Abstract:

The effect of ultrasonic treatment combined with nano-packaging as a novel preservation method for fresh-cut
lettuce was studied by measuring quality, physiological and microbial indexes of the treated lettuce during storage. Results
indicated that nano-packaging treatment was more effective in inhibiting the increase of weight loss rate and maintaining
the contents of chlorophyll, vitamin C and sugar than ultrasonic treatment. However, compared with nano-packaging,
ultrasonic treatment showed a better effect on the inhibition of POD and PPO activities and microbial growth. The best
preservation effect was achieved when nano-packaging was combined with 240 W ultrasonic treatment for 10 min at 20 ℃.
This combinatorial treatment reduced the loss of weight, maintained chlorophyll and sugar contents and controlled bacterial
growth. Moreover, the activities of PPO and POD were repressed, and the senescence and browning were delayed. Sensory
evaluation showed that lettuce treated with ultrasound and nano-packaging still had commercial value after 15 days of
storage at (4 ± 0.5) ℃ and a relative humidity of 85%–95%.

Key words: fresh-cut lettuce, ultrasonic treatment, nano-packaging, physiology, quality