The effect of wash water chlorine content on the pinking discolouration of fresh cut Iceberg lettuce

Abstract

Processed Iceberg lettuce incurs high losses of up to 47% due to cut-edge pinking, despite modified atmosphere packaging (MAP) with nitrogen flushing to achieve low oxygen (<0.2%). Breeding for reduced pinking response is costly and not a short-term solution. Treatments including inhibitor additives and heat shock are not cost effective, whereas chlorine, already used as a sanitiser, has been proposed to reduce pinking. This study examined effects of applying chlorine to wash water at ≈1 mg L-1, 50 mg L-1, 100 mg L-1 and 200 mg L-1 total chlorine. Lettuce packaged in air exhibited a U-shaped response to chlorine, with minimum pinking score close to 100 mg L-1 chlorine. For cut lettuce stored under atmospheres to simulate MAP with nitrogen flushing to achieve different initial oxygen concentrations, 3% initial oxygen eliminated pinking, while with 6% lowest pinking scores were for lettuce washed at the highest chlorine concentration of 200 mg L-1.