Chemometric approach to characterization of the selected grape seed oils based on their fatty acids composition and FTIR spectroscopy

Addressing the issues arising from the production and trade of low-quality foods necessitates developing new quality control methods. Cooking oils, especially those produced from the grape seeds, are an example of food products that often suffer from questionable quality due to various adulterations and low-quality fruits used for their production. Among many methods allowing for fast and efficient food quality control, the combination of experimental and advanced mathematical approaches seems most reliable. In this work a method for grape seed oils compositional characterization based on the infrared (FTIR) spectroscopy and fatty acids profile is reported. Also, the relevant parameters of oils are characterized using a combination of standard techniques such as the Principal Component Analysis, k-Means, and Gaussian Mixture Model (GMM) fitting parameters. Two different approaches to perform unsupervised clustering using GMM were investigated. The first approach relies on the profile of fatty acids, while the second is FT-IR spectroscopy-based. The GMM fitting parameters in both approaches were compared. The results obtained from both approaches are consistent and complementary and provide the tools to address the characterization and clustering issues in grape seed oils.O

Spectroscopic Studies of Intramolecular Proton Transfer in 2-(4-Fluorophenylamino)-5-(2,4-Dihydroxybenzeno)-1,3,4-Thiadiazole

Spectroscopic studies of the biologically active compound 2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thiadiazole (FABT), have been performed. Absorption studies in the UV-Vis region for FABT in polar solvents, like water or ethanol, exhibit the domination of the enol form over its keto counterpart, with a broad absorption band centered around 340 nm. In non-polar solvents such as n-heptane or heavier alkanes the 340 nm absorption band disappears and an increase of the band related to the keto form (approximately 270 nm) is observed. Fluorescence spectra (with 270 nm and 340 nm excitation energies used) show a similar dependence: for FABT in 2-propanol a peak at about 400 nm dominates over that at 330 nm while in n-heptane this relation is reversed. The solvent dependent equilibrium between the keto and enol forms is further confirmed by FTIR and Raman spectroscopies. As can be expected, this equilibrium also shows some temperature dependences. We note that the changes between the two tautomeric forms of FABT are not related to the permanent dipole moment of the solvent but rather to its dipole polarizability

Selected Physical and Spectroscopic Properties of TPS Moldings Enriched with Durum Wheat Bran

The impact of the amount of durum wheat bran additive used on the selected structural, mechanical, and spectroscopic properties of thermoplastic starch moldings was examined in this study. Bran was added to corn starch from 10 to 60% by weight in the blends. Four temperature settings were used for the high-pressure injection: 120, 140, 160, and 180 °C. The highest value of elongation at break (8.53%) was observed for moldings containing 60% bran. Moreover, for these moldings, the tensile strength and flexural strength were lower (appropriately 3.43 MPa and 27.14 MPa). The highest deformation at break (1.56%) were obtained for samples with 60% bran and injection molded at 180 °C. We saw that higher bran content (50 and 60%) and a higher injection molding temperature (160 °C and 180 °C) significantly changed the color of the samples. The most significant changes in the FTIR spectra were observed at 3292 and 1644 cm−1 and in the region of 1460–1240 cm−1. Moreover, notable changes were observed in the intensity ratio of bands at 1015 and 955 cm−1. The changes observed correspond well with the amount of additive used and with the injection temperature applied; thus it may be considered as a marker of interactions affecting plasticization of the material obtained

Effect of Solvent Polarizability on the Keto/Enol Equilibrium of Selected Bioactive Molecules from the 1,3,4-Thiadiazole Group with a 2,4-Hydroxyphenyl Function

Three novel 1,3,4-tiadiazole-derived compounds with biological-activity, i.e., 4-(5-(methylamino)-1,3,4-thiadiazol-2-yl)­benzene-1,3-diol (MDFT), 4-(5-(phenylamino)-1,3,4-thiadiazol-2-yl)­benzene-1,3-diol (PhATB), and 4-(5-(4-chlorophenylamino)-1,3,4-thiadiazol-2-yl)­benzene-1,3-diol (4-CIPhATB) were characterized with the use of several spectroscopic methods. Detailed UV–vis studies revealed keto/enol tautomerism of the examined compounds. The absorption spectra recorded in nonpolar solvents exhibited bands that were characteristic of keto tautomers, while in polar solvents the enol form is predominant. A number of spectra revealed the presence of both tautomeric forms in the solution. The keto/enol equilibria observed were both solvent- and temperature-dependent. The keto/enol equilibrium was also observed using FTIR spectroscopy. A detailed analysis of the spectroscopic data leads to a conclusion that the solvent-induced tautomerism of the selected compounds from the 1,3,4-thiadiazole group does not depend on the electric dipole moment of the solvent but more likely on its average electric polarizability. Additionally, a clear effect of the substituent present in the molecule on the tautomeric equilibrium in the selected 1,3,4-thiadiazole analogues was noted