The individual and combined effect of ozone and UV-C on mass loss, respiration, texture and colour changes of fresh-cut lettuce

Abstract

The aim of this study was to investigate the effect of UV-C and ozonation as individual and combined treatments on the quality characteristics (mass loss, colour, texture and respiration rate) of fresh-cut lettuce, employing three different UV-C fluences and one O3 concentration that have been reported in the literature to have a positive effect on disinfection of fresh-cut lettuce. Fresh-cut ‘Romaine’ lettuce (Lactuca sativa L. var. longifolia) was exposed to three fluences 0.20, 0.40 and 0.80 kJ/m2 of ultraviolet-C (254 nm) radiation, to gaseous O3 concentration of 5 mg/L for 5 min, and their combination. The produce was stored unpackaged for 5 days at 5.7oC and 91.95%. The applications of O3, UV-C and their combinations (UV-C+O3) gave good results in terms of quality characteristics preservation. Individual or combined treatments prevented mass loss throughout the cold storage compared to control samples. The combined treatment of UVC with O3 achieved more than 25% less mass loss (maximum values) compared to the other tested treatments and control samples. The respiration rate was increased in individual and combined treatments, especially in the UV-C treatment. The UV-C fluence < 0.80 kJ/m2 and O3 concentration 5 mg/L for 5 mins applications achieved improved texture quality in terms of positive peaks (crispness). The crispness of the treated samples was increased by 35% compared to control samples, especially for the UV-C+O3 combination. Limited colour degradation was noted since the UV-C fluence and O3 concentration and dosage were kept below the limits of UV-C fluence < 5 kJ/m2 and O3 concentration < 5 mg/L for which quality degradation has been reported in the literature.