Abstract
Clear melting points of three kinds of monoglyceride, measured by the Mettler automatic melting point apparatus, Model FP-5/FP-51, under various conditions were compared with those measured by the AOCS method. Measurement of Bomer number, used for judging purity of lard, was comparatively examined by the Mettler method and JAS method.
Results obtained were as follows :
1) The melting point of powdered monoglyceride by the Mettler method showed a higher value when the heating rate was rapid, and showed a good agreement with that measured by the AOCS method when the heating rate was 0.2 and 1°C/min. The dispersion of measured values tended to become greater with faster heating rate, but the values measured by the Mettler method were smaller than those by the AOCS method, σ being lower than 0.3.
2) The melting point of a sample, which had been aged at 50°C for 120h after solidifying rapidly, by the Mettler method was the same as that of the powdered sample, and the dispersion of measured values was smaller. The melting point, obtained from the melting curves by connecting with a recorder, showed a slightly higher value than the temperature indicated by a digital recorder.
3) The clear melting point of glycerides and fatty acids, prepared for the determination of Bomer number, was measured by the Mettler method. The values obtained for glycerides at the heating rate of 1 and 2°C/min were in approximation with the results obtained by the JAS method, but the values for fatty acids were slightly lower than those by the JAS method. However, the Bomer number calculated from these values was in good approximation with those obtained from the JAS method. Consequently, the Mettler method is simple in procedure and has better reproducibility, and is considered to be fully utilizable in practice.
