The USDA has specific rules that define what can and can't be labeled "ice cream." To bear the "Meets USDA Ingredient Standard for Ice Cream" stamp, it must contain at least 10 percent milk fat, a minimum of six percent non-fat milk solids, and a gallon has to weigh at least 4.5 pounds.
Along with the milk fat (butter fat), cream and delightful flavors, ice cream also contains stabilizers and emulsifiers. Stabilizers help hold the air bubble structure together and give the ice cream a better texture. Emulsifiers keep the ice cream smooth and aid the distribution of the fat molecules throughout the colloid.
"The key to producing a favorable ice cream lies within texture and ice crystal size," says Janae Kuc, senior research and development scientist at Gum Technology Corp. (www.gumtech.com), Tucson, Ariz. "Consumers do not want to dig their spoons into a block of ice. A good ice cream will have a decent amount of overrun [incorporated air], small ice crystal structure and a creamy smooth texture. Gums are a major player in achieving these attributes and maintaining them over time."
"It's very difficult in this day and age when you have mass shipping and changing temperature conditions to not give the ice crystals [in ice cream] a bit of help," says Maureen Akins, applications manager at TIC Gums (www.ticgums.com), White Marsh, Md. "If you stabilize ice cream correctly, you won't end up with frost on top, which can occur in ice cream formulations containing a minimal amount of stabilizers."
Gums such as tara, carrageenan, locust bean and cellulose are good choices for creating a smooth creamy ice cream texture with reduced ice crystal size.
"Gums are hydrophilic by nature and will bind and hold moisture," Kuc says. "These attributes can work to an advantage for the ice cream formulator. If the water in the system is bound properly the ice crystal structure will be minimized and controlled over time. This is especially true when there are galactomannans in the system such as tara gum or locust bean gum."
In addition to controlling ice crystal size, gums will also promote a creamy, fatty texture and mouthfeel. "This is a great attribute for regular ice cream as well as reduced fat or sugar free ice cream," she adds. "Adding carrageenan to an ice cream will round out the texture and provide a fatty mouthfeel. Tara gum also provides a silky texture in frozen novelties.
"Gums work synergistically when combined can improve upon texture and ice crystal size as well as overrun," points out Kuc. "A great combination of gums for providing overrun in frozen dairy desserts such as ice cream would be a combination of citrus fiber, tara gum, and cellulose gum. This combination will help to trap and hold air when the product is churning. It also promotes a creamy texture and moisture management, which in turn translates into a longer frozen shelf life due to ice crystal control."
"The best ice cream has both a high fat content and the presence of hydrocolloids," explains Akins. "The water in ice cream can migrate outside of the matrix that forms ice cream which includes sugars, proteins, fat and water. Hydrocolloids manage the water and keep it from coalescing and forming large ice crystals, which take away from the perceived quality of these frozen desserts," she adds.
As Akins explains, "Any ice cream goes through freeze-thaw cycling. Water, inherent in the milk used to make ice cream goes through phase changes. Some of those ice crystals are frozen, and as the temperature changes, they will start to thaw. As you start to lose that water from its ice crystal form into its liquid form, it can migrate. That migration is of water to the surface becomes the frost on top.
"When you add a stabilizer or good water binder like gums, it holds on to that water and keeps it in very small pockets," she says. "When the temperature goes down, and it freezes again, it will freeze back into a small ice crystal.
"For high quality ice cream, first look at the label for the quantity of fat," advises Akins. "The more fat you have, the more stable and higher quality it will be. Another area to pay attention to on labels in order to make sure it will be stable for the long haul during freeze-thaw cycling, is to look for guar (locust bean gum, tara gum, carboxymethyl cellulose) because they are excellent water binders."
For both food product developers and consumers, TIC Gums has created a series of You Tube videos (www.ticgums.com/icecream-video) titled "Does This Have Gum In It?" They're hosted by Marketing Manager Harold Nicoll and include applications specialists such as Akins.