Carbohydrate Flavor Interactions

The broad diversity in functionality of carbohydrates also offers substantial opportunity for than to influence the mass transport of flavorants. Their ability to form gels, impart viscosity, or promote emulsion formation in food systems are all factors that influence mass transport (dynamic release during eating) of odorants during eating. This section of this chapter will provide an overview of how carbohydrates will influence flavor release from foods. Discussion is organized by carbohydrate type. 

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In this chapter we will provide a broad overview of the flavor interactions that may occur in foods considering how flavors interaction with nonvolatiles in foods [6]. Initially the interaction of flavorings with the major food constituents (e.g., lipid, carbohydrates, and proteins) will be discussed. The final section will include some discussion of interactions with minor constituents (e.g., melanoidins, polyphenolics, and high potency sweeteners) as literature permits. The reader is encouraged to go to more detailed reviews included in books edited by Taylor [ 1 ] or symposia proceedings such as Roberts and Taylor [3], Schieberle and Engel [4], Teranishi et al. [2], or Taylor and Mottram [5]. 

Of the food matrix flavor interactions, the effect of fat/oil on flavor release is most understandable and thus predictable. In the case of fat/flavor interactions, the overriding effect is the role fat plays as a flavor solvent. Unlike carbohydrates or proteins where numerous undeflnable chemical interactions come into play, fat has little true chemical interaction, and thus its effect on flavor release is largely quantifiable. (The discussion that follows will look very much like that provided in Chapter 3 where partition coefficients in solvent extraction [and headspace methods] were discussed.)... 

When we consider the other chemical interactions (e.g., flavor interactions with carbohydrates, proteins, and high potency sweeteners), we understand that interactions take place but they are so complex that we cannot model them to even attempt to make corrections in the flavorings. Thus, we know that a substitution of one protein for another or one hydrocolloid for another will affect the flavor of a product, but we cannot quantify these effects and therefore make changes in flavor formulations. At this time, we can only expect effects and attempt to deal with them in a less than scientific manner, i.e., empirical efforts. 

The perception of flavor is a fine balance between the sensory input of both desirable and undesirable flavors. It involves a complex series of biochemical and physiological reactions that occur at the cellular and subcellular level (see Chapters 1-3). Final sensory perception or response to the food is regulated by the action and interaction of flavor compounds and their products on two neur networks, the olfactory and gustatory systems or the smell and taste systems, respectively (Figure 1). The major food flavor components involved in the initiation and transduction of the flavor response are the food s lipids, carbohydrates, and proteins, as well as their reaction products. Since proteins and peptides of meat constitute the major chemical components of muscle foods, they will be the major focus of discussion in this chapter. 

Many desirable meat flavor volatiles are synthesized by heating water-soluble precursors such as amino acids and carbohydrates. These latter constituents interact to form intermediates which are converted to meat flavor compounds by oxidation, decarboxylation, condensation and cyclization. 0-, N-, and S-heterocyclics including furans, furanones, pyrazines, thiophenes, thiazoles, thiazolines and cyclic polysulfides contribute significantly to the overall desirable aroma impression of meat. The Maillard reaction, including formation of Strecker aldehydes, hydrogen sulfide and ammonia, is important in the mechanism of formation of these compounds. 

Aspartame contains a free Af-terminal amino group. In its deprotonated form, this could be expected to react with carbonyl compounds, forming Schiff base compounds. Some evidence has been obtained for this type of reaction, involving aspartame and flavoring agents [41]. A similar explanation might also apply to the interactions with ascorbic acid and carbohydrate sweeteners described in the previous paragraph. 

Food flavor is a very important parameter influencing perceived quality. The volatile compounds contributing to the aroma of foods possess different chemical characteristics, such as boiling points and solubilities and the sensory properties of food cannot be understood only from the knowledge of aroma composition. This can be explained by interactions between flavor compounds and major constituents in food such as fat, proteins and carbohydrates (1). A number of different interactions has been proposed to explain the association of flavor compound with other food components. This includes reversible Van der Waals interactions and hydrogen bonds, hydrophobic interactions. The understanding of interactions of flavor with food is becoming important for the formulation of new foods or to... 

Taste. Taste Is the human perception of chemicals In the mouth due to their Interaction with receptors on the tongue. Taste consists of four dimensions sweet, salty, sour and bitter. Taste Is affected by odor and texture, which makes it a complicated, subjective quality attribute, difficult to measure objectively (22). In fruits and vegetables, taste Is mostly determined by the types and amounts of carbohydrates, organic acids, amino acids, lipids and phenolics (5.71). CA combinations, to the degree that they modify changes in these constituents, can affect the taste of stored fruits and vegetables. Usually, extremely low O2 or high CO2 will result In off-flavors and reduced quality due to anaerobic respiration. The specific effect of CA on flavor depends on the crop Involved (2). 

The main reactions that lead to the formation of flavor can be listed as Maillard reactions, the Strecker degradation of amino acids, lipid oxidation and microbial and enzymatic reactions, and interactions between lipids, proteins, and carbohydrates. 

The quality of flavor in food is attributed to low concentrations of volatile compounds in its head-space. The headspace concentration of volatile flavors in foods is determined by several factors vapor pressure of the flavor compound, its interaction with other components of the food, and temperature. Carbohydrates, fats, and proteins are all known to affect the vapor pressure of flavors. In addition to odor, the perceived flavor, i.e., taste, of foods is significantly affected by different rates and extent of flavor release (volatility and temperature) when food is chewed [79]. 

Carbohydrates can have a measurable influence on the release and perception of flavors. Carbohydrates change the volatility of compounds relative to water, but the effect depends on the interaction between the particular volatile molecule and the particular carbohydrate. As a general rule, carbohydrates, especially polysaccharides, decrease the volatility of compounds relative to water by a small to moderate amount, as a result of molecular interactions. However, some carbohydrates, especially the monosaccharides and disaccharides, exhibit a salting-out effect, causing an increase in volatility relative to water (Godshall, 1997). 

When one considers the effects of chemical interactions (carbohydrate aroma) on sensory perception, one would expect that aroma character and/or intensity will be altered. This is because the various polysaccharides will interact with different aroma compounds to varying degrees, i.e., change the balance of aroma compounds liberated from a food. However, the effect of carbohydrates on limiting mass transfer would be expected to likely affect flavor intensity and not character. This is because mass transfer effects would be more uniform across aroma compounds. 

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