Articles
EXPOSURE OF BROCCOLI TO DIFFERENT TEMPERATURES DURING STORAGE: SOME CHANGES IN POSTHARVEST PHYSIOLOGY AND ACTIVITIES OF AMMONIA-ASSIMILATING ENZYMES
Article number
768_74
Pages
551 – 557
Language
English
Abstract
The rate of quality deterioration in harvested produce is greatly influenced by storage temperature.
To determine its effects in broccoli (Brassica oleracea L.), heads were kept at 5 and 20°C for 5 d after harvest.
Important physiological traits and activities of ammonia assimilating enzymes were investigated.
Almost constant hue angle values and decline in respiration rate and ethylene production occurred at 5°C throughout storage.
However, keeping heads at 20°C resulted in rapid yellowing of the florets, which might be a consequence of higher C2H4 production.
Although CO2 production declined over time at 20°C, the rate of production was slightly higher than that of the heads stored at 5°C. Glutamine synthetase (GS; EC 6.3.1.2) activity in florets slightly increased throughout storage at 5°C but decreased at 20°C. In the branchlet portion, activity did not change.
At both storage temperatures, the amination and deamination activities of glutamate dehydrogenase (GDH; EC 1.4.1.2) gradually increased in florets over time while a decrease was found in the branchlet portion as storage progressed.
Ammonia content in all portions changed very little at 5°C. However, a sudden, seven fold increase in ammonia content was observed at the end of the experimental period in florets stored at 20°C when compared to that at harvest.
Ammonium toxicity is due to the decline in GS activity, while the higher ethylene production and respiration rate could be the major contributing factors affecting rapid quality deterioration of the commodity stored at 20°C. Changes in GDH activity may indicate its anabolic and catabolic roles when plant tissues are exposed to stress.
Ammonia content in broccoli could therefore be used as an indicator of product freshness.
To determine its effects in broccoli (Brassica oleracea L.), heads were kept at 5 and 20°C for 5 d after harvest.
Important physiological traits and activities of ammonia assimilating enzymes were investigated.
Almost constant hue angle values and decline in respiration rate and ethylene production occurred at 5°C throughout storage.
However, keeping heads at 20°C resulted in rapid yellowing of the florets, which might be a consequence of higher C2H4 production.
Although CO2 production declined over time at 20°C, the rate of production was slightly higher than that of the heads stored at 5°C. Glutamine synthetase (GS; EC 6.3.1.2) activity in florets slightly increased throughout storage at 5°C but decreased at 20°C. In the branchlet portion, activity did not change.
At both storage temperatures, the amination and deamination activities of glutamate dehydrogenase (GDH; EC 1.4.1.2) gradually increased in florets over time while a decrease was found in the branchlet portion as storage progressed.
Ammonia content in all portions changed very little at 5°C. However, a sudden, seven fold increase in ammonia content was observed at the end of the experimental period in florets stored at 20°C when compared to that at harvest.
Ammonium toxicity is due to the decline in GS activity, while the higher ethylene production and respiration rate could be the major contributing factors affecting rapid quality deterioration of the commodity stored at 20°C. Changes in GDH activity may indicate its anabolic and catabolic roles when plant tissues are exposed to stress.
Ammonia content in broccoli could therefore be used as an indicator of product freshness.
Authors
D.P. Baclayon, T. Matsui
Keywords
ethylene production, glutamate dehydrogenase, respiration rate, glutamine synthetase
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