Hydrocolloids are the active components of stabilizing systems. These gums provide a variety of functions, and each may need some specific handling to activate. For example, depending on the hydrocolloids, the system may require boiling.
“Alginates, carrageenan, guar gum and cellulose gums are considered cold-water soluble and do not need to be heated,” said Janae Kuc, principal technologist at Ingredion. “They are suitable for non-boiling stabilizers. Agar, pectin, gelatin and locust bean gum require heating to become functional and are used in the boiling type. Boiled icings and glazes typically have better stability and work well when applied by machine.”
Beyond controlling moisture migration, these gums deliver attributes that can make icings and glazes more functional and also more appealing to the eye. It’s just a matter of choosing the right hydrocolloid for the job.
“A small amount of gum acacia or gum tragacanth can provide greater extension and pliability, reducing the chance of an icing from breaking,” noted Matthew Berliner, vice-president, ISC Gums. “Gum tragacanth can be added to fondant icing. It will provide a more pliable consistency for moulding. It will also help the icing dry faster and set harder.”
From an aesthetic perspective, hydrocolloids provide a desirable finish. “Mix gum acacia with warm water to create edible glue for adhering sugar pieces together,” Mr. Berliner said. “It can also be used as a varnish for marzipan or sugar paste. One layer will provide a slight sheen, and subsequent layers will build up to a high-gloss finish. Let each layer dry before applying the next.”
When bakers need lengthy shelf life, agar gum is the answer, according to Bill Gilbert, certified master baker and principal food technologist, Cargill. Agar is a seaweed extract that forms a heat-reversible gel. It requires boiling to fully hydrate and can bind up to 100 times its weight in water. When used in icings and glazes, it prevents moisture migration, as well as reduces tackiness to prevent adhesion of the topping to packaging.
“Using a functional carbohydrate with very low hygroscopicity such as trehalose in the icing or glaze can also mitigate moisture migration,” he said. “Substitution of a portion of the sugar in the icing or glaze with trehalose raises its water activity, forming an effective moisture barrier.
“For example, with donuts, the addition of trehalose can keep the crumb moist while retaining the fresh appearance of the glaze,” Mr. Gilbert added. “The addition of trehalose enables bakers to achieve levels of freshness previously not possible in extended shelf-life and freeze/thaw scenarios.”
Gelatin is also used in icings and glazes as a stabilizer. “It retards sugar crystallization, so icings and glazes are smooth and do not become grainy,” said Michelle Montgomery, manager of technical affairs, Gelita. “Gelatin also binds water so that icings and glazes do not weep or stick to packaging.”
The gel-forming property of gelatin provides an elastic texture. This prevents cracks from appearing on the surface and imparts an attractive sheen to the bakery product.
“We use a soy-based protein to keep moisture in glazes to prevent cracking or from falling off baked goods,” said Elyse Bianchi, bakery applications scientist, Kerry. “It’s used at a 0.1% dosage and comes in a powder format that can be easily incorporated into formulas.”
Stabilizing agents can even help improve production efficiency when it comes to icings and glazes. “Our soy-based protein stabilizing ingredient speeds up the drying times of icings, glazes, drizzles and fondants, which allows production to increase packaging line speeds,” said Felicia Lashley, R&D scientist for emulsifiers at Kerry.
Another option to stabilize icings is to include some form of hard fat, which have a higher melting point and are solid at room temperature. “Hard fat flakes provide structure upon cooling over a wide range of temperatures,” said James Jones, vice-president, customer innovation, AAK USA Inc. “They also help protect icings from breakdown caused by moisture migration and contact with packaging.”
At the Institute of Food Technologists’ Food Expo 2016, held in Chicago this past July, AAK showcased colorful shortbread cookies made with palm oil-based icings. The palm oil delivered a well-structured icing that was fast setting, soft and pliable, with an excellent shelf life, according to Mr. Jones.
There are a number of minor ingredients that can assist with stabilization, according to Mr. Gilbert. “This includes hydrocolloids other than agar, in particular, locust bean gum and carboxymethylcellulose,” he said. “Calcium salts function as drying agents, while maltodextrins prevent sugar crystallization and some starches improve shine and cling.”
Mr. Gilbert offered some tips for working with icings and glazes. “Always use boil-type stabilizers to achieve the best shelf life, but make sure you don’t over-boil because you’ll drive off too much moisture and will have too thick of a topping,” he said. “High-speed blending is preferred after the boil stage but is not critical. Ensure operators have a safe transfer system in place to move from a boiling kettle to a floor mixer.”
If powdered sugar is part of the formulation, it must be handled properly. “Blending the powdered sugar depends on each type of equipment,” Mr. Gilbert pointed out. “Liquefiers can accept all the powdered sugar at once, while floor mixers require powdered sugar to be added in stages.
“Glazes are best applied between 110 and 130°F and icings between 120 and 140°F,” he added. “Sugars will re-crystalize if above 155°F, so keep all application tanks below that temperature.”