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Temperature and Time‐Dependent Relaxation of Compressed Cheese Curd Cubes: Effect on Structuring of Pasta‐Filata Cheese

Bähler, Balz, Nägele, Michaela, Weiss, Jochen, Hinrichs, Jörg
Journal of texture studies 2016 v.47 no.1 pp. 58-67
cheeses, confocal laser scanning microscopy, heat transfer, milk curds, scalding, stress relaxation, temperature, texture
Production of pasta‐filata cheese comprises a particular scalding and stretching step to obtain the unique fibrous structure. A simulation of this process on small scale was conducted with cheese curd cubes of 10 × 10 × 10 mm. Stretching was initiated with a texture analyzer and a custom‐built geometry in a water bath at 60C. Three parameters were varied: compression rate, pretempering time before compression and duration of compression. The force decline during compression was linearized to receive time independent parameters k₁ (y‐axis intercept), k₂ (slope) and stress relaxation (SR). Further, relaxation time (RT) and Deborah number (De) were calculated. The RT decreased from 2 to 0.6 s with a temperature increase from 40 to 60C. The SR after 20 s of compression increased from 10 to 23% with increasing temperature due to network formation as shown by confocal laser scanning microscopy. Anisotropy increased with decreasing De. PRACTICAL APPLICATIONS: When producing pasta‐filata cheese, time and temperature behavior of cheese curd has to be considered during plasticization to obtain the typical fibrous structure. Conclusions for the industry are: (1) plasticization needs time (preheating) as heat transfer in the curd is slow; (2) relaxation of the soft material limits anisotropic structuring; (3) with increasing temperatures relaxation time (RT) decreases, and the process time for stretching can be shortened; and (4) structural changes in the microgel particles during heating induce a continuous protein network with elastic properties which is typical for pasta‐filata cheese production. These results indicate that pasta‐filata cheese with less strings when manually teared, or less anisotropy when visualized by confocal laser scanning microscopy can be modified by adapting the process parameters. Fibrous, anisotropic structure (stringiness) is claimed to be enhanced with increasing residence times and/or higher process temperatures during the stretching process.