Flavor Compounds Vs Flavor Perception

Fat not only delivers its own flavor volatiles but also functions as a carrier for other lipophilic compounds present. These are bound to the fat molecules by weak, reversible Van der Waals and hydrophobic interactions (Plug and Haring, 1993). It follows, therefore, that in the case of total fat removal, with the flavor cocktail used remaining unchanged, the changed kinetics of the flavor release mechanisms will cause the perceived flavor of the product to be changed perhaps quite dramatically.

In this context, the effects of pH on flavor compounds need to be borne in mind. Thus, because of concerns regarding microbiological stability, it is common practice to make the pH of a food product lower when reducing fat content in order to ensure a sufficient shelf life. This can have a significant impact on acid-base flavor compounds, since mostly they exhibit a particular flavor only if in the associated state. Since this would depend on the pK value of the compound, changes in pH can result in more molecules in the dissociated state, thus leading to the loss of flavor perceived. According to Bennett (1992), lowering the pH of a product from 6.5 to 4.2 results in a ten-fold increase in the associated form of butyric acid which has obvious implications for fat replacement in dairy products.

Furthermore, the amount of fat that is removed and the amount of water added to a food system will affect not only the perceived intensity of both the lipophilic and hydrophilic flavor compounds present but also the flavor balance. This point is illustrated in Table 4.2 which compares flavor threshold values of flavor compounds when placed in a water medium and when placed in an oil medium (Bennett, 1992). Thus, the threshold value for decanoic acid, for example, will change by 5000% when moving from oil to water. In short, the need for changes in the composition of the flavor cocktail used when developing low-fat or fat-free foods is rather apparent.

Table 4.2 Comparison of Flavor Threshold Values for Fatty Acids in Water and Oil

Threshhold (ppm)

Table 4.2 Comparison of Flavor Threshold Values for Fatty Acids in Water and Oil

Threshhold (ppm)

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