Abstract:

Seven different molecular weight chitosans were tested for antimicrobial effect against Botrytis cinerea by spread plate method. Along with this, the effect of chitosan coating on hardness and soluble solids, VC and reducing sugar contents of strawberry stored at ambient temperature was investigated. Results showed that of the 7 chitosans, 6 water insoluble ones dissolved in acetic acid exhibited a higher inhibitory effect against B. cinerea, especially medium weight molecular chitosans (7.8×104, 4.8×104), whereas chitooligomer exhibited a poorer inhibitory effect. Exposure to water insoluble chitosans dissolved in acetic acid for 30 d significantly protected strawberry from Botrytis cinerea invasion, inhibited fruit softening and delayed the decreases in contents of reducing sugar and VC, thereby providing a good preservation effect. However, no significant preservation effect of chitooligomer was observed. According to experiments, within the concentration range of 5－10 g/L, chitosans with molecular weight between 5 × 104 and 20 × 104 demonstrated a better preservation effect on strawberry.

Key words: chitosan, molecular weight, strawberry, Botrytis cinerea, coating preservation