Questions & Answers
from "On Ice Cream" featured in Dairy Foods magazine
and sourced from "On Ice Cream" technical short courses.

Filtered Milks:

Question: What are filtered milk products and what is their potential application in ice cream?

Answer: The term “filtered milk” refers to a group of concentrated or dry dairy ingredients derived from the ultrafiltration of skim milk. They are also known as milk protein concentrates (<90% protein) or milk protein isolates (>90% protein). Ultrafiltration removes lactose and milk salts, thereby providing a range of products in which the level of total milk protein increases up to 90% or more while lactose decreases to 1% or less on a dry weight basis. These products can be used not only to improve the quality of existing ice cream products but in the development of new products that appeal to specific market segments.

Filtered milks contain the milk protein system in its native and most functional form. Therefore they provide superior performance in ice cream compared to products sometimes known as “total milk protein” that are produced by the co-precipitation of whey protein and salts of caseinate.

The reduced level of lactose is the key to the functional benefits of filtered milks. Those benefits involve two major objectives: the achievement of elevated protein levels (i.e., high levels of MSNF) without concern about sandiness associated with high lactose levels; the production of ice cream with reduced levels of lactose that are appealing to lactose intolerant consumers; and the potential development of true “sugar-free” ice creams.

Achieving higher protein levels using filtered milks can provide several advantages, including: greater water immobilization that would add to mouth feel and increase shelf life through control of ice crystal growth; added air bubble stability that would enhance the perception of richness and creaminess; and an increased bulking effect from the dairy components. Alternatively, if filtered milks were used to provide conventional protein levels, the ice cream would contain lower levels of lactose and therefore be less susceptible to sandiness and create a basis for “sugar-free” or modified lactose claim considerations.

The specific effects of filtered milks will vary depending upon the composition of the ice cream involved and the specific filtered milk product used. Those effects are illustrated by the examples described below. They use a reference ice cream composition in which 10% fat, and 12% MSNF are provided by 40% cream and non-fat dry milk (NFDM).

Replacing NFDM with filtered milk will increase milk protein level by up to nearly 60% and reduce lactose concentration by as much as 27%. Such a reduction in lactose will have the collateral effect of increasing freezing point, which has two potential benefits. First, it increases the firmness of the ice cream at any given temperature. Second, it decreases the amount of water involved in each episode of heat shock, thereby increasing shelf life. Or, if the higher freezing point causes difficulty with excess hardness, freezing point equivalence can be maintained by modifications in the sweetener component.

Filtered milks can also be used to minimize sandiness through lactose reduction while maintaining equivalent protein level. In the reference mix, matching the protein contributed by the NFDM would require about 9.0% MPC with 42% protein or 7.5% of a 56% protein MPC. This would provide reductions in lactose concentration of about 28% and 57%, respectively. Some adjustment in other compositional elements may be needed to maintain total solids and freezing point equivalency.

The production of a “lactose free” (or “sugar free”) ice cream using a very high protein MPC product would be possible only if the filtered milk were used in conjunction with butter or anhydrous milk fat as the fat source, since the MSNF portion of conventional fat sources would contribute too much lactose to permit any intended claim related to lactose content. However, high protein filtered milk can be used to achieve a useful degree of lactose reduction short of complete removal. For example, lactose level could be reduced by about 90% by using an MPI product with 87% protein (as is basis) and 1% lactose with 40% cream to supply all the supplemental MSNF, depending on the nature of the reference composition. Such a reduction in lactose would likely require a compositional adjustment to maintain freezing point parity.

In considering the use of filtered milks in the applications described it is important to remember that the higher levels of protein might modify the flavor properties of the ice cream to a degree that requires modification of the flavoring system. In addition, filtered milks can differ considerably in quality manufacturer-to-manufacturer. It is also important to assure that any MPC or MPI product under consideration is consistently available with bland flavor properties.