Explicating the effect of the ozonation on quality parameters of onion (Allium cepa L.) in terms of pungency, phenolics, antioxidant activity, colour, and microstructure

ABSTRACT Ozone is a powerful oxidizing agent, so its effect on quality parameters must be considered prior to any potential food application. The effect of gaseous ozone on the quality-related attributes of onion bulbs was examined. Onions were exposed to different ozone concentrations (100, 200, 300 ppm) at pulse mode (i.e., frequency of exposures 1, 2, 3). The pungency imparting pyruvic acid and ascorbic acid contents decreased with an increase in the concentration of ozone and the number of exposures, while total phenol and flavonoid content increased to an effective concentration of 400 ppm of ozone. Higher concentrations inadvertently decreased the antioxidant properties. Ozone treatment resulted in a non-significant decrease in firmness, anthocyanin content, and color of onion. Scanning electron microscopic analysis exhibited structural breakdown in the tunic (outer surface) of ozone-treated onion. At higher concentrations, structural changes were observed up to the first bulb scale.