Sour aroma substance

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. 

Many microbial metabolites are volatile compounds and in terms of their sensory properties can be broken into two broad categories odorants and tastants (Table 1). Tastants include salty, sour, sweet, and bitter compounds such as amino acids, peptides, and sugars. Primary odorants typically are quite volatile and include carbonyl compounds, esters, and terpenes. There is considerable overlap between the two categories lactones, for example, have both taste and odor properties. In keeping with the theme of this symposium, volatile aroma substances will be the primary focus. 

The butter-like note of unripened cheese can still be detected in Camembert and Emmentaler, but the intensity is lower, because other aroma substances formed during ripening become evident. Thus, Camembert also has mushroom-like, sulfurous and flowery notes and Emmentaler, nutty, sweet and fruity notes. In comparison with unripened cheese, the taste profile is extended to include a glutamate note and in the case of Emmentaler, an additional and characteristic sour/pungent impression. 

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. 

With the exception of the four primary taste sensations— sweet, bitter, salty, and sour—food flavors are the result of our sense of smell. Today, chemists can make chemicals in the laboratory which alone or in various combinations can imitate many of the natural food flavors. These are synthetic flavors. In many cases the synthetic flavors are superior to natural flavors in terms of (1) withstanding processing, (2) cost, (3) availability, and (4) consistent quality. Synthetic flavors may be substances that are prepared in the laboratory but chemically identical to those found in nature, or substances prepared in the laboratory which as yet have not been found to occur in nature but which produce familiar aromas. 

Flavor is defined as the blend of taste and smell sensations evoked by a substance in the mouth and is evaluated using sensory analysis. It results from the pCTception of (i) a few wate-soluble, taste compounds related to the five basic tastes (sweet, salty, bitta-, sour, and umami), and (ii) a diversity of aroma compounds, which are odorous volatile compounds, responsible for the variety of flavors encountered in fermented foods. 

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