<Emphasis Type="Italic">In situ</Emphasis> monitoring of solid fat content by means of pulsed nuclear magnetic resonance spectrometry and ultrasonics

An ultrasonic technique was developed to study the crystallization process of edible fats on-line. A chirp wave was used instead of the conventional pulser signal, thus achieving a higher signal-to-noise ratio. This enabled measurements to be made in concentrated systems [≈20% solid fat content (SFC)] through a 8.11-cm thick sample without significant signal loss. Fat samples were crystallized at 20, 25, and 30°C at a constant agitation rate of 400 rpm for 90 min. The crystallization process was followed by ultrasonic spectroscopy and a low-resolution pulsed nuclear magnetic resonance spectrometer. Specific relationships were found between ultrasonic parameters [integrated response, time of flight (TF), and full width half maximum] and SFC. TF, which is an indirect measurement of the ultrasonic velocity (v), was highly correlated to SFC (r ²>0.9) in a linear fashion (v=2.601 SFC+1433.0).     

Nucleation behavior of blended high‐melting fractions of milk fat as affected by emulsifiers

The effect of highly hydrophobic emulsifiers, the palmitic sucrose ester P‐170 (hydrophilic/lipophilic balance (HLB) = 1.0), the stearic sucrose ester S‐170 (HLB = 1.0), the polyglycerol ester decaglycerol decastearate DAS 7S (HLB = 3.7) and the polyglycerol ester decaglycerol dodecabehenate DDB 750 (HLB = 2.6), on the nucleation of a high melting point milk fat fraction (HMF) and its blends with sunflower oil (SFO) was investigated by polarized laser light turbidimetry, X‐ray diffractometry and polarized light microscopy (PLM). Addition of polyglycerol esters accelerated nucleation, giving shorter induction times for the same supercooling. On the contrary, sucrose esters inhibited nucleation since induction times were elongated in all conditions selected. Addition of emulsifiers modified the polymorphic behavior in the blends with SFO. The β' form was promoted especially with the addition of S‐170. DAS 7S and DDB 750 promoted crystallization. PLM images showed many small crystals that did not appear in HMF images. Addition of P‐170 and S‐170 delayed nucleation and inhibited crystal growth. Crystals were notoriously smaller than the ones that appeared in HMF images. The Fisher–Turnbull model was used to calculate activation free energies of nucleation. In all cases, sucrose esters elevated the energy barrier for nucleation. Polyglycerol esters, however, if they had an effect on the energy barrier, lowered the values.     

ATR-FTIR Study of the Decomposition of Acetic Anhydride on Fosfotungstic Wells–Dawson Heteropoly Acid Using Concentration-Modulation Excitation Spectroscopy

The decomposition of acetic anhydride in liquid phase on a fosfotungstic Wells–Dawson heteropoly acid (HPA) was investigated by in situ ATR-FTIR spectroscopy. Transient and concentration-modulation excitation spectroscopy (MES) experiments in combination with phase-sensitive detection (PSD) were used to monitor the solid–liquid interface. The MES method is based on the periodic variation of a parameter of the reaction media such as, the reactant concentration. That periodic alteration causes varying infrared signals of the surface adsorbed species that are subsequently demodulated with the PSD methodology. Thus, the separation of the static signals from the changing ones is achieved, and species with different response can be observed in the spectra. Using MES-PSD coupled with ATR-FTIR, acetic anhydride was observed to decompose to acetic acid, acetate and acyl [CH₃C(O)⁺] species, involving Brønsted acid sites of the HPA catalyst. The CH₃C(O)⁺ is a very unstable intermediate species and it is the key intermediate in the Friedel–Crafts acylation reactions. Moreover, the acetate groups are spectator species since remain strongly adsorbed on the catalyst surface and do not further react.     

Efficiency of 4,4′‐bis(N,N‐diethylamino) benzophenone for the polymerization of dimethacrylate resins in thick sections

The efficiency of 4,4′‐bis(N,N‐diethylamino)benzophenone (DEABP) for the polymerization of dimethacrylate monomers in thick sections ( 1 – 2 mm) was studied. DEABP (λ_max = 365 nm) represents a complete initiating system as it contains both ketone and amine functional groups. During irradiation, DEABP photobleaches at a fast rate causing deeper penetration of light through the underlying layers, but the photoinitiation efficiency (rate of polymerization per photon absorption rate) is relatively poor. As a result, irradiation of methacrylate monomers at 365 nm results in a slow average polymerization rate and a reduced monomer conversion for thick sections due to the light attenuation caused by the high absorptivity of DEABP and photolysis products. These results highlight the inherent interlinking of light attenuation and photobleaching rate in polymerization of thick sections. Copyright © 2011 Society of Chemical Industry     

Assessment of biodiesel blending detection capability of the on-board diagnostic of the last generation automotive diesel engines

Results of a research project aimed at studying the capability to develop a method (economic and simple) for on-board biodiesel blending detection are described. The method is based on the direct measurement of the Indicated Mean Effective Pressure (IMEP).The study was carried out on a 2.0L four-cylinder “torque-controlled” Euro 5 diesel engine for passenger car (PC) application. This engine, equipped with instrumented glow plug for combustion closed-loop control, represents the state of the art of the diesel engine control technology.Two biodiesels were chosen for the experiments: a rapeseed methyl-ester (RME) and an aged RME, while the conventional diesel fuel was an European (EU) certification diesel fuel.Results indicate generally a good response in blending detection of the method. However, in order to attain an acceptable accuracy, a pre-calibration appears necessary.     

Bonding ability of self-adhesive resin-cements after dentin biomodification with hyaluronic acid

Purpose: The present study evaluated the influence of the hyaluronic acid (HA) on the bonding ability of self-adhesive resin cements to dentin regarding the bond strength. Eighty bovine incisors were ground flat to obtain a 2-mm thick slices which received conical preparations. The specimens were randomly distributed into 4 groups (n = 15) according to the dentin pretreatment (1 – control: untreated dentin; 2 – application of HA) and the evaluation time (1 – control: immediate evaluation; 2 – hydrolytic degradation: 6 months of storage in water at 37 °C). Preparations received the application of a self-adhesive resin cement (RelyX U200 or MaxCem Elite). Push-out bond strength test was conducted (0.5 mm/min). The bond strength data was submitted to two-way ANOVA/Tukey’s test (α = 0.05). For U200, no significance was observed when comparing the immediate (24 h) and 6 months means for the control groups (unexposed specimens). Previous application of HA to dentin significantly reduced the bond strength of U200 to dentin in both evaluation times (p < 0.05). HA had no significant influence on the push-out bond strength means for the cement MAX in both evaluation times (p > 0.05). The type 1 failure mode (adhesive mode) occurred in 100% of the specimens, irrespective of the dentin treatment or evaluation times. Pretreatment of dentin with HA produces a material-dependent influence on the push-out bond strength. The bonding ability of RelyX U200 is negatively influenced by the pretreatment of dentin with HA, whereas the biomodification of dentin with this bioactive agent causes no impact for the cement MaxCem Elite.     

Influence of the nanofiber dimensions on the properties of nanocellulose/poly(vinyl alcohol) aerogels

The investigation of aerogels made from cellulose nanofibers and poly(vinyl alcohol) (PVOH) as a polymeric binder is reported. Aerogels based on different nanocellulose types were studied to investigate the influence of the nanocellulose dimensions and their rigidity on the morphology and mechanical properties of the resulting aerogels. Thus, cellulose nanocrystals (CNCs) with low (10), medium (25), and high (80) aspect ratios, isolated from cotton, banana plants, and tunicates, respectively, microfibrillated cellulose (MFC) and microcrystalline cellulose (MCC) were dispersed in aqueous PVOH solutions and aerogels were prepared by freeze‐drying. In addition to the cellulose type, the PVOH‐ and the CNC‐concentration as well as the freeze‐drying conditions were varied, and the materials were optionally cross‐linked by an annealing step or the use of a chemical cross‐linker. The data reveal that at low PVOH content, rigid, high‐aspect ratio CNCs isolated from tunicates afford aerogels that show the least amount of shrinking upon freeze‐drying and display the best mechanical properties. However, with increasing concentration of PVOH or upon introduction of a chemical cross‐linker the differences between materials made from different nanocellulose types decrease. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41740.     

Sorption of humic acids by a zeolite-feldspar-bearing tuff in batch and fixed-bed column

The sorption of humic acids (HA) on zeolite-feldspar-bearing Phlegraean Yellow Tuff enriched with calcium ions has been investigated at neutral pH both on fixed-bed columns and in batch. A two-step sorption kinetics and a relatively long time to reach the equilibrium were observed in batch. In line with this behaviour, the breakthrough curves and shipping curves from exhaust columns showed distinctive properties that cannot be easily modelled by the common mass balance equations; noteworthy, the breakthrough curves were dependent on the space velocity also for very slow processes and the bed sorption capacity decreased linearly with the space velocity. Moreover, after an initial high-rate burst, HA desorption from exhausted columns proceeded at a very slow rate, particularly so for columns loaded with higher amounts of HA.     

MT1‐Selective Melatonin Receptor Ligands: Synthesis,Pharmacological Evaluation,and Molecular Dynamics Investigation of N‐{[(3‐O‐Substituted)anilino]alkyl}amides

The design of compounds selective for the MT₁ melatonin receptor is still a challenging task owing to the limited knowledge of the structural features conferring selectivity for the MT₁ subtype, and only few selective compounds have been reported so far. N‐(Anilinoalkyl)amides are a versatile class of melatonin receptor ligands that include nonselective MT₁/MT₂ agonists and MT₂‐selective antagonists. We synthesized a new series of N‐(anilinoalkyl)amides bearing 3‐arylalkyloxy or 3‐alkyloxy substituents at the aniline ring, looking for new potent and MT₁‐selective ligands. To evaluate the effect of substituent size and shape on binding affinity and intrinsic activity, both flexible and conformationally constrained derivatives were prepared. The phenylbutyloxy substituent gave the best result, providing the partial agonist 4 a , which was endowed with high MT₁ binding affinity (pK_i=8.93) and 78‐fold selectivity for the MT₁ receptor. To investigate the molecular basis for agonist recognition, and to explain the role of the 3‐arylalkyloxy substituent, we built a homology model of the MT₁ receptor based on the β₂ adrenergic receptor crystal structure in its activated state. A binding mode for MT₁ agonists is proposed, as well as a hypothesis regarding the receptor structural features responsible for MT₁ selectivity of compounds with lipophilic arylalkyloxy substituents.