In-line measurement of tempered cocoa butter and chocolate by means of near-infrared spectroscopy

In the present work cocoa butter and chocolate were precrystallized by mean s of a newly developed shear crystallizer. The shear crystallizer was integ rated into a circular loop. The handling of precrystallized cocoa butter sh owed a high dependency on the timing of applied analysis. Differential scan ning calorimetry, calorimetry, rheometry, and in-line near-infrared (NIR) w ere all directly influenced by the fat crystal structure. Nevertheless, for cocoa butter it was shown that mechanical energy input (rpm) had a signifi cant influence on viscosity, melting enthalpy, and slope at the second poin t of inflection of a temper curve. Experiments with cocoa butter at constan t exit temperature showed a linear increase of viscosity between 0.1 and 0. 8 Pa.s in the range of 300 to 1300 rpm. Melting enthalpy increased in the s ame rpm interval from 0.02 to 2.5 J/g. Solidification time (from 4.5 to 0.5 min) and slope (from 0.82 to 0.15, second point of inflection of temper cu rve) consequently decreased (both with exponential approximation). For coco a butter, slope and solidification time correlated linearly whereas solidif ication time and viscosity followed a power law fit. This proved that defin ed relationships exist between rheological data and data from temper curve measurements. Viscosity was linearly dependent on crystal content. By means of NIR spectroscopy good correlation models for cocoa butter viscosity, en thalpy (crystal content), and slope values were found. For precrystallized chocolate, analytical values such as viscosity and slope values were detect ed off-line and used for calibration of NIR spectroscopy.