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Note: Polysaccharide content is expressed as anhydro-sugars. Wt% is on dry basis.

Note: Polysaccharide content is expressed as anhydro-sugars. Wt% is on dry basis.

and 5-caffeoylquinic acid (neochlorogenic acid)—occur at least in part on potassium-caffeine-chlorogenate complexes. They decompose in direct relationship to the degree of roast. Table 6 shows the changes that occur in these acids during roasting. Apparently, chlorogenic acids modify and control reactions that occur during the roast and are particularly important to the decomposition of sucrose.

Glycerides of linoleic and palmitic acids, along with some glycerides of stearic and oleic acids, make up the 7 to 16% fat content of coffee. Some cleavage of glycerides and some loss of unsaponifiables occur during roasting. Table 7 details these losses (7).

Aroma

Combinations of advanced chromatography and mass spectra analytical techniques have advanced the identification of volatile flavor components in roasted coffee to more than 800. Although present in minute quantities, they are extremely significant to the balance of flavor in a cup of coffee. A historical account of this work has been published (8). A partial summary of the volatile components by chemical class is in Table 8.

Freshly roasted ground coffee rapidly loses its fresh character when exposed to air, and within a few weeks develops a noticeable stale flavor. The mechanism for the development of staling is not known but is believed to be caused by an oxidation reaction that can be catalyzed by increasing levels of moisture (9).

Table 6. Changes in Chlorogenic Acids during Roasting by Percentage
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