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On Ice Cream
"On Ice Cream" featured in Dairy Foods magazine
and sourced from "On Ice Cream" technical short courses.
Light Ice Cream:
Foods magazine, May 1, 2010
A specific marketing subcategory of ice cream with less than 10% fat has recently come into existence. Products in this category are generally called “premium light” (PL) products. They are marketed as providing the eating quality of full fat ice cream with substantially less fat (usually half) and fewer calories (usually a one-third reduction).
Their success is reflected by the fact that an early PL product quickly became one of the top 10 U.S. ice cream brands; many others have achieved wide acceptance at the regional level. Frequently PL products are identified, or branded, as “churned,” with or without a modifier (e.g., “slow,” “double,” “perfectly,” “extra creamy,” etc).
A survey of 10 PL products, including national and major regional brands, shows that all are identified as “light ice cream.” That invokes the regulatory requirement that they represent either a one-third reduction in calories or a 50% reduction in fat compared to a reference ice cream, usually an average value for leading national or regional brands or a market basket norm.
Managing composition of PL products must include conformity to those requirements and effects on shelf life and delivery of the promised eating quality. Considerable formulation flexibility is possible, as indicated by the diversity in composition among the PL products surveyed. Values per serving for calories range from 100 to 120 (average 109); for fat, the range is from 2.5 to 4 grams (average 3.4 grams). Calculated fat levels range from 4.6% to 5.9% (average 5.5%), while serving weight (4 fluid ounces) ranges from 60 to 70 grams (average 65), reflecting overrun levels from ~90% to ~120%
Notable success in improving quality of PL products was first achieved using a radical change in the freezing/whipping process. (We first described this approach in our May 2004 column before its commercial application.) This involves a low-temperature extrusion process in which product passes from a conventional freezer to a refrigerated twin-screw extruder, where freezing continues as product is “worked” or “churned.” The extruder has the capability to reduce the temperature of the ice cream at packaging to an unprecedented low temperature, as low as 5 degrees F.
The effect of that additional freezing under agitation is such that the ice crystal size in the finished ice cream is much less than it would have been had it taken place quiescently during hardening. In addition, the “working” changes the structure of the product in ways that increase the perception of creaminess and richness. The mechanism by which that occurs involves the development of very small air bubbles and a change in the nature of the structure of the agglomerated fat system.
Combined with the effect of creating smaller ice crystals, these effects are responsible for the achievement of an eating quality usually associated with higher fat and lower overrun products.
Other successful PL products achieve the target properties in different ways. These include achieving small ice crystals by using the lowest possible draw temperature during conventional freezing. Pre-aeration of mix is effective. Pre-aeration involves using a high speed mechanical mixer or Venturi effects to whip the mix into a very fine foam before it passes into the freezer barrel. The small air bubbles produced add to the perception of richness and physically limit the growth of ice crystals.
It is also possible to achieve the desirable eating quality needed in PL products via compositional manipulation. This involves adding elements of water mobility control that affect the rheology of the unfrozen portion of the product via use of select stabilizers, bulking agents and/or certain concentrated milk proteins, being careful to avoid such consequences as gumminess and flavor masking. Success in that regard has been achieved using recent improvements in microcrystalline cellulose functionality.
Also, the recognized functionality of propylene glycol esters in minimizing ice crystal growth is said to include the ability to develop a fat matrix that produces a creamy eating quality similar to that of a higher fat product.
Beyond the special steps noted, the production of PL products requires diligent attention to all factors known to influence the sensory quality and appeal of ice cream, from ingredient selection and formulation through mix processing, freezing conditions and freezer maintenance, hardening, storage, distribution and retail display conditions.
Once considered and applied, these principles can help deliver true “premium” light ice cream.
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