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April 1, 1995
Maintaining Product Quality
By: Lynn A. Kuntz
As science continues to establish links between nutrition and health, consumers have become more inclined to choose nutrient-dense foods. At the same time, every food product now boldly exhibits a Nutrition Facts panel. So consumers can easily choose products that give them more nutritional bang for the buck. With nutrient density as a consumer-positive attribute, food companies are looking to increase product appeal by maximizing nutrient levels through fortification. With fortification, however, getting the product, as well as the "Facts," right requires more than plunking a vitamin pill in each batch. Designing fortified foods presents the food technologist with two major challenges: making certain that the finished product contains the nutrients required, and that the nutrients do not cause an undesirable effect in the finished product. It shouldn't come as a surprise to anyone familiar with food formulation that food ingredients, vitamins and minerals may change due to the product environment, the process and time, or they may cause some other product attribute to change - often for the worse. To complicate the procedure, vitamins and minerals come in different forms, and that can affect the end result. The forms range from different isomers to different compounds and different formats, such as encapsulation. Even a simple fortification project, like a vitamin C-enriched juice beverage, is not necessarily a piece of cake.In the beginningDesigning the product first and then deciding to fortify invites potential problems. The first step should be to determine what nutrients are wanted and at what levels. With some products, such as egg noodles, the types and levels of enrichment are mandated by the government. However, often fortification is at the discretion of the designer - or the marketing department. Setting realistic goals at the onset of a project can save a lot of headaches later. "Manufacturers need a rationale or philosophy behind product fortification," says Howard Gordon, senior technical service manager, Roche Vitamins & Fine Chemicals, Nutley, NJ. "The type and usage of the product helps determine the types of nutrients added and the appropriate targets - meal replacement, energy bar, and so on." "When we talk to companies about fortification, we look at it from two angles: where the science is, and where the supplement market is," adds Amanda O'Brien, marketing manager of Roche's food ingredient division industry unit. "We look at what nutrients people are interested in and the actual dietary intake. We look for data showing that people aren't eating the required amounts of essential nutrients from foods alone. Then we look at the products being designed and make recommendations." The level of fortification used affects a number of factors, including label statements, toxicity, economics, and the quality of the finished product. From a cost standpoint, the more fortification used, the more expensive it is. From a nutrient standpoint, in many cases, what the body doesn't use, it eliminates. Toxicity issues mainly involve mega-doses, which are not feasible in food fortification; here you are looking at percentages of the Daily Value. That brings us back to the initial problems. How does the presence and the level of a specific nutrient affect the product, and how does one make certain the label claim is met?A level playing field Now that the NLEA has mandated listing nutrient levels, ensuring that the finished product meets the label claims is critical. Minerals are easy to work with in this respect; once they're in, they don't go anywhere. Put 3 mg of a mineral per serving in a product at the beginning and - barring any special circumstances, like drip loss - an assay shows 3 mg after both the process and storage. Not so for vitamins. The fat-soluble vitamins (A, D, E and K) suffer substantial losses when heated in the presence of oxygen. Vitamin B1 (thiamin) degrades with heat. Vitamin B2 (riboflavin) will degrade somewhat with heat, but is much more prone to deterioration with exposure to light. Vitamin C is easily oxidized, and this can be accelerated by conditions such as temperature and pH. To compensate for these losses, the fortification industry works with overages. A certain percentage over the label amount is added so the finished product maintains the required level. The level required depends on several factors that relate to the degree and duration of exposure to the harmful conditions, both in processing and throughout the subsequent shelf life. Sometimes the process destroys the vitamin. "There's a lot of interest in fortifying baked products," notes Audra Davies, eastern regional manager, nutritional products division, Watson Foods, West Haven, CT. "Some of the bread processors have come out with calcium- and iron-fortified breads. But in terms of vitamin fortification, the biggest challenge is to have vitamin C survive the baking process. Some encapsulated versions offer moderate heat protection, but I haven't seen one that is a true survivor of the baking process. In addition, the mixing protocol may damage the coating." When foods must undergo heat processes, using the high-temperature, short-time processes retains more vitamins. Limiting the exposure to oxygen also helps. Retorted and aseptic products maintain vitamin C fairly well throughout the product's shelf life. "Most of these products have very little or no headspace," points out Pete de la Teja, manager, technical services, Takeda USA, Inc., Orangeburg, NY. "The culprit is vitamin C deterioration is oxygen. If you minimize the oxygen, you'll retain more of the vitamin C through the process. In a beverage with 5 ml versus 1 ml headspace, if all else is equal, the one with less headspace will be more stable." When feasible, manufacturers use a two-step addition process. The cereal industry uses this technique extensively. The stable vitamins are generally added at the beginning of the mix. After the cooking or baking process, the less stable vitamins are sprayed onto the cereal. "We have always recommended that you spray onto hot cereal and that you use a carbohydrate system in the spray," says Gordon. "Most of the water flashes off because you're applying it right as the product comes out of the oven and it's very hot. The carbohydrate that remains provides a coating that seals out the air, protecting the vitamin A." While this technique works well for products such as cereal, with a high surface-area-to-volume ratio, it would not work for standard baked goods like breads or cookies. The amount of moisture required to provide a significant vitamin dose would be too high. In cases where a filling or topping is added after the heat process, such as an icing or a donut glaze, it can make sense to add the sensitive vitamins to that component of the food. In addition, any vitamin acting as an antioxidant - especially vitamins A, C (ascorbic acid) and E (tocopherols) - does so by becoming oxidized. Once oxidized, the vitamin activity is destroyed. Proper dispersion of the vitamins and minerals ensures that products meet label claims. While from a stability standpoint added the supplements as late as possible decreases deterioration, it increases the risk that they may be poorly dispersed. Ingredients used at low levels - such as folic acid, biotin and selenium - can be difficult to disperse. Using premixes helps distribute such nutrients. In addition, some of the smaller ingredients can be plated on a carrier like mannitol or maltodextrin to increase the mass, giving better distribution. "You must control granulation and density to avoid de-mixing or segregation upon storage or shipment," warns de la Teja. "This is important to keep a homogeneous content throughout the product. With a liquid, the particle size becomes an issue if it is too fine. Then solubility can be a problem. It may cause lumps or dust." Packaging is another area that must be addressed in terms of vitamin stability. Oxygen and light barriers help ensure long-term stability of sensitive vitamins.Good form These considerations are only the tip of the fortification iceberg. Vitamins and minerals used for food fortification are not simple molecules and elements. The actual compounds used differ in their characteristics, including stability, solubility, bioavailability, reactivity and more. Vitamin E comes from natural or synthetic sources. Natural tocopherol consists of a mixture of four different molecules with similar structures - d-alpha, d-beta, d-gamma and d-delta. They differ from each other by the number and position of the methyl groups on the aromatic ring. All have some degree of vitamin E activity, with the d-alpha form, usually referred to as natural vitamin E, showing the highest level. This form also exhibits the highest level of bioavailability. Synthetic tocopherols, designated by the prefix dl, consist of eight stereoisomers, only one of which is molecularly identical to alpha tocopherol. "We tend to use the synthetic form, dl-alpha tocopherol acetate, especially in dry mixes," notes Ram Chaudhari, Ph.D., vice president and director of R&D at Fortitech, Inc., Schenectady, NY. "The vitamin E is much more stable, and that's what you need to retain the correct levels over a six-month or one-year storage." Solubility of vitamins and minerals can affect how well they are dispersed through a liquid. This may change with the product matrix, including pH or the presence of complexing agents. Many mineral salts exhibit poor solubility, which can create both processing and finished-product problems. For example, calcium is added to foods as a mineral salt. Several compounds are available, including calcium carbonate, chloride, citrate, lactate and the phosphates. These exhibit different characteristics in terms of solubility and bioavailability, as well as calcium density (amount of calcium per equivalent weight). Calcium citrate, for instance, is more soluble and, in theory, more bioavailable then either calcium phosphate or calcium carbonate. When designing products, technologists often use bioavailability as one of the major criteria for selection of fortification compounds. Some debate exists as to how much emphasis this should be given in most food products. There is no argument that in foods designed to provide optimal nutrition, such as baby formula, bioavailability is a top priority. But this may not hold true for mainstream fortified foods, especially since bioavailability is often coupled with increased reactivity. "You've got to be very careful when you talk about bioavailability," cautions Gordon. "For example, there have been a number of studies that have shown that even when you use the most bioavailable iron salts, depending on how you process the food product containing them, you can greatly affect the bioavailability of the mineral. "I recall a couple of papers where the researchers looked at several different calcium salts," Gordon adds. "They found that when the calcium salts were consumed with food, they were all bioequivalent, whether calcium carbonate or any of the gluconates. Taken by themselves as supplements, bioavailability of the compound alone does matter, but that's not the way we normally get our nutrition. It's hard to talk about bioavailability in foods because you are not talking about an individual compound; you're normally talking about nutrients consumed as part of a whole meal." In one paper, Charles Y. C. Pak, M.D., of the University of Texas Southwestern Medical Center at Dallas, and Louis V. Avioli, M.D., of the Washington University School of Medicine, St. Louis, proposed several food-related interactions with calcium absorption. These included foods that change the pH, those that affect the secretion of gastric juices, and those containing anions that affect calcium availability. More studies are probably required to resolve this controversy, but from a product designer's viewpoint, it brings up another issue: What's good for the human body isn't necessarily good for the food product.Fortification FX What happens to the food product itself when various nutrients are added? Several consequences can occur. Some are positive, but a number are quite detrimental to the finished product. The effects can vary widely depending on the product matrix, the characteristics desired, and the type and level of the nutrient added. Color and appearance. Adding nutrients may affect product appearance in several ways. It may contribute a distinctive color. It can take part in a reaction that changes the color of a product. It can also affect the clarity of a product. Consider the list of approved, non-certified colorants. Both beta-carotene and riboflavin appear on the list. When used for fortification, they still have their colorant properties. The degree and desirability of that effect varies with the level used and with the food product. Put them in a white or colorless matrix, such as Cream of Wheat, and based on the level, the product will be cream to bright orange. In a dark product, the color may be difficult to detect. Often the color produced by a required level gives the desired color, as in an orange beverage or a corn muffin. Altering this effect is difficult. Roche has developed a form of beta-carotene that minimizes color in many applications. It still can impart detectable color in certain products, such as a white cake mix. It consists of beta-carotene beadlets, compounded with fructose, fish gelatin, corn starch, glycerol and natural antioxidants. According to O'Brien, the beadlets may appear as tiny, reddish-orange specks in a product, but they will not impart color to the overall product. Some nutrients can change product color by reacting with other ingredients. Ascorbic acid is a good reducing agent. Some of the certified dyes are sensitive to reducing agents and will fade when the product contains high levels of vitamin C. Vitamin C and iron may react to create a grayish tinge in cereal products such as oatmeal. "Often the minerals induce reactions - generally oxidation-type reactions - especially iron or copper ions," says Davies. "If you expose the product to high levels of moisture and oxygen and you start catalyzing a lot of reactions during processing, certain vitamins are more prone to oxidation reactions. Some of the color difficulties encountered with vitamins may be attributed to these oxidation reactions." Solubility of mineral salts can affect a product's appearance. A clear liquid requires a highly soluble form or the product will appear hazy when the mineral is suspended. If the mineral is not in suspension, a sediment may form when using a less soluble or insoluble form. These problems increase with the level, so solubility can have a significant impact when adding minerals with a fairly high dosage, such as calcium, magnesium and phosphorus. "We have worked with micronizing calcium. It helps suspend the calcium, but it doesn't increase the solubility," notes Chaudhari. "It may product a milky appearance, but it doesn't settle out at the bottom." Flavor. As with color, flavors can come from the vitamin or mineral itself, or from some reaction promoted by the fortification. Thiamin is probably the worst culprit for contributing off-flavors. It contains sulfur, which promotes a characteristic "eggy" odor and flavor. Some minerals, such as iron and copper, create metallic notes at high levels. The impact of these flavors varies with the level and is more noticeable in delicately flavored products. Some ingredients, such as chocolate or whole grains, are fairly successful at masking these off-flavors. "I've heard people claim that if B1 were removed from bread products, the bread wouldn't taste or smell the same," says Gordon. "It has become so entrenched in the makeup and it fits in with the overall flavor, so it's a positive. Normally the flavor of even a very small amount comes through and can be surprisingly intense. That points out the need for deciding the necessary nutritional profile and designing a product to accomplish the goals. "Two B1 products are used: thiamin mononitrate and thiamin hydrochloride," Gordon continues. "But as far as flavor problems, they are essentially equivalent. A coated version gives some protection from the flavor, as long as you don't dissolve the coating. Even that isn't designed specifically to prevent flavor problems. It was designed for dry mixes to separate ingredients physically in order to avoid reactions." Often nutrients cause reactions that lead to off-flavors. One of the more common is the catalyzation of fat rancidity by metal ions. Encapsulation and the addition of oxygen scavengers can be used to reduce the propensity of the reaction. The more bioavailable the compound is, however, the more likely the oxidative reactions are to occur as well. This is one time when bioactivity and finished product quality can be at cross purposes. Ferric orthophosphate, with relatively low bioavailability, is often used for fortification because of its low reactivity. "There is often a happy medium," says Chaudhari. "Copper sulfate often causes rancidity problems, especially in milk-based products. Copper gluconate works fairly well, based on the feedback we've been getting. With magnesium, you have the same situation. The oxide form is not very soluble, so it is less reactive. But the sulfate is much more reactive and tends to form compounds that produce off-flavors." Texture. Less soluble forms of many of the minerals, such as calcium carbonate, may come across as gritty, especially in liquids. Also, reactions can cause precipitates to form and appear as floc. "If you are working with a high-protein beverage with a pasteurization step, depending on the type or the form of the mineral, sometimes you can end up with textural changes," says Davies. "Some of the meal-replacement beverages containing caseinate, for example, can sometimes be very sensitive to the presence of minerals, which may induce protein coagulation."Wrap it up Encapsulation is one method commonly used to protect vitamins and minerals from deteriorating or causing problems. Depending on the material, this can work for products that are not heated over 250 degrees Fahrenheit. Below that, encapsulation can prevent interactions and deterioration of oxygen-sensitive nutrients. Depending on the product characteristics, the encapsulate must offer different barrier properties. Different levels of encapsulation can be used, depending on the process conditions and the environment. "We usually use mono- and diglycerides as encapsulates," says Chaudhari. "We may use a cellulose-based encapsulate for higher-heat applications. The fat-based coating will melt over 195 degrees Fahrenheit to 200 degrees Fahrenheit. Another problem with lipid encapsulates is that they may float on the surface of a liquid product." Typically only the problematic ingredients are encapsulated. Iron and thiamin are likely candidates. Encapsulating the entire premix would be unnecessary and not very cost-effective. "In the past, when fortified foods weren't getting as much of an emphasis in the regular grocery store, processors were primarily interested in providing a good-tasting product," says Davies. "Now they still want to provide a good-tasting product, but they also want to promote some sort of health or nutritional benefit. Taste is still the bottom line, even if the product is fortified. Nobody will buy it if they don't like the quality."Back to top
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