Pg. 37-41 Research on Alternative Postharvest Treatments for Litchi Fruit

A study was conducted to evaluate a range of potentially effective postharvest treatments for HLH Mauritius and McLean’s Red litchis. In the search for an effective dye to improve the colour of export fruit, a water based dye used in food and cosmetics was evaluated. However, the dye was found to be ineffective on unsulphured fruit as browning of the peel still took place during storage. In sulphured fruit it was difficult to attain·sufficient dye absorption into the peel. The fruit were therefore first steam treated and this increased the absorption to an acceptable level after 1.5-2 hours of soaking in the dye solution. Prior bleaching of the litchi peel with hydrogen peroxide resulted in deterioration of the aril and a higher degree of mass loss. In addition to the above treatments, two antioxidants (electrochemically activated
water and methyl jasmonate) and two experimental litchi coating formulas (Agricoat formulas 2 & 3) were evaluated. Both antioxidants were found to be ineffective while the two coating formulas retarded pericarp browning to an extent,
especially when acidified with citric acid to pH 3. Further developmental research is, however, required with these coatings. The third set of experiments involved the use of controlled atmosphere (CA) storage of HLH Mauritius and McLean’s Red. With HLH Mauritius, the experiment entailed the use of six CA atmospheres in combination with five sulphur fumigation regimes. Only the most promising atmosphere and standard fumigation treatment was used in the McLean’s Red trial. In the HLH Mauritius trial it was found that sulphuring at levels that are lower than the commercial
standard can retard fungal growth effectively when stored under CA. However, the effect was negated during the ensuing shelf-life phase and the S0₂ residues were found to be considerably higher than those of the controls. In the
McLean’s Red trial, the results attained with CA were quite promising in that the fungal infection was significantly reduced, while the proportional increase in sulphur residues was less pronounced than in HLH Mauritius.