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Fortifying breakfast cerealsFortifying breakfast cereals

Cereal companies do all they can to appeal to a wide variety of consumers through cartoon characters on packaging to including unique nutritious ingredients.

Lynn A. Kuntz

April 1, 1994

16 Min Read
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A walk down the cereal aisle in any American grocery store dazzles the consumer with a glittering array of choices. Cereal companies try to appeal to every potential interest. Cartoon characters and fanciful shapes attract kids or kids or those who haven't quite grown up. Sports stars beckon from the carton, seeming to promise gold medals and multimillion-dollar contracts with every bite. Or for those who yearn for the good old days, the lure of stone ground grains, fruits and nuts may be irresistible. But for all the market differentiation, all breakfast cereals make a move toward improved nutrition by fortification with an assortment of vitamins and minerals.

Look at those ingredient legends. Whether the initial ingredient is sugar or whole wheat, a varying, but often quite substantial list of added nutrients brings up the rear. While the quantities may be small, the impact on breakfast cereal is not.

"Never assume that fortifying a breakfast cereal is going to be easy," warns Sam Sylvetsky, director of sales for Fortitech, Inc., Schenectady, NY. "It's actually quite difficult from a stability standpoint, from the organoleptic standpoint, as well as getting the chemical analysis to verify you've met the goal.”

As with any other product, fortification of breakfast cereals presents the product designer with a set of challenges to overcome in order to provide the best possible result. The major considerations include:

  • Type of nutrients

  • Level of nutrients

  • Product matrix

  • Process conditions

  • Storage conditions

The goal is to achieve the target levels of the selected nutrients in the finished product without any negative effects.

Stable or labile

In general, minerals will be stable -- the amount added will still be present in the finished product. The same is not necessarily true for vitamins.

"Many of the vitamins intrinsically are not thermally unstable," notes Michael Weibel, Ph.D., vice president, research and development, Watson Foods, Co., West Haven, CT. "The problem is that you speed up the reactivity with the matrix as well as other conditions such as the presence of oxygen. Typically you will double the rate of reaction for every 10°C increase. If your process temperature is up around boiling, you increase the degenerative reactions [by a factor] somewhere in the range of 26 or 28."

Thiamin, (Vitamin B1) is very heat labile and can incur significant losses depending on the severity and duration of the heat process. A lower pH can help to preserve this vitamin because of its increased stability in acidic conditions. Unfortunately, most breakfast cereals fall into the neutral range.

Ascorbic acid (Vitamin C) is very unstable; heating at low temperatures for long periods will destroy this vitamin. Oxygen and copper as well as certain enzymes accelerate the destruction.

Heating vitamin A in the presence of oxygen results in a sizable reduction in the finished product. If air can be excluded, the loss is minimized.

Vitamins E and D are relatively heat stable, but again, oxygen will accelerate the losses. The shorter the exposure to heat, the higher temperatures these vitamins can undergo without a significant loss. Beta-carotene, vitamin B12, and folic acid are also unstable.

According to Weibel, many of the vitamins with complex ring structures, such as thiamin, biotin and B12 are reactive. Stable ester forms, such as vitamin A palmitate and vitamin E acetate are fairly susceptible to hydrolysis. The resultant unprotected vitamin is then very labile.

In addition, some vitamin/vitamin interactions may occur according to Douglas Schmidt, Ph.D., manager of technical services for BASF Corp., Human Health and Nutrition, Parsippany, NJ.

"Niacinamide can react with ascorbic acid to form a complex called niacinamide ascorbate. But by in large, these types of interactions are very complex and not very important from the overall stability of the vitamin," he explains.

Several other things impact the level of vitamins in the finished products. Vitamin C and tocopherols act as antioxidants. While this may provide a benefit in the finished product, once the vitamin is oxidized, it is no longer available as a nutrient.

Some nutrients (notably riboflavin) degrade with light exposure. Although this is not a typical concern with breakfast cereal products, it affects the raw material storage and shelf life. Besides, marketing may someday decide that a clear package would be a unique feature. In general, packaging plays an important role in protecting the vitamin content of the finished product. A good oxygen barrier helps to protect the vitamins from degradation throughout the shelf life.

Another point to consider when setting nutrient levels is ingredient toxicity. Austra Bundza, nutritional product development manager for Watson Foods reminds us that vitamin D, particularly, is "one of the most toxic oil soluble vitamins, so you don't want to exaggerate the addition rate."

Reaction results

While the minerals remain in the final product regardless of the process conditions, they may result in several undesirable features in the finished product. Metal ions promote many reactions, especially oxidation/reduction reactions like the one causing oxidative rancidity. This can be a serious problem for grain ingredients containing high levels of unsaturated fats.

"When people want to achieve very high levels of mineral fortification, they may have to back off to get an acceptable product," cautions Bundza. "Zinc, copper, iron and magnesium can cause problems. Fortification to high levels requires rather large amounts of the mineral salts. These will typically affect the flavor.

"Calcium is fairly benign from a flavor standpoint," she continues, "but with high levels you get chalkiness. What also happens if you try to fortify to 100% of the RDI (Recommended Daily Intake) is that you get matrix problems. An RDI of 1200 mg. per day calcium transferred to a mineral salt means about three grams of that salt to be added to a one ounce serving. That's over 10% of the finished product. High percentages of phosphorus and magnesium are also difficult to incorporate because of the high recommended levels."

Minerals can cause other problems, too.

"It they are not added properly or the incorrect form is chosen, cereal flakes can turn green," warns Sylvetsky. "One also has to be aware that changing the form in which the minerals are added often impacts the finished product -- causing changes in flavor, color and even texture."

Depending on the addition level, vitamins also may create undesirable attributes to appear in the finished product. Along with iron, the B vitamins contribute unacceptable flavors to cereal, especially B1 and B6. Bundza likens the flavor produced to that exhibited by sulfur compounds. Iron, of course, provides a metallic flavor.

One other undesirable effect frequently occurs when fortifying breakfast cereals. Riboflavin and beta-carotene color products orange. While in the case of many breakfast cereals, a golden color is desirable, the amount of beta-carotene required to provide 100% the RDI of vitamin A results in a bright orange, only suitable for something that could be considered fruit flavored.

"High levels of beta-carotene, such as those needed to meet 100% of the RDI for vitamin A, are tough to add to breakfast cereal," Schmidt says. "It's going to color the cereal to an unacceptable level. One thing the food industry is looking for, but hasn't been developed yet to my knowledge, is a method of blocking the color."

Quantity quandaries

Difficulties can not only arise with getting the correct levels in the finished products but also with assuring that they are there. This feature already has discussed the problem of stability with certain vitamins. In addition to this there also can be difficulties in getting an even dispersion. Vitamins are typically applied to breakfast cereals in either one, or a combination of two ways: added to the initial mix or sprayed on at the end of the process. When mixing you need a homogeneous blend -- the method of addition and the mixing action provided by the equipment must result in even distribution. When spraying you need an even application of not only the spray, but the nutrients in the spray. If sensitive vitamins are held too long under less than optimal conditions, they can lose their potency.

"Heterogeneity or hot spots can occur even with high speed mixers," Weibel observes. "If the product is dry blended, that doesn't cause as many problems; but blending a dry mix into something with a plastic consistency often presents difficulties in achieving homogeneity."

"With spray processes, we frequently see that people aren't paying a great deal of attention to the metering equipment," he notes. "To achieve even distribution, you need good, positive displacement pumps that are well-calibrated. The manufacturers will be spraying at levels of 5 to 10%. Many of the minerals are insoluble and some of the vitamins when encapsulated form insoluble particulates. Spraying these has some inherent problems that must be addressed: blockage of nozzles, keeping your vitamin and minerals slurry well suspended – all the typical hydraulic problems encountered with liquid delivery."

Even with the product completed, there remains one more hurdle to cross – analyzing the product to ensure the levels hit the mark. Science already has figured out how to go to the moon and transplant organs, but in some cases, hasn't yet determined a procedure that yields accurate analyses of some of the micronutrients. Most of the mineral methods are fairly straightforward, especially with the use of an atomic absorption spectrometer.

"For many years, the only good way to analyze a number of the vitamins was to perform a microbial test in which the microorganism was sensitive to the nutrient and could only grow in its presence," explains Weibel. "Those are very laborious, time-consuming test methods. When fortifying cereal, many vitamins such as D, B12, and biotin are only present at levels measured in parts per million or parts per billion. Very sensitive instrumental assays are required and they are fraught with background complications. Cereal products are notorious for this – they are full of all kinds of biochemical materials that are coextracted when you begin to search for the vitamins. Even the best labs with state-of-the-art techniques can often only come up with plus or minus 20% accuracy in some cases."

Sylvetsky agrees. "There is a type of testing referred to as microanalysis that is very difficult to do and produces a fairly large margin of errors. But some vitamins are very straightforward and can be tested by HPLC. Problems here occur with the extraction out of the product matrix; you need to extract the vitamin without destroying it."

Some cereal solutions

Several solutions apply to eliminate or minimize the problems discussed.   First of all, designers can work with the levels; either finished product target or addition levels. In the case of the calcium, for example, it might be better to rethink the goal. One option is to decide if the cereal eaten with milk gives an acceptable level. With the beta-carotene color problem, the approach to take might involve using a blend of vitamin A and carotene to minimize the color contribution.

In the industry, the most common way to account for nutrient loss through processing is to add overages, the amount needed to result in the desired level in the finished product.

"You really need to run stability tests to determine the correct overages, there's no way around that," reveals Schmidt. "You can run accelerated tests, three months at 40°C, for example, but nothing really replaces ambient temperature data collected over the expected shelf life -- from six months to a year. At accelerated temperatures, you may even end up with reactions that may not happen in normal storage, especially with compounds like beta-carotene. There are some guidelines you can use for a starting point. In a dry system, like you see with cereals, you'd need to review the list of stable and unstable vitamins. For stable ones you would add between 10 to 20% overages. Since B12 or folic acid are only present in microgram quantities, they are difficult to detect analytically; and very high overages would be needed."

The best technique, according to Bundza, is to perform the required assays immediately after manufacturing, then run subsequent assays at regular intervals over the period of the expected shelf life.

"The assays can be expensive," she adds. "So you don't necessarily want to do a full assay. Focus on the vitamins that are the least stable, like vitamins A and C. For a QC marker, to ensure the correct amount has been added, use a mineral because atomic absorption is very inexpensive, fast and accurate."

Probably one of the best ways to ensure adequate dispersion of nutrients in the mix is the use of pre-mixes. By using a pre-mix you can add the required array as a single ingredient.

"Pre-mixes are tailor made for specific customers and applications," states Bundza. "They allow you to reduce your inventory level and simplify the QC assay procedures. They provide savings in labor, cost and time over the addition of individual ingredients."

Sylvetsky lists several more advantages to using a pre-mix from an experienced supplier. "You want to avoid demixing in preparing a pre-mix. Extensive mixing experiments can determine what the best procedure is for optimal dispersion. In our case we have extremely large blenders which can produce a large volume of a high quality, controlled product that can be added to a large number of cereal batches."

One of the techniques used to aid dispersion especially in a pre-mix is the use of carriers. They act as diluents which not only improve the distribution on the ingredients present in minute quantities, but also serve to keep the ingredients separated, forestalling any premature ingredient interaction. Ingredients commonly used as carriers for cereal products include sugar, dicalcium phosphate, maltodextrin and dextrose. The appropriate carrier will not affect the finished product. Since carriers are considered to be process aids, and are present at fairly low levels, they are frequently omitted from the product label. They provide no nutritional or ingredient functionality in the finished product.

By adding the nutritive ingredients at appropriate different points in the process, you can maintain the greatest amount of vitamins in the finished product. Any stable vitamins and the minerals which do not promote any deleterious reactions should be added at the start of the mix to obtain the maximum dispersion. Often the oil soluble and water soluble vitamins are separated into different pre-mixes to facilitate handling and aid dispersion.

"Using pre-mixes adds significantly to the effectiveness and quality control of the operation," notes Sylvetsky.

Another method discussed previously consists of dissolving or dispersing the vitamins and minerals in a spray solution, usually the sweetener solution.

This protects the sensitive vitamins from the high temperatures and pressures encountered during cooking, extrusion and drying. This method only exposes them to a relatively short, mild drying process.

"The order of addition of the premix is critical," Weibel advises. "You would add the stable components in the mixer or extruder to optimize dispersion. Ideally, those with a flavor impact or flavor interference go in at that time, too. The others should be sprayed, particularly when the manufacturer in already adding a coating to the cereal."

The sugar acts as a protectant as do some of the proteins and dextrins found in cereal products. According to Schmidt, sugar provides a good oxygen barrier.

Another effective method used to protect sensitive components is encapsulation. Although the vitamins remain exposed to heat, the coatings protect them from moisture and pH effects that exacerbate the problem. Encapsulation also prevents reactive compounds such as iron from catalyzing undesirable reactions. In addition, it can hide unpleasant flavors like those contributed by the B vitamins. As with any encapsulated material, the choice of the encapsulate depends on the process and the product matrix.

"With encapsulation you are `micropackaging' the ingredient – segregating it from the matrix to which it has been added," explains Weibel. "For example, vitamin A is frequently emulsified, then encapsulated by spray-drying into gelatin, gum arabic, maltodextrin and starch products. You frequently incorporate antioxidants such as BHT, TBHQ or tocopherols into the emulsion. Then you dry the mixture, suspending it in a glass. Sugar encrustation is also common. Another way is to use a polymeric film former such as methyl cellulose. This is a particularly good encapsulate because it is not water soluble and is often used to protect vitamin C. Fats are often used, but don't form a robust barrier and are thermally sensitive, typically melting at 120 to 160°F."

Future of flakes

Like any other food product, breakfast cereals are subject to the current nutritional trends. The current areas of interest include the use of antioxidant vitamins and the addition of folic acid.

"I think more foods are going to be fortified with more vitamins," says Weibel. "This will largely be driven by the Nutrition Labeling and Education Act (NLEA). Mandatory labeling includes four nutrients – vitamins C and A and iron and calcium. You can elect a host of others. I think as people begin to read labels, they're going to pay more attention to the levels. and the industry will respond by incorporating them into foods. Not a high level, just so the number doesn't read zero. In fact there will probably be a race to increase the vitamin C numbers – there's no practical limitation due to toxicity and a lot of controversy as to how high you can go."

While FDA doesn't allow any health claims for antioxidants, that shouldn't affect the consumer perception of their benefits.

"Hopefully, those who believe that fortification is important will encourage and support dissemination of the benefits of antioxidants to the public. Then, when a consumer sees a label indicating antioxidant content, he or she can make the connection," states Weibel.

Sylvetsky believes that the industry is moving to "designer" foods to help cure diseases.

"Most of the serious western culture diseases are diet-related: high blood pressure, heart disease, stokes and some forms of cancer. Research is starting to point out which nutrients are critical to good health. Until recently, the role of fortification was prevention of deficiencies. More studies are coming out to show that these nutrients can offer much greater benefits than that."

The Vitamins in Vogue

Two types of vitamins are currently grabbing the consumer's attention because of favorable test results widely reported in the popular media – the antioxidants and folic acid.

The antioxidants. A number of recent studies indicate that the antioxidants, vitamins A, C and E, beta-carotene (provitamin A), and selenium can contribute to a wide variety of diseases, including cardiovascular disease, some cancers, bone disease and even cataracts. Free radicals can damage DNA, proteins and cell membranes. The theory proposes that these nutrients may protect cells from damage caused by free radicals that are produced during certain biochemical reactions.

Folic acid. Sufficient ingestion of this nutrient has been shown to be effective in preventing birth defects such as spina bifida and anencephaly. About half of these potentially fatal conditions are linked to shortages of folic acid in the diets of pregnant woman. The FDA has recently indicated that it will require producers of bread and grains labeled "enriched" to add this nutrient. A level of 400(g per day should provide this benefit but not mask the symptoms of certain anemia, as an excess of folic acid can do.

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