The Effect of Different Concentrations and Exposure Durations of Ethylene Gas on Peel Colour Change of Citrus (Citrus nobilis) in the De-greening Process

Abstract

De-greening using ethylene gas is one of the methods to change the peel colour of an in-attractive fruit appearance. Therefore, this research aims to investigate the effect of ethylene concentration and exposure duration on the peel colour changes of Citrus. Ethylene concentrations of 0, 50, 100, and 150 ppm and exposure durations of 24, 48, and 72 h were researched in factorial design 4 x 3 with three replications. Green ripe Citruses were cleaned and selected as the samples which were treated with ethylene gas in a closed box, then removed and stored in the open room until the peel changed uniformly to orange. The colours were measured using a colourimeter (3nh, SC-10) every 12 h for 4 days. It was found that as the storage time passed, the redness value turned from negative to positive, while yellowness increased consistently. Statistical analysis indicated that ethylene concentrations and exposure durations had a significant effect on redness, yellowness, chroma, and hue angle. The largest value of the observed parameter was found at 150 ppm concentration and 72 h exposure duration. This de-greening also altered the Colour Index value from −5.51 to 6.77.