Effect of partial pressure infiltration of calcium into 'Kensington' mango fruit.
Shorter A. J., Joyce D. C.
Author Affiliation: CSIRO Plant Industry, 306 Carmody Road, St Lucia, Qld 4067, Australia.
Australian Journal of Experimental Agriculture 38 : 287-294
Abstract : Mango cv. Kensington fruits harvested at the mature-green stage were partial pressure (vacuum) infiltrated with calcium (4 g Ca 2+/litre, as CaCl2) at 3 reduced pressure levels (-33, -66 and -99 kPa). Concentrations of Ca2+ in unripened calcium-treated fruits were about 1-, 2- and 3-fold higher, respectively, than Ca2+ concentrations in the skin and flesh of control (untreated; i.e. not vacuum infiltrated) fruits. For example, skin tissue Ca2+ concentrations of control fruits and of those treated at -33, -66 and -99 kPa were 1.51, 1.93, 3.42 and 5.01 mg Ca2+/g DW, respectively. Concentrations of Ca2+ in the skin of both control fruits and of Ca2+-treated fruits were consistently higher, by about 2-fold, than those in the fruit flesh. Compared with the -33 kPa infiltration treatment, Ca2+ levels in the fruit flesh were increased by only about 2-fold by further reductions in the partial pressure infiltration levels to -66 or -99 kPa. Infiltration of Ca2+ into mango fruits was apparently via lenticels and along xylem conduits open at the cut pedicel. These infiltration pathways were revealed by inclusion of Brilliant Blue dye in the Ca2+ solution. Undyed and dyed lenticels were separately excised for Ca2+ analysis. Dark (dyed) lenticels had higher Ca2+ concentrations (1.86 ± 0.11 mg Ca2+/g) than light (undyed) lenticels (0.83 ± 0.19 mg Ca2+/g). Partial pressure infiltration of Ca2+ at any of the 3 subatmospheric pressure levels did not result in shelf life extension. Fruit infiltrated at -66 and -99 kPa exhibited injuries, which included exacerbated lenticel blackening and anaerobic off-odour and taste evident at the end of shelf life. In comparison, both control (untreated) mango fruit and those infiltrated with Ca2+ at -33 kPa ripened normally.