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Optimized packaging and storage help to maintain quality of fresh ready-to-use salad mixture. However, product keeping quality is also influenced by processing. Especially slicing should be highly optimized because it inevitably damages product tissue. The mechanical properties of a product affect the cutting resistance. Tissue toughness and stiffness are related to cell wall physical and biochemical properties. They are also influenced by tissue water status and temperature, and their interactions. Hence, these parameters also affect cutting.

The aim of this investigation was to characterize the fundamental effects of produce temperature and water status on the cutting force during processing of fresh carrots and radish tubers as model products. This should improve the knowledge about the basics of the processes involved. The results provide the database for reducing tissue damage during cutting procedure thus reducing losses and improving the keeping quality of the products.

Both carrot roots and radish tubers were sliced using a microtome knife adapted to a universal testing machine at a cutting speed of either 700 mm min1 or 600 mm min-1, respectively. In fresh carrots cutting force varied with tissue temperature (in the range from 0 to 40C) reaching highest values at 5C. Forces changed with the cutting position in both carrots and radishes. Force rapidly increased when the knife cuts the outer tissue of the tubers and obtained a more or less constant maximum in the middle section. The force-distance curves could be analyzed using a mechanical model that assumes two specific cutting resistances that were constant for both phloem and xylem (carrot), and periderm and cortex (radish) tissue, respectively. Mean produce water potential and mean produce cutting force were positively correlated in carrots and radish although the coefficients of determination were generally low. The results provide helpful information for optimization of the cutting process.