Cereals comprise a large part of the human diet. Rice, wheat, and maize make up 60% of the world’s energy intake. Grains and grain products feed the world, providing most of the calories and much of the protein consumed globally.
They are also a rich source of other nutrients. These include complex carbohydrates, heart-healthy unsaturated fats, B vitamins, and minerals. These cereal grains are consumed in a variety of ways— intact or through flours used in bread, pasta, tortillas, and baked goods such as crackers and cookies. Until the last century, grains were consumed as whole grains in the form of breads, porridges, and other dietary staples. But all this changed when the Industrial Revolution began in 1760, in which mechanization helped feed the growing population. Today, grains come in two forms: whole and refined grains. The form is determined by how it is further processed before it reaches the consumer.
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To better explain the difference between whole and refined grains, let’s discuss the structure of a grain first.
TURNING WHOLE GRAIN INTO REFINED GRAIN
The structure of all grains is similar. Each grain is composed of the bran, endosperm, and germ. The bran is the outer layer of the grain. It is full of B vitamins, and trace minerals, including fiber. Endosperm is the largest portion of the kernel. It is the interior layer that holds the majority of the material such as carbohydrates, proteins, B vitamins, and minerals. It also serves as the food source for the germ as it grows. The amounts of nutrients in the endosperm vary depending on the type of grain, although its predominantly starch. The germ is the seed part from which new plant sprouts. It contains the highest amount of nutrients since it is the embryo of the seed. It also has fat that decreases its shelf life.
If the bran, endosperm, and germ are all intact, the grain is referred to as “whole grain”. It becomes “refined grain” if the bran and/or germ of the seed are taken out or separated from the kernel, modifying its composition. This is achieved by grinding or selective sifting. The bran, specifically, is removed by abrasion or polishing in the milling. In some products, the grains are bleached to make it whiter. Examples of refined grains are white rice and white flour because they no longer have their bran and germ.
The terms “whole” and “refined” are most probably already familiar to the consumers as they are prominent in product labels. The USDA advises “making half of your grains whole.” Many grain-based food items that are sold to consumers, like whole grain crackers and cereals, also contain that recommendation. The Nutrition Facts and Ingredients labels provide information about the actual whole grain content.
So which one is better? Is it whole or refined grain?
THE DIFFERENCES
Each type of grain has its own advantage and disadvantage.
Whole grains contain more nutrients
The clear advantage of whole grain is that it is nutritionally superior to refined grain. As already mentioned, refining removes the bran and the germ, leaving only the endosperm. The process also removes significant amounts of nutrients that are in the bran and germ. For instance, white flour has fewer levels of fiber and protein compared to whole wheat flour, as well as lower levels of the vitamins B1, B2, B3, B6, E, K, and folate, as well as the minerals magnesium, potassium, iron, calcium, and selenium.
The Industrial Revolution allowed the milling technology to mass produce grains. But since refined grains contain fewer nutrients, it led to worldwide nutrition problems. To address this issue, many governments required refined grains manufacturers to have their products enriched. Enrichment refers to the addition of nutrients that were lost during processing. In the case of white flour, folate, iron, niacin, and thiamin are often added back.
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However, not all the nutrients are added back. When the bran is removed, the insoluble fiber is milled away, and antioxidants are typically not reintroduced back into refined flours. Additionally, refined grains could be lacking in phytochemicals. Although most refined grains are a good source of nutrients, whole grains are still a better option. Look for the words “whole grain” in the label, which indicates that the product contains the bran, endosperm, and germ.
Refined grains are more shelf life stable
Like most processed food products, refined grains contain fewer nutrients than whole grains, but have a longer shelf life. This is because refined grains already have their germ removed, which contains the highest percent lipid at 6 to 10%. The lipids in whole grains may undergo rancidity lipoxidase enzyme, or non-enzymatic oxidative rancidity, which favors deterioration. During oxidative oxidation, the fat is oxidized and breaks down into volatile molecules with shorter carbon chains including fatty acids, aldehydes, and ketones, all of which contribute to the undesirable odor and flavor of rancid fats. To prevent this, a whole grain product may undergo germ removal or incorporate antioxidants such as BHA or BHT. These anti-oxidants stop oxidation of any unsaturated bonds and donate a hydrogen atom to the double bond of a fatty acid, preventing rancidity. They stop the fatty acid chain reaction that would otherwise cause rancidity.
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Antioxidants extend the shelf life and improve the quality of fat-containing foods. Examination of food labels reveals that antioxidants are frequently employed in various food products, from cereals to potato chips. Without them, the quality of foods that contain fat would be lower, and oxidative rancidity-related off taste and aromas would be more prevalent.
References:
V. Vaclavik, E. Christian (2014). Essentials of Food Science (4th edition). Springer.
P.K. Newby (2018). Food and Nutrition (What Everyone Needs To Know). Oxford University Press.
Mayo Clinic, University of California, Dole Food Company, Inc. (2002). Encyclopedia of Foods (A Guide To Healthy Nutrition). Elsevier.
