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Consumer acceptance of tomato products is highly correlated to their organoleptic characteristics and quality parameters such as color and texture. Textural properties of tomato juice can be attributed to the activity of pectinolytic enzymes such as pectinmethylesterase and polygalacturonase. High pressure processing has been proposed as an alternative physical method for intrinsic tomato enzymes inactivation. The objective of this work was to evaluate the quality characteristics of slightly concentrated tomato juice produced under high pressure conditions. Whole tomatoes (var. Red Sea) were pressure-treated at 250, 400, 500 or 600MPa and 50°C for 10min. The processed tomatoes were then crushed, the peels and seeds were removed, and the resulted tomato juice was concentrated to 8.5°Brix. The viscosity, consistency and color of the concentrated juice were measured and compared to the corresponding properties of tomato juice, at the same concentration, produced under the traditional methods of both cold and hot break. High pressure processing did not affect the color of tomato juice at all pressure levels tested, while during hot break color deterioration was always observed. Pressure treatment at 400, 500 and 600MPa led to products of higher viscosity. Increase in applied pressure resulted in an increase in product viscosity and improved consistency. High pressure processing can be used to produce minimally heat processed products with nutritional and sensorial characteristics comparable to that of fresh fruit. It provides a successful alternative to traditional thermal processing leading to products with desirable, or even predesigned, characteristics.

The principles of application of a Shelf Life Decision System (SLDS) for the optimization of the distribution of chilled fresh and minimally processed food products are developed. The SLDS integrates predictive kinetic models of food spoilage, data on initial quality from rapid techniques, and the capacity to continuously monitor temperature history of the food product with Time Temperature Integrators (TTIs) into an effective chill chain management tool that leads to an improved narrow distribution of quality at consumption time, effectively reducing the probability of products consumed past shelf life end. The applicability and effectiveness of the SLDS is demonstrated and evaluated based on actual food spoilage and TTI kinetics and chill chain data employing the Monte Carlo simulation method.

Successful application of a time/temperature integrator (TTI) requires that it has on activation energy similar deterioration reaction of the food or drug it is to monitor. Based on the 3M Monitor Mark, a new tag was designed, the principal of which is a simultaneous diffusion and chemical reaction process. The combined process could be modelled by a response function f(x) = x2 = Kct*. The overall activation energy could be increased (compared to the simple diffusion process) if the activation energy and half life for the chemical reaction are chosen appropriately. An equation was development to estimate the amount of diffusing substance needed. Theoretically, it is feasible to design a new tag that will have essentially the same activation energy as food or drug quality loss.

Time Temperature Integrators (TTI) are simple devices to monitor temperature exposure history and relate it to food shelf life behaviour. Four colorimetric enzyme reaction systems are proposed as the basis for TTI use and results for their kinetic characterisation under isothermal conditions are presented. Nonisothermal experiments have shown that the proposed system response reflected accurately the dynamic nature of the environment temperature. The reliability of the proposed TTI systems was demonstrated by a case study on chilled fish shelf life prediction after storage temperature abuse.