Taste Compounds Nonvolatiles

Organic aromatic molecules are usually sweet, bitter, a combination of these, or tasteless, probably owing to lack of water solubiUty. Most characteristic taste substances, especially salty and sweet, are nonvolatile compounds. Many different types of molecules produce the bitter taste, eg, divalent cations, alkaloids, some amino acids, and denatoirium (14,15). 

Toxicity. Sodium fluoroacetate is one of the most effective all-purpose rodenticides known (18). It is highly toxic to all species of rats tested and can be used either in water solution or in bait preparations. Its absence of objectionable taste and odor and its delayed effects lead to its excellent acceptance by rodents. It is nonvolatile, chemically stable, and not toxic or irritating to the unbroken skin of workers. Rats do not appear to develop any significant tolerance to this compound from nonlethal doses. However, it is extremely dangerous to humans, to common household pets, and to farm animals, and should only be used by experienced personnel. The rodent carcasses should be collected and destroyed since they remain poisonous for a long period of time to any animal that eats them. 

Nontoxic chlorofluorocarbons, 24 188 Nontronite (iron smectite), 6 664, 696 structure and composition, 6 669 Nonuniqueness, 24 446 Nonvessel operating common carriers (NVOCC), 25 328 Nonvolatile compounds, as taste substances, 11 566 Nonvolatile food components,... 

In tests to better define this mixture of components (and their proper proportions) necessary for good orange flavor, volatile components believed from prior analytical studies to be important to orange flavor were examined (5). Individual taste and aroma thresholds in water were determined on the compounds selected. Then, the influence of nonvolatile juice constituents on the taste threshold of certain of the volatile components was studied. Finally, selected individual compounds and mixtures containing from two to six components were evaluated in a bland juice medium for their contribution to orange flavor. 

Comparison of the taste threshold with estimated concentration in orange juice (where available) in Table I reveals that in all cases except octyl acetate and a-pinene, the concentration in orange juice exceeds the taste threshold in water for most values reported. Patton and Josephson (17) postulated that components present in a food at above threshold level make a positive contribution to the flavor, while those present at below threshold level make little or no contribution to flavor. This generalization is now considered an oversimplification, for synergistic effects among food constituents have been shown to decrease the threshold level of some compounds, and nonvolatile constituents are known to either increase or decrease the taste threshold of certain volatile and nonvolatile constituents. 

Wine is one of the most complex and interesting matrices for a number of reasons. It is composed of volatile compounds, some of them responsible for the odor, and nonvolatile compounds which cause taste sensations, such as sweetness (sugars), sourness (organic acids), bitterness (polyphenols), and saltiness (mineral substances Rapp and Mandary, 1986). With a few exceptions, those compounds need to be present in levels of 1%, or even more, to influence taste. Generally, the volatile components can be perceived in much lower concentrations, since our organs are extremely sensitive to certain aroma substances (Rapp et ah, 1986). Carbohydrates (monosaccharides, disaccharides, and polysaccharides), peptides, proteins, vitamins, and mineral substances are among the other wine constituents. 

With alkaline degradation, the formation of 1,2-enols is also the initial step. This reaction in turn can produce three-carbon compounds which yield a series of intramolecular reactions involving condensation and polymerization. Both acidic and alkaline caramelization produce numerous volatile and nonvolatile compounds that significantly contribute to aroma, taste, and color. 

FIGURE 2-30. Comparison of lemon oils. Use of synthetic lemon oils gives lemon-flavored beverages an off taste. Natural lemon oils contain high molecular weight, nonvolatile components which are normally absent from synthetics. These compounds do not show up on the survey print of lemon oil No. 3, indicated by the arrow. This sample is probably synthetic. All the samples were identical by GC. 

Process flavourings are more related to cooking than to chemical synthesis. The reactions that occur are chemically very complex with hundreds of volatiles and nonvolatiles being formed. The final process flavouring is defined by the sum of the sensory effects of all aroma-active volatiles and taste-active compounds. 

At this point, it is important to clarify a few terms that are often used in the context of this chapter. Flavour is usually divided into the subsets taste and smell, which are perceived in the mouth and the nose, respectively [3], The terms aroma and odour are not well defined and often used as synonyms. Qdour is best reserved for the smell of food before it is put into the mouth (nasal perception) and aroma for the retronasal smell of food in the mouth. In this paper, we mainly use the terms aroma and taste , as well as flavour comprising sensory notes imparted by both volatile and nonvolatile compounds (odorants and tastants). In the public domain, however, taste is often used as a synonym for flavour . Proper definitions of these terms are ... 

The flavor of flying oils and fried products is mainly due to the volatile compounds which influence the aroma. Nonvolatile products may also change the taste and the mouth-feel. Billek et al. (Billek et aL, 1978) reported that RBD soybean oil contains about 1.2% oxidized triacylglycerols. The nonvolatile oxidized compounds include cyclic carbon-to-carbon linked dimers, noncyclic hydroxyl dimers, carbon-to-carbon or carbon-to-oxygen... 

Our interest in the analysis of nonvolatiles, thus, may involve taste substances or substances that indirectly influence taste or aroma. As mentioned earlier, in the first case, we are interested in the analysis of substances that impart sweetness, tartness, bitterness, saltiness, or unmami sensations. The analysis of these substances is reasonably well defined. In the latter case, the analyses employed are less well defined and are unique to the components one wishes to analyze. For example, we may wish to measure substances (e.g., melanoidins) that interact with sulfur aroma compounds (in coffee). There are no standardized methods for the analysis of melanoidins in foods and thus, the protocols have to be developed. In this chapter, we will only briefly discuss the established methods for the analysis of taste substances. Due to the specificity of methods for the analysis of nonvolatiles that may indirectly influence flavor perception, we will only refer the reader to the literature [93-100]. 

Meat aroma consists of (a) nonvolatile taste substances, (b) taste enhancers and (c) aroma constituents. The latter compounds or their precursors originate essentially from the water-soluhle fraction. The constituents listed in Table 12.22 have been identified as the taste substances of beef broth and roasted meat juice. Solutions of these substances in the given concentrations (Table 12.22) give the typical taste profiles, which are composed of sweet, sour, salty, and glutamate-Uke (umami) notes. The meat note is produced by odorants. 

The hot, burning pungent taste of paprika (red pepper), pepper (black pepper) and ginger is caused by the nonvolatile compounds listed in Table 22.9. 

However, RP-HPLC is challenging for the separation of polar compounds that are poorly retained on the hydrophobic stationary phase. This limits the application of RP-HPLC for the analysis of nonvolatile flavor compounds. Many taste-active compounds, especially those with reported savory (umami = glutamate-like) taste are of a hydrophilic nature. Hydrophilic di- to tetrapeptides consisting of high molar ratios of acidic and other hydrophilic amino acids such as Glu-Asp, Glu-Glu, Thr-Glu, Asp-... 

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