Monitoring acetic acid vapour concentrations during fumigation of fruit for control of post harvest decay

摘要

A fumigation technique using brief exposure of fruit to acetic acid (AA) vapour reduces post harvest decay if levels of AA are not exceeded that damage the crop. Two methods of monitoring AA vapour concentrations during fumigation are evaluated in this study. The first method uses a gas chromatograph (GC) for monitoring AA intermittently during fumigation. This method can be used to establish AA guidelines for fumigating fruit. For example it was determined that concentrations above 0.6 mg/L (224 ppm (v/v)) could blacken pears rendering them worthless. The second method relies on solid-state gas sensors to continuously monitor AA. An initial study with a methyl bromide gas sensor (International Sensor Technology, Irvine, CA), recalibrated to readAA, correlated reasonably well with the GC method but did not give a linear response from 0 to 1000 ppm (2.68 mg/L). In more recent studies, more advanced sensors (Model 4-20IQ and SM95) were evaluated. These sensors gave a linear response over the entire range from 0 to 1500 ppm AA. If these sensors could be manufactured so they would not easily lose their calibration, they could be used to maintain safe levels of AA during fumigation.