## 3 Results
### DSC Study of Cocoa Butter Extracted from Untroasted and Roasted Cocoa Beans Criollo and Forastero  
Table 3 shows the experimental onset oxidation temperatures (T\({}_{\text{on}}\)) obtained at seven heating rates (2.5, 4, 5, 7.5, 10, 12.5 and 15 \({}^{\circ}\)C/min). As the heating rate increases, the T\({}_{\text{on}}\) increases as well. This can be described by the following linear correlation (Equation (1)):  
\[\text{Log}\ \beta=\text{a}\left(1/\text{T}_{\text{on}}\right)+\text{b} \tag{1}\]  
where \(\beta\) is the heating rate, a and b are adjustable coefficients and T\({}_{\text{on}}\) is the onset oxidation temperature. During slow heating, primary oxidation intermediates are produced such as hydroperoxides which react with an excess of oxygen to form low molecular weight compounds such as aldehydes and acids that remain in solution and accelerate the degradation pro  
Figure 2: DSC melting curves of fats extracted from roasted and unroasted, Criollo (Peru) and Forastero (Ecuador) cocoa beans. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Heating Rate, \(\beta\)/\({}^{\circ}\)C**} & \multicolumn{4}{c}{**Oxidation Onset Temperatures T\({}_{\text{on}}\)/\({}^{\circ}\)C**} \\ \cline{2-5}  & **Forastero Unroasted** & **Forastero Roasted** & **Criollo Unroasted** & **Criollo Roasted** \\ \hline
2.5 & 188.08 \(\pm\) 1.90 & 185.44 \(\pm\) 2.08 & 185.61 \(\pm\) 0.04 & 195.82 \(\pm\) 0.11 \\
4 & 195.35 \(\pm\) 0.93 & 189.85 \(\pm\) 1.70 & 192.38 \(\pm\) 0.01 & 201.53 \(\pm\) 0.49 \\
5 & 196.64 \(\pm\) 0.34 & 194.13 \(\pm\) 1.27 & 195.75 \(\pm\) 0.96 & 205.36 \(\pm\) 0.45 \\
7.5 & 203.35 \(\pm\) 1.61 & 199.32 \(\pm\) 1.63 & 202.92 \(\pm\) 0.40 & 210.46 \(\pm\) 0.84 \\
10 & 208.44 \(\pm\) 1.36 & 203.97 \(\pm\) 2.24 & 207.77 \(\pm\) 0.02 & 217.20 \(\pm\) 0.06 \\
12.5 & 210.88 \(\pm\) 1.08 & 209.11 \(\pm\) 0.25 & 212.88 \(\pm\) 0.53 & 220.05 \(\pm\) 0.03 \\
15 & 213.43 \(\pm\) 0.54 & 210.83 \(\pm\) 0.39 & 213.99 \(\pm\) 0.33 & 222.34 \(\pm\) 0.73 \\ \hline \hline \end{tabular} Values represent means \(\pm\) standard deviations.  
\end{table} 
Table 3: DSC heating rates (\(\beta\)) and oxidation onset temperatures (T\({}_{\text{on}}\)) for cocoa butter extracted from cocoa beans. cess [37, 38]. At fast heating rates, in contrast, these intermediate products are lost through evaporation before they can further react with the melted fat, hence they do not shift distinctly the start of the DSC peak to higher values. The T\({}_{\text{on}}\) values obtained for each fat can be used as a primary parameter to assess the resistance of the tested cocoa butter isolated from two different species to its thermal decomposition. Generally, the higher the onset temperature, the more stable is the fat. The fat obtained from unroasted cocoa beans was more stable in the case of Forastero species than Criollo species as the values of T\({}_{\text{on}}\) for all the heating rates were significantly higher. Unlike the above, the fat from roasted Criollo cocoa beans showed better thermal stability than the corresponding fat from Forastero species. This trend was difficult to capture based on DSC melting curves which look very similar for all analysed fats. The effect of the roasting procedure on the stability of fats within the beans is ambiguous. For Criollo type of beans, the T\({}_{\text{on}}\) values increased after roasting whereas the Forastero beans showed the opposite tendency. In the DSC method which is based on the recording of released heat in non-isothermal mode, the consumption of oxygen can be neglected due to the large excess of oxygen generated by a constant flow rate. Therefore the auto-oxidation is a first-order reaction. This fact can be used to calculate kinetic parameters such as activation energy (E\({}_{\text{a}}\)), pre-exponential factors (Z) and reaction rate constant (k).