Mother Nature knew what she was doing when she created milkfat. Milkfat is the fat component of fluid milk which, in turn, is the lacteal secretion, practically free from colostrum, obtained by the complete milking of one or more healthy cows. Of course, milkfat also can be sourced as a milk component from a variety of mammalian species (i.e., goat milk). In most cases, we discuss milkfat from bovine-produced milks.

As an ingredient in frozen desserts, milkfat is critical when delivering sensory appeal (flavor, body, texture) and resistance to heat shock (shelf-life.) The old adage, “no fat, no flavor, no good,” may or may not apply.

The milkfat content of frozen dairy desserts (standardized dairy or non-standardized dairy) can vary greatly from near zero to more than 20% based on the weight of the mix and the market positioning of the final food. The actual percentage of milkfat depends on a number of factors, including regulatory considerations, market positioning of the final food, nutrition fact objectives and sensory appeal (i.e., flavor quality and intensity, body, texture, resistance to heat shock). 

Composition

Sources of milkfat (Table 1, below) including components, or fractions of milkfat, can vary compositionally lot-to-lot.  As non-fat fractions (casein, whey proteins, lactose, salts) of milk are separated and concentrated for a variety of end uses, so, too, are various fractions of milkfat separated and concentrated.

Table 1: Sources of Milkfat and Milkfat Fractions

• Cream (Sweet, Plastic, Frozen)
• Skim milk (fluid and dry)
• Whole milk (fluid and dry)
• Ultra-filtered milks (fluid and dry)
• Condensed (with/without sugar)
• Butter (with/without salt)
• Anhydrous milk fat
• Whey* (sweet, delactosed, demineralized)
• Whey* protein concentrates (34-80% protein, dry)
• Whey* protein isolate (90% protein; dry)
• Whole milk protein concentrates (34-80% protein, dry)
• Whole milk protein isolates (90% protein, dry)

*Type of cheese and cheese yields also influence milkfat content and composition.

It is beyond the scope of this column as to how, when or where milkfat may get fractionated (i.e., by fatty acid distribution, cholesterol, phosopholipid portions) by feed, breed of animal, seasonality, source, or lot to be used in any given frozen dessert composition. However, it is important from composition and functionality points-of-view to understand such fractionations exist and what “milkfat” or “milkfat fraction(s)” are being considered in the calculation of “total milkfat” in any given mix.

Influence on flavor

Milkfat directly and indirectly influences, for good or bad, the sensory appeal of frozen desserts. This includes contribution of its own flavor, compatibility with other flavors, and, ultimately, overall flavor quality and intensity. Milkfat has a mild “dairy” flavor. If oxidized or rancid, milkfat can offer less than desirable background flavor, and, thus, negatively interfere with any added characterizing flavor (e.g., vanilla.) In most cases, quality milkfat can enhance most added characterizing non-acid flavors. In some, cases milkfat may not be as desirable (e.g., select fruit flavors).

Milkfat also acts as a “sink” for lipid-soluble components of added flavors. This can be both good (synergistic flavor delivery) and/or bad (fractionating of components of added flavors resulting in less than desirable finished flavor delivery).

As milkfat content and composition changes and the composition of any given mix changes, the ability to deliver both desirable background flavor and the added characterizing flavor gets ever so complex.

Influence on body and texture

Milkfat offers its own element of “richness” and “creaminess.” Indirectly, milkfat, via proper homogenization and mix aging, can participate in partial fat coalescence, aka fat agglomeration, which can add strength to air cells across whipping/freezing. This results in desirable bite/chew (body) and smoothness/creaminess (texture) and adds resistance to heat shock. How each is influenced for good/bad by the percent of milkfat in any formula, the components of milkfat, and the condition/size of milkfat droplets in finished frozen dessert. Too much milkfat and/or fat agglomeration, yields “greasy” mouthfeel. Not so simple!

Influence on heat shock, shrinkage

When properly considered, formulated and processed, milkfat in any mix can contribute strength to air cells during whipping/freezing in the barrel of the ice cream freezer. This can add significant resistance to heat shock and shrinkage across the full intended shelf-life of finished products. 

It is also possible to “fool” Mother Nature by managing the behavior (mobility) of liquid water (flow, freezing point), mix viscosities during whipping/freezing, and manage air cell size/number to add more or less non-fat (non-lipid) “creaminess.” Milkfat, in turn, can act as “glue,” per se, and under such conditions and, in some instances, interfere with the perception of coarseness and iciness.

However, “too much of a good thing can be a bad thing.” Where milkfat can offer inherent richness and creaminess through air cell strength via fat agglomeration, if in excess, and/or if fat agglomeration in excess, milkfat also can cause areas of weakness around air cells, resulting in coarseness, iciness and shrinkage (loss of air cell strength and collapse of air cells) across the intended shelf-life of the finished frozen dessert.

Milkfat replacements and alternatives

Spanning more than 50 years, there has been continued interest (and associated struggle) with understanding the functionality of milkfat in frozen desserts that includes total or partial replacement of milkfat with a variety of replacements and/or alternatives. Replacements need not be lipid nor lipid-based (e.g., select water-soluble starches/starch derivatives, etc.) Alternatives are most likely one or more plant-based fats/oils including plant phospholipids, sterols, etc., or combinations thereof, that attempt to mimic the functionality of milkfat. 

All of the above become daunting when considering and managing milkfat functionality for reduced, low, milkfat-free frozen desserts when also seeking the very same finished product functionalities and eating characteristics.

Milkfat, and its functionality, is a pretty special component of nearly all frozen desserts. Mother Nature would be proud!