| Abstract: | The orange juice pasteurization is associated with enzymatic degradation (primarily pectin-methylesterase) of soluble pectin. Time-temperature curves were established to study different pasteurization conditions on enzyme inactivation, for fresh single-strength orange juice from Florida, containing natural PME enzyme. The orange juice was heated in a DeLaval, model P5-VRB plate heat exchanger with heating and cooling sections, and a 0.0101 m3 volume holding tube. The temperature in the heat exchanger was controlled by means of a pneumatic proportional controller. The residence time in the holding tube of the heat exchanger was monitored by adjusting the flow rate of the positive feed pump. The calculated holding times to obtain 90% reduction of enzyme activity ranged from 33.27 s at 80C to 17.85 s at 90C. |
