2.1. Fruit material and chemicals Mature litchi (Litchi chinensisSonn cv Kwaı Mi) fruit were supplied from a CIRAD experimental orchard near Saint-Pierre or from commercial orchards located in the North-East (Saint-Denis) and the East (Sainte-Suzanne) regions of La Reunion island. Five harvests were done between December 2002 and Jan-uary 2003. Fruit were delivered to the laboratory within 1.5 h. Fruit free from physical damage and fungal infec-tion were sorted according to maturity, size and colour of pericarp. Citric acid was purchased from RPS SA (Le Port, La R´ eunion), tartaric acid from Faure SA (S´ erignan, France) and chitosan (type 652) from France Chitine (Orange, France).