Hydrocolloids
Pages 67-76
DOI: https://doi.org/10.1094/1891127381.006
ISBN: 1-891127-38-1
Abstract
Topics Covered
- Frozen Desserts
- Cultured Milk Products
- Yogurt-Juice and Milk-Juice Drinks
- Chocolate and Flavored Milks
- Cheese
- Spreads
- Ready-to-Eat Milk-Based Desserts
- Troubleshooting
Introduction to Chapter
In milk-based frozen desserts, such as ice creams and frozen yogurts and their reduced-fat versions, two or more hydrocolloids are used in combination because they have to perform two functions. The typical use level for hydrocolloids is 0.20–0.25%. Box 6-1 contains a generic formula for ice cream.
First, hydrocolloids have to control the rate and size of ice crystal growth, both at the time of manufacture (freezing) and during subsequent storage and distribution (freeze/thaw cycling). In frozen desserts, the best texture, which is perceived by the consumer as being smooth and creamy, is achieved when many small ice crystals are formed. If there are fewer but larger ice crystals, the resulting product is perceived as being coarse or icy.
Hydrocolloids that control the growth of ice crystals are sometimes used in combinations for economic or marketing reasons or to prevent off flavors. For example, a typical “all natural” ice cream has a blend of locust bean gum (LBG) and guar gum as its primary stabilizer. Guar gum is usually much cheaper than LBG, but it can give the ice cream, especially vanilla ice cream, a “beany” off flavor. LBG is completely free of off flavors but costs more than guar gum. A blend of the two can be used, where the trade off is cost versus potential off flavors. If “all natural” is not a requirement, cellulose gum is used because it is completely free of off flavors and has a lower cost-in-use than LBG.
The second function of hydrocolloids is to control any syneresis, or “whey-off,” that may occur in frozen dessert mixes during storage and distribution. Soft-serve ice cream mixes and frozen yogurt mixes are particularly vulnerable to whey-off. They are shipped under refrigeration in the liquid, not frozen, state and then frozen at a retail outlet. If the gel network contracts slightly, some water, lactose, and whey protein can be “squeezed out” of the product. A stabilizer can bind to and slightly destabilize the insoluble protein (casein) in the system. Carrageenan is the stabilizer of choice because of the extremely low use level, typically 0.005–0.015%, required to stabilize the water and whey in a slight gel network.
A frozen dessert that contains no milk or other protein (such as sorbet or Italian ice) does not require a stabilizer to specifically prevent syneresis. Most sorbets and Italian ice products are fruit flavored and tend to have pH values below 4.5, in contrast to the dairy-based frozen desserts, which have pH values near 7.0. Thus, it is important that the ice crystal stabilizer used in sorbets and Italian ices be acid stable. Good choices are pectin or xanthan gum.
