The Effects of Ultrasound Treatments with Hot Water on Postharvest Quality of Fresh-Cut Green Onion

Abstract

The fresh onion, which has a short life after harvest, comes to the forefront with its nutritious and appetizing properties. Especially yellowing in the green parts and the elongation of white axle with dulling is known as a significant post-harvest losses of green onion. The aim of this study
is to determine the effect of ultrasound treatment at different temperatures on post-harvest quality of onions. In the study, onions were harvested and then cleaned, sorted, washed and cut into two halves. After this, 52 dB ultrasound for fifteen minutes was applied to fresh-cut onions in the ultrasonic bath containing water at 35o C, 40o C and 45o C temperature. Onions that have not been treated with ultrasound are used as controls. After the applications, the onions were dried and placed into the polystyrene foam dishes as it will be 200 g onion in each dish which is then
wrapped with polyethylene stretch film. After packaging, the onions were stored in cold room at a temperature of 4 ± 1 ° C and relative humidity of 85-90%. At the beginning of the experiment and at intervals of 5 days; color (L*, a*, b*), total soluble solids (%), chlorophyll (SPAD),
axle length (mm), axle diameter (mm) and weight loss measurements were performed in white and green areas. According to the results of this study, while 45o C temperature treatment decreased weight loss and increased brightness in white part, it accelerated chlorophyll breakdown. It is suggests to continue similar studies because of the positive effect of temperature application on the white part of onion.