# Aroma Compound Release from Starches of Different Origins: A Physicochemical Study
## 5 Discussion
This conclusion is further supported by the lower \(k_{\rm c}\) values observed in comparison with the other systems being studied. In contrast, the activation energy required for the evaporation of dl-limonene from wheat was determined to be equal to 9.03 kJ mol\({}^{-1}\), which is a lower value in comparison to those observed in the other systems being studied. 4. In all the other systems studied, the activation energies needed for the evaporation of diacetyl from rice-, corn-, and potato-based starch were calculated to be 19 kJ mol\({}^{-1}\), 20 kJ mol\({}^{-1}\), and 26 kJ mol\({}^{-1}\), respectively--values which are in accordance with those reported (with opposite signs) in the literature [56] for the enthalpy of adsorption of ethanol on starchy substrates and which indicate weak energy bonds. The highest value was observed in the case of starch from potato, which contains the bigger amount of proteins compared with the other two starches, while the other two values are almost the same, which could be attributed to their lower contents of protein. Also, the above results can be attributed to the number of chains per branch, which is zero for the potato starch, between 4.7 and 8.7 for the rice, 4.4 for the corn, and between 11.9 and 19.2 for the wheat [57]. 5. The activation energies needed for the evaporation of dl-limonene from rice, corn, and potato were calculated to be equal to 49 kJ mol\({}^{-1}\), 16 kJ mol\({}^{-1}\), and 44 kJ mol\({}^{-1}\), respectively. Since dl-limonene molecules cannot develop any bonds with starch granules, the formation of inclusions between dl-limonene and the substrate is possible and could lead to these differences in \(E_{\rm a}\). Also, these values are on the same order of magnitude with those reported (with opposite signs) for the enthalpy of adsorption of heptane and octane on cellulose [58]. 6. According to the literature [48], the enthalpy of the physicochemical interaction between diacetyl and starch of different origins adheres to the following pattern: wheat > potato > rice > maize. The values of the activation energy needed for the release of diacetyl from the different starches follow the same pattern. 7. On the other hand, for the interaction of dl-limonene with different starches, the following pattern has been proposed: corn > rice > potato > wheat, while for the activation energy required for the release of dl-limonene, the pattern has been found to be as follows: rice > potato > corn > wheat. This difference could be attributed to the size of the dl-limonene molecule and the fact that rice shows the biggest specific surface area (SSA), while all the other starches have a somewhat smaller SSA. 8. The activation energy values were statistically evaluated by one-way ANOVA. Differences between different systems were considered at a significance level of \(P\leq 0.01\) using [PERSON]'s post hoc test for multiple comparisons. From the calculated results of the interactions of diacetyl with different starches, we determined that the activation energy requirements for the diacetyl + corn, diacetyl + potato, and diacetyl + rice systems are not statistically different, while according to the interactions between dl-limonene and the starches, the activation energy requirements for the dl-limonene + rice and dl-limonene + potato systems have no statistical differences. Finally, the amounts of activation energy needed for the release of diacetyl from different starches are statistically different from the corresponding values for the release of dl-limonene from different starches. 9. Because complex algebraic equations were applied for the calculation of the physicochemical parameters, accuracy and uncertainties could not be calculated. However, by using Equation (7), the precision of the mass transfer coefficients and activation energies for all the systems can be determined, while the obtained results show that the RF-GC method appears to have good precision (90\(-\)99%).