The reduction or elimination of lactose in ice cream and other frozen dairy desserts goes back to well before the simple declaration(s) of “low carb” in the early 2000s. Lactose removal was, and is, many times related to its contribution to total carbohydrate, total sugars, calories, and glycemic index, not to mention market positioning related to prevalence of lactose intolerance.
Only about 10-12% of the U.S. population is truly “lactose intolerant.” Lactose intolerance is just that — an intolerance due to the lack of ability of certain individuals to make the lactase enzyme. Lactose is not a true food allergen.
Thus, the market for lactose-reduced products has been limited. However, there are now new significant features (facts) and benefits (reasons to buy) when considering reduced-lactose or lactose-free frozen dairy desserts of all types.
To understand technical opportunities, it is necessary to define “reduced lactose” as at least a 25% reduction in total lactose per serving. “Lactose-free,” in turn, is less than 0.5 gram total lactose per serving. This being said, lactose-reduced/lactose-free declarations may be considered implied nutrient content claims, and, as such, care is necessary to ensure the final frozen dessert is also inherently “low” in total fat, total unsaturated fat, total cholesterol and total sodium or otherwise compliant with regulatory considerations.
There are several ways to reduce lactose in frozen dairy desserts, which, in a standard ice cream with no added whey (whey adds significantly more lactose) would have ~ 5.5% lactose or ~ 6 grams of lactose (i.e.,~ 85 grams per 2/3-cup serving, at the minimum 4.5 pounds per gallon of finished ice cream).
Removing lactose via ultrafiltration
Ultrafiltration, or the process to physically remove lactose, is applied to incoming fluid dairy ingredients before the ice cream mix is made. An alternative is to seek a high-protein skim milk or skim milk powder (i.e., whole milk concentrates at 70% protein dry basis, whole milk protein isolate at 90% protein dry basis).
Regardless of the source, there will be some residual lactose present. However, managing overrun (pounds per gallon of finished ice cream and serving sizes) can help deliver lactose well below the 0.5-gram-per-serving “lactose-free” threshold.
Physical removal of lactose can negatively influence sweetness and freezing point depression, two key functions of lactose in any given mix. The good news is that an increase in sweetener solids may be necessary, and these can more than adequately compensate for elimination of lactose. The downside, of course: As lactose is reduced, total carbohydrates, total sugars, and calories may increase.
Removing lactose using lactase
Ultrafiltration requires a large capital expense, so a popular way to reduce lactose is with the enzyme lactase. Lactase is added to the finished ice cream mix after mix processing, but before flavoring and whipping/freezing. If added before mix processing, lactase activity will be reduced significantly.
A measured dose of lactase is added to the mix holding tank and allowed to agitate for as little as a few hours at ~ 40 degrees Fahrenheit, or up to a day or so, depending on lactase activity of the enzyme preparation, recommended use rate(s) and finished mix composition. In many instances, to maximize enzyme activity, the mix to be treated should be held on the “warmer” side of cold mix (40 degrees Fahrenheit maximum temperature is recommended to allow the enzyme activity to proceed without growth of psychrotrophic bacteria).
Lactose as source of sweetness?
One of the benefits of using lactase is a slight recovery of cost due to reduction of other sugars in the mix. Monosaccharides, glucose, and galactose, resulting from lactose hydrolysis, have a higher relative sweetness (~ 80% each) than lactose itself (~ 20%). In addition, full hydrolysis of lactose adds 5% by weight via its monosaccharides byproducts.
This minor increase in “sugars” is relatively insignificant nutrition labeling-wise. However, when properly considered and formulated, a ~ 4-5% increase in relative sweetness may allow for a small reduction in other more expensive sources of sweetness. If doing this, it is important to keep in mind compositional changes and their influence on mix freezing point depression and heat shock resistance.
When considering lactose removal, compensation with one or more sources of sweetness can retain whipping/freezing functionalities and resistance to heat shock. However, it also may mean reporting an increase in “added sugars.”
Depending on the specifics of the mix composition, using lactase should not add sugars, per se, in a significant amount to change nutrition labeling. However, reduced lactose content can reduce any ice cream’s tendency to result in classical “sandiness” (lactose crystallization) across distribution and storage. In some instances (e.g., frozen dairy desserts with salted inclusions), extension of textural shelf-life can be expected.
In the end, when properly formulated, “lactose-free” frozen dairy desserts are promotable, salable, functional, and economically beneficial. All well beyond the historical focus on lactose intolerance.
Steven Young, Ph.D., is principal, Steven Young Worldwide; Bill Sipple is principal, Wm Sipple Global Services.