Tharp&Young: On Ice Cream
The term "filtered milk" refers to concentrated or dry dairy ingredients derived from skim milk through ultrafiltration.
Q: What is filtered milk?
A: The term "filtered milk" refers to concentrated or dry dairy ingredients derived from skim milk through ultrafiltration. These ingredients are commonly referred to as MPCs, which is short for milk protein concentrates (<90% protein) or MPIs, which are milk protein isolates (>90% protein).
The process of ultrafiltration removes lactose and salts from fluid milk, which subsequently increases protein content. The milk protein system in filtered milk is in its native and most functional form.
Q: How can filtered milks be used in the manufacture of ice cream?
A: Filtered milks can improve the quality of existing ice cream products. They can also be used to develop new products that appeal to specific market segments, such as diabetics or low-carbohydrate dieters.
Some of the greatest functional benefits that filtered milks contribute to ice cream formulations are related to their low lactose levels. In ice cream, this allows manufacturers to achieve elevated protein levels without concern about sandiness, which is associated with high lactose levels. Filtered milks also enable a reduction in lactose levels, which is appealing to lactose-intolerant consumers. There even exists the potential to develop true "sugar-free" ice creams.
Achieving higher protein levels in ice cream has several advantages. This includes greater water immobilization, which can improve mouthfeel and increase shelflife through the control of ice crystal growth. Protein also provides bulk and helps stabilize air bubbles, which enhances the perception of richness and creaminess.
Filtered milks provide superior performance in ice cream compared to ingredients referred to as "total milk protein," which are produced by the co-precipitation of whey proteins and salts of caseinate.
The specific effects of filtered milks will vary depending upon the composition of the ice cream and the specific filtered milk product used. Effects are illustrated by the following examples where the reference ice cream composition is 10% fat and 12% milk solids nonfat (MSNF), which comes from the use of 40% cream and nonfat dry milk (NFDM).
Replacing NFDM with filtered milk can increase milk protein levels by up to 60%, while reducing lactose concentration by as much as 27%. Lactose reduction 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 shelflife. If the higher freezing point causes difficulty with excess hardness, freezing point equivalence can be maintained by modifications in the sweetener system.
Filtered milks can also be used to minimize sandiness through lactose reduction while maintaining equivalent protein levels. In order to match the protein contributed by the NFDM in the reference ice cream mix, one would substitute the NFDM with either about 9.0% of a 42% protein MPC or 7.5% of a 56% protein MPC. This would provide reductions in lactose concentration by 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 filtered milk were used in conjunction with butter or anhydrous milkfat as the fat source, since the MSNF portion of conventional fat sources contributes too much lactose to permit any claim related to the absence of lactose. However, high-protein filtered milk can be used to achieve a useful degree of lactose reduction short of complete removal. For example, lactose levels could be reduced by about 90% by using a product with 87% protein 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 and/or eating quality.
In considering the use of filtered milks in the applications described, it is important to remember that the higher levels of protein might impact the flavor profile of ice cream to a degree that requires modification of the flavoring system. In addition, filtered milks can differ considerably in quality from manufacturer to manufacturer. Therefore, it is important to assure that the filtered milk ingredient identified for a formulation be consistent, bland in flavor and readily available in the quantities needed to produce high-quality ice cream.