The temperature dependency of the solid‐fat content of a fat is important for predicting the consistency of the final product and for process control. Two direct analytical methods for determining the solid‐fat content and the melting characteristics of milk‐fat fractions have been developed. The fractions are analyzed during crystallization, and the results give reproducible information about the thermal behavior of the fractions and the actual crystal amount in the suspensions. The results are obtained within minutes, and no separation of the fractions before the measurement is necessary. New ways of reducing process time are proposed. It is possible to adapt crystallization time to seasonal variations of the initial milk fat and to the required properties of the final product. Partially crystallized milk fat was directly measured in a calorimeter and a pulsed nuclear magnetic resonance spectrometer. The data showed good correlations and even more accurate results than the conventional methods. The calorimetric method makes it possible to detect polymorphic changes and co‐crystallization in the crystals so that the influence of processing parameters, such as energy input, on crystallization behavior can be investigated.

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Dry fractionation of milk fat is a common technique used to produce fat fractions with physical properties that are suitable for a variety of food and pharmaceutical products. During milk fat fractionation, the partial crystallization of triacylglycerols from the melt is the most important step. The efficiency of the separation of the crystals from the suspension is also important, but the crystallization itself influences the chemical composition and thereby determines the properties of the crystal fraction. At low supercooling, the crystallization kinetics are slow, and thus process time is increased. With increased kinetics due to a strong supersaturation, the chemical composition of the crystals is changed compared to crystals formed under slow kinetic conditions. This study shows to what extent controlled temperature and supercooling during milk fat crystallization influence crystal amount and the physical properties of the resulting fractions. Differences of the thermal characteristics of the crystal suspensions are directly detected by differential scanning calorimetry and nuclear magnetic resonance. At slow crystallization kinetics, the melting temperature range of the crystals in the suspensions is broader, and the resolution of the melting peak is higher. It is shown that compound crystals are formed when supercooling is performed, even if the supercooling takes place only for a short period of time. Controlled temperature conditions during crystallization govern larger differences in the fatty acid and triacylglycerol composition of the liquid and of the crystalline phases, compared to fractions crystallized under supercooling conditions, which contain a high amount of compound crystals. JAOCS 75, 897-904 (1998).