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Poster De Conférence Année : 2016

Real time measurements of apple parenchyma thermal softening at different temperatures

Résumé

Thermal softening of fruit and vegetables involves different mechanisms: 1) loss of turgor pressure, characteristic of raw cells, by degradation of membranes; 2) enzymatic and chemical degradation of cell-walls, primarily of pectins. Endogeneous polygalacturonase (PG) is clearly linked to texture loss, while pectinmethylestaerase (PME) may facilitate PG activity but also strengthen tissues by enabling calcium cross-links. Thermal softening of apple was measured in real time at different temperatures. Thin parenchyma stripes were immersed in water at 40°C to 80°C and simultaneously subjected to creep tests during ten or twenty minutes. The apple parenchyma being softer at high temperatures, different levels of stress were applied and then the results were expressed in terms of compliance as a function of time. The main advantages of this experimental device were very rapid temperature increase in the thin slab (about 20 seconds) and continuous data recording. Below 50°C thermal softening was a one-step phenomenon and texture was little affected. At or above 60°C this first step was followed by a second mechanism, which could not have been evidenced with discontinuous experiments. The first step duration was reduced and the second step led to major increase of compliance for the highest temperatures. The order of magnitude of the compliances (0.7 ⋅ 10−6 Pa−1 and 4.3 ⋅ 10−6 Pa−1 respectively for low and high temperatures) and the corresponding characteristic times (respectively 250 s and 120 s) were comparable to the literature. The compliances for both thermal softening steps were modelled with classical three parameter Burger equation and thermal dependencies of the parameters were evaluated. These kinetics data should provide pertinent information for scaling cooking process and the methodology could be applied to other products. Further work is required to link the thermal softening steps to (bio)chemical mechanisms.
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Dates et versions

hal-02738672 , version 1 (02-06-2020)

Identifiants

  • HAL Id : hal-02738672 , version 1
  • PRODINRA : 357609

Citer

Jean Francois Maingonnat, Alain A. Baron, Catherine M.G.C. Renard. Real time measurements of apple parenchyma thermal softening at different temperatures. 2nd Euro-Mediterranean Symposium on Fruit and Vegetable Processing, Apr 2016, Avignon, France. 2016. ⟨hal-02738672⟩
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