The effect of pretreatment of ozone and citric acid on quality of fresh-cut lettuce ( Lettuce sativa L.) preserved into modified atmosphere packaging (MAP)

摘要

In this study, the effect of three levels of citric acid (0, 0.5 and 1 g l - 1 ) and three levels of ozonated water (0, 0.6 and 1 ppm) and the interaction of these two treatments on microbial load and qualitative features of fresh - cut iceberg lettuce were studied. After treatment, microbial load and qualitative features of cut lettuce were evaluated in modified atmosphere packaging (5% O 2 + 5% CO 2 + 90% N 2 ) in four different storage times (3, 6, 9 and 12 days). The effects of these treatments were also compared with percidine (concentration 1 ml to 1200 ml in water). After treatment, fresh - cut lettuce pieces were stored at 4 . C with relative humidity 75% for 12 days. The results showed that the total count of microorganisms and the weight loss percentage were increased by increasing the storage time, whereas parameters such as surface color, vitamin C and polypheno l oxidase activity were decreased. In lettuces treated with different concentrations of citric acid, the lowest total count of microorganisms was related to 1 g lˉ1 citric acid concentration and also treatment with 1 ppm ozonated water concentration. In to tal, treatments of citric acid and ozonated water, especially in high concentrations and interaction of these treatments resulted in better preservation of qualitative features and reduced microbial load of fresh - cut lettuces during storage time.