An application of chemometric techniques to analyze the effects of the wave function modifications on the intermolecular stretching frequencies of the hydrogen-bonded complexes

Factorial design and principal component models are used to determine how ab initio H-bond stretching frequencies depend on characteristics of the molecular orbital wave functions of acetylene–HX, ethylene–HX and cyclopropane–HX π-type hydrogen complexes with X=F, Cl, CN, NC and CCH. The results obtained for the three sets of complexes show that factorial design and principal component analyses complement each other. Factorial design calculations clearly show that these frequencies are affected mostly by inclusion of electron correlation on the calculation level. On average, their values are increased by about 25 cm⁻¹ due to a change from the Hartree–Fock (HF) to Möller–Plesset 2 (MP2) level. Valence, diffuse and polarization main effects as well as valence–diffuse, diffuse–correlation and polarization–correlation interaction effects are also important to better describe a factorial model to the H-bond stretching frequencies of these hydrogen complexes. This simplified model has been successful in reproducing the complete ab initio results, which correspond to two hundred and forty calculations. Principal component analyses applied only to hydrogen-bonded complexes whose experimental frequencies are known, has revealed that the six-dimensional original space can be accurately represented by a bidimensional space defined by two principal components. Its graphical representation reveals that the experimental intermolecular stretching frequencies are in closest agreement with the MP2/6–31+G and MP2/6–311+G ab initio results.     

Characterization of Microencapsulated Rosemary Essential Oil and Its Antimicrobial Effect on Fresh Dough

This study aimed to characterize rosemary essential oil particles obtained by spray-drying and to evaluate their antimicrobial activity. Measurements of mycelial growth of Penicillium and Aspergillus fungi, isolated from fresh dough, were made applying oil concentrations of 1.0, 5.0, 10.0, 20.0, and 50.0 μL/mL. Fungi and yeast counts in the fresh dough submitted to the control (no oil), pure oil, and microencapsulated oil treatments were also conducted. The microcapsules showed 50 % oil retention after drying, and the major oil components identified were 1,8-cineole (29.0 %), camphor (26.6 %), and α-pinene (10.6 %). The analysis of the particles revealed surfaces without fissures, with a mean particle size of 12.2 μm and presenting an amorphous structure. The growth inhibiting effect of Penicillium sp. fungus, compared to the control, was verified at concentrations of 1.0, 5.0, and 10.0 μL/mL rosemary essential oil, which did not differ among them. For Aspergillus sp., the application of 10.0 μL/mL oil provided greater inhibition compared to 1.0 and 5.0 μL/mL. Complete inhibition occurred with the application of 50.0 μL/mL for both fungal genera tested. At 8 days of dough storage at 25 °C, a decrease of at least 0.7 and 1.5 log cycles of fungal growth was observed in the dough with pure oil and that with microencapsulated oil, respectively, relative to the control. The microencapsulation process retained the antimicrobial property of rosemary essential oil and provided further extension of this activity over time when applied to fresh dough.     

Potential of migration of active compounds from protein‐based films with essential oils to a food and a food simulant

Migration tests at different temperatures and storage periods were performed to evaluate the release of active compounds from active whey protein films (WPFs) to a food and food simulants. Whey protein film incorporated with different levels of an optimized essential oils (EOs) blend (1%, 2%, 2.7%, and 5%, w/w) were prepared by casting. This blend contained EOs from rosemary and 2 species of cinnamon. Salami was packaged with WPF and stored during 180 days at 5°C. Temperature influenced significantly the migration of compounds (P<.1). It was observed that eucalyptol was the compound that presented the highest potential of migration into 95% ethanol (v/v). After contact of film with salami, it was observed that, in general, more than 50% of active compounds released from WPF to salami. It was observed that higher amounts of active compounds were released to salami than to fatty food simulant. Results suggested that the release of compounds depends on their affinity with the food/food simulant, temperature, their concentration in packaging, and composition of food. Active packaging may ensure the quality of food due the migration of compounds from EO with antimicrobial and antioxidant activity incorporated in the film to the foodstuff.     

Ames Test to Detect Mutagenicity of 2‐Alkylcyclobutanones: A Review

Food irradiation is an effective and safe method for preservation and long‐term storage, and it is approved for use in over 60 countries for various applications in a wide variety of food products. This process is performed by use of accelerated electron beams, X‐rays, or gamma radiation (⁶⁰Co or ¹³⁷Cs). 2‐Alkylcyclobutanones (2‐ACBs) are the only known radiolytic products generated from foods that have fatty acids (triglycerides) and are subjected to irradiation. Since the 1990s toxicological safety studies of 2‐ACBs have been conducted extensively through synthetic compounds, then and tests to determine if the compounds have any mutagenic activity are strictly necessary. The Ames test was chosen by many researchers to assess the mutagenicity of 2‐ACBs. The test uses distinct bacterial cell lines Salmonella typhimurium to detect point mutations at sites guanine–cytosine (G–C) and Escherichia coli to detect point mutations at sites adenine–thymine (A–T). This bibliographic research aims to bring together all the results obtained and a comparison and cell lines used, type of plates, and solvents. This research showed that no mutagenic activity was observed in any of the cell lines and concentrations evaluated by the works of authors, so the 2‐ACBs compounds showed no mutagenic substance in concentrations detectable by the Ames test.     

UHPLC-DAD Multi-Method for Determination of Phenolics in Aromatic Plants

The aim of this paper was to develop and validate a method of ultra high-performance liquid chromatography coupled with diode array detector (UHPLC-DAD), which allows quantifying simultaneously 19 phenolic compounds in aromatic plants. Twenty-one fresh and dried aromatic plants were extracted with methanol before their UHPLC-DAD analysis. The method was validated regarding specificity, working range, linearity, limit of detection (LOD) and quantification (LOQ), precision, and accuracy. The developed method allows detecting and quantifying the phenolic compounds at low concentrations (LOD < 0.15 μg/mL, except for carnosol and carnosic acid). The relative standard deviation obtained was lower than 5.73 and 8.75%, for repeatability and intermediate precision, respectively. The proposed method is straightforward and sensitive, with good precision and accuracy. Dried thyme presented the highest diversity of phenolic compounds and rosmarinic acid was present in most of the samples. This analytical tool is a valid alternative to conventional methods to quantify phenolic compounds in aromatic plants or in their extracts.     

Evaluation of spray drying conditions on properties of microencapsulated oregano essential oil

Response surface methodology (RSM) was employed to investigate variations in powder characteristics with respect to spray drying operating parameters including both feed rates (L min^?1) and inlet temperatures (°C). Inlet temperatures around 180 °C provided the lowest values for moisture. Powder recovery was significantly affected (P < 0.10) by inlet air temperature and feed rate, where a raise in inlet temperature and feed rate resulted in higher powder recovery. No significant difference (P > 0.05) was observed for water activity, solubility and hygroscopicity between treatments. Regarding oil retention, the results showed a significant (P < 0.05) interaction between the two studied factors. A tendency for higher values of oil retention was observed when using combinations of high inlet temperatures/low feed rates and low inlet temperatures/high feed rates. Particle size distribution averaged 2.0, 8.1 and 18.3 μm for D₁₀, D₅₀ and D₉₀, respectively. The morphology of particles showed no cracks in most capsules. The results indicate that high temperature (185 °C) and moderated feed rate (0.63 L min^?1) are the best spray drying conditions.     

Effect of the cross-linking degree on the morphology of poly(NIPAAm-co-AAc) hydrogels

Hydrogels of poly(N-isopropylacrylamide) co-polymerized with acrylic acid [P(NIPAAm-co-AAc)] were synthesized with cross-linking degrees of 2-7% using (N,N′-methylenebisacrylamide). SEM micrographs revealed that the morphology of dry hydrogels changes from interconnected spherical pores to channel-like pores, with the change in the cross-linking degrees from 3 to 5%. The change in morphology is associated with a significant change in the swelling ratio. It was found that the diffusion rates and permeabilities of methylene blue (MB) through the hydrogel with channel-like pores are significantly higher if the main axes of the pores are oriented parallel to the flow of MB molecules, than if it is oriented perpendicularly. These results show that different morphologies can be obtained by controlling the cross-linking degree of P(NIPAAm-co-AAc) hydrogels in a narrow range around 5% and by performing the polymerization reaction in moulds placed in horizontal and vertical positions, opening a new perspective for modulating their properties in applications as matrices for controlled release of drugs or as membranes for separation processes.