Brix of sample was measured at 20 ±0.5 C using ahand refrac-
tometer (WYT-80,Quanzhou Wander Experime ntal Instrument
Co., Ltd.,China).All the measure ments were performed in triplicate
and the prism of refractometer was washed with distilled water
after each analysis. The pH of apple juice sample was measured
using a digital pH meter (Delta320 pH meter,Mettler Toledo
Instruments (Shanghai)Co.,Ltd.,China).Ten mL of sample was
placed in a beaker and stirred continuo usly with amagnetic stirrer