Articles
POSTHARVEST METHODS TO REDUCE SULFUR DIOXIDE RESIDUES IN FRESH LONGAN
Article number
804_23
Pages
183 – 190
Language
English
Abstract
Fumigating fresh longan with sulfur dioxide (SO2) is commonly used in Thailand as an effective postharvest method for pericarp bleaching and rot control.
However, SO2 residues in both pericarp and arils after fumigation are a major concern for customers.
Results from 14 sampling sites in Chiang Mai and Lumpoon provinces showed that more than 80% of the samples had SO2 residues in the pericarp higher than 1,700 ppm and all of the samples had residues in the arils exceeding 10 ppm.
The SO2 residues in off-season longan were higher than in in-season fruit.
Washing longan with running water was more effective in reducing SO2 residues than soaking in water.
Washing longan for 5-10 min. within 24 h after fumigation reduced SO2 residues by up to 36% in pericarp and about 48% in arils.
Water temperature (0, 5, and 23°C) did not change the effectiveness of washing for reducing SO2 residues in both pericarp and arils.
Washing fresh longan for 5 min. had no effect on postharvest longan quality and overall acceptability as determined by a taste panel.
Postharvest shelf life of washed longan was not significantly different from that of unwashed longan, which was about 18 days compared to 11 days for non-fumigated longan.
However, SO2 residues in both pericarp and arils after fumigation are a major concern for customers.
Results from 14 sampling sites in Chiang Mai and Lumpoon provinces showed that more than 80% of the samples had SO2 residues in the pericarp higher than 1,700 ppm and all of the samples had residues in the arils exceeding 10 ppm.
The SO2 residues in off-season longan were higher than in in-season fruit.
Washing longan with running water was more effective in reducing SO2 residues than soaking in water.
Washing longan for 5-10 min. within 24 h after fumigation reduced SO2 residues by up to 36% in pericarp and about 48% in arils.
Water temperature (0, 5, and 23°C) did not change the effectiveness of washing for reducing SO2 residues in both pericarp and arils.
Washing fresh longan for 5 min. had no effect on postharvest longan quality and overall acceptability as determined by a taste panel.
Postharvest shelf life of washed longan was not significantly different from that of unwashed longan, which was about 18 days compared to 11 days for non-fumigated longan.
Authors
T. Jaroenkit, S. Ussahatanonta, J. Phimphimol
Keywords
SO2 residue, Dimocarpus longan, washing, shelf life
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