Color was measured by using a Minolta colorimeter (model CR400; Minolta Co., Osaka, Japan). The values forL*,a* andb* were recorded to evaluate the color changes of apple juice after each treatment with heat or combination of ozone and heat. Untreated apple juice was used as the control. A 2 ml of sample was poured into the bottom half of the measurement equipment. The measuring head of the colorimeter was placed on top of the measurement equipment. Before measurement, the treated juice was cooled to about 15 °C by dipping the bottle
in crushed ice. The parameterL* is a measure of lightness,a*isanindicator of redness, and the parameterb* is a measure of yellowness. All measurements were performed in triplicate