Need we remind ourselves, ice cream remains the only food produced with the express intent of being consumed frozen. Relevant “rules of engagement” (i.e., Mother Nature’s rules of chemistry and physics) are not likely to change any time soon. Thus, contemplating the demands on any given ice cream mix relative to compositional changes under consideration is daunting.
The good news is that multiple (and, in some instances, not fully understood nor vetted) indices based on sound science and technology can be used to guide the reformulation process. By adding experience to the use of the indices, decisions can be made to enhance the likelihood of success.
The indices can be applied individually, or in combination, as guidance for both dairy and non-dairy (plant-based) compositions. Each index has its own subtle technical (and sometimes non-technical) limits beyond which significant differences exist; hence, the importance of experience in interpreting their implications.
All represent the application of scientifically proven concepts. Some require further vetting and fine-tuning, which will only add value moving forward.
The indices discussed here are most valuable when applied on a relative rather than absolute basis; that is, when used to compare one or more reformulation candidate compositions with the original, or to consider differences between several candidates for a new product composition.
In most cases, these indices can serve as effective screening tools to reduce the number of products that must be produced at pilot level or, eventually, in the plant.
- Total solids.
- Total fat (amount, type, source of milkfat and/or other fat/oil/lipid sources).
- Sweeteners (amount, type, sweetness of each).
- Milk-solids-not-fat (amount, type of each component).
- Lactose (as-is basis and as % in water phase in the mix); important contributor to sweetness, freezing point depression and control of crystallization of the lactose itself.
- Amount/type of total protein (proteins vary in their structure, function, influence on background and added flavors, mix viscosities, and so on).
- % total protein as micellular casein (dairy-based products only, where it is critical to such structural influences as the effect of agglomerated fat.).
- Mix density (pounds per gallon). Match with targeted finished pounds per gallon ice cream to compare a given mix’s ability to take/hold air (overrun), to achieve any given final compositional targets that influence nutrition labeling, etc., to be compatible with desirable bulky and/or non-bulky flavors, and to be able to flow into the packaging (or mold) of choice, eventually affecting yield in terms of units of finished ice cream per unit of mix.
- Mix cost, cost per unit to be sold.
Freezing point and related indices
- Freezing point is the temperature at which ice starts to form in a mix. Differences in freezing point have a profound influence on key properties such as ice crystal size and stability, handling at the freezer, packaging behavior, dipping properties, melting properties and the like.
- Freezer Index: This is the amount of water frozen at a given temperature within draw temperature range, which is an important factor reflecting handling properties and the initial size of ice crystals.
- Firmness Index: This is the amount of water frozen at a given temperature in the range at which ice cream is distributed and dispensed. It reflects resistance to package shape deformation, relative firmness when served and eating quality.
- Texture Stability Index: This is the amount of water that melts and refreezes as the result of a specifically identified temperature fluctuation. It is an important reflection of the influence of heat shock on textural shelf life.
- Freezing profile: A graphic display of the amounts of water frozen at temperatures below the freezing point that provides at a glance a consolidated view of the individual indices described above.
- Theoretical sweetness: The perceived sweetness representing the sum of the contribution of all sweeteners used based on their individual sweetness relative to sucrose. Theoretical sweetness values within ± 0.5% of a given reference or target are considered equivalent.
- Water Control Index (WCI): WCI calculates the relative ability of nonstabilizer elements of mix composition to manage the rheology of unfrozen water during whipping, freezing, packaging, hardening and distribution. Mix WCIs within ±10% of a given control can be considered similar for decision-making purposes.
- Fat Agglomeration Index (under development): This reflects the combined influence of key factors on the involvement of fat agglomeration on such ice cream properties as whippability, behavior at the freezer, eating quality, shape retention, susceptibility to shrinkage, etc.
- Flavor: The perception of any flavor is a qualitative combination of appearance, acidity, aroma, taste, texture and temperature or, whimsically, “F= AAATTT.”
Thus, there are a number of individual indices that can be useful, in combination with experience and good judgment, to assess the influence of compositional variations on a broad range of ice cream characteristics as input into selecting compositions suitable for further consideration and, ultimately, decision-making.
Note: This column was adapted, in part, from a presentation given at the 2017 Clean Label Conference in Itasca, Ill.