Microwave heating of tea residue yields polysaccharides, polyphenols, and plant biopolyester.
Microwave heating was used to produce aqueous-soluble components from green, oolong, and black tea residues. Heating at 200-230 degrees C for 2 min extracted 40-50% of polysaccharides and 60-70% of the polyphenols. Solubilization of arabinose and galactose by autohydrolysis occurred with heating above 170 degrees C, whereas heating above 200 degrees C was necessary to solubilize xylose. Catechins were soluble in water by heating at low temperature (110 degrees C); however, new polyphenols having strong antioxidant activity were produced above 200 degrees C. The amount of solubilized materials and antioxidant activity increased with increased fermentation of harvested tea leaves (green tea < oolong tea < black tea). Cutin, a plant biopolyester, remained in the residue after heating as did cellulose and lignin/tannin. The predominant cutin monomer that was recovered was 9,10-epoxy-18-hydroxyoctadecanoic acid, followed by dihydroxyhexadecanoic acid and 9,10,18-trihydroxyoctadecanoic acid.
Tsubaki
Shuntaro
S
Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Japan. stsubaki@kais.kyoto-u.ac.jp
Iida
Hiroyuki
H
Sakamoto
Masahiro
M
Azuma
Jun-ichi
J
D000975:Antioxidants; D005419:Flavonoids / Q000737:chemistry*; D008872:Microwaves; D010636:Phenols / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry; D011091:Polyesters / Q000737:chemistry*; D059808:Polyphenols; D011134:Polysaccharides / Q000737:chemistry*; D012995:Solubility; D013662:Tea / Q000737:chemistry*
D000975:Antioxidants; D005419:Flavonoids; D010636:Phenols; D010936:Plant Extracts; D011091:Polyesters; D059808:Polyphenols; D011134:Polysaccharides; D013662:Tea