Order-disorder phase transition and molecular dynamics in the hybrid perovskite [(CH3)3NH][Mn(N3)3].

We present a temperature-dependent Raman scattering study of a [(CH3)3NH][Mn(N3)3] hybrid organic-inorganic azide-perovskite, in which we have analysed in detail the wavenumber and full width at half-maximum (FWHM) of lattice modes and internal modes of the NC3 skeleton, N3- and CH3 molecular groups. In general, the modes exhibited unusual behaviour during the phase transitions, including discontinuity in the phonon wavenumber, bandwidth, and unconventional shifts upon temperature variation. Spectral features on heating reveal the absence of significant distortions in the NC3 skeleton and a relatively restricted order-disorder process of the TrMA+ cations. On the other hand, linewidth anomalies of the δNC3 and νasNC3 modes have been attributed to the molecular dynamics of encapsulated cations. The unconventional blue shift of the symmetric stretching modes of azide ligands indicates the weakening of the intermolecular interactions between the TrMA+ cations and azido-bridges, and the strengthening of the intramolecular bonds. Additionally, we have used differential scanning calorimetry to confirm the subtle monoclinic to monoclinic (P21/c â†’ C2/c) phase transition at around 330 K; and the phase transition to trigonal structure (R3¯m) above 359 K, whose associated entropy variation turns to be |ΔS| ∼ 22.3 J·kg-1 K-1 and displays a barocaloric (BC) tunability |δTt/δP| ∼ 3.17 K kbar-1, according to our estimations using the Clausius-Clapeyron method. Although the obtained values of entropy change and BC tunability are very close to those reported on formate-perovskites and other important caloric materials, those parameters are much lower than the giant entropy change of ∼80 Jkg-1 K-1 and large BC tunability ∼12 K kbar-1 observed for the analogue azide-perovskite [(CH3)4N][Mn(N3)]3 (TMAMnN3). Very interestingly, our combined study shed light to understand such different behaviour, as they reveal that the hydrogen bonds created between the TrMA+ cations and the framework prevent an extensive order-disorder process that is needed to obtain large entropy changes and large BC coefficients as it occurs in the case of related azide-perovskites with no H-bonds between the A cations (for example TMA) and the framework.

Avaliação do modelo de produção e da inclusão de gordura nos parâmetros qualitativos e sensoriais do hambúrguer ovino / Evaluation of the production model and fat inclusion in qualitative and sensorial parameters of the sheep hamburgers

Carnes de 48 cordeiros Ile de France criados nos modelos orgânico e convencional, provenientes da dissecação da paleta foram submetidas à elaboração de hambúrguer, com fonte de gordura adicionada, nas proporções de 20 e 30%. Os modelos de produção (P<0,01) e o teor de gordura (P<0,01) influenciaram o pH dos hambúrgueres, entretanto apenas os modelos de produção afetaram a luminosidade (P<0,05) e o teor de vermelho (P<0,01), mas não influenciaram a capacidade de retenção de água, a perda de peso ao cozimento e o número de ácido 2-tiobarbitúrico (TBARS) dos hambúrgueres, com valores de 62,8%, 24,6% e 1,81mg malonaldeído/kg de amostra, respectivamente. No hambúrguer orgânico, houve menor força de cisalhamento (0,68kgf/cm²) em relação ao convencional (0,97kgf/cm²). Os teores de gordura afetaram a capacidade de retenção de água (P<0,05). Para perda de peso ao cozimento, força de cisalhamento e número de TBARS, os valores foram de 24,65%, 0,82kgf/cm² e 1,81mg malonaldeído/kg de amostra, respectivamente. Os modelos de produção e os teores de gordura não influenciaram a cor, o sabor, a maciez e a aceitação global dos hambúrgueres. Os modelos de produção e os teores de gordura não influenciaram a atividade de água na temperatura de 20,55ºC, no entanto, em temperaturas mais baixas, os hambúrgueres orgânicos tiveram maior atividade de água em relação aos convencionais.

The dissection of the pallete of 48 Ile de France lambs submitted to the organic and conventional production models was used for hamburger elaboration, with 20 and 30% fat. The production models (P<0,01) and the fat tenor (P<0,01) influenced the hamburgers' pH, the production models affected only the lightness (P<0,05) and the redness (P<0,01), and didn't influence, however, water holding capacity, cooking loss and 2-thiobarbituric acid reactive substances of hamburgers, with 62,8%, 24,6% and 1,81mg of malonaldehyde/1000g meat, respectively. In organic hamburgers, smaller shear force (0,68kgf/cm²) was observed in relation to conventional (0,97kgf/cm²). The fat tenors affected water holding capacity (P<0,05), however, they didn't influence cooking loss, shear force and 2-thiobarbituric acid reactive substances. The production models and fat tenors didn't influence color, flavor, tenderness and global acceptance of the hamburgers. The production models and fat tenors didn't influence water activity of 20,55ºC, however, in lower temperatures, organic hamburgers had higher water activity in relation to conventional hamburgers.