Flavor-Food Interactions - American Chemical Society

Chapter 2

Implications of Fat on Flavor L. C. Hatchwell

Downloaded by UNIV OF ARIZONA on March 9, 2017 | http://pubs.acs.org Publication Date: May 5, 1996 | doi: 10.1021/bk-1996-0633.ch002

NutraSweet Kelco Company, 601 East Kensington Road, Mt. Prospect, IL 60056-1300

Fat plays an important role in the flavor perception of foods. It influences temporal profile, flavor impact, perception of flavor notes, and order of their occurrence. Fatreplacersare composed of proteins and carbohydrates, which interact differently with aroma chemicals than fat does. Therefore, flavor challenges are faced whenever fat is reduced in a food product. The role of fat in flavor perception is reviewed, and the interaction of fat and fat replacers with aroma chemicals is discussed. The resulting effect on applications and some solutions to obtaining the appropriate flavor profiles are proposed.

One of the most challenging aspects of reduced-fat foods is the development of good flavor. Traditionally, the impact of fat on flavor perception was not well understood by the product developer. Understanding the functionality of fat as it pertains to flavor delivery and character facilitates the development of reduced-fat foods with optimum sensory qualities. This chapter will discuss fat and flavor interactions and some solutions to obtaining the desired flavor profiles. Functional Aspects Fats influence all aspects of food perception, including appearance, texture, mouthfeel and flavor. For appearance: sheen, opacity, oiliness, crystallinity, color development and color stability are important. Texture attributes include viscosity, tenderness, elasticity, cuttability, flakiness, emulsification, and ice crystallization. Mouthfeel can encompass cooling, lubricity, thickness, meltability, cohesiveness, mouth coating, and adhesiveness, all of which may contribute to the complex known as creaminess. Fat influences flavor attributes such as aroma, flavor character (fatty/oily, dairy), flavor masking, flavor release, and flavor development. In addition, fat plays an important role in the processing and preparation of foods, and 0097-6156/96/0633-0014$15.00/0 © 1996 American Chemical Society

McGorrin and Leland; Flavor-Food Interactions ACS Symposium Series; American Chemical Society: Washington, DC, 1996.

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in storage stability. When formulating any full-fat or reduced-fat food products, developers must be cognizant of the various functions of fat (i). Effect of Fat on Flavor Perception. Flavor compounds are inherent in lipid ingredients, whether they be desirable flavors such as those of milkfat, lard, olive oil, etc., or undesirable, such as those of emulsifiers. Flavors with "fatty" sensory attributes come from a variety of different aroma chemicals (fatty acids, fatty acid esters, lactones, carbonyl compounds and many others). These aroma compounds may contribute to give the sweet, buttery, creamy, "rich" flavor that comprise the entire range of dairy products, or combined differently, could give the notes peculiar to lard. Fats act as precursors to flavor development by interacting with proteins and other ingredients when heated. Examples of this are the flavors that develop during baking and roasting. A clear example is the flavor that comes from the combination of milk fat heated with sugar and eggs which results in the rich, caramellic notes of a full fat vanilla ice cream. In addition, fat participates in fermentation to result in the desired flavor components of cultured dairy products, particularly cheese (2). The ability of fat to mask off-flavors may be due to solubility. Off-flavors may not normally be perceived in full-fat systems because most are fat-soluble and are at or below threshold levels. However, in the absence of fat, the vapor pressure of the aroma chemicals responsible for these off-flavors may be increased. This results in a very intense perception of the off-flavor. Fat provides mouthfeel and richness. It interacts with flavor components to provide a specific sensory balance. In most food products, flavor components partition into the aqueous and lipid phases of the food, resulting in a balanced flavor profile (3). Flavor release is a critical factor governing smell and taste. The majority of aroma chemicals are at least partially soluble in fat (4). This means that they are dissolved to some extent in the lipid phases of food, releasing the flavor slowly in the mouth and resulting in a pleasant aftertaste. Altering the type of fat or total fat content of foods affects the rate and concentration at which food flavor molecules are volatilized during consumption (5). Removing any significant amount of fat (around 25% or more) from a product changes the flavor profile. As the concentration of fat is further reduced, the flavor challenges are increased significantly. In all cases of fat reduction, some flavor balancing is needed. As more fat is removed, the differences become much more apparent and the challenges to the product developer increase. When fat is removed from a formulation, the only ingredients available to replace it are water, protein, carbohydrates, minerals or air. Even i f nothing new is added to the formula, these items automatically increase proportionally. Each of these components interacts differently with flavor than fat does. A combination of these ingredients may mimic part of fat's function, but they cannot totally replace its functionality. It is important to remember that fat and water are solvents for aroma chemicals (6). Proteins and carbohydrates absorb, complex, and bind with aroma chemicals; they never act as solvents. A fat-soluble flavoring (for example, lemon oil) can be


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F L A V O R - F O O D INTERACTIONS

E3 Average 0% oil

•

Average 1% oil

•

Average 20% oil

Figure 1. Interaction of selected aroma chemicals with 0%, 1%, and 20% fat. (Reproduced with permission from ref. 8. Copyright 1994 Institute of Food Technologists.)



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solubilized in one of two ways — in oil or as an emulsion. Imagine lemon oil in a closed container in a water emulsion, and another container with oil and lemon oil. Since the lemon oil is hydrophobic, its molecules will not be held in solution as much by water molecules as they would be by those of a surfactant or oil. Therefore the lemon oil is more likely to surface and volatilize in a water system than in an oil system. In the closed container, the headspace of the volatiles will build up. When the container is opened and smelled, the water/gum blend will appear to be stronger in odor than the oil blend. It will be perceived as sharper and harsher. Most volatile components have a tendency to be more oil-soluble than water-soluble. Reduced-fat systems inherently have less fat and more water. Therefore, aroma chemicals may be perceived as strong and unbalanced. A small amount of fat can be utilized effectively to further flavor perception. As little as 1-2% fat is enough to affect the flavor components (7) and make a big difference in flavor perception. Figure 1 shows the headspace concentration of aroma chemicals in the presence of fat (8). The more water-soluble chemicals, such as acetaldehyde, propanal, diacetyl, pentanol, hexenal, do not show much change in interaction when fat is added. The fat-soluble chemicals, ethyl sulfide, ethyl benzene, styrene, and limonene exhibit dramatic differences in the amount of volatiles in the headspace when only 1% fat is added. Pragmatically, this means that a small amount of fat can be manipulated to alter flavor perception and result in a profile that is more similar to full-fat foods. Not only does fat affect the intensity of flavor perception, it influences the temporal profile (9). Temporal profile is the timing of the perception of aroma once food has been placed in the mouth. In a full-fat food, the initial impact and intensity of the flavor is suppressed. The flavor intensity then increases and plateaus into a balanced flavor profile which tails off into a pleasant aftertaste. The fat-free food, on the other hand, exhibits immediate impact, then severely diminishes. The immediate impact is not perceived as a balanced profile but manifests itself in a series of uneven and sharp flavor notes. Vanilla is a good example. In the full-fat ice cream, the bouquet reaches the nostrils on the way to the mouth. Once placed in the mouth, the fat melts, slowly releasing the flavor. In the fat free ice cream, the immediate impact of vanilla is characterized by a series of unbalanced and seemingly foreign notes: smoky, medicinal, alcoholic, beany, woody. This profile then fades, resulting in no aftertaste. This is perceived as unpleasant by the consumer. Fat Replacers A fat mimetic is a carbohydrate or protein that replaces one or more of the functions of fat (Table I). Carbohydrates often work by absorbing large amounts of water to increase perceived moistness. They can be a good source of dietary fiber. Some require special processing such as pre-making a paste or gel. Use of carbohydratebased fat-replacers in products with very low fat levels does not yield optimal results. Examples of carbohydrate-based fat mimetics are a modified low-methoxy pectin, polydextrose, maltodextrins, and dextrins made from oat flour or potato starch.


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Table I. Definitions and Examples of Various Fat Mimetics, Fat Replacera, and Fat Substitutes


Fat Mimetic Mimics one or more functions of fat Microparticulated protein Modified starch Cellulose and cellulose derivatives Gelatin Gums Dietary fiber Fat Barrier Retards absorption of fat during processing Gums Cellulose and microcrystalline cellulose Fat Extender/Sparer Maximizes the effect of fat Emulsifiers and emulsifier blends Fat Substitute/Analog Lipid-based ingredient with characeristics of fat, but with altered digestibility Sucrose polyester and synthetic oils (0 Kcal/g) Structured lipids (caprocaprylobehenin, triacylglycerols) (5 Kcal/g)

Effective protein-based fat replacers are micro-particulated. The microparticulated proteins function by binding water, but to a lesser extent than carbohydrates. They provide hydrophobic sites that aid in emulsification of the remaining fats in the reduced-fat system. These functionalities result in improved mouthfeel, ice-crystal control, and foam stabilisation in semi-solid food products, such as ice cream; increased tenderness and crumb quality in baked goods; and help retain moistness and retard rubberiness in reduced-fat cheeses. The functionality in cheese is due to the microparticulated protein's unique capability to be retained in the casein matrix of the curd. An example of a fat extender or sparer is the entire range of emulsifiers. These are derived from fat but are used at low levels. Therefore, their calorie contribution is low. As fat is removed, emulsifiers are needed to aid in moisture absorption, emulsion stability, aeration or defoaming (depending on the system). Emulsifiers help maintain tenderness in a reduced-fat baked goods. Some can be used as release agents in the machining of reduced-fat crackers. Emulsifiers improve the eating quality and shelf life of reduced-fat foods. A fat substitute is sometimes referred to as a fat analog (Table I). It replaces all of the functions of fat in a product with decreased or no caloric contribution. Fat



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substitutes are usually modified fats that are poorly absorbed. Because these substitutes are molecules whose physical and thermal properties resemble fat molecules, they can theoretically replace fat in all applications, even frying. A n example of such an ingredient is sucrose polyester (Olestra™, Procter & Gamble), which has been recently approved by the F D A for snack food applications. Another is caprenin, a transesterified fat used to replace the fat in a chocolate coating. A l l fat substitutes and fat mimetics interact differently with aroma chemicals than fat does (10). Figure 2 compares the relative vapor pressure (RVP) of a homologous series of aldehydes (7). The interaction of water and these aroma chemicals has a R V P of 1. Slendid™ (Hercules), Oatrim™ (Quaker Oats/Rhone Poulenc), Paselli™ (Avebe), and Stellar™ (Staley) are forms of carbohydrate-based fat replacers (pectin, oat dextrin, potato starch, corn starch, respectively). Simplesse™ 300 and Simplesse™ 100 (NutraSweet) are microparticulated proteins (egg albumin/casein combination, and whey, respectively). As the aldehydes increase in chain length, they become more oil soluble. This leads to less of the aroma chemical migrating to the headspace in the oil. It is clear that all of these ingredients interact with aroma chemicals differently than they do with fat. Carbohydrate-based fat replacers have little impact on the RVP, probably due to the fact that they exhibit no hydrophobic groups. Protein-based fat replacers, conversely, have hydrophobic sites and thus bind longer chain aldehydes. Even if a combination of these fat substitutes were used, the flavor interaction would be different than with fat (7). Therefore, one can see how use of traditional flavors may result in aroma and flavor imbalance when fat replacers are substituted for fat. The reduction of fat causes traditional flavors to be stronger and have immediate impact. However, careful blending of fat replacers and modified flavors can bring the flavor closer to the full-fat system. Remembering all the functions of fat on flavor perception—indigenous flavor, flavor precursors, flavor masking, flavor partitioning, and flavor release—what does the scientist need to take into consideration in the formulation of reduced-fat products? Key Issues Raw Material Quality. While changes in texture can be handled with a variety of fat substitutes and fat-replacement technologies, it is best to choose a fat-substitute that does not exacerbate the flavor difficulties. Raw material quality is one of the most important aspects that a scientist must take into consideration. Normally, windows of acceptability are established for ingredient quality. Reduced-fat products are less "tolerant" of off-flavors than full-fat products. Thus, there is a narrower range of acceptability. Any defects in raw materials become readily apparent. Off-flavors are more pronounced and the flavor of the raw materials used in the formulation are uncovered. For example, gums and starches develop stale, cardboard notes when exposed to light or aged too long; fruitiness and earthiness are inherent in sugar, depending on the source of manufacture; oxidized flavor and bitterness develop through the aging and storage of dry milk; and gelatin will


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Flavor-Food Interactions - American Chemical Society

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