No abstract

No abstract

Le rapport des mesures d'impédance de la viande à i kHz et 100 kHz s'établit entre 2 et 5 pour de la viande bovine 24 heures après l'abattage, puis subit une baisse au cours de la maturation. Après congélation puis décongélation, la valeur de ce rapport s'établit au voisinage de r. Cette modification, due aux changements apportés par la congélation aux structures du muscle, devrait permettre, en précisant les localisations anatomiques de mesure, d'identifier les viandes ayant subi une congélation.

A testing device specially designed to study rheological properties of meats and their relation to tenderness is described. Samples are submitted to a sinusoǐdal compression during 1 to 2 cycles with recovery delay of 0 to 10 s at frequencies between 0.05 and 25 Hz so that deformation rates thus attained overlapped those of chewing. The compression can be regulated between 10 and 90%, and adjusted to initial sample height from 3 to 30 mm. Sample strength is measured by a force quartz transducer connected to a high speed data acquisition and storage system, versus the deforming tool displacement whose specific law is given.

Flow properties of Fababean protein dopes were studied by capillary extrusion viscometry. The consistency of these dopes was time dependent for pH values between 11 and 13 and it increased slightly with time. At still higher pH values it decreased sharply after 1 h aging. For protein concentration between 11% and 15% (w/w), and pH 11–13.5, these dopes exhibited shear thinning behaviour in the shear rate range 500–20,000 s−1 and they followed the power law τ= cγn. This relationship could be written in the dimensionally homogeneous form: When the protein concentration of the dopes increased the power law index (n) decreased and the consistency index (C) increased. A maximum consistency was reached at pH 12.5 while the power law index was minimum. The results can be explained in terms of protein‐protein interactions and of macromolecule denaturation.