Pg. 17-22 Evaluation of Modified Atmosphere Packaging Products on Post-harvest Pericarp Browning in Litchi Fruit

In this study, four trials were conducted to test a range of new modified atmosphere (MA) packaging products, with South African litchis. The films included in the first trial were: Loni Life Solutions® (a low density polythene (L.D.P.) permeable film impregnated with natural minerals) Everfresh® (a MA film impregnated with an ethylene inhibitor) and Xtend®(a MA bag system of which two types were evaluated in the present study). In addition to untreated ‘HLH Mauritius’ fruit, the litchis were dipped for one minute in 1ml/l Desogerme®, a quaternary ammonium compound. All the bags reduced pericarp browning and mass loss after 25 days of cold storage at 1°C. The untreated fruit that were stored in the two types of Xtend® bags retained between 60-70% of their original colour and between 1.4-1.9 % in mass. The litchis stored in the Long Life Solutions® bags, retained 70-75% of their original colour and lost 1.3% mass during the storage period. The best results were obtained with the Everfresh® bags where colour retention was found to be between 80-85% . Unfortunately, the Desogerme® treatments exhibited a very high degree of pericarp browning. It was promising to note that no fungal infection was observed on the untreated fruit stored in the Everfresh® and Long Life® bags. The design of the second trial was similar to the first, but in this case, ‘McLean’s Red’ fruit were used. The results obtained in this trial were comparable with those of the first trial. In the third trial, a poly ethylene chlorine dioxide bag from BTC Products and Services (CC) was evaluated with ‘McLean’s Red’ fruit. The pre-cooled fruit were treated with Desogerme® (1ml/l) and combined solutions of Desogerme® (1 ml/I) and 1% calciumpropionate (C₆H₁₀CaO₄) or 1% sorbic acid (C₆H₇O₂K). The dipped fruit were either dried with a fan before packing or packed in a semi-wet state. The anti-fungal properties of the chlorine dioxide bags were not found to be superior to the control. The wet Desogerme® treatments showed promise in terms of fungal infection and colour retention. However, the effect was not enhanced by the addition of calciumpropionate or sorbic acid. In a fourth trial, the different bags were evaluated at 25°C in order to detemine their potential on the local market. Very good results were obtained for the BTC Products and Services (CC) polyethylene and Everfresh ® bags when packed wet after the Desogerme treatment. Both these bags promoted colour retention and inhibited moisture loss during the 7 day storage period.