Avrami Parameters
Table 4 shows the parameters obtained with the Avrami model for the different oleogels (R2>0.9). It was found that all the systems present a linear growth (1-2) according to the values of n , with a one-dimensional growth geometry (Toro-Vázquez et al., 2000). A non-integer value indicates the formation of irregularly shaped crystals. This aforementioned growth is characteristic of fibrillar-type structures found in monoglyceride systems. Fractional values have already been explained in other investigations where they are attributed to the formation of structures from different types of nuclei (heterogeneous nucleation) (García-Andrade et al., 2020). It was found that values of ngreater than 1 correspond to systems with lower MY concentration (Table 4). This can be understood by taking into consideration what was observed in Table 3, where oleogels with lower MY content showed longer nucleation times and consequently slower growth or branching times (z). A slower growth rate allows an almost two-dimensional growth due to a greater distance between the already formed nuclei and the freedom they present in the transfer of energy and interaction to form such structures. The concentration of structuring agents is a determining factor for the growth rate in oleogel systems.
Figure 5 shows the time evolution of the crystalline mass (F × 100), for different MY concentrations in CA and CN oleogels. The curves followed the same general sigmoidal trend of behavior, with a time difference of ≈4min, the crystallization rate increased beyond the TCSvalue until reaching zero crystallization rate at F × 100 = 100. The times where the increase from the baseline is presented corresponded to the TCS values shown in Table 2. The times obtained by DSC (tSC~TSC) (CAMGC=14.52min, CASAT=10.31min, CNMGC=14.24min and CNSAT=10.07min) were similar to those obtained by spectrophotometry (tn) and also to that reported in rheological analyses of the cooling process (Palla et al., 2019). However in the spectrophotometry graph (Fig. 4) it can be observed that there is an increase in absorbance during the 60min, while in by DSC (Fig. 5) a maximum of crystallization is reached in less time. This is due to two situations, the first is that in the spectrophotometry kinetics when reaching the ambient temperature (≈20°C), the programming was set so that the temperature remained constant due to the limitations of the equipment. This execution, together with the temperature differential generated between the spectrophotometer chamber and the recirculating water bath, resulted in a slower (almost isothermal) crystallization in the final stage of the experiment. In the DSC evaluation, it was possible to reach 0°C by maintaining a constant cooling rate and a fixed TSTOP for each exotherm. It should also be noted that very low regression coefficients (R2˂0.70) were obtained in obtaining the values of z and n by DSC. These R2 values are low compared to those obtained by Toro-Vázquez et al. (2000),. However, it should be noted that the analysis developed by them was under isothermal conditions (Toro-Vázquez et al., 2000), while in this work, non-isothermal conditions were used, which results in obtaining less symmetrical exotherms and an irregular distribution of the crystalline fraction. However, the values of the initial temperature versus nucleation temperature allow us to detect a range of temperatures where there is an initial crystallization process (nucleation) that could be omitted by conventional DSC. Therefore, nucleation kinetics from spectrophotometry is a good alternative to study the initial stage of microstructuring in OGs, which by DSC is not persived.