RHEOLOGICAL BEHAVIOUR OF POTATO TISSUE AS AFFECTED BY CALCIUM IMPREGNATION AT HIGH TEMPERATURE

MARÍA M. INDACO; VANESA Y. MARTÍNEZ; DANIELA M. SALVATORI; STELLA M. ALZAMORA

Río de Janeiro, Brasil

Congreso; 4rd MERCOSUR Congress on Process Systems Engineering, 2st MERCOSUR Congress on Chemical Engineering (ENPROMER 2005); 2005

UFRJ, IME, UERJ, etc. (Brasil), UNS (Argentina) y SCMC (Chile)

The objective of this work was to determine the effect of calcium impregnation at high temperatures on the viscoelastic properties of potato slices using oscillatory shear and creep tests. Impregnation at high temperature was conducted at atmospheric pressure under conditions of internal mass transport control by immersing potato slices in agitated isotonic calcium solutions (5.88 % w/w calcium gluconate and lactate salts). Experiments were carried out at 50°C , 65°C and at 80°C for different times. After treatments, potato cylinders (0.5 cm thick) were loaded between parallel plates (3 cm in diameter) of a Paar Physica CR 300 rheometer (USA). Storage (G´) and loss (G´´) moduli were obtained through the frequency sweep test (0.1-100 1/s), using an amplitude of 0.05 % (within the linear viscoelastic range). For creep test, samples were subjected to a constant shear of 30 Pa during 60 s. A generalized Kelvin model with four elements was found to satisfactorily describe the creep compliance behavior (correlation coefficients > 0.99). Mechanical behavior analysis of potato tissue subjected to heat treatments revealed that, when calcium was present in the solution, G’ values and creep parameters were more similar to those of raw tissue when compared to samples heated only in water. These results would make possible improvements in quality of calcium impregnated potatoes.