The effect of temperature (110, 120 and 130°C), rotation speed (5, 10 and 15 r.p.m.) and headspace (4, 8 and 12 mm) on heat transfer coefficients to canned green peas during end-over-end sterilisation was studied using response surface methodology. The models developed for fluid-to-particle heat transfer coefficient, h fp , and overall heat transfer coefficient, U, were adequate, showing no significant lack of fit and satisfactory correlation coefficients. For the two responses, temperature, rotation speed and headspace have a significant effect. U, ranged between 477 and 905 W m )2°C)1 , while h fp , fluctuated between 480 and 1950 W m )2°C)1 . The highest h fp and U values are obtained at high temperatures, rotation speeds and headspaces. The verification of the prediction models was satisfactory. Dimensionless correlations were developed for h fp and U, with equations showing a good agreement with the experimental data. Heat transfer to liquids and particles was modelled using the Reynolds number, the Prandtl number and adimensional headspace.

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Changes of ascorbic acid (AA) during canned fresh green peas sterilisation in a rotary retort were predicted. It was considered that AA is thermally degraded in green peas and simultaneously diffuses to brine, where it is also degraded; heat transfer, mass transfer and kinetics equations were simultaneously solved during heating and cooling of the sterilisation process. Kinetic parameters of AA thermal degradation in brine were experimentally determined, while all other parameters needed were taken from bibliography. Simplified assumptions were made to explore diffusion and thermal degradation mechanisms relevance. Experimental runs were performed at different retort temperatures, end-over-end rotation speeds and headspaces in a pilot plant rotary retort; experimental data obtained on concentrations of AA in green peas and in brine were used to evaluate predictions goodness. Deviations between experimental and predicted results were 8.44% for AA in green peas and 13.79% in brine.