[Kinetics of thermal inactivation of peroxidases in turnips and peas]. / Cinética de inactivación térmica de la peroxidasa en nabos y guisantes.

The heat inactivation of peroxidase in green peas and turnips grown in Venezuela was determined experimentally at temperatures ranging from 60 degrees C to 76 degrees C for turnips, and between 72 degrees C and 82 degrees C for green peas. The thermal destruction curves obtained were found to be biphasic, following first-order kinetics of inactivation, and with average times for the change of phase of 22.5 sec and 23.8 sec for the turnips and peas, respectively. The activation energies, as calculated by the Arrhenius equation for the first and second inactivation intervals, were 27.1 kcal/mole and 43.5 kcal/mole for turnips, and 34.5 kcal/mole and 28.9 kcal/mole for green peas.

[Optimization of the freezing process by load]. / Optimización de procesos de congelación pro cargas.

A model was developed for the optimization of batch freezing to maximize the daily production of a plate freezer. An equation for the prediction of the optimal product thickness was found. The model was evaluated experimentally in a one-plate freezer with a food model consisting of a 9% bentonite mixture. The model demonstrated it predicted adequately the freezing times and optimal product thickness. Under the experimental conditions used by the authors, an optimal thickness of 0.0142 m was found, with five batches per day. The maximum daily production was 3.152 kg.

[Effect of the position of the container in the retention of nutrients in food models heated by natural convection]. / Efecto de la posicíon del envase en la retención de nutrientes en modelos alimentarios calentados por convección natural.

The existence of statistically significant differences in the nutrient retention of products heated by natural convection in cylindrical containers of equal size when thermally processed in vertical and horizontal position was studied. The thiamine retention was found to be significantly greater for containers placed in vertical position. A modification to the model proposed by Barreiro (4) for the prediction of nutrient retention during thermal processing of vertically placed canned model systems heated by natural convection was also developed to adapt it to containers processed in a horizontal position. To achieve this goal, an equivalent characteristic length was found for the vertically placed containers, and several changes were introduced. The modified model was then evaluated through ten experiments with different thermal processing parameters. The theoretical thiamine retention values predicted by the model wee compared with the experimental retention. In all cases they were within the 99% confidence interval of the experimental values. This demonstrated that the modified model can accurately predict nutrient retention during thermal processing of products packed in cylindrical containers, and placed in horizontal position.

Optimizacion de processos de congelacion por cargas / Optimization of the freezer processes by loads

Se desarrollo un modelo para la optimizacion del proceso de congelacion con miras a maximizar la produccion diaria de un congelador de platos, proceso que culmino con una ecuacion para predecir el espesor optimo del producto a congelar. El modelo se comprobo experimentalmente en un congelador de un plato, con un modelo alimentario consistente en una mezcla de bentonita al 9%.Se demostro que el modelo desarrollado predice satisfactoriamente los tiempos de congelacion y el espesor optimo del producto. Asimismo, bajo las condiciones en que se llevo a cabo el experimento, se constato un espesor optimo de 0.0142m, con el cual era factible obtner en cinco cargas el dia una produccion diaria maxima de 3152 Kg

[Nutritional optimization of thermal processing of canned food]. / Optimización nutricional del procesamiento térmico de alimentos enlatados.

The model developed by Barreiro, Salas and Herrera (7) for the prediction of nutrient losses during the thermal processing of conduction heated foods was used in this work to optimize the thermal processing, maximizing nutrient retention in processes with equivalent sterilization values. The processes were stimulated in a digital computer (taking pea purée canned in cans 307 x 409 as the product analyzed). Aall of the processes had equivalent sterilization values with respect to Clostridium botulinum. The thiamine retention associated with each process was calculated by the model of Barreiro, Salas and Herrera (7). The maximum fraction of thiamine retained was of 0.688 for a process at 114.2 degrees C (237.5 degrees F) for 95 minutes. Also, the possibility of the existence of a can with optimum dimensions for maximum thiamine retention, with the same sterilization values, was studied. It was found that this optimum, with the same does not exist; on the contrary, the retention was at a minimum when the diameter approaches infinite and the height zero, and viceversa. For this reason, from the nutrient retention point of view, it is better to process the product in flat or slender cans for a given sterilization value.