Encapsulation basics

by FoodBusinessNews.net Staff
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Have you ever tried to keep two small children from quarrelling? Isolation is almost the only answer, so you send them to separate rooms. And thus it is when ingredients come into conflict in dough systems. Salt can inhibit yeast. So can cinnamon. Some nutrients will stain the crumb, and the oven’s heat will destroy the viability of others. Despite these conflicts, each ingredient performs a vital function to ensure the quality and appeal of the finished product.

Although doughs must be properly mixed for optimum results, formulators should avoid using antagonistic materials. Then there’s the matter of needing a particular response on a time-delayed basis. Encapsulation offers good solutions to these formulating problems. This form of food nanotechnology has been available for many years, but interest has never been higher as formulators seek ways to add value — not problems — to foods.

WHY CONSIDER? The first thing to know about encapsulated ingredients is they cost more because of their extra processing. Obviously, encapsulated salt isn’t the answer to yeast inhibition in low-margin items such as white pan bread or hamburger buns. Instead, you can delay the salt addition until final mixing. But it may be an answer for a high-value premium product with a delicate or problem-prone leavening system. Bowl costs must be part of the formulator’s decision.

Actually, improvements in the technology of encapsulation are bringing costs down and increasing the number of encapsulates now available. These materials also have inspired new categories such as frozen rising-crust pizza, take-and-bake foods and even improved refrigerated biscuits.

Formulators should consider encapsulated ingredients when they want to 1 — control release of an active ingredient to prevent ingredient interactions until a specified time or condition; 2 — protect unstable ingredients from heat, light or moisture in their environment; 3 — mask objectionable flavors and colors; 4 — reduce dusting; 5 — improve processing; 6 — reduce hygroscopicity or water-absorbing capacity; and 7 — protect vitamins, minerals and other sensitive ingredients to allow their properties to survive processing.

In other words, encapsulation systems shield ingredients from environmental conditions while delivering other ingredients in a protective or masking manner. This method also helps control costs by minimizing the concentration of often-expensive fortification ingredients that would have to be overdosed if added "naked" to the formula. Novel ingredients, especially controlled-release materials and sensitive live microbial cultures, may be easier to introduce into formulations if encapsulated.

WHAT’S AVAILABLE? Suppliers can count the number of encapsulated vitamins, minerals, amino acids, botanicals, prebiotics, probiotics and flavors in the hundreds and custom-designed blends in the thousands. Those of most interest to bakers and snack food processors include salt, leaveners, preservatives, antimicrobials, antioxidants and omega-3 fatty acids.

A few relatively new applications stand out: encapsulated fish oils and encapsulated vitamin C, plus the related matter of encapsulated minerals. Also, probiotic microorganisms are being encapsulated to preserve their vitality during processing; the only way the body benefits from probiotics is if they are consumed as live cultures and reach the gut intact.

Fish oils, a rich source of omega-3 fatty acids and highly desirable for health-and-wellness products, also have a reputation for flavor and odor problems. Encapsulation bestows the benefits of not only odor and flavor masking but also delayed activation of these polyunsaturated fatty acids (PUFA). By encapsulating them, fish oils and other PUFAs can be handled as dry, free-flowing powders. At least one manufacturer uses patented double-shell microencapsulation that makes its fish oil dispersible in water and gives it 1-year shelf life at 40°F. In this form, the encapsulated ingredient resists the demands of processing, including pasteurization, heat processing, homogenization and extrusion.

Well-recognized for its nutritional benefits, vitamin C is very labile, and many aspects of ordinary proceeding destroy its stability. Bakers know this ingredient as ascorbic acid, a useful oxidizer and dough strengthener. As a dough improver, it must be released at an early point during processing, but as fortification, vitamin C must stay intact until the product is eaten. Getting enough into bakery formulas to justify the vitamin claim — and to ensure that it survives the baking process — required usage rates in dough of 125 to 150% more than levels in the finished product. Encapsulation solved this problem.

Vitamin C degrades quickly when it comes into contact with any iron-bearing ingredient such as ferrous sulfate or ferrous fumarate. Iron can be highly reactive in foods, especially in its most bioavailable form, ferrous sulfate. Even the less reactive elemental iron can cause problems at some temperatures. In fact, nearly all common minerals used for fortification (iron, zinc, magnesium and copper) present problems and are easy to overuse unless scaling is controlled as with encapsulated forms.

Metallic ions also may cause depletion of vitamin stability, and then there’s the matter of color. Brown spotting can occur in the crumb when vitamin C and iron combine.

Fumaric acid provides a good example of the benefits of encapsulation. As used in tortillas, its primary function is to drive down the pH in the finished product for optimal mold inhibition from the antimicrobial system (calcium propionate and sorbic acid). It also acts as a dough conditioner, relaxing the gluten structure, but it will interfere with sodium bicarbonate, releasing the leavening gasses too early in the process. Undesirable large blisters and translucent spots can result. When encapsulated for heat release, fumaric acid is protected during mixing and releases its activity at the appropriate time in the oven.

HOW DOES IT WORK? Encapsulation is the general term covering the enrobing of one material in another at the microscopic scale, and microencapsulation describes an even finer scale, qualifying as a form of food nanotechnology.

Strictly speaking, nanotechnology concerns itself with structures ranging from 1 to 100 nm (1 nm equals 1-billionth of a meter). Encapsulated ingredients fit the upper limit of that range and are part of the emerging field of food nanotechnology. The Institute of Food Technologists published a scientific status summary, "Functional materials in food nanotechnology," in its November/December 2006 issue. It is available online as document S-052 at http://members.ift.org/IFT/ Research/ScientificStatusSummaries.

For bakery applications, two coating choices dominate: hot melt and aqueous. Hot melt choices include fats (vegetable oils), monoglycerides and diglycerides. Melting point dictates the choice of coating for a particular application. Aqueous coatings comprise hydrocolloids, starches, maltodextrins and other water-soluble materials. Moisture resistance characterizes these coatings, which remain intact until solubilized in the application.

The coating material is typically atomized by pressurized air. The material to be enrobed is suspended as solid particles in an upward moving column of air while being sprayed with the atomized coating. Uniformly shaped granular ingredients with particle sizes of 20 to 2,000 microns work best in this process. The temperature of the fluidizing air enables solidification, lower for hot melt coatings and higher for aqueous solutions.

A variety of technologies can be used to apply the coating: fluid bed with top spray, fluid bed with bottom spray, extrusion, pan coating and spray chilling. A recent patent for handling sensitive substances such as probiotics describes how these are plated onto a solid substance and encapsulated, all the while under controlled atmosphere and airflow conditions.

The technology of encapsulation is remarkably flexible. It allows close control over the ratio of ingredient to coating. Encapsulated vitamin C, for example, is available in a range of 5 to 50% coated. The thicker the coating, the more it resists release. Additionally, multiple layers of differing coatings may enrobe the active material, giving additional protection as well as controlling the release rate.

HOW TO HANDLE? Typically, encapsulated ingredients require no special handling during inventory storage, although some suppliers of encapsulated PUFAs recommend refrigerated conditions. Encapsulation actually eliminates dusting, a big problem when using dry powders, and improves the accuracy of measuring micro ingredients.

Most suppliers recommend adding these ingredients to formulations along with other dry materials, but they caution bakers to avoid subjecting encapsulated materials to excessive shear during mixing.

Formula adjustments are generally minor, although some materials like encapsulated omega-3s will require an increase in water.

So if problems with nutrient carry-through or flavor and odor masking or even excessive dusting are limiting formulation projects, consider what encapsulated ingredients can bring to the bench. The technology for preparing and using such materials is constantly improving to add the flexibility formulators need.

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