Cell wall properties of kiwifruit affected by low temperature breakdown

Low temperature breakdown (LTB) is a physiological disorder that can affect kiwifruit (Actinidia deliciosa cv Hayward) and some selections of Actinidi a chinensis fruit after several months of cold storage. One of its symptoms manifests as the 'grainy' appearance of the outer pericarp, followed by wa ter-soaking associated with extreme softening of the fruit. Observation by light microscopy and SEM suggested that the 'grainy' appearance of LTB-affe cted kiwifruit was associated with the presence of gas bubbles, occurring i n some cells. Bulk porosity of the cell wall, determined using polyethylene glycol (PEG) of different molecular mass, decreased with increasing severi ty of the symptoms. Cell wall analysis revealed that the amount of cell wal l material (CWM) was 30% higher in 'grainy' tissue than in unaffected tissu e, and that galactosyl content in the CWM of outer pericarp tissue was 70% higher in affected compared to unaffected tissue. The same trends in LTB-af fected tissue were observed in two selections of Actinidia chinensis. Since tissues were excised from fruit of the same firmness, differences reported here are related to the development of LTB. (C) 1999 Elsevier Science B.V. All rights reserved.