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. 

Curious Cook in the New York Times: The pungent chemistry of garlic and onions

In my June 9 Curious Cook column I present the culinary highlights from a new and surprisingly readable treatise on Garlic and Other Alliums written by Eric Block, the world's leading authority on the chemistry of the onion family and a professor at SUNY Albany. In addition to many fascinating cultural and botanical details, the book describes the several Allium flavor tribes, explains how to control their pungency, notes the source and treatment of garlic breath, and warns of the hazard posed by garlic and onions to household pets.

Curious Cook in the New York Times: Tomato leaves

In today's Curious Cook column I write about tomato leaves, which have an undeservedly toxic reputation. Like other members of the disreputable nightshade family, tomato plants do contain alkaloids, but the tomato alkaloid is poorly absorbed in the body and lowers LDL cholesterol levels. Tomato leaves have occasionally been used as a herb without any reported problems. Their flavor runs from viney to grassy to tea-like, depending on how they're handled.

Curious Cook in the New York Times: Asparagus snapping

In the May 6th edition of The Curious Cook, I write about asparagus: why and how it toughens after harvest, how to slow its toughening, and whether snapping the stalk really separates the tough from the tender.

Curious Cook in the New York Times: Organic produce and yak cheese

In today's Curious Cook column I write about nutritional claims made for organic fruits and vegetables and for yak cheese made in Nepal.

___________________________

 Benbrook, C. et al. New Evidence Confirms the Nutritional Superiority of Plant-based Organic Foods. The Organic Center, March 2008.

http://www.organic-center.org/science.nutri.php?action=view&report_id=126

 

Or-Rashid, M.M. et al. Fatty acid composition of yak (Bos grunniens) cheese including conjugated linoleic acid and trans-18:1 fatty acids. J. Agricultural and Food Chemistry 2008, 56: 1654-60. http://dx.doi.org/10.1021/jf0725225

 

Curious Cook in the New York Times: Clarifying liquids with gelatin

In my column in the September 5 New York Times, I describe a recently discovered method for making intensely flavored liquid essences, or "consommés," from all kinds of foods, from meat stocks and fruit juices, baked potatoes and chocolate. 

The Times prints a recipe for brown butter consommé from H. Alexander Talbot and Aki Kamozawa, authors of the remarkable blog Ideas in Food. David Kinch, chef-owner of the acclaimed restaurant Manresa in Los Gatos, California, generously sent me a recipe for a pumpkin consommé, but the the Times didn't have space to print it. With chef Kinch's kind permission, here it is.

Curious Cook in the New York Times: Potato chips

In today's Dining section of the Times I write about potato chips: the sounds they make, the music that has been made from them, and the forces that shape them.

My source for those shaping forces was Paul Green, a professor of plant biology at Stanford, and a friend. Paul died in 1998. In the column he became "Mr. Green." When I find a near-perfect chip and think of him, I don't think of Mr. Green, I think of Paul.

For helping me understand and explain the physics of chip shape, I thank two people who worked with Paul as postdoctoral fellows: Jacques Dumais of Harvard University and Sidney Shaw of Indiana University. Of course the simplifications and approximations are my doing, not theirs.

__________________________________

Kim, S.-E. et al. Development of a method for the musical expression of cognitive food taste. Food Sci. Biotechnology 2005, 14, 738-42. 

Zampini, M. and C. Spence. The role of auditory cues in modulating the perceived crispness and staleness of potato chips. Journal of Sensory Studies 2004, 19, 347-63.

Green, P. Transductions to generate plant form and pattern: An essay on cause and effect. Annals of Botany 1996, 78, 269-81.

New developments in tomato flavor, part 1: Save the seeds

Two interesting studies of tomato flavor have appeared in the last month. One originated in the kitchen and may immediately change the way you taste and use tomatoes. The other involves genetic engineering, and offers a scent of tomorrow's tomatoes. Here's the first; check back in a few days for the second.

Acrylamide: an update

Acrylamide is the industrially useful but toxic chemical that reared its ugly head among our potato chips and fries in 2002, when Swedish food chemists first thought to look for it in foods. Acrylamide is known to cause cancer and other illnesses in animals, and nerve damage in humans. It's suspected to be a human carcinogen as well. Acrylamide concentrations in drinking water are regulated by the Environmental Protection Agency, and the Swedish chemists found food levels hundreds of times higher than the EPA limit.

Since 2002, we've learned a lot about acrylamide in food.