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H02CCH(NH2)CH2CH2C0NHC2H Figure 3. Theanine (14).

present at a level of 30 to 45 mg/cup. Its tendency to complex with polyphenols affects the organoleptic properties of tea beverage and the technology of instant-tea manufacture. The properties of caffeine and tea decaffeination processes are not discussed in this article.

Amino Acids

In addition to the normal plant leaf amino acids, theanine (5-7V-ethylglutamine) (14) (Fig. 3) is unique to tea and correlates with green-tea quality (15). Several of the other amino acids in the leaf take part in aroma formation during manufacture.

Carotenoids

Carotenoid compounds constitute only 0.03 to 0.06% of tea flush but are important in aroma generation during manufacture. They include ^-carotene, lutein, zeaxanthine, and violaxanthine (Fig. 4) (16).

Volatiles

More than 50 volatile compounds have been reported in fresh leaf, although some of these may be artifacts of the isolation procedures (17). Aroma components, their origin, and their significance will be discussed in the manufacturing section as it is during leaf processing that most aroma character is developed.

Lipids, Waxes, and Pigments

The presence of unsaturated fatty acids is also of significance to aroma generation, as will be shown. Linoleic and linolenic acids are present at a level of ca 1.2% in fresh leaf

P-carotene

P-carotene

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