Thermal Characterization of Cocoa Butter

Samples

Three different lots of cocoa butter obtained from Swiss chocolate manufacturers

Conditions (a)

Measuring cell: DSC20 (placed in a deep freezer at -20 °C)

Pan: Aluminum standard 40 µl, hermetically sealed

Sample preparation: The samples are melted at 60 °C in 20 ml beakers for homogenization. Approximately 10 mg of each are weighed in

DSC measurement: Cooling from 60 °C to -10 °C at 1 K/min

Interpretation

The shape of the DSC curves indicates a two step crystallization process with reproducible onsets of 21.2 °C, 22.2 °C and 23.6 °C for the butter samples 1, 2 and 3 respectively. When the crystals formed are heated in the DSC, the peak temperatures are in the region around 23 °C, which indicates the presence of metastable products. It is known that crystallization of a few milligrams requires lower temperatures than gram or kilogram quantities. In other words, the supercooling is greater with small samples. Therefore the use of small samples (crystallizing at a very low temperature) gives rise to extremely metastable products.

Evaluation

In this case only the onset temperature of crystallization is evaluated.

Lot             Sample weight, mg         Onset, °C                 

1                            10.82                          21.2

2                            10.32                          22.2

3                            10.87                          23.6

Conditions (b,c)

Sample preparation: To overcome the problems of severe unrealistic supercooling, the course of crystallization is studied using approximately 10 g each of melted cocoa butter in glass beakers. After complete fusion at 60 °C the beakers are kept at room temperature for crystallization and samples are taken (10.5 ±0.5) during the first 3 days of recrystallization.

DSC measurements: Heating from 0 °C to 45 °C at 1 K/min

Interpretation

The DSC melting curves show the course of crystal formation in samples of lot 3 in comparison with the unheated original product. The integral above 28 °C represents the fractional amount of the stable modification. Both the heat of fusion and the peak temperature increase towards the values of the unmelted original sample.

Evaluation

_{Thermal Characterization of Cocoa Butter | Thermal Analysis Application No. HB 1017 | Application published in METTLER TOLEDO TA Application Handbook Food}