To evaluate the molecular dynamics and the molecular regions presented in the cinnamon types it was chosen to evaluate them without any treatment, and for that it was used low-field nuclear magnetic resonance (NMR) through the pulse sequence such as MSE-FID, an NMR sequence in the time domain, and from the longitudinal relaxation time (with a time constant T1), employing the inversion-recovery pulse sequence. The low-field NMR results indicate that the techniques chosen were a very good alternative to evaluate these types of samples food and their structural organization according to their constituents. The molecular mobility is different.
To analyze the substances or materials in the solid state some techniques can be used, one of them is NMR spectroscopy, since this technique permits us to evaluate the sample without any treatment [
The time-domain NMR technique (TD-NMR) was used to analyze the cinnamon types to obtain information on the molecular structure/organization and properties of the material, as well as the molecular dynamic that may infer about crystalline and amorphous domain [
In this work, three types of cinnamon were bayed from the market and were analyzed as was received.
The solid samples were analyzed employing the time domain nuclear magnetic resonance (TD-NMR) pulse sequence, in order to determine the nuclear relaxation data. Maran Ultra 23 equipment was used, operating at a frequency of 23 MHz (for the hydrogen nucleus) and equipped with an 18 mm probe, the analyses were carried out at temperature of approximately 30˚C.
The Magic Sandwich Echo pulse sequence (MSE-FID) was used to measure the transverse relaxation time ( T 2 * H ), which is sensitive to the segmental dynamics of the sample constituents. For the acquisition of each decay signal, 140 points spaced by 2 μs through 64 scans with a waiting time of 5 s were used.
The Inversion-Recovery pulse sequence was used to determine the longitudinal relaxation times of hydrogen nuclei (with a time constant—T1H) in diffusion domains of approximately 20 nm. A logarithmic list with 40 values was used, recovery times between 0.1 and 5000 ms, with a recycle time of 5 s between each value. From the relaxation curve obtained, an Inverse Laplace Transform was performed to obtain the distribution curves of relaxation domains for each sample with the aid of the WinDXP® software (1.8.1).
To study the molecular dynamic of the materials to understand the differences among them, we used pulse sequences MSE-FID (Magic-sandwich echo—Free induction decay) a sequence of nuclear magnetic resonance in the time domain.
Cinnamon samples showed 4 to 5 domains of longitudinal relaxation (T1H), as can be observed in
| Amostra | T1,1/% | T1,2/% | T1,3/% | T1,4/% | T1,5/% |
|---|---|---|---|---|---|
| Cinnamon 1 | 1.7 ms/15 | 6 ms/14 | 43 ms/63 | 944 ms/8 | ------ |
| Cinnamon 2 | 1.5 ms/23 | 17 ms/55 | 102 ms/6 | 992 ms/6 | ------ |
| Cinnamon 3 | 0.8 ms/19 | 3 ms/13 | 18 ms/64 | 186 ms/3 | 1420 ms/1 |
| Amostra | FR/% | FSR/% | FM/% | 2> |
|---|---|---|---|---|
| Cinnamon 1 | 20 μs/50 | 163 μs/24 | 254 μs/26 | 4450 rad·ms−1 |
| Cinnamon 2 | 19 μs/50 | 180 μs/27 | 245 μs/23 | 4360 rad·ms−1 |
| Cinnamon 3 | 19 μs/64 | 200 μs/21 | 348 μs/15 | 3790 rad·ms−1 |
Measurements by MSE-FID identified 3 distinct molecular mobility regions of transverse relaxation (
According to the results illustrated from
its molecular organization and the intra and intermolecular interactions. Cinnamon 2, in turn, presents the highest percentage for the T1,4 domain (15%) associated with the unbound water fraction (absorption water). The results obtained by MSE-FID indicate that bound water and essential oil interact with the 3 fractions, leading to lower percentages of RF (50%) compared to cinnamon 3 (64%). The highest value of 2> for spool 1 (4450 rad·ms − 1) indicates that this sample presents a rigid fraction with more compact and oriented fibers, slightly higher than the fibers of spool 2 (4360 rad·ms − 1), which indicates that its molecular organization is different from the others cinnamon type.
Cinnamon 3 has its water fraction more incorporated into the semi-rigid and mobile fibrous fractions and a lower unbound water content, indicated by the small T1,5 domain at 1420 ms with only 1.1%. Through longitudinal relaxation this is observed by the minors of T1,1, T1,2, T1,3 and T1,4 suggesting greater mobility of the matrix promoted by the presence of water and essential oil in the internal structure of cinnamon. Through the MSE-FID, this sample presents more accentuated T 2 * values for FSR and FM, corroborating that in this cinnamon the water and oil fraction interacts more strongly with the semi-rigid and mobile fibers and less with the rigid fraction, which, consequently, presents a value of 64%. Therefore, due to the high mobility gain, the interaction between the chain segments of the cinnamon solid fraction becomes smaller, resulting in the lowest value of 2> among the 3 samples.
In this work, the characterized cinnamon types, from NMR relaxation data one could see that the three types of cinnamon differ among them; the cinnamom 3 showed to be less rigid and very much heterogeneous. All of them are different due to the distribution of their major components such as: water, oil, and fibers. It also can be observed that the three types of cinnamon presented a particular molecular organization, and the low-field NMR relaxation data was a very good technique to show it.
The authors would like to acknowledge CNPq and FAPERJ and CAPES Code 001 for the support of this work.
The authors declare no conflicts of interest regarding the publication of this paper.
Merat, P.P., Neto, R.C., Ramos, V.S. and Tavares, M.I.B. (2023) Evaluation of Cinnamon by Solid-State NMR Employing Relaxometry. Materials Sciences and Applications, 14, 142-147. https://doi.org/10.4236/msa.2023.143009