Sticking with it - managing food coatings

Prepared Foods, Oct, 1996 by Claudia D. O'Donnell

The quality of products such as savory snacks and sugar-coated sweets requires the coating material to evenly cover and adhere to the food...rather than rest wastefully on the bottom of a package. Topically applied snack food seasonings are generally dusted onto a product which has been sprayed with or fried in oil, or are incorporated in an oil slurry. Aqueous-based systems with functional adhesion (a tack solution) are also used for snacks, crackers or sugarcoated cereals and can provide a low fat alternative to oil-based surfaces.

Here are just a few considerations in achieving a problem-free process.

* Particle size of coating material.

Finer particles adhere more easily than larger ones. For example, "salt should be flour salt or powdered salt with at least 80% passing through a U.S.S. #100 screen," says Tony Grenis, technical sales representative, with a seasoning supplier. Additionally, when the seasoning is applied in an oil slurry, larger particles may clog spray nozzles.

"Sesame seeds applied with a tack solution may require so much of a functional ingredient for adherence that it takes away from the integrity of the food product," says Darla Byerly, food technologist with a seasoning supplier. Gums, starches, sweeteners (e.g. corn syrup solids, honey, sugar) can all work as adhesion agents.

The water in which these ingredients are dissolved must eventually be evaporated. As a result, the concentration of solids in the slurry is kept as high as possible to minimize production costs, including energy use. For some sugarcoated foods in which the particle size of the end product's coating falls within a very narrow range, the raw material's sugar granulation becomes critical. "The high concentration means too large particles may not completely dissolve in the slurry and too large crystal end up on the finished product," says a technologist with one processor. "Of course whenever we have a problem with our coating process, we always blame it on the ingredient supplier."

* Adhesion agents.

"Cost, ease of hydration, functionality, and flavor (or lack of)" are a few considerations in choosing an adhesion system, says Byerly.

Florian Ward, vice president R&D with a stabilizer supplier, outlines the mechanics of applying one slurry that "replaces" oil in reduced-fat snacks. "The gum acacia and corn syrup solid system are made into a 12% solid slurry, heated to 160 [degrees] F and then sprayed on the snack at 10% by weight. The seasoning is then applied," she says. However, "Some choose to retain a 3-4% level of oil for the flavor," she adds.

While this is an effective application method for rough-surfaced products such as broken pretzels or a "corrugated" cereal, other tactics must be taken with hydrophobic smooth surfaces (e.g., bread-type products). Here, "A plasticizer such as lecithin or polyol [glycerin] should be added to the aqueous gum acacia mixture so that the slurry will adhere," says Ward.

* Equipment.

Seasonings with a concentrated flavor may require "diluting" with filler or bulking agents which makes it easier to apply an even coating. Although the use of one item makes for a shorter ingredient list, when two or more are used, they will each fall lower on the list (preferably after the seasonings themselves). Typical fillers include whey, dextrose, maltodextrin, starches, wheat flour, and so on, says Grenis.

Flowability of dry coatings is improved by using anticaking agents (up to a 2% level). Too much of a good thing, however, is possible since the tendency to dust increases as well. Depending on the type of anticaking agent, their actions include moisture or oil absorption and physical separation of particles. Typical agents include silicon dioxide (i.e., silica gel), calcium stearate, tricalcium phosphate, and sodium silicoaluminate. Bone meal has also been used for products sold in health food stores.