Technical Talk – July 2011

The definition of “whole grain” varies from one jurisdiction to the
next. Generally speaking, a whole grain contains all the edible
components of the intact grain in the same proportions after the
inedible husks and hulls are removed. In some cases, the endosperm, bran
and germ may be separated during processing, then recombined after.
Whole grains can be cracked, rolled, ground into flour or flaked.

The trend toward whole grains reflects consumer interest in health and nutrition

Mounting scientific proof highlighting the health benefits of whole grains is driving new product development.

The definition of “whole grain” varies from one jurisdiction to the next. Generally speaking, a whole grain contains all the edible components of the intact grain in the same proportions after the inedible husks and hulls are removed. In some cases, the endosperm, bran and germ may be separated during processing, then recombined after. Whole grains can be cracked, rolled, ground into flour or flaked.

Many parts of whole grains can provide proper nutrition and overall well-being. These include digestible compounds that our bodies metabolize for energy and to build up tissues. Indigestible compounds help with regularity, and other compounds that are fermented in the large intestine to provide many health benefits.

Many parts of the grain are nutritious.

Both insoluble and soluble dietary fibre is concentrated in the outer layers of the grain, such as the bran. These layers are removed by traditional milling processes, so a whole grain has more fibre than a refined flour. Some manufacturers have developed whole grain flours in order to deliver more fibre and nutrition to health-conscious consumers. These flours are often made from white wheat and are finely ground, resulting in baked goods that are much lighter in colour than those made from whole wheat flours. These products may be more appealing to some consumers, especially children accustomed to white bread. Whole grain flours can be ground from wheat, as well as from other cereals, such as oats, rye, and ancient grains.

Whole grains are also a major source of carbohydrates in the form of fibre, starch and some simple sugars that supply energy for our bodies. Starch is mainly concentrated in the endosperm (the interior part of the grain). The endosperm constitutes between 80 and 90 per cent of the total weight of the grain, depending on the type of grain.

The bran and germ in whole grains also contain minerals that are largely removed during traditional flour milling. These minerals – including calcium, potassium, phosphorus, copper, zinc and iron – are mainly found in the aleurone layer of the kernel. However, although these minerals are present, they may not be readily available to our bodies. The phosphorus
in whole grains is mainly bound to phytic acid, limiting the extent to which it can be used by the body. To counter this, a phytase enzyme can be incorporated into a food to break down this bond, increasing bioavailability.

The various vitamins present in the outer layers of the grain kernel and germ include B1 thiamin, B2 riboflavin, B3 niacin, B5 pantothenic acid, B6 pyridoxine, B7 biotin and folic acid, all easily recognized as important to human health and nutrition. In fact, some countries add these vitamins, as well as iron, to refined flours as part of a fortification program. For example, adding folic acid results in a dramatic reduction of neural birth defects like spina bifida.

Vitamin E, which is found mainly in the germ and aleurone layers of a grain, is an antioxidant that contributes to the prevention of chronic diseases.

Whole grains are also a source of proteins and lipids. Gliadin and glutenin, which form gluten protein, serve a functional purpose in baking. Some proteins deliver nutrition and health benefits. Some proteins form small chains of amino acids (peptides) that have been found to aid in disease prevention. For example, lunasin, a peptide found in wheat, barley and rye, is believed to lower cholesterol levels.

Although lipid levels are low in wheat, barley, rye and other cereals (ranging from one to four per cent), levels are higher in oats (up to nine per cent). In many grains, the lipids are concentrated in the germ. Lipase enzymes are also found in the germ. These enzymes are activated when the kernel is disturbed during milling. They cause the lipids to oxidize quickly, resulting in rancidity. Moist heat will deactivate these enzymes, extending shelf life. Oats are often kilned prior to milling in order to neutralize these enzymes. 

Many other beneficial bioactive compounds are found in the outer layers of grain kernels. These include phytosterols, stanols, phytoestrogens and lignans. Plant lignans are fermented in the large intestine by prebiotic bacteria, forming mammalian lignans. Research has shown that these modified lignans can prevent certain cancers. Other phenolic compounds found in whole grains, and known for their antioxidant and possible anti-cancer properties, include betain, choline, alkylresorcinols and avenanthramides.

Incorporating whole grains into our diets enhances overall nutrition and can offer important health benefits. When developing whole grain ingredients or products, remember to adhere to any regulations applicable in your jurisdiction, as well as those in jurisdictions where you distribute your products.

For more information, or fee-for-service help with product or process development needs, please contact Dr. John Michaelides at Guelph Food Technology Centre 519-821-1246 ext. 5052, by fax at 519-836-1281, by e-mail at jmichaelides@gftc.ca or j.jmichaelides@gmail.com.