Use of irradiation in combination with preservation techniques to extend the shelf-life of tropical fruits and their products

Gamma irradiation in combination with other treatment processes was investigated with a view to extending the shelf-life of some tropical fruits in fresh and processed conditions. A low dose of irradiation (0.6 kGy) combined with hot water treatment (at 55 degrees C for 20 min) extended the shelf-life of fresh mangoes from 15 to 32 days at 20 degrees C storage. The shelf-life of fresh lychees was extended to 16 days by irradiation (1 kGy) and storage at 5 degrees C through reducing the rotting and preserving the fruit colour. A shelf-life of up to 30 days was obtained by a combination of hot benomyl dipping of the lychees (at 55 degrees C for 2 min) and polyethylene packaging, whereas modified atmosphere storage in CO2 did not control pericarp browning. Irradiation as a means of preservation was investigated in processed fruits such as semi-dried mangoes and longans, and mango puree. A minimum dose of 2 kGy extended the shelf-life of the semi-dried mangoes and longans for up to 75 days when stored at 14 degrees C, without mould growth, whereas these fruits deteriorated at 30 degrees C storage, as indicated by discoloration and a deterioration in the flavaur. On the other hand, doses of up to 4 kGy and storage at a low temperature (5 degrees C) were necessary to maintain microorganism growth (as determined by the aerobic plate count) at the lowest level; no microorganisms were observed at 6 kGy and higher. The chemical attributes of the puree tended to remain unaffected by the irradiation treatment but were more sensitive to the storage duration and conditions. The puree was preserved for as long as 60 days at 5 degrees C, without compromising the keeping quality.