Effects of rapid refrigeration and modified atmosphere packaging on litchi (Litchi chinensis Sonn.) fruit quality traits

Litchi (Litchi chinensis Sonn.) is a tropical fruit characterized by a rapid pericarp browning and dehydration during postharvest, resulting in an accelerated shelf life and in a loss of consumer appreciation and consequently of its market value. The aim of our study was to assess litchi fruit chemical-physical and sensory quality changes during postharvest and shelf life using rapid refrigeration (RR) and active modified atmosphere packaging (MAP). Litchi fruits were picked at commercial harvest and were divided in 4 groups: not treated fruit (CTR); rapid refrigerated fruit (RRF); modified atmosphere packed fruit (MAP); hydrogen peroxide treated and modified atmosphere packed fruit (MAP+). CTR and RRF fruit were packed in microperforated plastic bag whereas MAP and MAP+ fruit were packed in unperforated high-density polyethylene package in which a gas mixture (60 kPa N2, 30% CO2 and 10 kPa O2) was flushed and then the bag was hermetically sealed. RRF, fruit were submitted to cooling in order to rapidly reduce their temperature using a blast cabinet which allows to reach 4° C in 15 minutes in three different steps. Finally, all the treated fruit were submitted to cold storage (5°C) for 12 days. Chemical-physical and sensory characteristics were analyzed after 4, 8 and 12 days of cold storage and their shelf life was monitored after 2 and 4 days at 20° C. Generally, the fruit submitted to RRF treatment presents a more intense red color in particular referring to L parameter and the best chemical-physical characteristics. Moreover, RRF fruit revealed having more consistency, juicy flesh, fruity flavour and exotic flavour after 4 days and of fruity odor and exotic odor after 8 days of cold storage. After 12 days, MAP and MAP+ showed a sensory decay. Finally, RRF technique, by rapid refrigeration, permits to prolong fruit color and taste during cold storage and consequent shelf life.