Microscopic investigations of fruit texture.
Hallett, I. C.; Harker, F. R.;
Acta Horticulturae Year: 1998 Issue: No. 464 Pages: 411-416 Ref: 13 ref.
1998
บทคัดย่อ
European pear (cv. Packham's Triumph) and Asian pear (cv. Shinseiki) fruits were harvested at early or late maturity, stored at 0 deg C for 2 months and ripened for 7 days at 20 deg C. Some fruits were sampled within a day of harvest and after 7 days at 20 deg C. Firmness was measured by penetrometer tests, tensile strength was assessed by Low Temperature Scanning Electron Microscopy (LTSEM) and tensile fracture was observed using video microscopy. All techniques gave similar results. Shinseiki fruits exhibited little change in firmness during storage and and the force x distance plot generated from tensile measurements showed a consistent pattern, where force increased steadily as distance increased, followed by a sharp and rapid decreased in force as the tissue fractured (showing characteristic curves of cell breakage as tissue fractures). Packham's Triumph fruits generally showed a similar trend; however, after cold storage, ripening resulted in tissue softening which was accompanied by a cha
nge in the force x distance plot to a rounded peak, indicating a less abrupt tissue failure which was associated with the cells pulling apart rather than breaking. The fracturing of tissues at 4 levels of firmness, as observed by video microscopy, showed different characteristics. Overall, the results showed that when fruits soften during ripening there is a change in the pattern of tissue fracture, from being due to the physical breaking of cells to being due to loss of cell-to-cell bonding. Thus, in Shinseiki fruits, which do not soften significantly, all cells consistently fracture across the equator. In contrast, as Packham's Triumph fruits soften, cell-to-cell debonding is more frequently observed.