Abstract
Characteristic off-flavor derived from the so-called “Natsucha-shu” is one of the major problems in summer crop of green tea. The scope of this research is to identify the key odorants in summer crop of green tea. An aroma extract dilution analysis (AEDA) has been applied to the volatile fractions isolated from three different forms of tea leaves, headspace above infused tea leaves and its infusion. Although an aroma extracts isolated from tea leaves had freshly green note, those from the headspace and infusion had its characteristic “Natsucha-shu” note. AEDA revealed 46 odor-active peaks with the flavor dilution factors between 10 and 1000. Among these odorants, 2-isopropyl-3-methoxypyrazine and 2-sec-butyl-3-methoxypyrazine were identified for the first time among the tea volatiles. An aroma extract dilution analysis has deduced that (Z)-1,5-octadien-3-one (metallic-like), 2-isobutyl-3-methoxypyrazine (earthy) and 3-methynonane-2,4-dione (green) were the most prevalent odorants in the headspace above infused sencha; while a odorant, namely, (E,Z)-2,6-nonadienal (green) was also potent odorant present in the infusion.
