EFFECT OF PARTIAL-PRESSURE INFILTRATION OF CALCIUM INTO KENSINGTON MANGO FRUIT

'Kensington' mango fruit harvested at the mature green stage were part ial pressure (vacuum) infiltrated with calcium (4 g Ca (2+)/L as CaCl2 ) at 3 reduced pressure levels (-33, -66 and -99 kPa). Concentrations of Ca2+ in unripened calcium-treated fruit were about 1-, 2- and 3-fol d higher, respectively, than Ca2+ concentrations in the skin and flesh of control (untreated; i.e, not vacuum infiltrated) fruit. For exampl e, skin tissue Ca2+ concentrations of control fruit and of those treat ed at -33, -66 and -99 kPa were 1.51, 1.93, 3.42 and 5.01 mg Ca2+/g dr y weight, respectively. Concentrations of Ca2+ in the skin of both con trol fruit and of Ca2+-treated fruit were consistently higher, by abou t 2-fold, than those in the fruit flesh. Compared with the -33 kPa inf iltration treatment, Ca2+ levels in the fruit flesh were increased by only about 2-fold by further reductions in the partial pressure infilt ration levels to -66 or -99 kPa. Infiltration of Ca2+ into mango fruit was apparently via lenticels and along xylem conduits open at the cut pedicel. These infiltration pathways were revealed by inclusion of Br illiant 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 dry weight) than light ( undyed) lenticels (0.83 +/- 0.19 mg Ca2+/g dry weight). Partial pressu re 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 blacke ning and anaerobic off-odour and taste evident at the end of shelf lif e. In comparison, both control (untreated) mango fruit and those infil trated with Ca2+ at -33 kPa ripened normally.