2.5. Color measurement
Color was measured by using a Minolta colorimeter (model CR400;
Minolta Co., Osaka, Japan). The values for L*, a* and b* 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 themeasurement equipment. Themeasuring head of the colorimeter
was placed on top of the measurement equipment. Before measure-
ment, the treated juice was cooled to about 15 °C by dipping the bottle
in crushed ice. The parameter L* is a measure of lightness, a*isanindi-
cator of redness, and the parameter b* is a measure of yellowness. All
measurements were performed in triplicate.