破碎时蒸汽热处理对混浊梨汁稳定性的影响

Effect of steam heating during crushing on the stabilization of cloudy pear juice

梨破碎时蒸汽热处理使果浆温度在80 s内达90℃以上,这不但可以改善梨浑汁的色泽,而且增强了果汁的混浊稳定性.果汁的颜色明显受果浆所达到的最高温度的影响.梨浆温度达90℃和95℃虽然Vc损失较多,但果汁的总酚损失较小,有好的色泽稳定性.梨破碎过程中发生的褐变主要为酶促褐变,但热处理温度高于98℃,非酶褐变会变得显著.果汁的混浊稳定性受果汁中悬浮颗粒尺寸、果汁黏度的影响.热处理增加了果胶的聚合度,促进果胶从果浆中释放,从而增加了果汁的黏度.热处理还可减小果汁中悬浮颗粒的尺寸.

The color and cloud stability of cloudy pear juice could be improved when it was made by heating the puree to above 90 ℃ during 80 s. The color of juice was affected by the heating temperature of the puree. Though Vc in the puree was lost more when being heated to 90 ℃or 95℃, the total phenols in the juice were lost less and juices had good color stability. The browning occurring in crushing was mainly enzymatic browning,but non-enzymatic browning would occur when heating temperature was above 98 ℃. The cloud stability was affected mainly by the size of particles in the juice and the viscosity of the juice. The heating treatment of increased temperature could improve the viscosity of juices by releasing more pectin from the puree to juice and avoiding the depolymerizing of the pectin caused by PG, and the size of particles in the juice was also reduced by the heating treatment.