title: Pre-extraction preparation (fresh, frozen, freeze-dried, or acetone powdered) and long-term storage of fruit and vegetable tissues: effects on antioxidant enzyme activity.
abstract: Activities of the antioxidant enzymes ascorbate peroxidase, catalase, dehydroascorbate reductase, glutathione reductase, guaiacol peroxidase, monodehydroascorbate reductase, and superoxide dismutase were assayed in honeydew (Cucumis melo L.) fruit and spinach (Spinacia oleracea L.) leaves either as fresh, frozen to -80 degrees C, frozen in liquid nitrogen, freeze-dried, or acetone powder, representing the various ways tissues are treated prior to enzyme extraction. Treated tissues were analyzed following treatment or stored for up to 8 weeks at -80 degrees C. Enzyme activities in fruit frozen with or without liquid nitrogen and leaves frozen with or without liquid nitrogen or freeze-dried were equal to those of fresh tissue. Enzyme activities in freeze-dried or acetone-powdered fruit and leaves and in acetone-powdered tissues were significantly higher or lower than those in fresh tissue. Enzyme activities in both tissues frozen with or without liquid nitrogen and stored for 8 weeks at -80 degrees C changed little; those in freeze-dried and acetone-powdered tissues, however, significantly increased/decreased over the same period. Fresh tissue should be used in antioxidant enzyme assays, but if storage is necessary, tissues should be placed directly into a -80 degrees C freezer.
authors.affiliation: Kika de la Garza Subtropical Agricultural Research Center, Agricultural Research Service, US Department of Agriculture, Building 200, 2413 East Highway 83, Weslaco, Texas 78596, USA. glester@weslaco.ars.usda.gov
authors.forename: Gene E
authors.initials: GE
authors.lastname: Lester
authors.forename: D Mark
authors.initials: DM
authors.lastname: Hodges
authors.forename: Robert D
authors.initials: RD
authors.lastname: Meyer
authors.forename: Kathleen D
authors.initials: KD
authors.lastname: Munro
mesh_terms: D000975:Antioxidants; D060387:Ascorbate Peroxidases; D002374:Catalase / Q000032:analysis; D005519:Food Preservation / Q000379:methods*; D005612:Freeze Drying; D005615:Freezing; D005638:Fruit / Q000201:enzymology*; D005980:Glutathione Reductase / Q000032:analysis; D009247:NADH, NADPH Oxidoreductases / Q000032:analysis; D010088:Oxidoreductases / Q000032:analysis; D009195:Peroxidase / Q000032:analysis; D010544:Peroxidases / Q000032:analysis; D010936:Plant Extracts; D011208:Powders; D013482:Superoxide Dismutase / Q000032:analysis; D014675:Vegetables / Q000201:enzymology*
chemical_list: D000975:Antioxidants; D010936:Plant Extracts; D011208:Powders; D010088:Oxidoreductases; D010544:Peroxidases; C121048:guaiacol peroxidase; D060387:Ascorbate Peroxidases; D002374:Catalase; D009195:Peroxidase; D013482:Superoxide Dismutase; D009247:NADH, NADPH Oxidoreductases; C023927:monodehydroascorbate reductase (NADH); D005980:Glutathione Reductase; C020666:glutathione dehydrogenase (ascorbate)