Wednesday, October 31, 2012

A Frightful Harvest

The link between Halloween, corn, and pumpkins
has more to do with harvest time than vampires or
ghosts.  But there is a lot of biology in Halloween,
and it’s not because biology is scar
Dead (or undead) humans have often been associated with the "dying" of summer and the end of the growing season. The Celts believed that there was a link between the death of the growing period and the affects that the dead could have on the sun's life-giving power. Thus, Halloween and Fall have always been linked.

Because of the time of the harvest, several food crops have been pulled into the Halloween traditions. Let’s talk about two of them - from more of a biological point of view.

Jack O’ Lanterns
The pumpkin is native to North and parts of South America, but Halloween originated in Europe. So how did the pumpkin get so involved with the holiday?

Besides making great pies, Native Americans had been eating pumpkin for thousands of years. They are healthy as can be, with lots of fiber, vitamin A, and potassium; plus they are low in fat. But their health value goes beyond what even the natives might have considered.

The point is that pumpkin flesh is useful for
preventing or treating diaper rash. But the
picture is a blatant attempt to keep you on the
page longer.
Recent studies have looked at the health benefits of various parts of the pumpkin. The rind has antimicrobial peptide activity, it has been a well-used herbal remedy for diaper rash for years. But it may be that pumpkin seeds are truly the bee’s knees when it comes to cure alls.

It turns out that the seeds (aka pepitas) have some amazing talents. In ostriches, they are being used to prevent and treat gastrointestinal worm infections. In fact, pumpkin seeds have been used for centuries to expel parasites. The question still remains as to how they do this.

Even without a worm infection, pumpkin seeds can do you much good. While they are often considered a waste product (or more politely termed, an “agro-industrial residue”) from production of canned pumpkin, the ground or pressed seeds have much potential as food additives. A study from the Journal of Food Science in June, 2012 has determined the amount of bioactive compounds (components of foods that have actions beyond their caloric value) in the seeds of various pumpkin species - it turns out they are a superfood.

Pumpkins have high levels of carotenoids and tocopherols, the building blocks of vitamins. The fats are mostly polyunsaturated, which is better for us, and they tend to have a relaxing effect on gastrointestinal and bladder sphincters, so they can been used to treat irritable bowel and bladder.

Stingy Jack carried his lantern and wandered the
countryside – a spirit with no place to go. For
spending a life of drinking and debauching, he looks
to be a fine physical specimen.
Maybe most amazing, the seeds of the pumpkin are reported to reduce or eliminate the intestinal damage caused by methotrexate, a potent anti-cancer drug. They are anti-inflammatory and antioxidant, and provide a potential adjunct to cancer therapy.

This is all very interesting, but it doesn’t explain Jack O’ Lanterns and Halloween. I like the story of Stingy Jack as a viable connection. In brief, Stingy Jack lived in Ireland. He was fond of drink and gambling. These led him into a series of bets with the Devil for the fate of his soul. In each case, Stingy Jack was able to trick the Devil into both giving him something he wanted, and putting Stingy Jack’s soul out of the Devil’s reach.

Once Stingy Jack died, heaven didn’t want him because of his transgressions, and Hell couldn’t take him because of his deal with the Devil. So he was forced to wander the Earthly night, using only a coal ember in a hollowed out vegetable to light his way. He became Jack of the Lantern = Jack O’ Lantern.

The Irish would hollow out potatoes or turnips and put hot coals in them to ward off Stingy Jack in the night. If big enough, they would carve out faces in their lanterns to ward off the spirit of Stingy Jack.  So where does a pumpkin fit into this story?

C. maxima pumpkins can grow are favorites at fall
festivals. All giant pumpkins (>100 lb.s) are of this
variety, but other C. maxima varieties include banana
squash and buttercup squash; these only get to be a
couple of pounds each.
When the Irish began their emigration pattern to the United States, they brought their traditions to America as well, including Stingy Jack. In North America they found pumpkins. Bigger than turnips or potatoes, pumpkins were easy to hollow out. This made them perfect for Jack O’ Lanterns. The change stuck and that is how we came to use pumpkins at Halloween.
The largest pumpkins are of the variety C. maxima. The current record is over 1818 pounds (824.6 kg). However, they are tough to use as Jack O’ Lanterns, as their rinds can be 10 inches (25cm) thick, requiring electric saws to get into and hollow them out. I think Stingy Jack can be warded off without resorting to power tools.

Candy Corn
Candy corn was invented in the 1880’s by a candy manufacturer named the Wunderlee Candy Company. It was instantly popular with the largely agrarian society of that time; a much larger portion of the population were farmers, and they enjoyed the sweetness of bringing in their corn harvest.

Pouring three differently dyed mixtures into molds one after another resulted in the layered effect, a revolution for the time. Dried corn (like in the picture below) are indeed yellow, white, and orange, just like the candy. The order is different, but that may have had more to do with possible mixing of the layers than with a misremembered early life on the farm by the inventor, George Renninger.

Some companies now sell Indian candy corn as well, and the colors of even the traditional candy corn remind one of the colors in Indian corn. Indian corn is sometimes called flint corn because it has a thicker, harder shell, hard as flint. Indian corn isn’t as sugary as sweet corn for roasting or boiling, but it can be used for popcorn and is actually preferred for making hominy. In some future post we should talk about the use of corn in the discovery of genes that can jump around in the chromosomes.

Dried corn turns colors as the sugars change to starch and
the carotenes in different parts mature or resorb. The order
of the colors is different in candy corn, but it is amazing to us
city folk that the colors of candy corn have a basis in biology,
not in marketing.
So is there more to know about corn in the candy corn story? You bet. It takes a lot of corn to make candy corn. Take the endosperm for instance. This is the area under the shell that has the sugars that provide energy for the embryonic plant as it germinates - before it has leaves and can produce its own carbohydrates.

The corn endosperm is full of starch as it matures, but sweet corn has a recessive mutation which slows the conversion of sugars to starch. This makes it sweeter, but once it is picked, the ears mature rapidly as a survival mechanism and the glucose is converted to starch. This is why it is it is best to eat sweet corn as soon as possible after it has been picked.

As a long chain of glucose molecules, starch is not sweet; the glucoses are not available to our taste buds. Break down the starch into smaller units, and then it becomes something tasty, like candy corn. You can achieve this breakdown with heat (boiling the corn will break up some of the starch), but it is more likely that this will be done with enzymes.

This enzyme activity is good for us; it gives us corn syrup, which is the main ingredient in candy corn! Even more amazing, we owe our corn syrup (and thus our candy corn) to bacteria and fungi, because they are the sources of the enzymes industry uses to break down the cornstarch.

To make corn syrup, mix some cornstarch (the dried and powdered endosperm) with some water and add a healthy portion of alpha-amylase. This enzyme is secreted by bacteria and can be isolated from their growth medium. The alpha-amylase breaks starch chains into short oligosaccharides (oligo = few, sackaron = sugar). This is a little sweeter than starch, but is hard to work use.

To make it even sweeter and more liquid (starch doesn’t melt in water as well as glucose; it is less soluble), a second enzyme is added. Glucoamylase is isolated from a fungus called Aspergillus. This enzyme chops up the oligosaccharides into individual glucose molecules. Now it is sweet and liquid enough with which to work.

Glucose and fructose are very similar chemically.
They both have six carbons; they both have twelve
hydrogens and six oxygens. But the devil is in the
details, and the different position of one oxygen
makes fructose sweeter and more soluble.
Of course that isn’t good enough for industry. They have given us a newer product, called high fructose corn syrup (HFCS). One additional enzyme is enough to make the change; glucose isomerase isolated from bacteria converts some of the glucose to fructose, making the concoction sweeter and more fluid.

There have been health concerns about HFCS, including that it promotes obesity. The latest research suggests that there is no relationship between HFCS specifically and increased obesity. However, other concerns are more grave. A recent review of studies about epigenetics (epi = beyond) and autism proposes links between HFCS and heavy metals. HFCS may be low in zinc, and zinc is crucial for heavy metal detoxification as well as controlling the expression of some learning genes. This may be exacerbated by mercury or high levels of copper in HFCS.  But good old candy corn still uses regular corn syrup. 
But this isn’t the end of corn in the process. The molds used to make candy corn are pressed out of cornstarch. The powdery substance is compressible enough to hold a shape, but can be disrupted with minimal force (give it a whack). The finished product is turned out, the cornstarch becomes powder, and can be reused to make new molds. This Halloween candy turns out to be very corny.

Next week we will return to our investigation of immune system functions, beneficial diseases, and immune system malfunctions - did you know plants have immune responses?

El-Boghdady NA (2011). Protective effect of ellagic acid and pumpkin seed oil against methotrexate-induced small intestine damage in rats. Indian journal of biochemistry & biophysics, 48 (6), 380-7 PMID: 22329239

Thais Ferreira Feitosa, Vinícius Longo Ribeiro Vilela, Ana Célia Rodrigues Athayde, Fábio Ribeiro Braga, Elaine Silva Dantas, Vanessa Diniz Vieira and Lídio Ricardo Bezerra de Melo (2012). Anthelmintic efficacy of pumpkin seed (Cucurbita pepo Linnaeus, 1753) on ostrich gastrointestinal nematodes in a semiarid region of Paraíba State, Brazil Tropical Animal Health and Production DOI: 10.1007/s11250-012-0182-5