Thursday, February 27, 2014

Pass the OJ, mate: Why it took more than 400 years to stop scurvy

Avast, ye scurvy dogs! Ahoy, me limeys!

What’s that? You’re not wearing your eyepatch? You’ve misplaced your cutlass and parrot? Well, you’re forgiven. We’ve just got pirates on the brain over here because we’ve been learning about how citrus has been used to treat and prevent the terrible disease of scurvy.

As pirates of old could attest, you really don’t want to get scurvy. It’s a truly wretched condition, which starts with fatigue and only gets worse from there–potentially even life threatening.

Fortunately, scurvy is very easy to avoid. Its cause is quite simple: a lack of vitamin C. Because today’s diets, which include plenty of fresh fruits and vegetables, usually contain adequate amounts of this crucial nutrient, scurvy is fortunately now quite rare.

But between 1500 and 1800, scurvy is thought to have killed as many as two million sailors. On some long sea voyages, as many as two-thirds of those on board perished of the disease. These figures may seem almost unbelievable today. Yet there was confusion about scurvy’s exact cause for hundreds of years.

As early as the 1500s, people saw a connection between citrus juice and scurvy prevention. But they didn’t know exactly what was working to prevent the sickness. Some came to the conclusion that it was the acidity of the citrus that was effective.

In 1747 James Lind conducted the
world's first clinical trial to find
a treatment for scurvy.
In 1747, a Scottish doctor named James Lind conducted the world’s first clinical trial on a group of scurvied sailors. The seamen were divided into six experimental groups and received daily doses of six potential “cures.” Group 1 got seawater, group 2 got vinegar, group 3 got a “spicy paste” and barleywater, group 4 got sulfuric acid, group 5 got cider, and the fortunate group 6 got two daily oranges and a lemon.

Well, they ran out of fruit in six days’ time, but it was enough. By then, one fruit-eating sailor had recovered enough for full duty, and the other was almost better.

Oddly enough, this successful experiment didn’t fully convince Lind himself. However, he did recommend that sailors consume citrus juice and watercress (also high in vitamin C) while on voyages. The British Navy also began issuing daily rations of lemon juice to sailors, which worked very first.

History intervened, and the idea that citrus cured scurvy was almost lost. You see, lemons were hard to come by in the British empire, but limes, which grew well in the Caribbean colonies, were not. So the British navy started supplying its sailors with lime juice instead. (Hence, the term “limey” for a sailor.)

The problem? Limes are significantly lower in vitamin C than lemons. (Of the common citrus fruits, oranges and lemons are the highest in C, with grapefruit next, and limes in last place.)  What’s more, at sea, the lime juice was stored in conditions that destroyed what vitamin C it did have. In other words, the limeys’ lime juice wasn’t actually working, and some travelers consuming lime juice still got scurvy.

It had also been noticed that people who ate fresh meat, and only meat, didn’t seem to suffer from the sickness. (This is because fresh meat contains small amounts of vitamin C from the diet of the animals.) Yet those who were living mostly on salted and preserved meat definitely did. This observation did even more damage to the “fresh fruit” theory of scurvy. Never mind the oranges and lemons! the thinking began to go. Scurvy is caused by spoiled meat!

Early polar explorers did not prepare correctly to prevent
scurvy, and suffered severe consequences.
It was this thinking that sent expeditions to the South Pole in the early 1900s without any sources of vitamin C. Oh, they were concerned about scurvy, all right—so they obsessively ensured that all their preserved and canned meat was in great condition. Of course, this didn’t work, and scurvy ensued, much to the men’s despair.

Indeed, scientists didn’t figure it all out until 1932, when vitamin C, or ascorbic acid, was finally discovered and its role in preventing scurvy was confirmed (in fact, ascorbic basically means “no scurvy”). After centuries and literally millions of deaths, at last we truly understood how to prevent and cure this terrible and deadly sickness. The cure really was as simple as eating an orange (or another good source of vitamin C).

If you’re anything like me, you’re now feeling pretty grateful that you don’t have to spend months on end at sea with nothing to eat but salted meat and hardtack. Maybe you’re also craving some delicious, fresh citrus. Although the chances are good that you’re not at risk for scurvy, the high vitamin C content of these fruits is, of course, still extremely good for you in other ways. Studies suggest that Vitamin C may help to protect against cancer and cardiovascular disease, and to reduce the length of the common cold.

In honor of those lost on high seas, then, how about a fresh tangerine, or a glass of  OJ? In keeping with our nautical theme, you could even mix with it with some rum. That’s a drink sometimes known guessed it....the Scurvy Medic.

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Friday, February 7, 2014

Baby, It’s Cold Outside: How We Protect Our Citrus Trees From Freezing

Have you ever left a tender houseplant on the porch or patio during a cold snap? What about that time there was an early frost and you forgot to cover the tomatoes? If you remember how frustrated you felt at finding your plants killed or damaged by the chill, can you imagine what it would be like for a citrus grower to see this?

After effects of a killing freeze.
Yes, that’s thousands of ruined oranges on the ground after a killing freeze (a long time ago, fortunately). In the past, citrus growers often lost their whole livelihood in a single episode of below-freezing weather. It’s happened many times in Florida’s history.

Various ways citrus trees were protected from cold weather.
Over the years, growers have tried all kinds of methods to protect Florida’s citrus crop from cold weather. Sand and hay have been piled around trunks. Wooden and canvas tents have been built—around each individual tree! And some growers have even tried building a roof over their groves

Later, in-grove heaters, which kept the air warm around the trees, and wind machines, which “mixed” ground-level cold air with cooler air higher up, became very popular. But today, Florida growers overwhelmingly use a method called micro-irrigation to protect their groves.

You might have seen a photo of oranges after micro-irrigation. It’s eerily beautiful, but it doesn’t really look like it would be good for the tree, does it?

Surprisingly, though, all that ice is actually keeping the tree warm! When water freezes and changes its state from a liquid to a solid, that process actually gives off some heat.  This is called “heat of fusion”--and as long as irrigation machines continue to apply a fine spray of water, it continues, keeping the plants warm. However, growers do have to watch out for wind. That’ll make the ice evaporate...which will lower the temperature again.  (Here's a Wikipedia article for the science-minded who’d like to read more about “heat of fusion”.)

If this sounds kind of complicated, it is. Growers use some pretty high-tech equipment to monitor conditions and make sure the trees don’t accidentally get damaged, while also conserving water as much as possible. Growers often don’t get much sleep on cold nights. But at least we don’t have to build a little shed around each tree anymore!

If you happen to have your own citrus trees at home, you may now be wondering if you should be covering them with ice when the mercury drops. The answer is no. This method is too fiddly and too risky for the home grower.

A tiny tent protecting a small orange tree from the cold.
So what should you do? It depends in part on what type of trees you have, since some types of citrus are much more tender than others. In general, though, you probably don’t need to be concerned about your trees or their fruit till temperatures drop to 28 degrees or lower for four hours or more.

If this is in your forecast, there are a few things you can try. First, water your trees well. It will help keep them warm, and reduce their stress. If your tree is small enough, drape it with a fabric cover; if it’s too big for this, wrap its trunk with cloth.  You can also try putting strings of Christmas lights or another electric light on the trees to generate a bit of heat. And if the forecast looks really dire and your fruit is ripe, do pick it.

Yes, it’s true; growing citrus in Florida, especially its more northern areas, can get a little complicated sometimes. But we’re sure you’ll agree that the sweet, juicy fruit we harvest makes it all worthwhile.

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