Culinary Cures: Calcium Fortification

Culinary Cures:
Calcium Fortification
September 1997 -- Cover Story Plus

By: Barbara van Mossevelde
Contributing Editor

  The demand for vitamin- and mineral-enhanced products in the United States continues to steadily rise, especially in the beverage industry. A 1996 study by Nicholas Hall & Company, United Kingdom, shows that about 8% of the U.S. fruit juice and drink market consists of vitamin- and mineral-enriched brands, and this figure is expected to continue to climb. Calcium ranks among the more popular minerals used to fortify these beverages.

  Several factors are driving the growth of products fortified with this important mineral. First of all, the total amount of calcium in the body is about 1,500 grams. Because of this level, it is widely regarded as one of the most important minerals. Secondly, the U.S. population continues to be at high risk for calcium deficiency, and consumer recognition of this risk is high. And finally, food processors have taken an increasing interest in introducing calcium-fortified products. Regulations allow processors to include on product labels health claims associating calcium with a reduced risk of osteoporosis. To make this claim, the product must contain 20% or more of the reference daily intake (RDI) per reference amount. The RDI for healthy U.S. adults is established to be 1,000 mg.

Getting choosy

  Many different calcium sources are at food technologists' disposal: calcium phosphates, carbonates, citrates, gluconates and lactates. Several factors influence their selection in beverage applications:

  Flavor. Each calcium source impacts product flavor and mouthfeel differently. This is quite important, because no matter how healthy a product might be, it also should taste good.

  For example, calcium lactate is neutral-tasting. However, at high levels, even neutral-tasting calcium salts can affect flavor. The extent depends largely on the type of product and other ingredients. Using a combination of different sources to minimize the flavor impact of one salt could alleviate flavor problems in high-calcium formulations.

  Solubility. Depending on the application, the solubility requirements of the calcium source varies. For dry applications, a small added volume might be important, which would require an ingredient with a high mineral content and a neutral taste. In a liquid or moist product, an insoluble calcium salt often imparts undesirable grittiness or a sandy mouthfeel.

  Additional thickeners used to keep an insoluble calcium source in suspension change the texture of the product dramatically. Therefore, solubility is a much more important characteristic than the mineral content itself.

  Calcium lactate is so highly soluble that it is possible to dissolve more than two times the RDI in 8 oz. of water. This high solubility can be useful, for instance, in a concentrated juice requiring a high mineral concentration, or in products with a low water content. From an appearance standpoint, solubility plays an important role in sport drinks and clear liquids, such as apple or cranberry juice.

  Solubility also affects the mineral intake by the consumer. When the calcium settles on the bottom of the package, it causes variations in the calcium content of each serving from that package.

  Bioavailability. Solubility also may influence bioavailability, or the amount of calcium available for absorption by the human body. Although various research fails to provide a unanimous verdict on this correlation, it is widely held that calcium must be soluble to be absorbed.

  Additional factors affecting calcium absorption include: other constituents of the diet; intestinal conditions; calcium load in the diet; and an individual's calcium status. In an effort to eliminate or minimize these factors, Purac Biochem, the Netherlands, performed various in vitro studies (simulated gastrointestinal digestion) in 1995. These studies investigated the influence of the food product on calcium availability and the influence of the source. Sources tested included lactate, gluconate, citrate, phosphate and carbonate in 11 different food products, including dairy products, infant nutrition, sport nutrition and fruit juices. Results showed that calcium lactate was one of the best bio-available sources in all the products tested. The graph titled "Calcium Bioavailability" shows the average bioavailability of the calcium salts in the different products tested.

  The study also shows that food product composition influences the calcium availability from calcium lactate to a lesser extent than the calcium availability from other sources, such as phosphate or carbonate.

  Stability during processing. High bioavailability in minerals often means increased reactivity, and thus a lower stability during processing. For calcium, this is only partly true. The calcium will not change ionic form, as in the case of ferrous salts, which can oxidize and change color. However, calcium ions can react with proteins, resulting in unwanted coagulation during heat treatment.

  Certain methods help avoid this problem, such as adding sequestrants that lower the calcium activity to help prevent reactions with proteins. This method does not have as much impact on the texture of the product as the hydrocolloid thickeners that would be needed to keep insoluble sources in suspension.

  The market for calcium-fortified beverages and other products still is growing. Keeping these factors in mind helps food scientists make the right choice for calcium fortification in a particular food product.

Barbara van Mossevelde has a degree in Food Science and Technology from the Agricultural University in Wageningen, the Netherlands. She is a technical service representative at Purac America, Inc., Lincolnshire, IL.

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