Icy Sparks from your Carrots !!

If you often cook mixed vegetables from frozen in a microwave, on a microwaveable plate you may notice that carrots produce sparks during cooking and, on closer examination, they display small burns. Why is this? several factors make frozen carrots susceptible to the effect described (although other vegetables also do this).

Mark Morgan, professor of food engineering at Purdue University states that chopping mineral-rich vegetables into small pieces and heating them close together increases the likelihood of sparks due to variations in the electric field created by the microwaves. The sparks don’t harm the food but they may prevent it from cooking evenly and leave a black mark or burned taste. If the food is very dry it might actually catch fire. Robert Wolke, in his “What Einstein Told His Cook,” explains that this is most likely to happen to carrots, because they are cut in cubes with corners, which act like the tip of a lightning rod, attracting electrical energy toward itself. The highly concentrated energy makes the sparks.

Main reasons -

Firstly, dense vegetables such as carrots have a higher amount of minerals in them - iron, magnesium and selenium - than other food items and sometimes create an arcing effect in a microwave.  This tends to happen more in glass dishes. Sparks result as the microwaves reflect or bounce off the metal. the "arcing" does not harm the food, but it does prevent it from heating thoroughly because reflected microwaves will not cook.  Also, extensive arcing can damage your oven's magnetron tube.

 If arcing occurs, turn off the microwave oven and finish cooking the food on the range top. Arcing may occur in other vegetables, and most often appears in green peppers and green beans.

Secondly, while microwaves are extremely good at heating liquid water, ice is almost totally transparent to them, so it is actually quite difficult to get ice to melt in a domestic microwave oven. The "defrost" option on a microwave oven relies on intermittent heating of a small amount of liquid water present on the food, and heat conduction from these areas into frozen material. By putting frozen material into the microwave oven with continuous energy input, no time is given for thermal conductivity effects, and therefore a colossal heating effect occurs on a very localised surface area. These areas, typically at the extreme point of the carrot, will dry out rapidly and then char, essentially forming small carbon points.

Thirdly, carrots are relatively large objects (compared to, say frozen peas) and because microwaves are essentially varying high voltage fields, a large alternating electrical potential exists between the highly conductive charred sections.

Finally, carrots are generally given quite angular cuts, giving sharp points which will yield the highest field gradients. The combination of a large alternating field across a good electrical conductor with sharp points causes electrical breakdown of the air and the sparks which accompany this. Depending upon the precise conditions, it is equally possible for charring to be a secondary effect, rather than a cause. In this case, the discharge may originate from un-charred points, with charring only occurring as a huge current passes through a relatively small point.

What is "arcing"? Arcing (pronounced "AR-king") is sparks inside the microwave oven caused when microwaves react to gold paint on dishes, twist ties and other metallic materials. Some foods such as raw carrots can cause arcing while being microwaved. In carrots, it can be due to the minerals in the soil in which they were grown. Whatever the cause, turn off the oven immediately to end the sparks. Prolonged arcing can damage the oven and/or the utensil. If caught at once, arcing should not damage the oven. Remove the offending utensil or food from the oven and either substitute a microwave-safe utensil or cook the food by other methods.

Sodium is known to have the effect of making a microwave arc.

USDA advice on microwave ovens and food safety here.

Was Henry Ford Carrot Crazy?

Henry  Ford was anti-milk ("the cow is the crudest machine in the world") and anti-meat (he promoted soybeans in lieu of beef and oatmeal crackers as a substitute for chicken), but he was devoted to the carrot which, he was convinced, held the secret to longevity.

In the 1920's , the American automobile maker Henry Ford tried to impress upon his business associates the value of a vegetable-based diet. He held a banquet in a Detroit hotel that highlighted carrots in all their splendour, complete with a master of ceremonies dressed in a carrot suit who proclaimed, “I am King Carrota! I am full of vitamins, full of iron, full of iodine, full of bottled sunshine. I have no enemy but a bad cook. I am a friend of flappers and the bald-headed, the spindly baby and three-chinned monsters, but who shall mix me with canned peas shall be consigned to outer darkness.”

At one point he was the guest of honor at a twelve-course all-carrot dinner - consisting entirely of carrots - starter was carrot soup, followed by carrot mousse, carrot loaf, carrot au gratin, carrot torte, carrot salad, pickled carrots, and carrot ice cream, all accompanied by glass after glass of carrot juice. A doctor remarked that he had seen children who ate too many carrots turn yellow, which certainly dampened the festivities, at least at his table.

One story holds that Ford became interested in the painter Titian when his son Edsel donated a Titian painting ("Judith and the Head of Holofernes") to the Detroit Institute of Arts. It wasn't the artist's work that interested him; it was the fact that Titian had reportedly lived to be ninety-nine. He wanted to know if Titian ate carrots.

The Flaming Carrot -

Bob Burden the writer/artist and ingenious mind behind the Flaming Carrot came up with a superhero not quite like any others ever seen before in the comic book industry. The Flaming Carrot was a mysterious and demented Flaming Carrot/person that went on rampages battling monsters, gangs, communist hoards, old girlfriends, journalists, and sometimes his own morality (yes, it is as crazy as it sounds). The entire print run of 30 epic stories lasted from 1984 to 1993. See Tattoos below.

Carrots make antifreeze!!

A team of plant biologists at the University of York  (England) have isolated the first plant antifreeze protein. The naturally occurring 'antifreeze' in carrots might lead to improved frozen foods, more efficient freezing of tissue for medical use and better frost tolerance for crops.

The discovery of the antifreeze protein by a team from the Plant Stress Response Group led by Professor Dianna Bowles, is reported in the international journal, "Science"

"Antifreeze proteins act in a different way to the antifreeze you put in your car radiator," said Maggie Smallwood the senior scientist involved in the project. "These proteins specifically bind to ice crystals and stop them growing." The stress response team showed that extracts from carrots which had been growing under cold conditions could prevent ice crystal growth. They went on to purify the protein which kept the ice crystals small and identify the gene which encoded the protein. They transferred the gene into a model plant which does not normally express antifreeze activity and showed that extracts from these plants stopped ice crystals growing.

Dawn Worrall, a postdoctoral scientist working on the project, pointed out that much of the damage which plants and other organisms experience when they freeze is due to the growth of ice crystals over time. "Large ice crystals disrupt tissue structure more than small ones and regulation of ice crystal growth may be important to survival of a carrot root in the field over winter," she said.

Professor Dianna Bowles expects the carrot antifreeze protein to have a number of potential applications. "Simple natural extracts from carrots may be useful in enhancing the quality of frozen food products and prolong their life in the domestic freezer," she says. "The pure carrot protein might also prove to be useful in cryoprotection (freezing) of medical tissues. In addition, transfer of the gene into temperate crop species may increase their frost tolerance and widen their season or region of cultivation. Similarly there may be applications for horticultural species that suffer from early frosts."

The antifreeze protein discovered in this study is produced by a carrot plant: it is an example of a commercially important product that can be grown in a 'plant factory'. Plants can be used to produce large quantities of industrial or speciality chemicals in a highly energy-efficient manner. Researchers in the Plant Laboratory at the University of York are exploring the potential of this environmentally friendly technology to manufacture products for a wide range of industries.