Review of Thawing Time Prediction Models Dependingon Process Conditions and Product Characteristics.

Determining thawing times of frozen foods is a challenging problem as the thermophysical properties of the product change during thawing. A number of calculation models and solutions have been developed. The proposed solutions range from relatively simple analytical equations based on a number of assumptions to a group of empirical approaches that sometimes require complex calculations. In this paper analytical, empirical and graphical models are presented and critically reviewed. The conditions of solution, limitations and possible applications of the models are discussed. The graphical and semi--graphical models are derived from numerical methods. Using the numerical methods is not always possible as running calculations takes time, whereas the specialized software and equipment are not always cheap. For these reasons, the application of analytical-empirical models is more useful for engineering. It is demonstrated that there is no simple, accurate and feasible analytical method for thawing time prediction. Consequently, simplified methods are needed for thawing time estimation of agricultural and food products. The review reveals the need for further improvement of the existing solutions or development of new ones that will enable accurate determination of thawing time within a wide range of practical conditions of heat transfer during processing.

New food technologies and processes and their impact on nutrition.

An evaluation of new technologies already applied or still under investigation has shown that those procedures allow a mild treatment mostly of liquid food materials. If also Osmotic Processing, Ionising Irradiation, Carbon-Dioxide High-Pressure-Gas treatment, Ultra-Sound treatment and Gas-Plasma treatment are considered a large array of new processes is available for processing of food with minimum impact on compounds of nutritional relevance. Those processes must however be operated under very special conditions in order to comply with hygienic standards. Since all this processes require very sophisticated equipment it is too early at the moment to predict which one of the New Technologies will survive the fierce competition with the classic and well established processes and which do not fall under the Novel Food Regulation of the EU. It must be stated however that the pressure which did arise from the New Technologies has initiated many developments in the area of the classical technologies which had at the very end an impact also on the quality of products produced with those procedures.