Flavor, grapes, importance

Acid content calculated as tartaric acid is about 6—7 g/L for best flavor and stabiUty. It is higher for tart low Brix musts and less important for sweet high Brix musts. High acid levels coiacide with a higher level of the second acid of grapes, malic acid. 

Feeding repellents for pest birds are the most important application of chemical stimuli to manipulate bird behavior. Methyl anthranilate (Fig. 13.1) and dimethyl anthranilate, esters of benzoic acid, are found in concord grapes and are used as artificial flavorings. Starlings, Sturnus vulgaris, have an aversion to methyl anthranilate, which irritates the trigeminal nerve, and they feed less on food flavored with a variety of anthranilates. They avoid the more volatile anthranilates most. The odor is partly responsible for the effect contact is not necessary. In one particular experiment, only volatile compounds were aversive (Mason and Clark, 1987). If only anthranilate-treated food is offered, the birds will accept more of the flavored food than they do if they offered a choice between... 

The next step of the biotechnical sequence, yeast fermentation, is of the utmost importance to the chemistry of winemaking as well as to the formation of flavor substances. We have investigated this previously using 14C-tagged compounds (16). Amino acids, for example, enter the yeast fermentation with a quasi biochemical valence with regard to the formation of metabolic side products like alcohols and esters. In that respect, the composition of the fermentation substrate, the grape must, is highly important to the formation of aroma substances by yeasts. 

Certain aroma components from fruits are responsible for the characteristic odor of many wines. An example is the typical aroma of many V. labrusca grapes which often gives their wines a distinctive aroma and flavor. Furthermore, some volatile constituents are characteristic of certain varieties and their wines are recognized by these distinctive aromas. This is significantly important for varietal wines (grape) where their distinct aromas are a prerequisite in rating the quality at the highest level. In addition to the importance of variety in the aroma and flavor of wines, other variables known to influence the volatile components within the fruit variety are maturity, location, climatic conditions, and cultural practices. 

Because they are important, the phenolics and their roles in wine have been studied considerably (I), but more needs to be known. Since different classes of phenols behave quite differently in the various roles as pigments, oxidation substrates, flavors, etc., separate consideration and analysis is essential to completely understand them. Every individual phenol should be separately determined precisely and quantitatively. Chromatography may solve these problems, but for now, chromatography and other detailed separatory methods have drawbacks, particularly for economical application to many individual wine or grape samples. 

Phenolic compounds are of interest due to their potential contribution to the taste (astrin-gency, bitterness, and sourness) and formation of off-flavor in foods, including tea, coffee, and various fruit juices, during storage. Their influence on the appearance of food products, such as haze formation and discoloration associated with browning in apple and grape products, is also significant. Furthermore, analysis of these phenolic compounds can permit taxonomic classification of the source of foods. The importance of each phenolic compound and its association with the quality of various foods is described further in Sec. IV, on food applications. 

In this review an original and unique approach was undertaken to unite the notions "heterocycles" and "wine principles." Indeed, it is astonishing that natural wines contain numerous heterocyclic principles in varying quantities (as low as nanograms ) that contribute to flavor, smell, taste, and aftertaste ("finish") sensations, all of which are characteristic of the different grape types. During aging and maturation of the wines in barrels and bottles, manifold additional heterocycles are formed or extracted. The odor threshold plays an important role in all cases, which is ultimately dependent on the chirality centers of the isomers involved in aroma. 

Cold Duck is a blend of white and red sparkling wines. It probably originated in the Middle States, and the flavor of Concord grapes is predominate, or at least recognizable. For this reason, some California producers import Concord grape juice or concentrate from other states for use in this product. 

Tannins are present in the skins of red grapes and play an important part in the flavor profile of red wine. Tannins in grapes are usually estimated in terms of the content of gallic acid (Amerine and Joslyn 1970). 

Kolor, M.G. (1983). Identification of an important new flavor compound in concord grape Ethyl 3-mercaptopropionate. J. Agric. Food Chem., 31, 1125-1127. 

Blanc, a connection has been established by sensory descriptive analyses between the aroma attributes of hydrolyzed flavor precursors from the grapes and wines of these varieties (7-10). These studies have demonstrated that grape glycosides are of importance to white wine flavor, in particular after a period of wine storage. Similarly, for the black grape variety Shiraz, a sensory study has indicated that juice glycosidic hydrolysates have aroma characteristics in common with those of wines of that variety (11). 

Recognition of these phenonena in grapes and wines ( ), and the importance therefore of the glycosides as precursors of flavor in those systans 8) has stimulated much research interest in the role of non-volatile flavor precursors in other fruits (9-11), processed fruits (12), and leaf products (13, 14). For convenience this line of investigation is described here as the "precursor analysis approach" to flavor research. 

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