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I’m a Midwestern girl. I grew up in a small town in Illinois, went to college in Iowa, and took frequent trips to northern Wisconsin throughout my life, including the multi-state road trip from Texas to Wisconsin that I completed earlier this month.
During the many hours in the car, I reflected on the ubiquitous presence of corn growing alongside the roadside and how it is used. From the farm fresh sweet corn to packaged snacks in convenience stores to fuel at the gas pumps, corn makes its way into a wide variety of foods and goods we consume.
This week’s blog will navigate the different types of corn and their applications, methods of processing corn, nutritional value, and more. Buckle up!
Farm Fresh Sweet Corn
Let’s begin with the final destination of my road trip – the area near Ashland, Wisconsin, which sits on the south shore of Lake Superior. That’s where we found a farmer the locals refer to as the “Corn Man”, who sells farm fresh produce while sitting on the tailgate of a white pickup in a parking lot off Lake Shore Drive.
Lines to purchase his corn can get pretty long – people will sometimes get in line for up to an hour before he arrives in order to get corn before he sells out. Luckily, we caught him at a good time and easily secured a dozen within minutes. Let me tell you, it’s worth the wait for the juicy, sweet goodness of a fresh ear of corn on the cob.
Sweet corn, also known as sugar corn or pole corn, has a much higher sugar content than other types of corn because its genetic composition results in a higher production of sugars rather than starches. Additionally, it is harvested young in its “milk stage”, which you may notice as the juicy liquid that escapes the kernel as you break an ear in half or take a bite into the cob.
Corn is by nature a cereal grain, though many consider sweet corn as more like a vegetable when consumed fresh. Like all types of grains, corn is naturally high in carbohydrates – after all, it is called sweet corn for a reason!
Nutrition of Sweet Corn
One ear of sweet corn contains roughly 17 grams of carbohydrate, 3 grams of protein, and one gram of fat. Corn also contains a variety of vitamins, minerals, and phytonutrients including:
- Vitamin C
- Vitamin B3 (though this vitamin may not be well absorbed in corn – more on this later)
- Vitamin B5
- Vitamin B6
- Carotenoids – lutein, zeaxanthin, beta-carotene, and beta-cryptoxanthin
Blue and purple varieties of corn also contain antioxidant molecules called anthocyanins, though they are much less common than their yellow hued counterparts.
Fiber is also an important nutritional feature of fresh sweet corn as it helps lower the glycemic index (i.e. the measure of how quickly a food raises blood sugar) of this high carbohydrate food. With about 2.5 grams of fiber per ear, corn is a good source of this vital nutrient. Corn also has a high ratio of insoluble fiber to soluble fiber, which is why corn bits may pass through the digestive system intact.
Corn is the largest field crop in the United States, which is plain to see as you take a drive through America’s heartland. However, sweet corn makes up less than 5% of corn grown in the US. The remaining majority consists primarily of dent corn.
Dent corn, aka field corn, is the main type of corn grown in the United States. On my trip, I passed through 6 of the top 10 corn producing states – Iowa (#1), Illinois (#2), Minnesota (#4), Kansas (#6), Missouri (#9), and Wisconsin (#10) – seeing rows and rows of field corn on repeat.
In contrast with sweet corn, farmers harvest dent corn in the mature stage, i.e. leaving the cob on the plant until it dries up in order to prevent spoiling. Dried corn kernels have an indentation for which this type of corn is named.
Dent corn has a high starch content and is used primarily for animal feed. This type of corn is wet or dry milled for human culinary applications, such as:
- Syrups, including high fructose corn syrup
- Corn starch
- Corn oil
- Corn meal
- Grits, including brewer’s grits used for making liquor
- Breakfast cereals
Non-food applications of field corn include ethanol for fuel, polymers, coatings, and adhesives.
As you can see, corn transforms in many different ways into products that hardly resemble corn at all, like candies, coatings, gasoline, and more. In fact, for dent corn to be suitable for human consumption at all, it requires a certain amount of processing because this grain is not easily broken down by our digestive systems and the nutrients within are not readily available.
Some nutrients, in particular niacin (vitamin B3), are not readily available in corn, especially dent corn, because they are bound to insoluble fibers and phytates. One processing method that enhances the availability of niacin in corn is known as nixtamalization.
Nixtamalization is the treatment of corn kernels with limewater. And no, I don’t mean the green citrus fruit. Lime in this case refers to an alkaline treatment with a dilute solution of calcium hydroxide.
The process involves boiling corn in limewater for up to an hour, then letting the mixture soak overnight. In the morning, the corn is drained and rinsed. At this point, the corn has transformed from a hard, inedible kernel into a soft, chewy product called hominy. The now soft grain may also be ground into dough known as masa, which is used to make tortillas, chips, and tamales.
Following alkaline treatment niacin availability improves, as well as that of calcium, lysine, tryptophan, and isoleucine. Drawbacks to nixtamalization include losses of B vitamins, such as thiamin and riboflavin, fat, and fiber. Niacin losses also occur, but the increased bioavailability makes up for the amount lost in processing for a net gain of this nutrient.
Fermentation is another method that improves the availability of nutrients in corn. This method is more widely used in Africa, while nixtamalization is more prevalent in the Americas.
Other Types of Corn
Popcorn is another tasty treat that’s made from an entirely different type of corn: flint corn. Flint corn has a hard exterior and lower moisture content. A small amount of water is trapped inside the kernel, which causes it to explode when heated to produce the fluffy treat known as popcorn.
Nebraska is the largest producer of this type of corn in the US, growing about 25% of the nation’s popping corn.
Many varieties of corn have gone by the wayside over the years. Diversity of species has dwindled as corn growers adapted to plant varieties with the greatest yield. As a result, heirloom varieties of corn with rich colors are relatively rare. There is, however, a resurgence in interest for growing heirloom corn, particularly among producers of artisan moonshine in the south.
Considerations for Corn Consumption
Though corn allergy is relatively rare, it can be severe and life-threatening. Not to mention difficult to completely avoid in our modern environment.
In addition, the vast majority of corn grown in the US uses genetic modification. According to the USDA, 80% of corn seeds planted in the US were genetically engineered.
Corn is a staple crop in many non-industrialized areas, yet it is deficient in many nutrients. Niacin, of course, is not widely available from corn and requires special processing techniques. Deficiency of niacin may result in pellagra, a disease resulting from severe niacin deficiency.
Protein is also lacking in corn and what little amount is present is deficient in lysine and tryptophan. However, there is a fungus that grows on corn that may improve the protein content of corn, particularly the amino acid lysine. Corn smut, caused by the fungus Ustilago maydis, infects corn with a fuzzy gray coating. This limits yields, yet it improves the amino acid and nutritional profile in some ways. It is enjoyed in Central America as a delicacy known as huitlacoche.
Finally, since 5% or less of corn consumed in America is fresh off the cob, it is worth considering the implications of food processing. Though grits, tortillas, corn meal, and other corn products have nutritional value, much of the fiber and nutrients are lost during processing methods. This is especially true of sweeteners and syrups, where basically everything is removed except the sugar.
Here’s a simple recipe using flint corn with my own special twist. Popping corn utilizes the whole grain and contains slightly higher mineral content than sweet or dent corn, including substantial levels of iron, zinc, copper, and manganese.
- ⅓ c popping corn
- ⅙ c sugar (I like to fill the measuring cup I use for the corn halfway)
- ⅙ c coconut oil (slightly less than 3T)
- Optional: squeeze of lime (and this time I do mean the green citrus fruit)
Combine all ingredients and a medium saucepan and stir well. Heat the pan over medium heat or slightly lower. Swirl the pan around occasionally until the corn starts popping. Turn off heat when popping slows to about 1 pop per 2-3 seconds. Pour into a large bowl, salt to taste, and top with lime juice if desired.
About the author:
Karyn Lane is a current student of NTI’s Nutrition Therapist Master Program. She finds her chemistry degree a useful tool in her study of nutrition and loves to treat herself as a laboratory for new recipes and cooking techniques. You can follow her on Instagram @feel.alive.nourishment.
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