The Perception of Creaminess - May 2007
Understanding how creaminess can be equated to product quality is complex. However, research indicates that certain ingredients that impart texture and flavor lend themselves to consumer perception of this trait. Fat content is one such component. As such, food formulators are presented with a challenge when fat is reduced or removed from food systems.
Although fat remains a significant contributor to the sensation of creaminess, it is not the only one, demonstrated by the fact that creaminess has been frequently cited as a phenomenon of both taste and aromatic components. This article will explore some of the research that further defines creaminess and the ingredients used to achieve this sensation.
Creating an IllusionTo a flavorist, creaminess may be thought of in terms of “a smooth mouthfeel with an enhanced balance of flavor” that a product delivers, says Mary Maile, senior flavor chemist for a global ingredient supplier. Martha Llaneras, senior manager for the North American food division of an international supplier of specialty products, describes creaminess “in terms of the rate of dissolution in the mouth, the perception of ‘oiliness’ in the mouth, the degree of mouth coating and the degree of cling.” Some researchers speculate that creaminess is perceived only when a certain viscosity threshold is reached.
Consumers frequently associate oil-in-water emulsions with creaminess. Emulsions are formed when one immiscible phase is dispersed in another through mechanical action such as homogenization. Oil-in-water (O/W) emulsions are formed when oil is dispersed in an aqueous phase (e.g., mayonnaise, heavy cream). Viscosity of the continuous or aqueous phase reportedly plays a significant role in the perception of an emulsion’s creaminess. On the other hand, the droplet size of the dispersed phase does not appear to influence creaminess.
Fat content and viscosity are attributes frequently associated with the perception of creaminess, particularly in dairy products. Fat content not only affects the texture and body of a food matrix such as ice cream, but also the balance, intensity and duration of flavors. The latter phenomenon becomes especially apparent in reduced fat or non-fat formulations.
To some, the perception of creaminess may actually be equated with the absence of defects such as ice crystallization, sandiness or grittiness, notes Rodger Jonas, national business development manager for a global ingredient supplier. Sandiness, a defect generally associated with ice cream, may be perceived when lactose crystallizes—a defect that cannot occur unless lactose nuclei are present.
Ice cream texture is adversely affected by the formation of large ice crystals. Numerous, small ice crystals that are indiscernible in the mouth form when the ice cream mix freezes initially. However, heat shock or large temperature fluctuations cause some of these tiny crystals to melt and refreeze. During this process, the number of crystals decreases as their size increases. These larger crystals give the ice cream an icy, coarse texture, thereby reducing the perception of creaminess.
Building a FrameworkProduct developers use a variety of different methods to impart creaminess, or at least the perception of such into a formulation. Flavor chemists use ingredients that complement the application’s textural attributes, notes Maile. For instance, in a cream soup, ingredients such as various lactones and sweeteners might enhance the dairy component in the soup base. Vanilla is another ingredient that helps boost the perception of creaminess, especially in milk-based products and various baked goods.
“Fat tends to coat in the mouth, and as such, delivers the perception of creaminess,” explains Llaneras. “Different fats have different melting points. A solid-type fat (at room temperature) can melt in the mouth and change to a liquid form that gives a very different impression than that conveyed by a liquid fat (at room temperature).”
A stabilizer system comprised of gums, emulsifiers or often a proprietary mix of both types of ingredients can help achieve a desirable ice cream texture. For instance, locust bean and guar gums work synergistically with one another and are frequently used as viscofiers in ice cream blends. Hydrocolloids form gel-like structures and control water mobility during freeze/thaw cycling. For instance, “The reduction of ice crystallization in frozen products can be achieved with the use of a specialty carrageenan,” says Jonas. “This product forms a soft gel immediately in ices so that you don’t get a freezer burn effect on your tongue.” Stabilizers also help keep cream fillings from drying out in bakery products. “A specialty hydrocolloid binds the water and holds ingredients in solution for products such as canoli,” Jonas adds.
Preventing such defects as lactose crystallization can induce the perception of creaminess. Ingredients such as stabilizers and sugar alcohols typically prevent lactose nuclei from forming, which in turn prevents lactose crystals from growing. According to the Dairy Research and Information Center at the University of California, Davis, lactose in the form of dried whey powder or instant dry milk can actually be used to “seed” the ice cream mix before it is frozen, so a large quantity of crystals form throughout the batch—these are less than 10 microns long and thus are not detectable in the palate.
The seeding process mentioned above is also used during the manufacture of chocolate to achieve its desirable creamy mouthfeel. Tempering produces small crystals that “seed,” or serve as nuclei for proper crystal formation, so that the finished chocolate is glossy, firm and melts near body temperature (94°F). Also at issue is the particle size of the cocoa nibs that are processed into chocolate. The conching process effectively grinds the sugar and cocoa particles into a size that is undetectable when consumed.
Sucrose can readily crystallize from a syrup phase into a solid form, causing grittiness in certain types of confections. Whether or not large sugar crystals are present depends on factors such as processing conditions, the type and ratio of sweeteners used and the presence of other ingredients such as starches, gums and proteins in the formulation. For instance, if grittiness occurs in caramels from sugar crystallization, cooking temperature can be decreased, as can the sucrose-to-glucose ratio. Milk proteins also inhibit sugar crystallization and thus contribute to the confection’s characteristic smooth and creamy texture.
Big Fat CompensationNon-fat and low-fat products are common in today’s health-conscious market. Fat not only adds richness and fullness, but acts as a flavor carrier as well. Thus, flavors dissipate more rapidly when the fat is reduced. Fat replacers that mimic the structure of lipids are either carbohydrate or protein-based. When heat denatured, whey protein molecules unfold and may bind to other substances. The resulting size of these particle formations reportedly bridges the difference between a creamy mouthfeel and one that is gritty.
Inulin, a non-digestible carbohydrate, may also be used as a fat replacer. Inulin binds water and forms a gel-like matrix that contributes rheological properties (i.e., viscosity) to products such as ice cream or yogurt. The formation of a gel-like network improves the textural stability of the food system and enhances mouthfeel.
It is not uncommon for consumers to associate melt rate with creaminess. In an article entitled “Perception of Melting and Flavor Release in Ice Cream Containing Different Types and Contents of Fat,” published in 2003 in the Journal of Dairy Science, L. Hyvönen, et al. describe melting as “the sensation of liquefying of both ice and fat crystals…The ice crystals (melt) at lower temperatures than the fat crystals.” Full-fat ice cream mixes tend to melt more slowly than those made without milk fat, as milk fat slows the rate of heat transfer in the blend. Non-fat or reduced-fat ice cream mixes that are high in viscosity can theoretically impart the perception of creaminess more comparable to that observed in a full-fat formulation.
Hyvönen, et al. studied the effects of different types of fat (i.e., milk fat vs. vegetable fat) at a range of contents (0% to 18%) on the perception of strawberry flavor release, ice cream melting rates and nine sensory attributes, including creaminess. According to the authors, “To be perceived as creamy, a smooth but viscous fluid layer is needed between the tongue and palate. Creaminess is, however, also used to describe the typical flavor of dairy products, which explains why the ratings of creaminess tend to be higher for dairy than for vegetable fat ice creams.” (See chart “Fat Types and Amounts vs. Creaminess.”)
Also of interest are the modified formulations described by Hyvönen, et al. Polydextrose and maltodextrin were used as modifying ingredients and added to the fat-free, 18% dairy fat and 18% vegetable fat formulations. The dry matter of the non-fat formulation was raised from 24% to 34% with the modifying ingredients. The texture of the 18% fat-based mixes was modified to resemble the blend containing 14% when whipped, and the emulsifier levels were reduced accordingly. Results indicate that modification with polydextrose and maltodextrin significantly increased fattiness and creaminess perception.
Hydrocolloids can help replace some of the characteristics that are lost when fat is removed or reduced in food applications, notes Llaneras. For instance, functional hydrocolloid systems containing specially formulated propylene glycol alginate and microcrystalline cellulose provide creaminess, opacity and mouth coating as well as stability, structure and texture to various products such as dressings and sauces.
Diet fads have not only fueled the proliferation of non-fat and reduced-fat products, but those with low or no-added sugar as well. Polydextrose replaces the bulk of sugar, adds creaminess and provides heat-shock stability in frozen desserts such as these. Other carbohydrate-based products such as inulin and maltodextrin can also replace at least some of the bulk of sugar and contribute to texture.
Consumer product research pertaining to creaminess perception can be helpful to the food formulator who is given the task of delivering this key attribute in an application. Although by definition, the word creaminess seems to imply a textural quality such as smoothness or oiliness, when applied to dairy products it would hardly make sense not to include inherent flavor attributes as well.
When asked whether consumers’ perception of flavor and texture are inextricably linked, Maile replied in the affirmative and cited the following example: “Flavor brings in the taste factor that contributes to the definition of the overall finished product. Take guacamole, for instance, which contributes mouthfeel along with its characteristic flavor/spice contributions. The product would not be acceptable without both of these factors.”