Prediction of optimal process conditions for freezing of ready prepared vegetables using numerical simulation

MARÍA V. SANTOS, ALICIA N. CALIFANO, NOEMI E. ZARITZKY

Santiago de Chile

Congreso; XXV Interamerican Congress of Chemical Engineering; 2011

Interamerican Confederation of Chemical Engineering

Vegetables are a great source of essential nutrients in the human diet and there is a strong demand of these frozen products in the market. Brussels sprout (Brassica oleracea) is a cruciferous vegetable with excellent nutritional properties that contain antioxidant compounds such as carotenoids, flavonoids, cinnamic acids, folic acid, ascorbic acid, tocopherols and tocotrienols. The industrial sector of frozen ready meals requires information about processing times during all the production stages, which include in the case of vegetables, blanching,cooking and freezing.When trying to numerically simulate the different heat transfer processes for producing semi-elaborated frozen vegetables, the systems? geometry is a very important aspect to be considered; the assumption of a regular shape would be an oversimplification leading to erroneous results. Finite element is the appropriate numerical method for solving the heat transfer partial differential equations in irregular domains . The freezing process is a highly non-linear mathematical problem, with severe convergence issues due to the large latent heat release that causes abrupt changes in the thermophysical properties . Therefore modified methodologies in irregular bi or three-dimensional transfer systems have to be implemented when using finite element formulation. The objectives of the present work were:1) To develop a finite element algorithm implemented in a numerical code to simulate heat transfer process during blanching/cooking and freezing of Brussels sprouts, considering the irregular shape of the product.2) To consider the enzyme inactivation and the quality changes during the thermal treatments (blanching/cooking) by coupling the desired kinetic equations (quality, enzyme, microbial lethality) within the main program in order to determine the optimal process conditions.3) To validate the numerical simulations with experimental resultsfor the heating and freezing processes.