Document Type

Theses, Ph.D


Available under a Creative Commons Attribution Non-Commercial Share Alike 4.0 International Licence


The market of ready-to-fresh vegetables has grown rapidly in recent decades as a result of changes in consumer attitudes. Chlorine solutions are widely used to sanitise fresh-cut fruit and vegetables in the industry. However, the possible formation of carcinogenic chlorinated compounds in water has called into questions the use of chlorine in food processing plants. There is a real need to find new alternatives fro the preservation of minimal processed vegetables in order to maintain their quality attributes after processing. The aim of this study was to examine the influence of novel preservation methods on the quality of minimally process Iceberg lettuce and carrot. The results showed some suitable alternatives to chlorine. Calcium lactate in combination with heat-shock (1.5% calcium lactate at 50°C for 1 min) resulted in one of the best alternatives tested, retarding browning appearance and keeping textural properties longer with no quality impairment due to the treatment. Exposure to steam (5 to 10 s) helped to reduce textural and colour changes of Iceberg lettuce during storage, but with the negative effect of reducing antioxidant capacity. Whey permeat (0.5 to 3.0%) reduced polyphenol oxidase (PPO) and peroxidise (POD) activity, enzymes involved in enzymatic browning; however, the antioxidant capacity of the samples was also reduced, but to a lesser degree than with steam. Ozone (1 ppm) was effective in reducing enzymatic activity, but negatively affected the textural quality, probably doe to its high oxidising potential. Neutral electrolysed water (12 to 120 ppm free chlorine) retarded browning appearance in Iceberg lettuce by reducing enzymatic activity of PPO and POD, but the high oxidising power of this treatment affected the quality, causing loss of turgor. Further research, e.g. based on the hurdle concept of combining some of these methods, might find new alternatives to minimise possible quality deterioration caused by the treatments.