'Not particularly good news': Processing strips maize of healthy nutrients

By Niamh Michail contact

- Last updated on GMT

Corn flakes: Not a good source of healthy phenolic compounds. © GettyImages/Aksenovko
Corn flakes: Not a good source of healthy phenolic compounds. © GettyImages/Aksenovko
The process of making corn flakes strips maize of its healthy phenolic compounds and tocopherols, meaning fortification with additives is the best solution to make corn products healthier, scientists have found.

Diets rich in phenolic acids are linked to the prevention of cancer, neurodegenerative diseases and cardiovascular disease, and while corn is a good source of phenolic acids, many of these are in the insoluble-bound form.

The researchers from the University of Illinois wanted to test the impact of corn flake processing - where the maize is dry-milled, steamed, rolled and then toasted, on the nutritional content and if it releases the more bioavailable soluble phenolic acids. 

They were hoping to find a maize cultivar that maintained a higher proportion of phenolics during processing into cornflakes, and selected 19 genetically and phenotypically diverse maize inbreds and hybrids to test this.

"What we found was not particularly good news, but it was interesting​," said Carrie Butts-Wilmsmeyer, lead author of the study and research assistant professor at the University of Illinois’ department of crop sciences. “Regardless of the concentration in the grain at the beginning, the dry-milling process removes the majority of phenolics.”

As heat can release some of the soluble phenolic compounds, they then heated the starchy leftovers during later processing stages – similar to the steaming process when making corn flakes – to see if this increased the remaining soluble phenolic content.

The researchers, who received support from the Kellogg Company and Dow AgroSciences for the study, said the resulting increase was “negligible​”.

Similar losses ‘very likely’ in other grains

Butts-Wilmsmeyer told FoodNavigator: “Most of our processed grain-based food products are made from one portion of the grain. In this particular case, the phenolics are predominantly located in the bran of cereals. The bran is removed during milling. This is why we saw such a drastic decrease between the whole kernel and the large flaking grit processing stages. 

“We also briefly considered the tocopherol content of maize. Most of the tocopherols are located in the germ, which is often removed during milling to extend the shelf life of processed food products. When we removed the germ, we removed almost all of the tocopherols.” 

She said it was “very likely​” that similar nutrient losses would occur in other grains, such as rice or wheat, during processing.

While whole grain products typically contain more nutrients, it is not possible to make all maize-based food products from the entire grain. 

“Whole corn products do exist, such as some cornmeal – although these typically have the germ removed to improve shelf life. But, most maize-based snack products and ready-to-eat breakfast cereals are entirely endosperm based. Including other portions of the grain may impact the cooking, baking or toasting qualities, or sensory properties such as smell, taste or texture.”

Fortification the most likely solution

The scientists suggested that alternative processing methods must be developed to retain the nutrients. A shorter-term solution, however, would be recovering the lost phenolics and using them to fortify the same products.

Co-author Martin Bohn said: “In most instances, nutrient fortification will likely be the most sustainable long-term solution. Phenolics have the benefit of being health-promoting compounds as well as natural antimicrobial food preservatives.

“If these phenolics could be recovered from the bran-containing co-products of milling, they could be used as all-natural biofortifying agents with a multitude of positive benefits.”

Despite the somewhat disappointing result, the researchers said they hoped it was “an exciting find​” for food manufacturers.

The researchers also developed a miniaturised, bench-size process of cornflake production​process, which they say could help companies evaluate manufacturing alternatives that may yield healthier cornflakes.

Previous studies have shown that nixtamalization, the most commonly used method to make tortillas and nachos, also removes most phenolics while extrusion, to make puffed corn snacks, retains slightly more. 

Source: Journal of Agricultural and Food Chemistry​ 

"Changes in phenolic acid content in maize during food produce processing​"

Published 16 March 2018, DOI: 10.1021/acs.jafc.7b05242

Authors: Carrie Butts-Wilmsmeyer, Rita Mumm, Kent Rausch, Gurshagan Kandhola, Nicole Yana, Mary Happ, Alexandra Ostezan, Matthew Wasmund and Martin Bohn

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2 comments

Wow. What a surprise!

Posted by Vic Cherikoff,

There's not much in the way of processing that preserves all but the toughest micronutrients eg lycopene. But is this a surprise to anyone? As we grow just for calories from mass volume and apply blunt force strategies to yet another industry, we get a lot of a few crops and most of scant nutritional value. We turn oil into 'food' and think that we can feed the world and ignore hidden hunger.

Indeed, the lack of micronutrients and the consequent early deaths and cases of parents outliving their children is good for the planet particularly as fecundity is also falling.

Obviously, highly processed, micronutrient-poor human fodder also increases the incidence of a wide range of the diseases of nutrition adding to the profits of Big Pharma and the medical industry.

We can always fortify with synthetic versions of simple alphabet vitamins even though recent studies have shown they as either ineffective (vit C) or dangerous (vits A, D, E) in some instances. Let's ignore the concept of antioxidant capacity as the sum total of the interplay of a range of antioxidants supported by anti-inflammatories, anti-allergens, anti-proliferatives, pro-apoptotics, anti-carcinogens, adaptogens, good (smart) sugars, organic acids, enzymes, enzyme regulators, minerals and more.

What do you mean we need some raw, wild and near wild foods? Bah. That's only if you want to survive 65,000 years as the world's longest living culture.

Processed foods? Bring it on, We need less people on the planet so better not farm foods for our ideal nutrition, just maximize shareholder value.

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What about the benefits of nixtamalization?

Posted by Chris Aylmer,

From ancient times, according to Wikipedia, nixtamalization (soaking in alkali) has been used to help remove or break down the tough skins of corn kernels from dried maize and make the cornmeal more digestible. In so doing it is known to help release niacin from the maize and prevent pellagra disease, a vitamin B deficiency prevalent in regions which are dependent on cornmeal and do not use the process. Soaking in alkali such as lime or ash preparations is therefore reasonably claimed to enhance the nutrition of corn in the diet. Also the removal of the skins is considered the best way to guard against aflatoxin mold contamination. This process may remove phenolic compounds, but deficiency of these compounds is not known to cause disease.

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