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

Authors: Lorraine H.C. Fisher; Deborah Rees

Addresses: School of Biosciences, University of Kent, Canterbury, Kent, CT2 7NJ, UK ' Natural Resources Institute, University of Greenwich, Medway Campus, Central Avenue, Chatham, Kent, ME4 4TB, UK

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.

Keywords: chlorine; pinking; discolouration; cut-edge; lettuce; modified atmosphere.

DOI: 10.1504/IJPTI.2022.121880

International Journal of Postharvest Technology and Innovation, 2022 Vol.8 No.2/3, pp.184 - 195

Received: 22 Apr 2020
Accepted: 18 May 2021
Published online: 07 Apr 2022 *

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