Separation of cytokinin nucleosidase from adenosine nucleosidase by affinity chromatography and the study of postharvest calcium treatments on sliced tomato
Tarng, Jessica Jiashi.
Ph.D., The Ohio State University, 1992, 132 pages.
1992
บทคัดย่อ
Adenosine (Ado) nucleosidases were extracted from ripe tomato fruits and separated by affinity chromatography on an N6- (isopent-2-enyl) adenosine (i6Ado)-Agarose column. Three distinct forms of adenosine nucleosidase were present in the extracts. Two fractions of the nucleosidases were capable of deribosylating Ado and i6Ado, and one of these contained the majority of the total nucleosidase activity. The third fraction, cytokinin nucleosidase, deribosylated i6Ado but not Ado and had a Km of 55.0 uM for i6Ado. Cytokinin nucleosidase showed a single band having a molecular weight of 40 Kd after SDS electrophoresis and silver staining.
Postharvest calcium treatments by dipping and vacuum infiltration increased the firmness of tomato slices. The action of calcium seemed to be dependent upon concentration with the higher concentration having a greater influence on texture of tomato slices. All calcium infiltration treatments improved both the visual appearance and the reflected color of tomato slices at time zero. The effect of calcium lactate on reflected color decreased with storage time. However, the overall visual appearance of tomato slices treated with calcium lactate was superior to that of tomato slices treated with calcium gluconate and untreated slices at the end of 11 days storage. 100 mM and 250 mM calcium lactate appeared to have the greatest antimicrobial effects. The sensory evaluation at day zero showed no significant difference (alpha = 0.01) for overall acceptance between the samples infiltrated with 50 mM, 100 mM calcium lactate, 100 mM calcium gluconate, and untreated.