Abstract: ‘Nanfeng tangerine 97-1’and‘Nanfeng tangerine 97-2’were used as materials，and ‘Shatangju’with superior mastication was selected as control. The cellulose contents and the activities of exoglucanase（Cl），endoglucanase（Cx）and β-glucosidase that related to cellulose metabolism were measured in the fruit segment membrance and juice sac during the fruit development. The results showed that the segment membrance fiber strength，ductility and tenacity were significantly higher in‘Nanfeng tangerine 97-1’than those in‘Nanfeng tangerine 97-2’，and those in‘Nanfeng tangerine 97-2’were significantly higher than in‘Shatangju’. Sensory evaluation indicated that the mastication trait of ‘Shatangju’，‘Nanfeng tangerine 97-2’and‘Nanfeng tangerine 97-1’was superior，moderate and inferior，respectively. The cell wall ultrastructure of segment membrane displayed that the distribution density of cellulose microfibrils was the highest in‘Nanfeng tangerine 97-1’，followed by‘Nanfeng tangerine 97-2’and‘Shatangju’. The cellulose contents in the three cutivars showed a decline trend during the fruit development. It declined rapidly from the early stage to the medium stage of fruit cell expansion. The cellulose content in‘Nanfeng tangerine 97-1’segment membrance was significantly higher than that in ‘Shatangju’during the fruit development excerpt for early expanding stage. Compared to segment membrance，juice sac had lower cellulose content. Moreover，the cellulose content in‘Nanfeng’tangerine juice sac was lower than that in‘Shatangju’. In addition，the activitives of Cx，C1 and β-glucosidase increased rapidly in the medium-term of fruit cell expanding stage，and were generally higher in‘Nanfeng’tangerine than those in‘Shatangju’at the same fruit development stage. In segment membrance，significant negative correlation was generally or significantly found between Cl and cellulose content，β-glucosidase and cellulose content，and Cx and cellulose content，respectively. In conclusion，the mastication of ‘Nangfeng’tangerine is possibly related to cellulose in segment membrance. Moreover，the critical period of cellulose degradation is from the early stage to the medium stage of fruit cell expansion when the Cx and β-glucosidase play key roles in the process.

Key words: Nanfeng tangerine, mastication, cellulose, cellulose metabolic enzymes