, papelón) of Latin America, or North American maple sugar.

But I had my doubts about whether unrefined beet sugar would be anything close to delicious. I'd read that unlike the molasses left over from cane sugar manufacture, beet molasses is fit only for livestock feed. I wondered whether that's because the beet residues are intrinsically unpleasant, or are somehow made so by the particular way beets are handled. Where sugar cane grows above ground and is processed shortly after harvest, beets are dug from the soil, have that distinct earthy odor, and may be stored for months in piles 20 feet high, where they remain alive and can deteriorate. Even fully refined beet sugar sometimes ends up with off flavors.

I ended up making small batches of beet sugar in three different ways. Each time I started by washing the beets, and then trimming and peeling them--two steps not in the industrial flowchart that I hoped would minimize off flavors.

The first time around I ran the beets through a juicer, and got about half the starting weight in juice. Rather than boiling it down over high heat, I gently evaporated it in a gas oven set at 250^oF. (Gas ovens are well vented, so evaporation-slowing humidity doesn't build up.) The juice quickly turned an unappealing brown-gray and developed a strong beet odor, probably due to browning enzymes and perhaps also enzymes that generate earthy-smelling volatiles. After a few hours, I had a beety sweet syrup that cooled into a dull-colored paste. It was edible, but not especially nice.

Next I shredded the beets in a food processor, simmered the shreds in three times their weight in water to extract their juices, strained out the shreds, and evaporated the liquid down. This syrup and paste had a pleasantly mild beet aroma, but they were still an unfortunate grayish brown.

Finally I tried precooking the beets to kill the enzymes before I shredded them and extracted the juices. I sliced the beets, rinsed them to remove enzymes from the surfaces, then microwaved the slices in batches so that they reached the boiling point quickly, in a couple of minutes. The syrup developed only a faint beet aroma and a light gray color that soon disappeared into a cool-toned brown.

All of the beet syrups and pastes were mainly sweet, but with an edge of acidity and saltiness from the other plant materials that were extracted and concentrated along with the sugars. When I cooked them down to the point that they turned dark brown, all had the pronounced acidity and bitterness  of cane molasses along with its characteristic aroma, which mostly masked any beetiness. 

So it is indeed possible to make a good unrefined sugar from a vegetable that can be grown almost anywhere. True, it's not very efficient to do so: evaporating off water burns a lot of energy for the amount of sugar you end up with. (At least you can use the beets efficiently: the greens are essentially the same as chard, and you can squeeze or pan-dry the spent shreds to remove excess moisture, add salt and a little of their own sugar to restore some taste, and then toss with starch or beaten egg to make beet hash browns or latkes). 

But it's an interesting process and product. Along the way I learned that in the beet-growing areas of Germany, Zuckerrübensirup is sold as a spread and to flavor pumpernickel bread dough and sauerbraten.  Earthy sweetness has its uses. 

Back into the garden

 

Digging up a long-neglected corner of my San Francisco garden a few weeks ago, I came across what look like the skeleton bulbs of garlic or some other lily relative, the skins and flesh gone, only the reinforcing cellulose fibers left behind.

They reminded me of a garden find I made one spring about twenty years ago, after I'd grown a couple of crazily prolific purple tomatillo plants. The winter had had its slow way with some stray tomatillos, etching away all but the veins of their papery outer husks and in some cases the flesh within, leaving just the seeds to rattle around. The remnants made an absorbing anatomy lesson, an image of the passing pleasures and durable purpose of fruits.

I've been neglecting this blog as I have my garden, and for many of the same reasons. But I'm starting to work both again. There's plenty to unearth and cultivate and share.

 

Bending the rules on bacteria (New York Times)

PEPPERED as we are by government warnings about the potential health hazards of eating and drinking just about everything, it was refreshing (and perplexing) to see a widely respected food writer assert recently that “people are unnecessarily afraid of bacteria” in the kitchen.

In April, Michael Ruhlman, author of “Ratio” and “The Elements of Cooking” and co-author of books by Thomas Keller and other chefs, said on his blog that he likes to make chicken stock and leave it out on the stovetop all week, using portions day to day to make quick soups and sauces.

But what about the harmful microbes that could grow on foods if they were not kept either chilled or hot? “Once your stock is cooked, it’s safe to eat,” Mr. Ruhlman wrote. “If there were bad bacteria in it, you’d have killed them.” After the stock has cooled, simply reheat it, he continued, and “any bacteria that landed there and began to multiply will be dispatched well before the stock hits a simmer.”

Sounds plausible, and Mr. Ruhlman and his family are alive and well. But after checking with an independent expert on food safety, I wouldn’t follow this recipe without slapping a biohazard label on my stockpot.

The Food and Drug Administration sets regulations for commercial food production. These specify that cooked foods should sit out at temperatures from 41 degrees to 135 degrees, the range in which bacteria can grow and multiply, for no more than four hours.

Guidelines for the consumer and home cook, which come from the Department of Agriculture Food Safety and Inspection Service, are even stricter. The current brochure, “Keep Food Safe! Food Safety Basics,” on the U.S.D.A. Web site, says not to leave prepared foods in the bacterial growth zone for longer than two hours. And if it’s a 90-degree summer day, cut the two hours to one.

Mr. Ruhlman’s stock spends days in the bacterial growth zone, and he happily makes it into chicken soup for his children.

I’ll admit to violating the guidelines in my own stock-making, though by a few hours, not days. When I cook a roast for dinner, I use leftover scraps and bones to start the stock, simmer it while I clean up, and take the pot off the heat right before I go to bed. At that point it’s too much trouble to cool the hot stock so it won’t warm up its neighbors in the refrigerator. Instead, I cover the pot, leave it at room temperature and reheat it in the morning, about eight hours later, before straining, cooling and refrigerating it. And my stock hasn’t made me or my family ill, either.

Can I be even more relaxed about my stock-making? Or have Mr. Ruhlman and I just been lucky? For an expert opinion, I sent our recipes to O. Peter Snyder, a food scientist and veteran educator and consultant to the food-service industry, who has at times taken issue with government guidelines he considers unnecessarily conservative.

Dr. Snyder replied in an e-mail: “The process described by Mr. Ruhlman is a very high-risk procedure. It depends totally on reheating the stock before it is used to be sure that it doesn’t make anyone ill or possibly kill them.”

It’s a basic fact that every cook should know: bacteria that cause illness inevitably end up on nearly every ingredient we cook with, and even boiling won’t kill all of them.

Boiling does kill any bacteria active at the time, including E. coli and salmonella. But a number of survivalist species of bacteria are able to form inactive seedlike spores. These dormant spores are commonly found in farmland soils, in dust, on animals and field-grown vegetables and grains. And the spores can survive boiling temperatures.

After a food is cooked and its temperature drops below 130 degrees, these spores germinate and begin to grow, multiply and produce toxins. One such spore-forming bacterium is Clostridium botulinum, which can grow in the oxygen-poor depths of a stockpot, and whose neurotoxin causes botulism.

Once they’ve germinated, bacteria multiply quickly in nourishing stock. They can double their numbers every 90 minutes at room temperature, every 15 minutes at body temperature. A single germinated spore can become 1,000 bacteria in a matter of hours, a billion in a few days.

As Dr. Snyder put it, “After sitting on the stove and growing bacteria for two or three days, Mr. Ruhlman’s stock almost certainly has high levels of infectious Clostridium perfringens cells, or Clostridium botulinum or Bacillus cereus cells and their toxins, or some combination thereof.”

Why has the Ruhlman family survived? Because Mr. Ruhlman boils the stock before he serves it, Dr. Snyder wrote. Any active bacteria are killed by holding the stock for a minute at 150 degrees or above, and botulism toxin is inactivated by 10 minutes at the boil.

But quickly reheating a contaminated stock just up to serving temperature won’t destroy its active bacteria and toxins, and the stock will make people sick.

“If Mr. Ruhlman ever has a cup of his three-day-old stock without thoroughly boiling it first, he will probably only do it once,” Dr. Snyder wrote. “It is irresponsible of any cook to prepare food in a way that actually creates a new and significant hazard, even though the hazard may be eliminated in a later step.”

Safety is one problem with keeping a stock at room temperature. Flavor is another. A reboiled three-day-old stock may be safe to eat, but it is now seasoned with millions to billions of dead bacteria and their inactivated toxins. It’s conceivable that they might add an interesting flavor, but more likely that the bacteria have feasted on the stock’s sugars and savory amino acids, the air has oxidized and staled the fat, and the stock has become less tasty.

I spoke with Mr. Ruhlman about Dr. Snyder’s analysis of his stovetop-stored stock. “I agree that I should have been clearer about the importance of the ‘kill step,’ a good 10 minutes at the boil,” he said. “And certainly to make the freshest, cleanest stock, it’s always best to strain, cool and chill it as rapidly as possible.”

What about my lazy method of letting stock cool overnight, then reboiling and refrigerating it first thing in the morning? Dr. Snyder gave it a pass because it would spend only a few hours below 135 degrees, not enough time for the bacterial spores to germinate, start growing and reach hazardous numbers.

Like meat stocks, all moist cooked foods are susceptible to being recolonized by survivalist bacteria. (Baked goods are generally too dry for bacteria; they’re spoiled by molds.) That’s why we should avoid leaving cooked foods out at room temperature for long when we’re preparing for a party or holiday feast (or enjoying their lazy follow-ups), or having a picnic, or packing lunch boxes for young children, who along with the elderly and ill are more vulnerable. It’s best to keep moist lunch items either cold or hot, surrounded by cold packs or in a thermos.

What are the actual odds of getting sick from casual food handling at home? No one really knows. There are many variables involved, and only a small fraction of illnesses are reported, even to a family doctor, since they’re usually brief. But one unambiguous and heartbreaking story can bring home the value of handling food carefully.

In 2008, a 26-year-old Japanese mother in the Osaka region shared a meal of leftover fried rice with her two children, ages 1 and 2. She had prepared and served the rice the day before and kept it at room temperature.

All three became ill 30 minutes after eating the leftovers, and were hospitalized. Both children lost consciousness, and the youngest died seven hours after the meal. Pathologists later reported in the journal Pediatrics that the rice contained a very common spore-forming bacterium, Bacillus cereus, along with a heat-resistant toxin that the bacterium tends to make on starchy foods, and that can cause vomiting even after being heated to the boil.

It may be true that most cases of food-borne illness aren’t that serious, and that most reported cases can be traced to foods that were contaminated during their production or processing. But it is also true that one simple mistake at home can be fatal.

Even though I know this, I tend to discount specific government guidelines because they seem to change arbitrarily, and they don’t seem workable in real life. This is true of the latest U.S.D.A. numbers. It’s unrealistic to expect home cooks to chill or reheat or discard dishes every two hours during a dinner party, or every hour at a summer barbecue.

Dr. Snyder agreed that official pronouncements on food safety can be inconsistent and self-defeating. “The F.D.A. Food Code is very conservatively written,” he wrote. “Four hours after it’s cooked is plenty fast enough to get food into the refrigerator.” And slow enough to relax and enjoy the meal.

Dr. Snyder added that it’s safest to cool leftovers uncovered and in a mass no thicker than two inches, so they cool through quickly. If they’re still hot, start the cooling on the countertop. When the container is no longer hot to the touch, put it in the refrigerator, and cover it once the food is good and cold.

My own everyday approach to safety is to try to keep cooked foods either hot or cold until I’m ready to serve them, get leftovers in the fridge during the pause before dessert or soon after, and reheat leftovers that need it until they’re boiling or steaming.

This set of habits isn’t dictated by an unnecessary, pleasure-killing fear of microbes. It simply acknowledges their inevitable presence in my kitchen, and the fact that both my food and anyone who eats it will be better off if the care I give it doesn’t end with the cooking.

August 23, 2011

Copyright 2011 The New York Times

Curious Cook in the New York Times: Survivalist bacteria and dealing safely with leftovers

In this month's Curious Cook column in the New York Times, I write about dealing safely with leftovers.

Last April,  the noted food writer Michael Ruhlman suggested on Twitter and in his blog that many home cooks are unnecessarily afraid of bacteria, and that it’s okay to prepare a chicken stock and keep it on the stovetop for days at a time.  Michael—Mr. Ruhlman in Times parlance—heard back from many “mystified” readers,  and suggested to Pete Wells, the editor of the Dining section,  that the Times address the issue of safe stock handling.  And Pete suggested it to me.

So the column is in no way aimed at Michael, a fine writer with whom I’ve worked in the past. In fact it was his idea. He wanted to understand a complicated issue better, not simply justify his own perspective. I admire him for that.

It turns out that keeping stock on the stovetop is not such a good idea. For an expert opinion I checked with O. Peter Snyder,  a consultant and educator whose writings about food safety are unusually crisp and down to earth.  His website includes an extensive list of downloadable guides to handling food. Most of these are aimed at the food industry, but there are also guides for the home cook and for organizers of large group events, where a simple mistake can make many people sick. 

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For the case of the Japanese family I describe in the column, see

Shiota, M. et al., Rapid Detoxification of Cereulide in Bacillus cereus Food Poisoning. Pediatrics 2010, 125: e951. Doi 10.1542/peds.2009-2319

Iced coffee and tea: [not] taking the heat (NY Times)

ICED coffees and teas should be some of summer’s simplest pleasures, especially when we just steep them in cold tap water, with no kitchen heat and next to no effort. But if you make even a desultory search for advice on cold brewing, you may find yourself mopping your brow deciding how, and even whether, to proceed.

Ratios of tea or coffee to water differ wildly from recipe to recipe; brewing times can be minutes or hours. And while some respected coffee authorities praise the virtues of cold-brewed coffee, others say it’s just not as good as brewing a fresh hot cup right onto the ice.

I’ve found it calming to take a leaf from China and Japan, where one batch of tea is briefly infused as many as seven or eight times and each infusion enjoyed for its particular qualities. Variety can be just as pleasing as consistency, and it can be a way to discover new sides of our most familiar ingredients.

When we brew coffee or tea, we’re doing a very basic thing: bringing plain water into contact with dried plant materials to imbue the water with flavor, color and various active substances, like caffeine and antioxidant polyphenols. It is a basic process, but not a simple one.

As water moves into the coffee particles or tea leaves, it dissolves or suspends hundreds of different substances and extracts them from the solids. If the water is hot, it extracts more rapidly and completely. Hot water also cooks as it extracts, forcing chemical reactions that transform some of the extracted substances into other things, and driving some aroma substances out of the liquid. Cold water, in contrast, extracts more slowly and selectively, produces a simpler extract, and doesn’t change the original flavor substances as much.

So cold-brewed teas and coffees are chemically different from their hot counterparts. They tend to contain less caffeine and less acid. And, of course, they taste different. If the flavor of hot tea or coffee is your gold standard, then cold brews won’t measure up. If you think of hot and cold brews as different drinks, just as a lager isn’t the same as a pale ale, then you may find that you enjoy both.

There are a variety of specialized devices for cold-brewing coffee, including showy ones that pass water very slowly through the grounds, drop by drop, and plain functional ones in which the coffee is left to infuse in all the water overnight, then the brew drained from the grounds. The best known of these, the Toddy, is a plastic container with a thick feltlike pad that fits over a stoppered hole in its bottom. When the stopper is removed, the liquid drains through the mass of grounds and the pad, which filter out tiny coffee particles, letting a dark yet clear coffee concentrate drain into a pitcher. The concentrate can be diluted with either cold or hot water for a quick drink. Because it’s quadruple-strength, it is also handy in cooking, to flavor things like ices and ice creams.

You can improvise a cold-brewing system using a French-press pot or just a pitcher or bowl, with fine sieves, cheesecloth, or cloth or paper filters to strain out the grounds. Infuse coarsely ground coffee overnight in cold water, about 5 cups for every 1/2-pound of coffee, then press or filter the brew from the grounds. In my experience this can become tedious because fine particles clog the filters. And if you leave particles in the brew, they cloud it and give it a rougher body.

Cold-brewed coffee is controversial. To summarize the substance of many recent interviews and blog posts: advocates praise its low acidity and lack of bitterness, and its intense but smooth flavor. Detractors find it lacking in aroma and body and say they get more of both by starting with a double-strength hot pour-over or French press. The pour-over, or a Chemex brew, can be made directly over ice cubes, the French press coffee added immediately to ice. With each, the ice melts and dilutes the coffee to an appropriate drinking strength. Some automatic coffee makers now offer settings and pre-measured coffee doses for brewing strong coffee onto ice.

The hot-brew argument sounded convincing to me, and I’d be happy not to need any special kit or forethought. But when I compared a 12-hour cold brew of freshly roasted Ethiopian coffee side by side with double-strength pour-overs brewed onto ice, each was good, and it was the cold brew that consistently tasted fruitier and more refreshing. That experiment made me a fan of cold-brewed coffee. It’s certainly worth trying. Both are an improvement over simply brewing hot coffee and chilling it for hours in the refrigerator, which gives a cloudy, less flavorful drink on its own, one that benefits from mixing with milk or cream and sugar.

When it comes to tea, there’s less controversy and more flexibility. The standard proportions for American iced tea are about 4 teaspoons or 2-gram bags per quart, with a brewing time of 8 to 12 hours. In Taiwan, where cold-brewed tea has become increasingly popular in recent years and spurred studies of its chemistry, about twice that ratio of tea to water is used for a similarly long infusion. And one purveyor of fine Japanese teas in Kyoto recommends making small cups of cold sencha with 5 times that ratio, infusing first for 15 minutes, then for briefer times. The first couple of infusions are like no other version of green tea I’ve had, intensely grassy and bitter, with subsequent brews progressively milder and more refreshing.

Since cold infusion is a relatively slow and gentle process, proportions and times aren’t critical. There’s plenty of leeway for both. As a general rule, the more fragile the tea leaves, or the smaller the particles, the less tea and time you need to get a strong brew. If a cold brew infuses too slowly, just add more tea.

Two of my favorite cold-brewed teas come from Maricel Presilla, who serves a number of them at her Latin restaurant Zafra in Hoboken, N.J. One perennial on her list is a mojito iced tea, in which oolong tea scented with osmanthus flowers, or with a sliced peach and its pit, suggests the sweet aroma of white rum.

Ms. Presilla also makes an unadorned agua fresca de jamaica, the tart, deep-red sepals that surround the flower of a particular species of hibiscus.

“Nothing compares to the bright color and flavor of the cold-infused drink,” she wrote in an e-mail. “It can steep for as little as two hours and needs nothing but some sugar, though you can include spices like cinnamon, allspice or star anise for a subtle but nice flavor.”

I like to use allspice and then muddle some fresh basil in the infusion just before serving.

Jamaica (pronounced ha-MY-ka) is especially rich in antioxidant polyphenolic compounds, including its anthocyanin pigments, and food chemists are investigating its potential as a nonalcoholic alternative to red wine. They have found that a two-hour cold infusion extracts as much of the pigments as a standard hot infusion, and that the flavor is fruitier and less marked by green-leaf, clove and cooked aromas.

Less heat may mean less flavor in coffees and teas, but not necessarily less pleasure.

July 20, 2011

Copyright 2011 The New York Times

Curious Cook in the New York Times: Cold-brewed tea and coffee

In this month's Curious Cook column, I write about making iced tea and coffee by preparing them with cold water instead of hot. Aficionados differ on the relative merits of cold- and hot-brewed drinks. Cold brewing does extract a different balance of flavors compared to a standard hot brew. If you think of them as different drinks, then you can enjoy each for its particular qualities. I also describe recent studies of tea made with jamaica, the outer flower parts of a kind of hibiscus, and give recipes for jamaica and "mojito" teas from Maricel Presilla of Zafra and Cucharamama in Hoboken NJ.
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Mayer, F. et al. Sensory study of the character impact compounds of a coffee beverage. European Food Research & Technology 2000, 211:272-76.

Ramirez-Rodrigues, M.M. et al. Physicochemical and phytochemical properties of cold and hot water extraction from Hibiscus sabdariffa. Journal of Food Science 2011, 76:C428.
doi: 10.1111/j.1750-3841.2011.02091.x

Ramirez-Rodrigues, M.M. et al.  Hot and cold water infusion aroma profiles of Hibiscus sabdariffa: fresh compared with dried.  Journal of Food Science 2011, 76:C212.
doi: 10.1111/j.1750-3841.2010.01989.x

Wright, J. et al. Effect of preparation conditions on release of selected volatiles in tea headspace. J. Agricultural and Food Chemistry 2007, 55:1445-53.
doi: 10.1021/jf062657v

A hot-water bath for thawing meats (New York Times)

EVEN in kitchens where fresh is king, the freezer remains a handy tool. There’s no easier way to deal with a bounty of meat from a big-box store or a butchering class or a C.S.A. share, or the haul from a fishing trip, or the unpredictable sighting of partridge and other rare birds in the Chinese market. In my house, the freezer is essential for drawing out the enjoyment of the prime mail-order meats that my mother sends for my birthday, and that arrive rock-hard under a block of dry ice.

Less handy, however, is the thawing process, which often requires planning a day or more ahead of the cooking. Food thaws slowly in the refrigerator, especially when kept in its plastic packaging, which is the method recommended by purveyors and the Department of Agriculture to minimize bacterial growth and the loss of juices. Thawing in cold water, 40 degrees or below, is safe and much faster — water transfers heat far more efficiently than air — but it can still take hours. I’ve never had much luck with the defrost setting on microwave ovens, which can start to cook one part of the food while the rest is still frozen.

Now there’s good news for last-minute cooks. It turns out that we can thaw frozen steaks and other compact cuts in as little as 10 minutes, without compromising their quality, and with very little effort. All you need is hot water.

This information comes, surprisingly, from research sponsored by the Department of Agriculture, though the methods aren’t yet officially recommended. The studies have been published in the Journal of Food Science and in Food Control.

At the U.S.D.A. labs in Beltsville, Md., Janet S. Eastridge and Brian C. Bowker test-thawed more than 200 one-inch-thick beef strip loin steaks in three different groups: some in a refrigerator at 37 to 40 degrees Fahrenheit, some in a constantly circulating water bath at 68 degrees, and some in a water bath at 102 degrees.

Air-thawing in the refrigerator took 18 to 20 hours, while the room-temperature water bath thawed the steaks in about 20 minutes, and the hot-summer-day bath in 11 minutes. These water-bath times are so short that any bacterial growth would remain within safe limits.

The water-thawed steaks actually leaked less juice than the air-thawed steaks. The researchers grilled the steaks, too, and found that all the thawed steaks lost about 26 percent of their original weight once cooked, while never-frozen steaks lost 21 percent. The study found no significant differences in tenderness between slow- and quick-thawed steaks.

Eleven minutes is pretty quick, but Brian A. Nummer and colleagues at Utah State University in Logan shaved away another couple of minutes by heating the water bath to 140 degrees, the standard temperature of steam tables in food service kitchens.

The Utah State group found that chicken breasts about a half-inch thick thawed in a little more than 3 minutes, and inch-thick breasts in less than 9 minutes. Although 140-degree water would eventually cook the chicken to medium-rare, they saw no signs of cooking. The quick-thawed breasts did lose slightly more juice than the refrigerator-thawed breasts, but when the chicken was grilled and served, a panel of 18 tasters was unable to tell them apart. And based on their mathematical modeling, the researchers concluded that any bacterial growth would remain well within safe limits.

So there’s no downside to quick-thawing steaks, chops, fillets and other relatively thin cuts in warm water right before cooking. Large roasts are a different story. They take long enough to thaw that there may be time for significant bacterial growth on their surfaces. Prompt cooking might well eliminate that problem, but until this has been studied, it’s safest to continue thawing roasts in the refrigerator or in water under 40 degrees.

Quick-thawing is easy to adopt in the home kitchen. But don’t expect your thaw times to match the lab times I’ve quoted unless you have an immersion circulator or another method to keep the water in motion and at a constant temperature. If the water is still, a cold zone develops around the food and insulates it from the remaining warm water. And without infusions of hot water or heat from a burner, the icy food cools the water bath.

Unless I’m in a rush, I’m happy to let the thawing proceed more slowly on its own while I take care of other tasks. I fill a large pot with 125-degree water from the tap, immerse the plastic-wrapped meat, weigh it down with a slotted spoon to keep it under water and stir the water occasionally. The water temperature drops, but stays above 100 degrees for a half-hour or so, depending on how much food is thawing.

Last week, I thawed 2-inch-thick filets mignons in an hour, whole squab in 40 minutes, a 1-pound whole fish in 20 minutes, and 1 ¼-inch-thick salmon fillets in 15 minutes. Thawing times can vary, depending on the volume, temperature and movement of the water as well as the food’s thickness and how it’s wrapped. (A lot of plastic swaddling interferes with heat transfer. It’s best to remove it and place the food in a thin resealable plastic bag, partly immersing it to force the air out before zipping it shut.)

So when you scan your larder to improvise a quick meal, don’t forget to look in the freezer. The makings of the main course may be just minutes away.

June 8, 2011

Copyright 2011 The New York Times

Curious Cook in the New York Times: Thawing meats in minutes

In this Wednesday's Curious Cook column I write about using a pot of hot water to thaw steaks, chicken breasts, and fish in minutes, rather than the few hours required in cold water or the many hours in a refrigerator. According to recent research funded by the USDA, rapid thawing can minimize the freeze-thaw damage to meat tissues, and taste panels couldn't tell the difference between meats that had been cooked after gradual or quick thawing.

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Eastridge, J.S. and   B.C. Bowker. Effect of rapid thawing on the meat quality attributes of USDA Select beef strip loin steaks. Journal of Food Science 2011, 76: S156-S162.
doi 10.1111/j.1750-3841.2010.02037.x

Shrestha, S. et al., Sensory quality and food safety of boneless chicken breast portions thawed rapidly by submersion in hot water. Food Control 2009, 20: 706-08.
doi 10.1016/j.foodcont.2008.09.011

In salts, a pinch of Bali or a dash of Spain (New York Times)

WHENEVER I’m flying home and the plane passes over the south end of San Francisco Bay, my eyes can’t linger long enough over its startling patches of orange and red.

They’re sea salt ponds, cultivated to produce pure snow-white sodium chloride for industry and for the table. The colors in the ponds come from unusual microbes that thrive in the evaporating brine and produce pigments to cope with the intense sunlight.

A few months ago I finally encountered the colors of that briny life up close, in a jar of salt from the Murray River region in southeastern Australia. The remains of salt-loving bacteria and algae give the crystals a beautiful pink blush and a faint, pleasant aroma.

These days, salts come from all over the world, in many hues and crystal forms and textures. But this welcome blizzard is borne on a whirlwind of obfuscatory hype.