Thermal Values for Fats: DSC Analysis or Dropping Point Determination - METTLER TOLEDO

Thermal Values for Fats: DSC Analysis or Dropping Point Determination

Many of the pure starting materials used in the pharmaceutical industry and in food technology can be routinely analyzed and characterized with the help of melting point determination. The situation is quite different, however, for edible oils, fats, and waxes.

 

 

 

 

 

Thermal values

The variable composition and different crystal modifications of such products mean that they cannot effectively be characterized by one single thermal value, e.g. the melting point. Nevertheless, at least for comparison purposes, a number of different procedures have been developed to obtain thermal values that can be easily measured in routine analysis, e.g. softening points, dropping points, slip melting points, melting point according to Wiley and Ubbelohde, etc.

 

DSC

In contrast, DSC analysis, which measures the heat absorbed when the temperature of a sample is raised at a linear rate, offers many more possibilities. The result is now no longer a single temperature value, but a complete measurement curve that records all the thermal effects occurring in the temperature range investigated. This technique allows a much more detailed comparison and characterization of oils, fats and waxes to be made. But can we convert the data from such complex measurement curves into the numerical values that in the end are required for comparative assessments and as characteristic values? One method often used is to measure the area between the measurement curve and the instrument baseline at discrete temperature intervals. These areas are then calculated as percentages of the total area under the melting curve and the results presented in tabular form. In the literature, the values obtained by this method are referred to as the liquid fraction, LF, or the complementary term solid fat index.

Comparison DSC - Thermal Values

Can the results from different methods be correlated in order to obtain a uniform set of results from various different sources? In principle, no, because in fact very different properties are measured. In the slip melting point and dropping point methods, the temperature-dependent viscosity of the sample plays an important role in addition to the actual physical melting. In comparison, DSC measures only the heat required to melt the crystallites. The following table compares the results obtained from the analysis of five different samples with both techniques. The dropping point temperatures were measured with a METTLER TOLEDO FP900 system and FP83HT measuring cell. The DSC results were obtained using a METTLER TOLEDO DSC821e equipped with an IntraCooler accessory and shows the temperatures at which 95% of each sample (as measured by the surface area under the curve) melted.

 

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Keywords
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 edible fats and oils, dropping point, FP83HT
 

Thermal values of fats: DSC analysis or dropping point determination? | Thermal Analysis Application No. UC 113 | Application published in METTLER TOLEDO Thermal Analysis UserCom 11 

Edible Oils and Fats Analysis