Flavor perception studies

In other flavor perception studies, the PTR mass spectra of the headspace of seven different brands of mozzarella cheese held at 36 C have been first compared with the judge panel flavor profile [157]. A PCA of the mass spectral data was used to discriminate different cheese types. And a trained panel of sensory judge was employed to give qualitative and quantitative analysis of mozzarella cheese. It was found that there was an interesting and clear similarity between the classical sensory and the instrumental analysis. More recently, a robust and reproducible model was developed to predict the sensory profile of espresso coffee, and the model was derived from 11 different espresso coffees, which had been analyzed by a trained panel and PTR-MS, and further validated using eight additional espressos [158]. Flavor studies of whey [159], custard desserts [160], other types of cheeses [148,161], milk [162], wine [163,164], apples [165],olive oils [166],bread [167], and butter and butter oil [168,169] were also conducted by the PTR-MS system. 

In cheese, a matrix effect could modulate salty and bitter perception in different ways and evolve during the maturation process. The composition of the matrix and physiological parameters had to be taken into account to better understand temporal release and perception of flavor. The study of the relationships between sensory and aroma release gave reliable results only for sulfury note which was the most intense and due to well identified and specific compoimds. 

Another area of food research is the study of flavor perception. This involves attempts to detect VOCs emitting from foods on-line, with the flavor characteristics perceived by human beings, and to quantify the concentrations of flavor compounds with PTR-MS. To date, only a few specific groups have been studied mainly including foodstuffs, vegetables, and dairy products. 

Analytical methods involving exhaustive extraction of flavor compounds (i.e., liquid/liquid extraction, dynamic headspace) do not take these matrix effects into account. However, new instrumentation and methodologies are yielding improved information on the mechanisms involved in flavor/matrix interactions and the effects on flavor perception. For example, spectroscopic techniques, such as nuclear magnetic resonance (NMR), can provide information on complex formation as a function of chemical environment and have been used to study both intra- and intermolecular interactions in model systems [28,31]. In addition, NMR techniques, initially developed to study ligand binding for biological and pharmaceutical applications, were applied in 2002 to model food systems to screen flavor mixtures and identify those compounds that will bind to macromolecules such as proteins and tannins [32]. Flavor release in the mouth can be simulated with analytical tools such as the retronasal aroma simulator (RAS) developed by Roberts and Acree [33]. These release cells can provide... 

Studies on pumped mixtures of sucrose, citric/malic acids, and strawberry aroma gave evidence of the perceptual interactions among these three components in determining overall perceived strawberry flavor. Sucrose was the key driver of strawberry flavor perception and caused the most drastic and rapid reductions in perceived intensity when it was removed from the mixture. 

In the present chapter, we have thus chosen to study the influence of the nature of fat and protein on the aroma release by solid-phase microextraction measurements and on the flavor perception by time-intensity sensory analysis. 

To determine correctly the influence of random coil polysaccharides on aroma and flavor perception, further investigation of the influence of experimental factors such as those considered is required. In addition, a technique to determine release of tastant, e.g., sucrose, must be developed. Finally, further studies with different thickeners, different tastants, and volatile compounds of different aroma character are needed as the interactions found will most likely be compound- and hydrocolloid-specific. 

Human perception of flavor occurs from the combined sensory responses elicited by the proteins, lipids, carbohydrates, and Maillard reaction products in the food. Proteins Chapters 6, 10, 11, 12) and their constituents and sugars Chapter 12) are the primary effects of taste, whereas the lipids Chapters 5, 9) and Maillard products Chapter 4) effect primarily the sense of smell (olfaction). Therefore, when studying a particular food or when designing a new food, it is important to understand the structure-activity relationship of all the variables in the food. To this end, several powerful multivariate statistical techniques have been developed such as factor analysis Chapter 6) and partial least squares regression analysis Chapter 7), to relate a set of independent or "causative" variables to a set of dependent or "effect" variables. Statistical results obtained via these methods are valuable, since they will permit the food... 

Reviews of taste sensations normally concentrate on four basic tastes - sweet, salty, sour and bitter (7,2) however, other oral sensations can contribute important information to the perceived flavor (3), Examples of stimulants evoking these very different sensory sensations are shown in TABLE I. Studies on the mechaiusms of perception are usually restricted to sensation-specific stimuli however, food flavors represent an interaction among the various sensations. This chapter describes recent... 

Figure Gl.7.lisa comparison of chromatograms from a solid-phase microextraction (SPME) from a beverage in a sealed container and from the same beverage in a mouth simulator. This comparison demonstrates that a very different volatile ratio is produced from the same food under different sampling conditions. Due to these differences, it is important to use a sampling method that simulates mouth conditions when studying flavor compositions that produce a human perception. Most methods intended to increase headspace volatile concentration, such as adding salt for salting out, do not uniformly affect volatility. For some compounds,...

The knowledge of the composition of volatile compounds in food has greatly increased during the past decade. Many studies continue to report the identity and the concentration of volatile compounds in food matrices. However concentration alone appears insufScient to explain flavor properties of food. The lack of our knowledge concerning the influence of non-volatile constituents of food on the perception of aroma has to be filled by studies such as those presented in this paper. Data on interactions between aroma and matrix in wine are scarce compared with other food matrices studied. Flavor-matrix interactions in wine have generally been obtained in model systems and with instrumental experiments. However it is possible to develop some hypotheses on the possible sensory contribution of some non-volatile compounds of wine on overall aroma. 

This chapter gives an overview of new trends and developments in flavor chemistry. One Important development was made possible by advances in analytical methodology, that is, the Identification of numerous compounds with known flavor characteristics. As more and more compounds are correlated with characteristic flavors, there is a trend to study flavor precursors and to explain how flavor is developed and released. Many of the newest developments in flavor chemistry are in the area of flavor production from plant and animal sources this trend has come about because of the public s fear of the words "chemical" and "synthetic". In this chapter, words such as these are discussed in terms of the public s perception of them versus a chemist s viewpoint. Another new trend is to understand the chemical reactions involved in the processing and storage of foods in order to bring foods to consumers at optimum acceptability. 

In a review, Dufosse et al. (1994) mentioned the flavor thresholds of some lactones, particularly the olfactory perception after dispersion in water and the perception in mouth after dispersion in aqueous or deodorized oily solution. They also insist on the different sensory properties of y-lactone enantiomers isolated by Mosandl and Gunther (1989). Guichard et al. (1990) studied the lactones in apricot cultivars and found that the (7 )-enantiomer is always predominant for the y-Q, to y-C)2 lactones (Q, C9 and Go lactones have been identified in green coffee). Certainly because of the small amount present, no study has been conducted in coffee, to our knowledge, on the enantiomeric distribution of the lactones. 

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