Changes in Peroxidase Activity in the Peel of Unshiu Mandarin (Citrus unshiu Marc.) Fruit with Different Storage Treatments
Hrvoje Lepeduš1*, Marko Jozić1, Ivna Štolfa1, Nikola Pavičić2, Branimir K. Hackenberger1 and Vera Cesar1
1Department of Biology, University of J. J. Strossmayer, L. Jägera 9, HR-31000 Osijek, Croatia
2Department of Pomology, Faculty of Agriculture, University of Zagreb, Svetošimunska 25, HR-10000 Zagreb, Croatia
Article history:
Received August 12, 2004
Accepted February 28, 2005
Key words:
Citrus unshiu fruit, hot water dip, peroxidase, postharvest cold storage
Summary:
The Unshiu mandarin (Citrus unshiu Marc.) is the major Citrus crop in Croatia. Limiting factors for longer consumption of Unshiu mandarin are low storage performance and the appearance of chilling injuries during storage. Previous studies indicated that oxidative stress might be involved in cold-induced peel damage of harvested Citrus fruit. The aim of the present study was to investigate peroxidase distribution, isoenzyme pattern and activity in the peel of Unshiu mandarin fruit. Special goal of our study was to investigate the changes of peroxidase activity in respect to two different hot water dipping (HWD) treatments (3 min at 48 and 52 °C) and two different storage temperatures (1 and 3 °C) combined. Peroxidase activity was detected at the border of oil glands, in the peel surface and in the conducting elements positioned in the inner part of the peel. Electrophoretic analysis revealed the presence of two peroxidase isoenzymes. There were no differences in the electrophoretic pattern after the HWD treatments and cold storage. Lowering of both total and specific peroxidase activity was measured in HWD-treated samples in comparison with the control ones. However, it appeared that significant decrease in total peroxidase activity was influenced by the storage temperatures, while the increase in total soluble protein content was influenced by the HWD pretreatment.
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