The issue of nutrient stability and bioavailability in foods and beverages is not new. In the past century, the expanding knowledge base of nutrition and food science enlightened scientists on the effects of processing, handling and storage on bioactive components. Restoration, standardization, enrichment, supplementation and fortification became the methods for ensuring the food supply's nutritive value and addressing health concerns. Today, the newer world of functional foods challenges product developers to identify what's important and how to deliver it effectively. Elementary issuesSimply put, the basic laws of chemistry are key to understanding and managing the potency of vitamins and minerals. Ram Chaudhari, Ph.D., senior vice president, research and development, Fortitech, Inc., Schenectady, NY says: "You have to take into account that vitamins, minerals and bioactives are chemical compounds that can react with each other." He cites copper, iron, zinc and water-soluble vitamins as examples of reactive nutrients affected by processing and storage conditions as well as pH and enzymes in food systems. The vitamins C, A, D, B1, and B12 are generally considered to be the least stable. C, A and B1 tend to be more suseptable to oxidization in the presence of metal ions. In addition, interactions between certain vitamins - particularly C, B1, B2, B12 and folic acid - may accelerate the rate of breakdown of some vitamins. In addition, the solubility and complex-formation characteristics of minerals frequently create problems in food systems. For example, copper sulfate added to milk with fat becomes insoluble and catalyzes fat oxidation, resulting in rancidity. Another factor that can affect stability is pH. For example, vitamin A is susceptible to oxidation when the pH is less than 5. In addition to the ingredients in the food matrix, exposure to temperature, light, oxygen and water may affect stability during processing and storage, and consequently, the actual amount of nutrient delivered to the consumer. Minerals tend to be much more stable under extreme processing conditions than vitamins. Chaudhari says processing conditions are very important - dry mixing has very little effect, but water, oxygen and heat are catalysts for many chemical reactions. Time of exposure to a damaging factor can help or hinder the rate of nutrient retention. Heat is a prime example. Various time/temperature combinations result in differing vitamin-retention levels during oven-, drum- and spray-drying. In general, lower combinations of time and temperature are better. Since drum-drying employs high heat and shorter exposure time, less loss occurs than in oven-drying. Spray-drying, however, exposes the nutrients to more oxygen, making additional controls necessary to limit oxidative damage. A number of ingredients found in functional foods and dietary supplements present challenges to product manufacture and acceptability. According to Chaudhari, branched-chain amino acids, popular in sports drinks, are difficult to work with. And high processing temperatures cause omega-3 fatty acids to develop a fishy odor, as well as discoloring and caking/lumping with choline and carnitine. He adds that calcium carbonate, an economical ingredient used for calcium supplementation, becomes insoluble and chalky in some applications. But with the increase in nutraceutical fortification, other issues will arise. "Information is lacking on how things like lutein and lycopene will act in applications. There is no simple answer," he says. An ounce of preventionInteractions, bioavailability, and wholesomeness all are factors to consider when designing a system for fortification, according to Chaudhari. "You must make sure the final product is cost-effective and that the customer is getting what they are paying for," he says. "To maximize a nutrient, think about the minimum exposure (to the factors that will destroy it). You must also consider the stability of each and every ingredient in the final application. You need to know their chemistry and characteristics-how they react, their compatibility." He adds, "Food systems are more complex. In general, shorter-chain compounds are less reactive. For example, hydrolyzed proteins react less than amino acids." He also says that stabilizing systems help with very reactive nutrients such as calcium, iron and vitamin C. Food manufacturers can retain a greater level of nutrients in finished products simply by changing processing steps. For example, manufacturers can minimize exposure of heat-labile and oxygen-sensitive vitamins to high temperatures and air by using HTST processing, or by adding nutrients mixed with flavors as a final step after heat treatment, mixing and aeration. During storage, packaging with oxygen and light barriers can limit losses, as does temperature control. Chaudhari says that encapsulation and time-release compounds offer other ways to ensure utilization of nutrients. "This is a very fascinating area. People are working on microencapsulation with mono- and diglycerides which withstand room and slightly elevated temperatures." A number of nutrients and bioactive substances are candidates for encapsulation. Obvious choices include reactive minerals, such as iron, magnesium and copper, and heat- and oxygen-sensitive vitamins, such as A, C and E. However, microencapsulation of probiotics, choline, amino acids and B-vitamins also offers delivery and flavor-masking advantages.
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