Flavor astringency

The formol index (total free amino acids) was the best predictor of browning rate of concentrates during storage for a given commodity. While haze and sediment formation were quality factors of major interest in this study, none of the juices or concentrates produced were particularly troublesome in this regard. The phenolic and protein profiles should still provide a reference with which unstable experimental or commercial samples can be compared in the future, however. In addition to color and appearance, quality factors of flavor, astringency, bitterness, viscosity and mouthfeel warrant investigation. 

Beer phenols issued from malt and hop can contribute directly to several characteristics of beer, mainly flavor, astringency, haze, body, and fullness. Some phenolic structures can also impart very interesting health properties. Yet phenolic structures also evolve through storage. Low-molecular-weight phenols like 4-vinylsyrmgol can impart off-flavors in aged beer, while oxidized... 

The natural moisture of the cocoa bean combined with the heat of roasting cause many chemical reactions other than flavor changes. Some of these reactions remove unpleasant volatile acids and astringent compounds, partially break down sugars, modify tannins and other nonvolatile compounds with a reduction in bitterness, and convert proteins to amino acids that react with sugars to form flavor compounds, particularly pyrazines (4). To date, over 300 different compounds, many of them formed during roasting, have been identified in the chocolate flavor (5). 

Tea oxidation is generally referred to as fermentation because of the erroneous early conception of black tea production as a microbial process.66 Not until 1901 was there recognition of the process as one dependent on an enzymically catalyzed oxidation.67 This step and further reactions result in the conversion of the colorless flavanols to a complex mixture of orange-yellow to red-brown substances and an increase in the amount and variety of volatile compounds. Extract of oxidized leaf is amber-colored and less astringent than the light yellow-green extract of fresh leaf and the flavor profile is considerably more complex. 

The organoleptic properties of black tea depend to a considerable extent on the astringency resulting from the interaction of caffeine with the oxidized galloyl ester of the flavanols. The aroma components of black tea also constitute a unique flavor profile that blends well with the taste of the nonvolatile materials. The caffeine provides a moderate level of stimulation, which adds further to the appeal of the beverage, although tea has been shown to provide relaxation as well as revival of character.119... 

The flavors of Chinese teas range from extremely mild white teas to astringent green teas to heavy, black, strong-flavored varieties. 

Green, B. G. (1993). Oral astringency A tactile component of flavor. Acta Psychol. (Amsterdam) 84, 119-125. 

Noble, A., Why do wines taste bitter and feel astringent In Wine Flavor (eds A.L. Waterhouse and S. Eberler), American Chemical Society, Washington, DC, 1998, p. 156. 

Phenolic compounds are important components of many fruits, vegetables, and beverages, to which they contribute to flavor, color, and sensory properties such as bitterness and astringency. Recent interest in functional foods and the medicinal use of phenolic compounds have also stimulated interest in their chromatographic separation. 

The complexities and interaction of composition on the quality perception of vermouth is illustrated with wild-apricot-based vermouth (Figs. 8.5-8.7). It shows that sweetness, flavor, and astringency are preferred at a sugar content of 8%, whereas body, appearance, and aroma were preferred at 12% sugar (Fig. 8.5). Body, flavor, aroma, and total acidity were scored better at an alcohol content of 19% (Fig. 8.6). The spice concentration preferred for volatile acidity, total acidity, flavor, and bitterness was 5% (Fig. 8.7), whereas body, sweetness, appearance, and astringency were preferred at a 2.5% level (Joshi et al, 201 la,b). 

Phenolic compounds also contribute directly to the flavor due to their astrin-gency and bitter taste characteristics [11]. In fact, astringency is believed to be due to the interaction between tannins and salivary proteins, resulting in the formation of protein-tannin aggregates in the mouth, as discussed in more detail below [12-15],... 

It has been shown that the aroma of tea is affected by the heat treatment received. Tea aroma and flavor are greatly influenced by catechins and proceeds by more than one pathway. The catechins influence tea aroma and flavor in three ways. First, catechins have a bitter, astringent taste. Second in order to reduce the level of soluble catechins (i.e. in var. assamica), a second heat treatment is required. This refiring produces a stronger roast aroma. Third catechins strongly influence the pyrolysis of B-carotene and L-theanine. 

The manipulation of the cap, the length of time the juice is kept in contact with the skins, and the temperature of fermentation are three important variables available to the enologist to produce a wine of the depth of color and flavor, degree of astringency and bitterness, and general texture and longevity that he wishes his wine to have. Later in the process there are additional variables but none is more important than these three. 

By careful processing, the winemaker brings the wine to a finished state. The white and rose wines will have maintained their bouquet and aroma and flavors. The red table wines will have been softened by careful fining with such agents as gelatin and PVPP, will be fruity, and will have distinctive varietal aromas and flavors with minimal astringency. 

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