Prediction of pH Change in Processed Acidified Turnips

The acetic acid uptake by turnips was studied during an acidification process in containers. The process was successfully described by a Fickian diffusion, using a correlation for the buffer effect. Diffusion coefficients (0.629 to 3.99 × 10-9 m2/sec) and partition coefficients (0.8 to 1.1) were obtained by optimization of the fit between experimental and theoretical values, using the simplex method. The partition coefficient did not show an evident dependence on temperature, while diffusivity followed an Arrhenius type behavior. The relationship between acid concentration and pH was described using a cubic model with parameters independent of temperature. Results showed that the combination of these models describing the acid diffusion into the food and the buffering effects of the food allowed accurate prediction of pH evolution in the acidification process

Processamento e conservação de manga por métodos combinados Mango processing and conservation by combined methods

A tecnologia de métodos combinados foi empregada na conservação da manga (Mangifera indica, L.) em pedaços. A estabilidade físico-química, microbiológica e sensorial da manga em pedaços foi obtida através do branqueamento com vapor saturado por 2 min, ajuste da atividade de água (Aw) para 0,97, do pH para 3,6, adição de 600 ppm de ácido ascórbico, 1000 ppm de benzoato de sódio e 600 ou 900 ppm de dióxido de enxofre. Os produtos da manga processados nas condições descritas apresentaram, ao longo de 120 dias de armazenamento, teores de umidade, atividades de água e pH na faixa para produtos de fruta de alta umidade; aumento dos açúcares redutores; acentuada perda de SO2 (cerca de 60%) e vitamina C; redução da contagem microbiológica, demonstrando que a seleção de obstáculos e suas intensidades foram capazes de assegurar a estabilidade microbiológica do produto. O teste de aceitabilidade mostrou que a manga conservada por métodos combinados teve boa aceitação e que as médias dos atributos se assemelham aos resultados de testes sensoriais mencionados na literatura.<br>The technology of combined methods was used in the conservation of mango (Mangifera indica, L.) pieces. The phisical-chemical, microbiological and sensorial stability of mango pieces was achieved through blanching using saturated vapor for 2 minutes, ajusting water activity (Aw) to 0.97, pH to 3.6, addition of 600 ppm of ascorbic acid, 1000 ppm of sodium benzoate and 600 to 900 ppm of sulfite dioxide. The mango products processed, under these conditions, presented at 120 days storage moisture content, water activity and pH in the range for fruit products with high moisture; increasing in reduced sugars; high loss of SO2 (about 60%) and of vitamin C; decreased microbiological counting showing that the obstacles seletion and their intensities were capable to assure the microbiological stability of the product. The test of acceptability showed that the mango preserved by combined methods had good acceptability and that the averages of the attributes are similar to the results of sensory tests mentioned in the literature