Panna Chaudhari, PhD, vice president, scientific affairs at Fortitech, explained the considerable impact that storage and processing have on the stability of ingredients used in foods with added vitamins and minerals.
Common issues include knowing which form of a vitamin is appropriate for a specific application: should ascorbic acid or sodium ascorbate be the source of vitamin C? Also, should the nutrients be added to the food as a dry powder or in a solution?
Negative interactions might include an increased reactivity of minerals when added to low-pH foods, resulting in color problems. In this case, a different source of the mineral often can be used, and added at a different stage in the process. For example, iron dry-blended into the finished product might have better color than when it is added during the liquid stage. Another example is copper and iron, both pro-oxidants in foods containing lipids, which can lead to rancidity and off-flavors. Some trace minerals can increase the rate of destruction of vitamin C.
Positive interactions also can occur. Vitamin C improves the absorption of iron. Vitamin E seems to increase the availability of vitamin A, due to antioxidant activity of the former for stabilization of the latter in the gastrointestinal tract.
Through a combination of chemical manufacturing and analytical testing, vitamin and mineral premixes can be developed to accommodate each situation. Ideally, it is good to have vitamins and minerals added separately as two different premixes to avoid interactions. However, some components can be encapsulated if a separate addition is not possible for vitamins and minerals.
A thorough knowledge of the chemical characteristics of nutrients and an understanding of their possible interactions with other ingredients enables food technologists to estimate the rate of addition of each nutrient.
To confirm the accuracy of an estimate, the required level of nutrients are added to the food and evaluated immediately after processing. Evaluation should continue at regular intervals over a period of time equivalent to their effective "use by"? date. This analytical work then will enable the necessary addition rate of each vitamin to be fine-tuned.
An effective prebiotic is a non-digestible food ingredient that increases the overall well-being of the gastrointestinal tract, decreases risk of gastrointestinal diseases and is safe. Michael H. Auerbach, senior science advisor of regulatory affairs at Danisco USA Inc., explained the role of polydextrose as a prebiotic fiber.
Polydextrose is a low molecular weight, randomly bonded polysaccharide of glucose with energy utilization of 1Kcal/g. It is prepared by the bulk melt polycondensation of glucose and sorbitol, with small amounts of food-grade acid in vacuo. All possible glycosidic linkages with the anomeric carbon of glucose are present: a and b 1-2, 1-3, 1-4 and 1-6; the 1-6 linkages predominate. It has an average degree of polymerization (DP) of 12 and an average molecular weight of 2000.
The low-calorie content of polydextrose is a result of its limited digestibility in the small intestine and incomplete fermentation in the large intestine. This property has led to acceptance of polydextrose as a dietary fiber in many countries. Numerous published studies show how polydextrose ingestion leads to beneficial effects on gastrointestinal function.
Polydextrose improves bowel function by increasing fecal bulking and softening, and decreasing fecal transit time. The prebiotic effect stimulates growth of beneficial bacteria, decreases fecal pH, increases short-chain fatty acid (SCFA) production, and promotes colonocyte growth and attenuation of blood glucose and lipids. As long as carbohydrates are present in the colon, saccharolytic (carbohydrate) instead of putrefactive (protein) fermentation takes place. Putrefactive fermentation is associated with adverse effects in the colon.
Polydextrose is digested as a soluble fiber, and is well-tolerated. The mean laxative dose is 90g/day with a tolerance level of 50g in a single dose. Osmotic effects are minimal, due to the large size of the molecule. Gastric discomfort is minimal or nonexistent at even the highest consumption levels. Polydextrose is a sustained prebiotic with effects in both the proximal and distal colon.
Recent definitions of fiber (such as those endorsed by AACC, FSANZ, NAS/IOM, Codex Alimentarius) include polydextrose. In addition, AOAC method 2000.11 allows for the determination of polydextrose in foods, and can be used in conjunction with AOAC enzyme-gravimetric methods. Accordingly, labeling of polydextrose as a dietary fiber has been formally approved and tacitly accepted in many countries.
Setting the Protein Bar
Nutritional food bars are a rapidly growing segment of healthy food products, showing a growth of 245% from 1999 to 2004. Sales topped out at $858 million in 2004. Currently, there are over 4,000 SKUs of food bars marketed in North America—70% of them contain soy. Food bars combine a number of ingredients into a solid, low-moisture form designed for specific market positioning (i.e., energy, weight loss, meal replacement, snack and nutrition), explains Steven Taillie, director, applied technology, The Solae Company, in a discussion about soy protein functionality in nutritional bars.
Soy protein is a high-quality protein (PDCAAS = 1) that can be used in a wide range of forms in baked bars, granola bars, sheet and cut bars, and cold-formed extruded bars. Isolated soy protein (ISP) contains 90% protein, soy concentrates have 70%, soy flours contain 50%, and textured pieces and extruded nuggets have from 40% to 70%, and 50% to 80%, respectively. Bar formulators face many challenges that include developing a product that maintains its quality over a shelflife of nine to 15 months; exhibits a range of textural profiles from chewy to crunchy; has a water activity of 0.45 to 0.65; is cost effective and achieves high sensory scores. In addition, the formulator must make the proper protein selection, meet protein fortification levels, include adequate fiber sources and work with multiple carbohydrate sources that target various levels of carbohydrate and sugar content.
A variety of chemical and physical attributes of soy protein affects its functionality in food bars, including solubility, water-holding capacity, granulation, density, viscosity, gel strength and dispersibility/wettability. Factors affecting the bar's texture include the protein source, the fiber source, ingredients incorporated into the mobile phase and various processing variables such as mix time, processing temperature and shear rate. For instance, sugar-based formulations produce softer bars with increases in mix time, processing temperatures and shear rates, whereas polyol-based formulations produce softer bars with a decrease in each of these processing parameters. In terms of protein selection, hydrolyzed ISP makes softer bars when compared to gelling ISP, which makes a harder bar. Soy protein is an effective source of protein that, in combination with other ingredients, produces a bar offering a number of health benefits for the consumer.
"Use and Functionality of Soy Proteins for Nutritional Bars and Snacks," Steven Taillie; for more information: Ken Bopp, firstname.lastname@example.org, 800-325-7108, The Solae Company, www.solae.com.