MELTING AND SOLIDIFICATION CHARACTERISTICS OF SWISS RACLETTE CHEESE MEASURED BY SMALL AMPLITUDE OSCILLATORY SHEAR MEASUREMENTS

Three successive seasonal products of Swiss Raclette cheese were characterized and compared to each other using small amplitude oscillatory shear experiment (SAOS). Melting and solidification transitions were observed during a “time-sweep” experiment from 20 to 80C and back to 20C in 60 min. The G′-G″(transition temperature) crossover was considered a good indicator of the Raclette cheese melting quality. Typical values were also established for elastic (or storage) modulus (G′), viscous (or loss) modulus (G″), loss tangent (tan δ) and the complex viscosity at predetermined temperatures, to distinguish between good or poor melting quality. Significant differences were found between the three series of cheese for water and nitrogen content, sensory testing, G′ and G″ at 20 and 80C. Highly significant correlations were found between the SAOS method and the softening and dropping point method as well as with the sensory evaluation and the compositional analysis. The main advantage of this method was that in addition to the melting process of Raclette cheese, the solidification process was readily accessible. PRACTICAL APPLICATIONS Every year, cheese producers of Swiss Raclette participate in a quality testing program in Switzerland organized by Agroscope Liebefeld-Posieux. Meltability and sensory criteria are, among others, important functional properties of Raclette cheese. Basic knowledge on fabrication and/or new trends of Swiss Raclette cheese can so be followed up. For many years, the softening (EP) and dropping point (TP) method was adopted together with sensory testing. A new method for the melting and solidification transitions of Raclette cheese from three successive seasonal productions (summer production 2003 and summer and winter production 2004) were tested using a rotation and oscillation rheometer. By comparing sensory evaluation of the Raclette cheese to the dynamic oscillatory method, a list of typical rheological values was established that may serve as guideline to differentiate between good and poor melting qualities of Raclette cheese. The main advantage of this new method is that in addition to the meltability of Raclette cheese, the solidification process is readily accessible.