Influence of temperature treatment and season on the dilatometric behaviour of butterfat

The melting dilation of butterfat between 10° and 30° C. has been determined from results obtained for the thermal expansion of solid and liquid butterfat. Measurement of the solid fat percentages obtained with different cooling treatments showed that at higher rates of cooling there was an increase in the solid fat content, which is in accordance with the theory of mixed crystal formation. A cooling rate existed beyond which no further increase in solid fat content took place, since butterfat cooled by immersion in a 5° C. water-bath had practically the same solids content as it had when cooled in a 0° C. water-bath. Differences in cooling rate changed the solid fat content mainly in the region of lower melting-point glycerides. Seasonal variations in solid fat content indicated relatively large differences in the content of higher melting glycerides. There is an indication that not only the quantity of solid fat, but also the composition of the crystals is important as a factor influencing the hardness of butter. It was possible to recrystallize mixed crystals in butterfat at 22·5° C. and thereby lower the solid fat content of the butterfat.