29C-22 |
Textural properties of vegetable tissues: mechanical resistances distribution |
P. CIBELLI1, D. M. Salvatori1, and S. M. Alzamora2. (1) Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Av. Segurola 3842, piso 2, "D", Ciudad Autónoma de Buenos Aires, Buenos Aires, 1419, Argentina, (2) Departamento de Industrias, Facultad de Ciencias Exactas y Naturales - Universidad de Buenos Aires, Santa Maria 300. Tortuguitas, Buenos Aires, 1667, Argentina The great variability of vegetable tissues often makes difficult the interpretation of texture instrumental values. If a given material, such as vegetable tissue, is subjected to a given stress and deformed until its rupture, the distribution of fracture stresses in the material can be considered to follow a certain distribution function of probability. The Weibull’s statistic has been widely used to explain the mechanical behaviour of a large collection of materials, including those where fracture occurs after a period of deformation. The objective of the present work was to characterize the mechanical response of fresh, blanched and impregnated apple tissue considering that rupture resistance obeys Weibull’s distribution. Compression tests were applied to cylindrical specimens from apple until rupture of tissue. From the force-strain curves, rupture forces (Frup) and deformation to rupture point were obtained. One hundred replicates were performed for fresh apple, as well as for treated apples. Vacuum impregnation (VI) experiments were conducted at room temperature by immersion of samples in an agitated isotonic glucose solution in order to study the effect of VI per se. A vacuum pressure (30 mm Hg) was applied to the system for 10 min and then atmospheric pressure was maintained for 10 min. For blanching, samples were exposed to saturated vapour (1.5 min) and then cooled in water (1.5 min). Weibull´s parameters and probability distribution functions were determined from Frup values obtained for each condition (fresh, blanched and impregnated apples) by means of simulation. The distribution’s mode, mean, variance and coefficient of skewness were calculated. The results showed how the mechanisms of rupture of a specific food material could be explained as a probabilistic process due to the natural variability that exists in the population and how the different treatments affected the resistances distribution’s mode and also its skewness.
Session 29C, Food Engineering: Rheology and texture
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