Food Product Design: Health/Nutrition - January 2005 - Preventing a “Nutrient” Breakdown

January 2005

Consumers have become increasingly aware of their dietary shortcomings. Surveys have shown growing numbers of shoppers claim that supermarket purchases are influenced by health concerns. It is this mounting concern that has fueled growth into the tens of billions of dollars of items fortified with vitamins, minerals and other healthful ingredients.

Addition of nutrients is not always a simple task, though, as many cannot withstand the rigors of processing, storage or further preparation. Luckily, technology for maintaining nutrients has grown almost as quickly as the industry it serves.

Nutrient addition multiplies
Adding vitamins to foods is not a new concept. In 1924, American salt producers began fortifying table salt with iodine to help remedy the symptoms of severe iodine deficiencies, such as goiter. Soon thereafter, the addition of vitamin D to fluid milk facilitated rickets prevention. In 1943, government-mandated enrichment of flour aimed to replace the iron, riboflavin, thiamin and niacin lost during milling. More recently, FDA began requiring manufacturers to fortify most grain products, such as enriched breads, flours, rice, pasta and breakfast cereals, with folic acid to reduce the incidence of spina bifida. In addition, products like enriched flour and bread usually contain added thiamin, riboflavin, niacin and iron, while skim milk, low-fat milk and margarine are usually enriched with vitamin A in addition to D.

Many manufacturers fortify products, such as juices, nutritional drinks and bars, and meal-replacement items, with nutrients by choice. Alice Wilkinson, director of research & development, nutritional ingredients division, Watson Foods Co., Inc., West Haven, CT, notes that growing concern over children's health and weight is creating increased demand for nutritious foods and snacks directed toward that market.

Food and beverage fortification continues to expand. "There are so many fortified products these days, from simple fortified flours to complex solutions for tube feeding," says Ram Chaudhari, senior vice president, research & development, Fortitech, Inc., Schenectady, NY. "The technology is advancing at an incredible rate."

With each advance in fortification comes a need to develop ingredients that maintain their stability through a host of applications and processes.

Strong, but not indestructible
Vitamin A, an oil-soluble micronutrient, affects vision, skin and mucosal integrity. With five double bonds and a free hydroxyl group, vitamin A is very susceptible to oxidation by light and oxygen. Degradation can occur from exposure to elevated temperatures and pH levels lower than 5. Increasing humidity also has been shown to adversely affect vitamin A. The alcohol form of vitamin A, retinol, can be esterified with acetic, palmitic or propionic acids to yield retinyl acetate, palimitate and propionate. Esterification protects the hydroxyl group. However, it does not eliminate the oxidative threats posed by the double bonds. Provitamin-A carotenoids, such as alpha or beta carotene, are more-stable sources of vitamin A. However, the body's rate of conversion from carotene to vitamin A is only six to one (6 mg beta carotene is equivalent to 1 mg retinol).

B-complex vitamins affect countless systems in our bodies and are, therefore, crucial nutrients. "Many consumers are looking for energy-boosting effects from B vitamins in sports beverages and nutritional-bar applications," says Chaudhari. Thiamin (B1) is one of the most heat-labile, losing up to 50% of its content through baking, boiling or pasteurization. Thiamin is one of the least-stable B vitamins at neutral or alkaline pH. Studies have shown that thermal degradation of thiamin can be as much as three times greater when pH is elevated from 4.5 to 6.5. Thiamin is also affected by humidity, and can cause off-flavors after exposure to heat. Riboflavin will withstand thermal-processing temperatures, but will degrade quickly when exposed to light. Although very stable in general, niacin losses can occur when the vitamin leaches out into cooking water. This is the case with most water-soluble vitamins.

Vitamin B6 losses will vary with thermal processing methods. Sterilized liquids will experience high losses, while dough made with enriched flour will see little change in B6 level. Folic acid is very stable through storage, in addition to heat and humidity. However, it will lose activity from exposure to light, oxidizing or reducing agents, and high-acid or -alkaline conditions. Premixes, baked goods and flours retain virtually 100% of added folic acid. Pantothenic acid's stability is good except under alkaline conditions. In addition, freezing destroys pantothenic acid. Biotin is sensitive to acidic and alkaline environments.

Vitamin C, often referred to as ascorbic acid, is necessary for synthesis of collagen, norepinephrine and carnitine. An important factor in cholesterol metabolism and a potent antioxidant, research is ongoing into the role of vitamin C in preventing cardiovascular disease, cancer and cataracts. Although commonly used to fortify products such as juices, dairy drinks and some cereals, vitamin C is very unstable under typical processing and storage conditions. High heat during processing can lead to degradation. Moisture contents greater than 7% in aerobic conditions have been shown to have deleterious effects on vitamin C in cereal products. Oxidation can result from interaction with metals, such as copper and iron; exposure to light or oxygen; non-neutral pH; and elevated water activities.

Vitamin E is a powerful antioxidant that has been studied for potential benefits to cardiovascular, neurologic and immune systems. Its addition to foods is a growing area of interest as some studies suggest that absorption is improved when the vitamin is consumed with food versus as a supplement. Research conducted in the early '90s indicated that increased vitamin E intake could provide protection against certain degenerative diseases.

Vitamin E's stability depends on the form utilized and application. The term "vitamin E" refers to eight compounds, alpha, beta, gamma, and delta-tocopherols and -tocotrienols. Alpha-tocopherol is the most stable of the group, and the most active in the human body. Like other oil-based vitamins, addition to products other than oils and spreads can be difficult. Also, naturally occurring alpha-tocopherol will oxidize slowly when exposed to air. Vitamin E's strong antioxidant nature can also be a problem in fats and oils, as it doesn't really "know" when to act as a fortificant and when to act as an oxygen scavenger.

Building strength
"When speaking of nutrient shelf life, we're really talking about meeting the label claim on a product label," notes Lucien Hernandez, business manager, Balchem Corporation, Slate Hill, NY. In order to ensure that the nutrients being added are present at the point of consumption, formulators typically utilize two basic approaches.

"The first step toward stability is correctly choosing the right form of a given nutrient for a given application," notes Chaudhari. "Vitamin C added as ascorbic acid is a better choice than sodium ascorbate for high-acid systems, like orange juice."

The concept of "overdosing" or "adding overage" refers to the practice of adding enough of a given nutrient to compensate for losses incurred through processing and storage. By accounting for deterioration of the nutrient, the developer knows that at the final day of shelf life, the product will contain at least the amount stated on its label. This is an acceptable approach when shelf life is short, and losses are minimal.

At the other extreme, though, high overage requirements can have negative effects on finished product taste, cost and, in some markets, labeling. "Some markets' regulations see the overage amount as high enough to be considered a drug instead of a vitamin," notes Hernandez.

Vitamin C, for example, is a very popular fortificant. Its instability requires substantial overage levels, in some cases over 50%, causing many developers to consider more-economical options.

"Vitamin C is well suited for cold-formed nutritional bars and beverages," suggests Wilkinson, "where there are no losses to heat degradation."

Encapsulation covers a broad spectrum of processes that provide various effects. Coating an ingredient with another material "seals it off" from its surroundings, protecting it from the various elements in the product. This barrier can also serve as protection from the encapsulated material, locking off flavors or colors within the capsule.

Spray-drying is a basic form of encapsulation where a fluid material is mixed with a carrier and atomized into a chamber with hot air currents, encasing the fluid within the carrier. After spray-drying an oil-based vitamin with a modified starch, a liquid material is transformed into a dry powder. Selection of the appropriate carrier will depend on the final application. For example, a cold-water, dispersible beverage would call for a more-soluble carrier than would a tablet or bar application.

The spray-drying process also affords the opportunity to incorporate additional ingredients. Antioxidants may be added to the mix to improve the shelf life of the resulting powder.

Optimizing the mixture can also create desirable effects that improve overall performance and stability of the foods to which it is added. For example, Wilkinson notes that optimizing the pre-drying blends of beta carotene yields unique vitamin-A fortificants that can be added to products without imparting the typical colors that could be seen as undesirable in certain applications.

Spray-chilling is another encapsulation process in which cool particles of the encapsulate are mixed with hot coating materials, and then cooled with air to create a powder. "Spray-chilling is a good choice for products that require higher coating levels, up to 80%, on the substrate," says Hernandez.

Microencapsulation typically describes more-refined processes for coating materials. The technology is similar to that which yields scratch-and-sniff stickers and duplicate copies used in checkbooks. Hernandez suggests that in food-related applications, "these processes are usually being applied to create much-smaller particles than traditional agglomeration or beadlet-type technologies in systems where the performance parameters, such as release rates and times, are more clearly defined."

The oldest microencapsulation process is pan-coating. Dry material is blended with a coating material, usually a lipid, in a jacketed mixing vessel. As the temperature rises, the lipid melts and coats the dry material. "An older system with limited flexibility and control," notes Hernandez, "it is well suited for coating simple materials, like salt, for incorporation into meat applications." However, this system is not suitable for the complex needs of nutrient encapsulation.

Fluid-bed systems are more intricate and allow for greater control and modification to create very-specific effects. This process suspends particles in a controlled airstream, where they are coated with the material of choice. These systems take many forms and may be utilized for drying, granulating and agglomerating, as well as coating. "Fluid-bed encapsulation is ideal when release profiles are narrowly defined," continues Hernandez.

Many encapsulation systems use lipids for coating. Soy or corn oils with varying degrees of hydrogenation are selected based on price, melt temperature and stability in the target application. Much study has gone into creating encapsulating materials with continually higher melting temperatures. "Creating a more-heat-stable coating for vitamin C with lipids," says Wilkinson, "will protect the vitamin for a baked-bar-type application."

Mining for health
Minerals are, in general, more stable in processing conditions than vitamins. However, reactions do take place when minerals are exposed to light, air and heat. Moisture in a food system can also interact with minerals, such as copper, iron and zinc, leading to adverse interactions with other nutrients. Iron has been shown to increase the rate of degradation of vitamins, notably vitamins A and C, as well as thiamine. Iron can also catalyze oxidative rancidity in fats and oils, resulting in off-colors and -flavors. In addition to creating a rancid taste, the potency of the added iron is lost.

In addition to building strong bones and teeth, calcium helps maintain bone strength and cell membranes and is involved in muscle contraction and blood clotting. Like iron, calcium is very stable, yet it can be very reactive, often complexing with a variety of ingredients, depending on the parameters of the fortified product. Excess calcium can also affect other minerals, such as zinc, magnesium and iron, present in products. Calcium's presence in a product does not necessarily guarantee its efficacy, as absorption can be dramatically reduced when the consumer's vitamin D intake is inadequate. Calcium from different sources might be absorbed differently, as well. Studies have shown that calcium malate's rate of absorption can be almost 30% greater than that of calcium carbonate, and 40% greater than tricalcium phosphate.

Unlike vitamins, minerals are not usually coated to protect the mineral from its environment, but rather to protect the environment from the mineral. Many of these compounds have been shown to adversely affect the systems to which they are added. Iron, a highly reactive metal, can catalyze oxidation of fats and oils in infant formulas, reducing the potency of the iron along with the health benefits of the added oils. Copper can react with some ingredients to impart a blue tone to foods. Calcium can mask some flavors, affecting the overall taste of a product. In all these situations, encapsulation isolates the minerals, improving the product's stability.

By land and by sea
Phytochemicals are a group of compounds gaining attention for their healthful effects (see "Fruit's Plentiful Phytochemicals," by R. J. Foster, Food Product Design, Sept. 2004, Functional Foods Annual). Many of these compounds possess tremendous antioxidant activity, reduce LDL , aka "bad" cholesterol, and affect innumerable systems in our bodies.

As previously mentioned, carotenoids, like alpha and beta carotene from yellow and orange fruits, serve as precursors for vitamin-A antioxidants. Lycopene, the carotenoid that gives tomatoes their rich, red color, has been linked it to reductions in the risk of cancers of the prostate, colon, breast, lung and digestive tract. Zeaxanthin, an oxygenated cousin of lycopene, is believed to help prevent age-related macular degeneration, one of the leading causes of blindness.

Leonard Johnson, Ph.D., director of food technical services, DSM Nutritional Products, Parsippany, NJ, notes that both lycopene and zeaxanthin are available as oil suspensions or dry powders, allowing for use in a variety of applications. Encapsulation of the carotenoids provides additional flexibility of use, as well as protection from oxidation. "Lycopene can be stabilized in foods by limiting exposure to air; adding antioxidants, such as ascorbic acid; and using appropriate packaging," continues Johnson. Similar approaches should be used for zeaxanthin, as well.

Consumer awareness is growing with regard to the health benefits of long-chain polyunsaturated fatty acids (lc PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Fortification with these omega-3 fatty acids is in demand, but difficult. Johnson notes that the oils' high degree of unsaturation makes them very susceptible to rancidity and development of fishy odors.

Manufacturers develop innovative techniques for purification and encapsulation as demand increases for foods fortified with these oils. "DSM has a patented antioxidant system," notes Johnson, "to help keep the oil more stable." Additional steps to consider include adding antioxidants, like sodium ascorbate or tocopherols, and delaying the incorporation of the omega-3s as long as possible to reduce exposure time to the air.

The biotic man
Over the last several years, interest in probiotics -- bacteria that are part of our intestinal flora and help metabolize foods and limit the growth of harmful bacteria -- has increased. These "good bugs" are reduced in numbers, though, by age, stress and even the antibiotics we take to fight off unwanted infections. Consumption of foods with probiotics helps restore the levels we need to maintain a healthy gut, and might provide additional benefits, such as prevention of diarrhea and colon cancer, reducing cholesterol, and improving immune functions.

Although the "good bugs" fight the "bad bugs" in our gut, these probiotic bacteria are susceptible to the rigors of processing and storage. Sensitivities to moisture, heat, oxygen, compression and acidity result in reduced stability and efficacy, and limit their number of potential applications.

Selection of strains with higher resistance to various processing conditions provides some measure of stability for probiotic bacteria, allowing for addition to dairy beverages and yogurts. Encapsulation of the probiotics, however, provides a greater protection, opening up myriad application possibilities. For example, the patented microencapsulation process developed by Institut Rosell/Lallemand, Montreal, Quebec, applies a vegetable fatty-acid matrix to a freeze-dried bacteria -- specially selected strains of bifidobacteria and Lactobacillus. This coating allows the probiotics to better resist heat shock and compression during processing, as well as stomach acidity that could degrade the organism before reaching the intestine.

As consumers become more aware of what's missing from their diets, they will undoubtedly continue looking to food manufacturers to provide the missing pieces to their health puzzles. It is fortunate for developers that new technologies are emerging to help sustain the most delicate of nutrients through the potentially perilous journey from processing plant to plate.

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R. J. Foster, with over a decade of experience in research & development and technical service to the food industry, is a processing consultant specializing in technical communications. He can be reached at askrjfoster@sbcglobal.net .