Impact of different washing procedures on quality of fresh-cut iceberg lettuce (Lactuca sativa var. capitata L.) and endive (Cichorium endivia L.)

The objective of this study was to determine the effects of alternative washing procedures on fresh-cut iceberg lettuce and endive, applying warm water (45 A degrees C), warm water with CaCl2 (1 g/L), and chlorinated water (4 A degrees C, 120 ppm), respectively. Processing was conducted on pre-industrial scale, and the produce was subsequently stored in consumer-sized bags (4 A degrees C, 10 days). O-2 and CO2 levels in the modified atmosphere, and activities of phenylalanine ammonia-lyase (PAL), peroxidase (POD) and polyphenoloxidase (PPO) of the samples were analyzed. Counts of total aerobic bacteria and pseudomonades were determined on the produce and in the process water. In both commodities, wound-induced PAL activities were significantly reduced by warm water treatment. In iceberg lettuce, adding CaCl2 to warm water resulted in a further reduction of PAL activities. Chlorinated water was less effective than warm water in suppressing wound-induced PAL activity in endive, but proved to be most effective in reducing total microbial cell counts by 1.1 and 2.1 log(10) cfu/g in iceberg lettuce and endive, respectively. Warm water treatment exhibited reduction rates of similar magnitudes. For process water, chlorine proved to be the most efficient sanitizer. PPO and POD activities were only marginally affected by the different washing procedures. As indicated by respiration of the fresh-cut produce, warm water treatments applied retained the vitality of both plant species. The results suggest that warm water treatments are suitable measures to improve the quality of iceberg lettuce and endive, but were less efficient in sanitizing the process water.