Popped corn Photo: D3 San Francisco, flickr (click to see photo in original context

Popping corn, or anything else, all comes down to pressure. Pop-corn has a particularly impermeable pericarp (the corn kernel’s shell), so as it is heated, the water inside the kernel vaporizes into steam and the starch turns into something close to a liquid. Eventually the heat creates enough pressure to split the pericarp and the starch of the corn kernel bursts out, resolidifying into the distinctive shape of popcorn. If there is even the smallest hole in the pericarp, the steam can escape from the kernel as it’s generated so the pressure never builds up enough to explode the pericarp — the reason some kernels will fail to pop in every batch. The explosive build up of steam is also the reason tea kettles need to be able to release steam while they’re used to boil water. The alternative would be exploding tea kettles which are a lot more dangerous (and a lot less tasty) than exploding corn kernels.

Un-popped popcorn photo: MissTessmacher, flickr (click to see photo in its original context)

It was this reason (along with my discovery of the website on April 1st) that I was so suspicious of the idea of popped sorghum a few days ago. Thanks to Party Cactus and Jeremy, I now know that sorghum does indeed pop like corn (there’s even a variety called “Tarahumara Popping”) and, in fact, thanks to the link Jeremy provided, I’ve discovered that most grains and even some other things (including cowpeas!) can be popped using the proper equipment.

By using a machine that is in some ways similar a pressure cooker, even grains without hard impermeable pericarps can be popped. The popping machine lets pressure rise equally inside and outside of whatever grain is being popped. When the outside pressure is released, the grains/kernels/seeds instantly pop.

It doesn’t sound as visually satisfying at the pop-corn popper I remember from my childhood, where half the fun was watching in anticipation for the first kernels to leap into the air, but a very cool invention never the less.

I’ll certainly be keeping an eye open for popped sorghum to show up out here in the bay area.

A. Normal popcorn kernel. Applying heat makes the pressure build up inside the kernel until the kernel pops open. B. A popcorn seed with a hole in the pericarp. Heat creates pressure, but it escapes through the hole so it never builds up enough to pop open the kernel. C. Even in grains with permiable pericarps, the pressure can build up inside, if the pressure outside is also high. Dropping the outside pressure suddenly still caused the grain to pop.

Corn Smut photo: oceandesetoiles, flickr (click to see photo in its original context)

And no that doesn’t mean corn pornography*. Corn smut, or Ustilago maydis, is a fungus that infects corn plants. It’s an old acquantance from my days working in the field. We always used to tell the new hires that corn smut was a rare delicacy in some countries (as we’d been told ourselves), but this was in the days before iPhones so until recently I never actually checked on this bit of received wisdom.

Turns out this particular bit of knowledge was true:

The immature galls, gathered two to three weeks after an ear of corn is infected, still retain moisture and, when cooked, have a flavor described as mushroom-like, sweet, savory, woody, and earthy.

More corn smut. Photo: moskatexugo, flickr (click to see photo in its original context)

I haven’t been able to figure out what the trade off in nutrition is between the ear of corn that is produced by a normal plant and the fungal galls that can be harvested from a plant infected with corn smut. I’d imagine corn smut provides more (and more complete) protein than an ear of corn (assuming corn smut is nutritionally similar to mushrooms.) But what’s the comparison in number of calories? The fungus is certainly sold at a higher price pound for pound.

My renewed interest in corn smut comes courtesy of a new paper** that came out in PLoS Biology describing how the fungus steals energy from infected corn plants without triggering the corn’s usual anti-fungal defenses. It’s an interesting read, you can check out the paper itself since PLoS Biology is open access, or Diane Kelley’s summary at “Science Made Cool.”

I’d seen a number of talks recently about another fungal parasite, powdery mildew in Arabidopsis, but somehow it’s much easier to focus on this stuff now that I can connect it back to corn. Even mammalian systems can be interesting*** once the make that connection.

*Please PLEASE don’t let that phrase start showing up in the search terms people use to find my site!

**Wahl R, Wippel K, Goos S, Kämper J, Sauer N (2010) A Novel High-Affinity Sucrose Transporter Is Required for Virulence of the Plant Pathogen Ustilago maydis. PLoS Biol 8(2): e1000303. doi:10.1371/journal.pbio.1000303

***The talk I’m practicing for Monday actually uses an example of a pheromone receptor in new world monkeys that was lost 23 million years ago in old world monkeys (including us humans).

MAT points out another more pragmatic reason yellow corn may not be favored in Africa that I hadn’t heard of before. Apparently the extra carotenoids make yellow corn more susceptiable to spoilage than white corn varieties, a very pertenent issue in areas without access to the kinds of storage facilities we take for granted in American agriculture.

Jeremy at the Agricultural Biodiversity Weblog picked up the torch, highlighting a number of their own previous posts relevant to the discussion, including one by fellow blogger Luigi that relates the reaction of his own wife, originally from Kenya, on ordering polenta** at a restuarant and receiving a yellow dish.

Fortunately breeds of corn that contain even more beta carotene (the carotenoid most easily converted into vitamin A by our bodies) aren’t even yellow all the time. Although I wasn’t able to find a freely available picture, sometimes they’re ORANGE.*** While it turns out the correlation between color and beta carotene content isn’t perfect****, there’s still reason to hope varieties bred for the highest pre-vitamin A content will end up a striking orange color. For a visual examples of how orange corn can get, check out check out Dr. Rocheford’s lab website.

Will the distinction between orange and yellow***** be enough to get over the Africa’s lack of enthusiasm for yellow corn? Will the benefits of a diet with more vitamin A be enough to outweight the issues with yellow corn going “off” if stored improperly? I certainly hope the answers to both these questions are yes, but we won’t know for sure until we try. And there are some hopeful signs. For example this segment in a story from NPR:

Winter-Nelson and one of his graduate students took some of this orange corn to an open-air market in Mozambique for a taste test. The market-goers still preferred their white corn, but almost half of them agreed to exchange it for bags of orange corn when they heard it was more nutritious.”Probably the most encouraging part of it for me was that people who reported that they didn’t have much dietary diversity,” Winter-Nelson says. “People who reported that they didn’t eat very many fruits and vegetables, [or] that they very rarely ate animal products of any kind — eggs, meat, or chicken — were the most likely to take the trade.

“So, the ones who need it were attracted to it.”

So that’s a hopeful sign.

Two ears where some kernels received C1 from both parents, some from one parent and some from none. In a whole field full of C1 homozygotes, almost the kernels would be dark purple/black. Image courtesy of MaizeGDB and MG Neuffer

As I was proofing this post today, one other thing occurred to me. If the objection to yellow corn is primarily based on the color (let’s leave aside the issue of flavor for a moment), wouldn’t the simplest solution for the biofortified corn be to breed in an allele like C1 that turns corn kernels purple/black? There’d be absolutely no chance of the corn being mistaken for normal yellow corn, and since C1 acts on the production of anthocyanins, a completely different kind of plant pigments, it shouldn’t impact the level of beta carotene in the biofortified corn. Please point out in the comments if I’ve missed something obvious.

*This isn’t to say the food aid itself is unpopular, only that people prefer not to eat corn that resembles it when they’re NOT starving.

**A dish made of boiled corn meal, see photo below. A few years ago my mother discovered a lasagna recipe that substituted well cooked polenta for lasagna nuddles. About which, all I can say is that if you otherwise couldn’t eat lasagna (for example people who avoid eating gluten found in grains like wheat, barley, and rye by choice or necessity), polenta lasagna is a lot better than no lasagna at all.

Polenta. photo: Marilyn M., flickr (click to see photo in its original context)

***The amazing genetic diversity of maize also means these varietes can be produced without the need for genetic engineering. Which means getting the seeds to those would could most benefit from them would be faster and cheaper than something like golden rice which governments will hopefully approve someday.

****Harjes, C.E., Rocheford, T.R., Bai, L., Brutnell, T.P., Kandianis, C.B., Sowinski, S.G., Stapleton, A.E., Vallabhaneni, R., Williams, M., Wurtzel, E.T., Yan, J.B. and Buckler, E.S. (2008). Natural genetic variation in lycopene epsilon cyclase tapped for maize biofortification. Science DOI: 10.1126/science.1150255

****It occurs to me one factor in whether the distinction between yellow and orange is important may turn out to be whether different local languages contain a word for orange. Languages have been studied that contain as few as two words for colors (roughly: dark and light) and a color name describing orange is almost never found in languages with less than 7 color names. … sorry a distribution requirements class that I had to take in college just became arguable relevant. This is exciting!

Sprouting onions. Photo: J. C. Rojas, flickr (click to see photo in its original context)

This isn’t a lot that is biologically exciting about the EverMild onion from what I can tell. Hopefully there will be more details on Monday when these onions are officially announced on Monday, but the short version seems to be that plant breeders at Seminis have developed a variety of sweet onion that can be grown in the pacific northwest over the winter, supplying sweet onions grown within the US at a time when they normally must be shipped in from the tropics or southern hemisphere.

So plant breeding has produced a new hardier variety of sweet onion* and is taking part in the new trend towards “branded” breeds of produce (like the Jazzman rice I talked about earlier this year). This would normally hardly be news (Seminis sells over 3500 kinds of seeds and they’re adding one more), and if it was at all, would be a story of reducing the demand for imported food with new varieties adapted to the US (again there are parallels to the Jazzman rice story). But I expect we will be hearing a fair bit about the EverMild onion at some point, because Seminis was bought by Monsanto several years ago, and I’ve alreadying read comments from people convinced it is a “secret GMO.” Nevermind that sweet onions (onions breeds that are lower in sulpher) have been around for a century.

Coverage of the branded onion in the St. Louis Post-Dispatch, though unfortunately the coverage seems written by and for MBAs and marketing majors not biologists. If you see any coverage that actually gets at the breeding behind this onion, please let me know.

Random onion fact: Onions (and Garlic) are actually monocots, more closely related to pineapples and bananas (and yes, corn) than to most of the vegetables in the produce section.

*Or bred a hardier variety of onion to be less pungent, or introgressed traits from one into the other. These are the questions I wish I knew the answers too, and it’d be fascinating to talk to one of the onion breeders who worked on this project. Plus I could ask them if Seminis still practices what I’ve been told is the traditional pairing of onion and carrot breeding at vegetable seed companies, which is entirely unrelated to the EverMild Onion, but I’m just curious.

A stalk of brussels sprouts photo credit: cbmd, flickr (click for photo in original context)

Last week Greg over at Pie-ence was talking about the amazing variety of vegetable crops breed out of a handful of species within the genus Brassica, specifically Brassica rapa and Brassica oleracea.* I’m referring to these as cruciferous vegetables, which is actually a wider category including all the vegetables within the mustard family of plants (scientifically this is called the Brassicaceae). But one of the cool things about having so many kinds of vegetables within the same couple of species is that, because they’re the same species, they can still be interbreed with each other to create “new”** vegetables.

I still remember the first time I saw such a new vegetables, the broccoflower***. I didn’t even LIKE vegetables back then but I was still fascinated by this strange new plant in the produce aisle. Needless to say, others didn’t share my excitement as the broccoflower did not, in fact end up taking the world by storm (I’m not bitter!), although I do still spot them from time to time at the grocery store. I was able to dig up this very enthusiastic article on the broccoflower from twenty years ago. The internet is a wonderful thing.

The internet is also responsible for telling me about the latest development in cruciferous vegetables. The “flower sprout”, the result of breeding work using brussels sprouts and kale, both breeds of the species Brassica oleracea. Right now they’re only available in England, otherwise I’d have tried it already. How could I resist a vegetable described as:

“a purple and green triffid-like crop”

Assorted colorful cauliflowers (orange ones make lots carotenoids the group of molecules that includes pre-vitamin A, the purple ones make anthocyanins another kind of plant pigment). photo: Le Grande Farmers' Market, flickr (click to see photo in its original context)

Both the links in the above paragraph are to stories that also contain pictures of the flower sprout.

I guess my point here is that plant breeders can produce all kinds of cool new vegetables given the chance. The limiting factor really is what people will buy, not the variability of plants.

*Brassica oleracea is responsible for Broccoli, Brussels sprouts, Cabbage, Cauliflower, Collard Greens, Kale, and Kohlrabi. Brassica rapa is responsible for Bok choy, Komatsuna, Mizuna, Rapini, Chinese cabbage, and Turnips. And Brassica napus, a species that resulted from the hybridization of Brassica rapa and Bassica oleracea adds Rutabaga and Canola (not a vegetable, but a key crop none the less) to the count.

**I’m putting new in quotes throughout this article because I don’t know what the actual definition of what makes vegetable different enough to qualify as a new type is.

An Arabidopsis flower (also a member of the mustard family that produces so many kinds of vegetables). The name cruciferous vegetables comes from the pattern of four petals. Apparently it looks like a cross to some people, hence cruciferous. In Arabidopsis the flowers are only a few millimeters big. photo: BlueRidgeKitties, flickr (click to see the photo in its original context)

***From everything I was able to read the broccoflower really is the result of a cross between broccoli and cauliflower (followed by many more generations of selective breeding of course). It is generally lumped in with the cauliflowers because its head is made of up inflorescence stem tissue, while broccoli heads are made up of immature flower buds. Cauliflower plants (and broccoflower plants) have broken copies of the CAL gene, which (when it isn’t broken) is helps the plant decide to switch from producing stems that were bear flowers to the flowers themselves. Without a functional version of CAL, cauliflowers just keep making denser and denser stems, producing the distinctive heads of cauliflower. If you have journal access, you can read more about the CAL gene at this science paper: http://dx.doi.org/10.1126/science.7824951

Since the effect of breaking this gene suggests to me that it is probably a recessive mutation (it won’t have an effect on the plant unless the plant inherits a broken copy from both parents) I imagine developing the broccoflower involved mating the offspring of a broccoli / cauliflower mating and mating them with normal cauliflowers again, since plants with one cauliflower and one broccoli parent should inherit a working copy of the CAL gene from their dad (or mom) the broccoli. But this last paragraph is purely my own speculation.

Because SFUSD has focused on reducing fat and empty calories in cafeteria items, the meals are now very close to the USDA minimums, and are based on a meal which includes either 1-percent white milk or skim chocolate milk. “Replacing skim chocolate milk with skim white milk would cause the calorie count of the meal to drop below the USDA-mandated minimum,” says Woldow [A member of the San Francisco School District Student Nutrition Committee]

I feel weird thinking about this. Cutting sugar (regardless of whether it originates in sugarcase, or corn, or sweet sorghum, or the sugar beet) from school lunches is a laudable goal. But free and reduced price school lunches are also the closest thing some kids will have to a real meal all day. So San Francisco School District, in the push to make school lunches more healthy, if nothing else could you please increase the portions for healthy things as you cut out the foods you don’t approve of?

Cutting calories from a program that has a real impact on childhood hunger and malnutrition in our country isn’t something you should be proud of.

And just to be clear all that happened in the article linked above was to substitute sugar (produced from sugar beets, or sugar cane) for corn syrup on a calorie for calorie basis.

Delicious pumpernickel bagel.

Its tasty but what is it? First, a disclaimer. I’m going to be discussing traditional pumpernickel bread. The kind pictured to the right is almost certainly modern pumpernickel which gets its color from dark substances like molasses or cocoa powder, and often is made with wheat flower rather than the traditional rye. But that’s a boring story. This one is more exciting!

Pumpernickel is a form of slowly cooked rye bread first created in parts of present day germany. The bread would cook at low temperatures for up to a full day. By the end of the baking, a chemical process called the Maillard reaction has taken place which generatedboth the darker color and one component of the characteristic pumpernickel taste. The simplest (though it’s probably not perfectly accurate) way to think of pumpernickel bread is that the long cooking darkens the whole loaf the way toasting (without burning) can darken a single slice.

But why were the germans eating (and growing) rye instead of wheat in the first place?  Rye is a relatively close relative of wheat (and barley)* and the currently accepted wisdom is that it initially was domesticated through Vavilovian mimicry**. Wild rye grew as a weed in early wheat fields, when farmers went out to pull weeds, individual rye plants that looked the more like wheat were the most likely to be missed by exhausted farmers (and as a result survive long enough to reproduce and seed the next generation). Farmers were unintentionally selecting for rye that looked more and more like wheat.***

Rye seed head. Photo manu claude, flickr (click to see it in original context)

The end result was a weed that was even more difficult for farmers to control, but also one with larger seeds that was already adapted to the lifestyle of an agricultural crop. Which would all just be an obscure, if interesting, bit of agricultural ecology if it weren’t for the fact that rye is in many ways a tougher, hardier, plant than wheat. Farmers could grow rye where wheat would fall, feed children who would otherwise starve.

Rye bread was apparently considered less desirable than wheat and I can imagine the unique cooking process of the original pumpernickel bread could have been devised as a way to make it look and taste different from regular rye bread.****

The plant biologist’s perspective on pumpernickel: a little chemistry and a lot of crop domestication.

Oh, and one final note, I was NOT impressed with the wikipedia article on pumpernickel. Here’s the first source cited:

From the label of a German-style pumpernickel sold by Trader Joe’s in eastern Massachusetts.

*If you’ve read Jarad Diamond’s Guns, Germs, and Steel, one of the points he makes is the the middle east (the origin of wheat, barley, rye, and oats) was much richer in potentially domesticable grain species than other parts of the world as agriculture was first emerging.

**Yup, the same Vavilov I’ve been talking about this week, but this article was inspired by a pumpernickel bagel, not the book on him I was reading. Vavilovian mimicry describes a weed that has evolved to look more like a crop species. Vavilovian mimicry is an adaptive response to hand weeding as herbicide resistance is to chemical control of weeds.

***Since I’m a maize geneticist at heart I also have to point out that some kinds of teosinte have been evolved to look much more like domesticated corn in areas of mexico where teosinte grows as a weed in cultivated corn fields and intensive hand weeding is still practiced. It’s not as clean an example of vavilovian mimicry though, because maize and teosinte can mate to produce fertile offspring, so genes can flow between the two populations, unlike wheat and rye.

****Of course now traditional pumpernickel bread (the kind made with solely rye flour) will often be paired with foods like caviar and smoked salmon (or at least so wikipedia tells me).

Square watermelon. Photo: laughlin, flickr (click photo to see in original context)

This is an addendum to my previous post: Not Genetically Engineered: Watermelons

At the time I thought the only awesome thing about watermelons that people calling genetic engineering was seedlessness. It turns out there are also square watermelons. Are they genetically engineered? I guess my title does kind of give away the answer.

Square watermelons aren’t the product of genetic engineering, or radiation mutagenesis, nor even conventional breeding. Instead they are a result of a technology known as “the container.”* Farmers, primarily in Japan, place a box around a fertilized watermelon flower. As the watermelon grows it fills the container, eventually filling even the corners. When the box is removed, it reveals a cube shaped watermelon.

There’s no real benefit to growing a cube shaped watermelon, yet some people will pay more for one. Interest in strangely shaped or colored foods in a natural response for many of us human beings.

Pears inside bottles, when they clearly couldn't fit through the neck. Isn't biology fun? photo: kasiaeryn, flickr (click to see the photo in its original context)

It’s the same things (fruit growing inside containers, and a fascination with strange food and drink) which results in complete pears inside bottles**. The bottle is put around the fertilized pear flower, and the pear develops inside. A great way to puzzle people who usually think in terms of buying food rather than growing it.

*<sarcasm>Clearly we’re playing with forces beyond our control here. When will we crazy scientists stop trying to play god!</sarcasm>

**If you’re interested, there’s a six minute youtube video with all the info you could ever possibly want on the proper technique for growing pears inside wine and liquor bottles. <- Be forewarned! If, like me, you don’t actually have access to a pear tree, watching this video will just leave you frustrated with your life.

Powdered sugar at the local grocery store

First of all I’ve never understood why people care wether a given cup of sugar come from sugar cane or sugar beets. Regardless of source, white sugar is at least 99.9 percent pure* sucrose. Sucrose is a single molecule with an exact structure that is the same regardless of source. (Like salt crystals, or de-ionized water it’s a pure substance, only one step up from elements like carbon and oxygen).

A model of the sucrose molecule. All sucrose, regardless of source, will have this same structure. If it doesn't, it's not sucrose. Image from wikimedia and distributed under the creative commons 3.0 share alike license.

That said, I’ve never before seen a label on a bag of sugar that proudly announced what it is NOT (beet sugar). I don’t know if this is a reaction to the current publicity about herbicide resistant sugar beets, or the old feelings about the, non-existent, differences between sugars refined from different plant sources taken to their logical extreme, but either way, in this christmas of all christmases, is not the time to be kicking beet farmers when they are down.

Early this fall Jeffery White, a federal judge based in San Francisco, ruled that the approval of herbicide resistant sugar beets was invalid because the environmental impact report didn’t take into account economic effects. Even though his ruling raised absolutely no concerns about the safety of beet sugar, the ruling in one stroke delivered a huge a publicity boon to anti-GMO groups that are trying to frighten Americans away from beet sugar, and left sugar beet producers unsure if they would even be able to sell this year’s crop, let alone whether they would be allowed to plant next year’s.

While it looks like farmers have indeed been allowed to sell this year’s crop, it remains an open question if there will be enough seed that meets the new restrictions imposed by this ruling to continue sugar beet production for the next two years. Given that in 2007, farmers produced over 7 million pounds of sugar beet seeds to plant over one and a quarter million acres of sugar beets, finding enough seed to keep planting for two years without new production (new non-GM sugar beet seed will take two years to begin production**) is no trivial task.

All in all it has been a tough year for sugar beet farmers. My thoughts are with them, and, while I can’t do much, I did at least hunt down some powdered sugar I’ve since been told confectioners and powdered sugar are the same thing anyway which made no statements about its crop of origin rather than support the company whose packaging is pictured above.

If you celebrate Christmas, have a Merry Christmas. If you don’t, I hope you’re having a great time anyway.

*20 pounds of white sugar contains less than one teaspoon of anything other than the molecule sucrose.

**Sugar beets are biennial, and since seed companies can’t plant new seed beets in reaction to the Judge White’s ruling until this spring, an increase in non-herbicide resistant beet seed production won’t result in any new seed until the planting season of 2011. For more on the subject, see this news report.

Botanical illustration of Eleocharis dulcis, the Water Chestnut

The water chestnut is one of those foods I’ve eaten my whole life without knowing anything more about it than flavor and appearance (and that only because it so often shows up in frozen vegetable mixes).

The scientific name for the Water Chestnut is Eleocharis dulcis, and it’s often classified as a sedge.* It’s also a quite awesome plant. Consider:

• The visible parts of a water chestnut plant are leafless stems that perform photosynthesis. (The water chestnut has almost completely abandoned leaves!)
• The edible part of the plant is a botanical structure called a corm** which is a modified underground stem used by a plant to store energy (water chestnut plants are very much about stems). Not to be confused with bulbs like those of onions and garlic, which can look similar, but are instead made up mostly of leaves
• The reason water chestnuts remain so crunchy after cooking is that their cell walls are reinforced by special phenolic compounds, the same class of molecules as capsaicin, the molecule that makes chilli peppers spicy.

The genus Eleocharis also contains species like Eleocharis vivapara which switch between C3 and C4 forms of photosynthesis depending on whether they’re grown on dry land or in swamps. The relative advantages and costs of these two different forms of photosynthesis are worth a post on their own, but I’d always assumed it was an either/or choice and didn’t realize ANY plant species could pick to use whichever system was best suited to the local environment.[citation]

Domestication:

Canned Water Chestnuts photo: kattebelletje, flickr (click photo to see in original context)

The ancestors of water chestnuts were weeds in early rice paddies. It’s easy to imagine some rice farmer living six thousand years ago sampled the weird bulbous corms attached to the roots of the weeds she had just finished pulling from herfield and found them delicious (or at least not poisonous). Over time this rice farmer encouraged this edible weed at the expense of other, useless weeds, even saving corms or seeds from the occasion bigger, or better tasting, or in some other way more desirable plants and planting them in a separate field the next year. Eventually the practice spread to other farmers, and the domesticated water chestnut was selected into existence.

And that, as nearly as I can piece it together, is the story of the water chestnut, an awesome domesticated weed that does amazing things with stems.

More detail on the agriculture of water chestnuts.

*Sedges can look a lot like grasses, but botanically aren’t. They do belong to the same group of species, monocots, as the grasses do, but it’s a group that also includes everything from bananas to pineapples.

**Not just cool because it looks sounds like corn