commercial use is actually able to resolve the problem
(Tongdee, 1994). However, there have been numerous reports
on the negative effects of its use such as toxic residues in
humans and asthmatics and other reactions with sensitive
individuals. Therefore, alternative treatments for SO2 fumigation
are required. Citric acid (CA) is an anti-browning
agent, which prevents polyphenol oxidase by suppressing
the food pH and binding the Cu2+ in an active site of PPO to
form an inactive complex (Martinez and Whitaker, 1995).
It has also been widely used in the food industries for
controlling the browning. Although applying CA as a dipping
solution has been reported in postharvest fruits with very
satisfactory results for fruits such as longan