Cell wall compositional differences between mealy and non-mealy ‘Forelle’ pear during ripening
Elke M. Crouch and Marius Huysamer
Abstracts Book, 6th International Postharvest symposium, 8-12 April 2009, Antalya, Turkey. 256 pages.
2009
บทคัดย่อ
Mealiness of 'Forelle' pear during ripening is a problem for the South African fruit export industry. The aim of this work was to investigate differences in cell wall polysaccharides between mealy and non-mealy 'Forelle' pears. Fruit were harvested at optimum maturity (6.4 kg), cold stored for 3 to 21 weeks at -0.5°C, and ripened at 15°C for 0, 4, 7 and 11days during which samples were taken for cell wall analysis. Only dates where mealiness occurred are reported on. Cell walls (CW) were extracted and de-starched with 90% DMSO and total neutral sugar (NS) and uronic acid (UA) contents measured. Samples were sequentially extracted with water, CDTA, Na2CO3, 1M KOH and 4M KOH to determine differences in binding strength of the cell wall constituents between mealy and non-mealy tissues. Total NS and UA content were measured for each of these fractions; after dialysis. The UA content of the water soluble fraction was lower in mealy tissues after 6 weeks of cold storage plus 11days: of ripening, and 9 weeks of cold storage plus 7 and 11 days of ripening. In the CDTA soluble fraction, UA content was also, lower in mealy tissues of fruit cofd stored for 6 weeks and ripened for 11 days. The total NS content after sequential extraction did not differ for mealy and non-mealy tissues. NS were more easily extracted in the water, 1M KOH and 4M KOH fractions after prolonged storage and ripening. Mealy and non-mealy cell walls of 'Forelle' showed compositional differences. The lower water soluble pectin and CDTA soluble pectin without a substantial increase in the Na2CO3 soluble pectin for mealy tissues; suggests a more broken down cell wall in mealy tissues. The significance of these findings will be further discussed.