Effect of milk fat fractions on fat bloom in dark chocolate

Anhydrous milk fat was dissolved in acetone (1∶4 wt/vol) and progressively fractionated at 5°C increments from 25 to 0°C. Six solid fractions and one 0°C liquid fraction were obtained. Melting point, melting profile, solid fat content (SFC), fatty acid and triglyceride profiles were measured for each milk fat fraction (MFF). In general, there was a trend of decreased melting point, melting profile, SFC, long-chain saturated fatty acids and large acyl carbonnumbered triglycerides with decreasing fractionation temperature. The MFFs were then added to dark chocolate at 2% (w/w) addition level. In addition, two control chocolates were made, one with 2% (w/w) full milk fat and the other with 2% (w/w) additional cocoa butter. The chocolate samples were evaluated for degree of temper, hardness and fat bloom. Fat bloom was induced with continuous temperature cycling between 26.7 and 15.7°C at 6-h intervals and monitored with a colorimeter. Chocolate hardness results showed softer chocolates with the 10°C solid fraction and low-melting fractions, and harder chocolates with high-melting fractions. Accelerated bloom tests indicated that the 10°C solid MFF and higher-melting fractions (25 to 15°C solid fractions) inhibited bloom, while the lowermelting MFFs (5 and 0°C solid fractions and 0°C liquid fraction) induced bloom compared to the control chocolates.     

Hazelnut oil migration in dark chocolate – kinetic,thermodynamic and structural considerations

The objective of this study was to assess the effects of three storage temperatures (11, 20 and 26 °C) on the migration kinetics and equilibrium states of a model filled confection consisting of dark chocolate and a hazelnut oil‐based filling. HPLC, atomic force microscopy and X‐ray diffraction were used to study the migration behaviour of hazelnut oil into simulated filled confections and the associated changes in microstructure. Using a Fickean model, the mechanism for the migration of foreign triacylglycerols (TAG) into chocolate was evaluated. Deviations from Fickian diffusion were noted with increasing temperature, and resulted from the breakdown of the chocolate matrix. At higher temperatures, filled dark chocolate exhibited accelerated fat bloom formation due to the increased ingress of foreign incompatible TAG. The rate of migration and the diffusion coefficient increased 20 and 400 times, respectively, when the storage temperature was raised from 11 to 26 °C. The amplified rate of migration at elevated temperatures resulted in a confectionary product with a severe loss in quality. There was significant degradation in the texture and gloss of the product within 24 h of storage at 26 °C. However, the storage of filled dark chocolate at 11 and 20 °C showed negligible deterioration over 8 wk. Overall, the results from this study offer some insight into the optimisation for the production and storage of filled chocolates.     

Voltammetric resolution of dopamine in the presence of ascorbic acid and uric acid at poly (calmagite) film coated carbon paste electrode

The poly (calmagite) film was synthesized on the surface of carbon paste electrode by electrochemical method. The synthesized polymer film coated electrode exhibits excellent electrocatalytic activity towards the detection of dopamine at neutral pH. The scan rate effect was found to be adsorption controlled electrode process. The concentration effect of dopamine was studied. The redox peak potentials of dopamine were depend on pH. This polymer film coated electrode was very good at simultaneous study of dopamine in the presence of high concentrated ascorbic acid and uric acid. The incorporation study was done by varying the concentration of one species while other two are kept constant. The proposed method was applied to the detection of dopamine in injection samples.     

Detection of dopamine in non-treated urine samples using glassy carbon electrodes modified with PAMAM dendrimer-Pt composites

Composites of hydroxyl-terminated PAMAM dendrimers, generation 4.0 (64 peripheral OH groups) containing Pt nanoparticles were synthesized at different reaction times using a microwave reactor. The synthetic procedure resulted in dendrimer encapsulated nanoparticles of Pt (DENs-Pt) of 1.53 ± 0.17 nm diameter that was calculated from transmission electron microscopy, and the Pt nanoparticles had single crystal plane in (1 1 1) orientation determinate by selective area diffraction.Each composite was electrochemically immobilized on a pre-functionalized glassy carbon (GC) electrode that was incorporated as a flow injection amperometric (FIA) detector, for the selective detection and quantification of dopamine (DA) in untreated urine samples.Comparison of the analytical performance of the novel electrochemical detector revealed that the DENs-Pt modified GC electrode with the composite synthesized for 30 min in the microwave reactor, showed the best response for the detection of DA in samples of non-treated urine, being the detection and quantification limits smaller (19 and 9 ppb, respectively) than those corresponding to the naked a GC electrode (846 and 423 ppb, respectively) using the FIA detector. In addition, it was found that this electroanalytical approach suffers minimal matrix effects that arise in the analysis of DA in untreated samples of urine.     

Influence of thermal conditions and presence of additives on fat bloom in chocolate

This study focused on the analysis of the effects of thermal history and presence of additives on fat bloom in chocolate. Magnetic resonance data obtained on specific chocolate samples were useful in evaluating the effect of thermal history on the appearance of fat bloom and also in understanding the underlying mechanism. Fat bloom was induced by thermal history such as storage for 3 d at 32 or 28°C. Increasing storage time at 21°C after each thermal treatment also promoted fat bloom. Differential scanning calorimetry experiments confirmed the appearance of polymorphic form VI in the bloomed samples. Also, three different components were added separately to the initial composition of dark chocolate and the appearance of fat bloom was monitored. 1,3-Dibehenoyl, 2-oleoylglycerol (BOB) did prevent fat bloom. However, magnetic resonance and differential scanning calorimetry data collected on chocolate samples did not confirm that either added sucrose or milk powder prevented fat bloom. Indeed, fat bloom occurred for these samples, but its characteristics were different from those with pure chocolate.     

Influence of shearing and time on the rheological properties of milk chocolate during tempering

The quality of chocolate is highly dependent on proper tempering. During tempering, crystals are formed as the chocolate is subjected to shear. The aim of this work was to evaluate the applicability of traditional rheological techniques to gain a better understanding of the relationship between rheological properties and the degree of shearing and time of tempering. Treatments of two shearing rates (15 and 30 s⁻¹) covering four tempering times (0, 400, 600, and 800 s) were investigated. As samples were cooled from a melt temperature of 50°C, the apparent viscosity followed the Arrhenius equation. An induction time, which was affected by shear rate, was observed during tempering, followed by an increase in apparent viscosity, caused by formation of crystalline structures. Various characteristics of the rewarming curve were attributed to polymorphism. Steady-shear constitutive models assessed after rewarming showed that the yield stress was dependent on shear and tempering time. Collectively, findings showed that traditional rheological methods may be used as tools to investigate crystallization and flow properties of molten chocolate indirectly during tempering.     

Sol–gel derived multiwalled carbon nanotubes ceramic electrode modified with molecularly imprinted polymer for ultra trace sensing of dopamine in real samples

A new class of composite electrodes made of sol–gel derived ceramic-multiwalled carbon nanotubes is used for the growth of a nanometer thin film adopting “surface grafting-from approach”. For this the multiwalled carbon nanotubes-ceramic electrode surface is first modified with an iniferter (benzyl N,N-diethyldithiocarbamate) and then dopamine imprinted polymer, under UV irradiation, for differential pulse anodic stripping voltammetric sensing of dopamine in aqueous, blood serum, cerebrospinal fluid, and pharmaceutical samples (detection limit 0.143–0.154 ng mL⁻¹, 3σ), without any cross reactivity, interferences and false-positive contributions. Such composite electrodes offer higher stability, electron kinetics, and renewable porous surface of larger electroactive area (with insignificant capacitance) than carbon ceramic electrodes. Additional cyclic voltammetry (stripping mode) and chronocoulometry experiments were performed to explore electrodics and kinetics of electro-oxidation of dopamine.     

The effects of adding water and polyglycerol polyricinoleate on the texture,appearance, and sensory qualities of compound milk chocolate

Water and polyglycerol polyricinoleate (PGPR) contents were varied to investigate the effects of these parameters on the textural properties, surface color, and sensory qualities of compound chocolates. The content levels of water and PGPR were manipulated between 3–10 and 0.3–3.3%, respectively (content expressed as % by weight of finished product). Simultaneous variations in water and PGPR levels, especially in high ratios, resulted in a drastic reduction in the hardness values (p<0.001), darker color (p<0.01), and an unusual taste (p<0.05) but the effect of water addition was more pronounced than PGPR. It was observed that compound chocolates with 3% water content were not dissimilar from the control with respect to all properties. In the samples of the same water content, the effect of PGPR addition was nearly insignificant. For these confectionaries, the best proportion of ingredients for producing water‐containing compound chocolate was considered the one which has the least negative effects on bloom surface area and the texture. Practical applications: Manufacturing water‐containing imitation chocolates represent a general approach for adding all water‐base materials to chocolate such as cream, yogurt, milk, etc. or water‐soluble substances like trace elements and vitamins. Conventional chocolates become soft at above 28°C, and lose shape retention at above 32°C. Water addition provides a heat‐resistance compound chocolate with shape retention at a temperature above 40°C, being not sticky to the direct touch. However, there has been very limited information about water addition's effects on the chocolate structure. In order to be able to predict the structural variations, it is important to study how water affects the physical properties of the chocolates.     

Stability and performance of a spouted bed in drying skimmed milk: Influence of the cone angle and air inlet device

This paper investigates the skimmed milk drying over inert particles in a 30?cm diameter spouted bed. Drying was evaluated for conical bases of three cone angles (45°, 60°, and 75°) operating with 4.5?kg of inert particles, and two air inlet devices with different geometries—a Venturi-type nozzle and a straight section pipe. The drying capacity was evaluated from the maximum paste feed rate that allowed stable operation and spouting dynamic behavior throughout drying. It was observed that drying capacity and dynamic stability were greatly affected by the cone angle and the inlet device geometry. From the conditions evaluated, the best configuration with regard to the drying capacity was obtained for the 45° conical base using the Venturi-type inlet device. In this dryer, a rate of 40?mL/min of skimmed milk was processed and a powder with a moisture content of about 10% was produced. The good performance on this configuration was attributed to several factors that affected positively the solid circulation rates and the dynamics stability. Such factors include the operation under a higher static-bed height, the spouting on conical configuration, and the improved aeration of the annular region provided by the inlet device. At this configuration, and for paste feed rates up to the maximum admissible value, the spouted-bed dynamic was almost not affected by the liquid and the wet bed operated under dynamic conditions very similar to those of the dry bed. Using a 75° conical base with the Venturi-type inlet device under a slightly lower drying capacity (35?mL/min) also resulted in quite stable dynamic conditions. The 60° conical base with the Venturi-type device was the configuration that performed worst with regard to drying capacity (30?mL/min).     

Computerized cyclic voltammetric detection after HPLC of the antineoplastic agents etoposide,teniposide, adriamycin and its metabolite adriamycinol in urine samples

A computerized electrochemical detection system for application after HPLC, provided with a cyclic voltammetric oxidative and reductive module, is described for the on-line qualitative determination of electroactive antineoplastic agents and metabolites in urine samples, collected from cancer patients, following intravenous administration.The application of two cyclic voltammetric detection modes provides an insight into both oxidative and reductive electrode reactions of compounds, passing the detector and the occurrence of (it)reversible chemical and electrochemical processes at the electrode surface. In this way, redox properties of drugs and metabolites characteristic of their molecular structure, can be established, which may provide information related to their (enzymatic) bioactivation.In the cyclic voltammetric mode, the system permits automatic detection of a compound in the cell, recording, storage and plotting of voltammograms and calculation of the retention times, the half-wave potentials and the peak potentials of each scan of all individual compounds. For routine use, storage of 68 voltammograms on-line is sufficient for the analysis of biological samples in clinical-pharmacological research. Special attention has been paid to automatic, multi-reference-point component detection.Based on their concentrations in urine, the oxidative cyclic voltammetric mode, using a glassy carbon electrode, permits the determination of etoposide and teniposide, whereas the reductive cyclic voltammetric mode, with a static mercury drop electrode, permits the determination of adriamycin and its metabolite adriamycinol.     

Effects of minor lipids on crystallization of milk fat-cocoa butter blends and bloom formation in chocolate

Minor lipids, such as diacylglycerols, monoacylglycerols, cholesterol, and phospholipids play a key role in crystallization of fats. In this study, the effects of minor lipid components on crystallization of blends of cocoa butter (CB) with 10% milk fat or milk-fat fractions, and on bloom formation of chocolate were investigated. Both removing the minor lipids from milk fat and doubling the level of minor lipids from milk fat resulted in longer nucleation onset time, slower crystallization rate, and rapid bloom development in chocolate. Removal of minor lipids resulted in the formation of irregular primary and secondary crystals with inclusions of liquid fat, whereas the crystals were spherical and uniform in shape in the presence of minor lipids. Minor lipids from milk fat, even at the low concentrations typically found in nature, affected the crystallization of milk fat-CB blends, impacted the chocolate microstructure, and affected bloom development in chocolate.     

Enhanced host–guest electrochemical recognition of dopamine using cyclodextrin in the presence of carbon nanotubes

A novel application of multiwall carbon nanotubes (MWCNT) for biosensor use is presented. β-Cyclodextrin (β-CD) as molecular receptor and MWCNT as enhancer of electron transfer are integrated in a dopamine (DA) electrochemical sensor system. The proposed molecular host–guest recognition based sensor has a high electrochemical sensitivity for the determination of DA. The electrochemical behaviour of DA is investigated by cyclic voltammetry (CV). The response mechanism of the MWCNT/β-CD modified electrode for DA is based on the combination of electrostatic and inclusion interaction of β-CD with DA which is distinguished from the response mechanism of non-modified electrode. The proposed integrated sensor showed improved analytical performance characteristics in catalytic oxidation of DA compared with non-modified electrode: excellent sensitivity, repeatability, stability, selectivity and recovery for the determination of DA. Under optimized conditions linear calibration plots were obtained for amperometric detection of DA over the range 0.01–0.08 mM.     

Indium tin oxide-coated glass modified with reduced graphene oxide sheets and gold nanoparticles as disposable working electrodes for dopamine sensing in meat samples

Sensitive, rapid, and accurate detection of dopamine (DA) at low cost is needed for clinical diagnostic and therapeutic purposes as well as to prevent illegal use of DA in animal feed. We employed a simple approach to synthesize reduced graphene oxide sheets (rGOS) and gold nanoparticles (AuNPs) at room temperature on indium tin oxide-coated glass (ITO) slides as disposable working electrodes for sensing DA. Graphene oxide (GO) was directly reduced on ITO to remove oxygenated species via a rapid and green process without using chemical reducing reagents. AuNPs were electrochemically deposited in situ on rGOS-ITO with fairly uniform density and size. The sensitivity of the AuNPs-rGOS-ITO sensor for DA detection is 62.7 μA mM(-1) cm(-2) with good selectivity against common electrochemically interfering species such as ascorbic acid (AA) and uric acid (UA), and the detection limit measured by differential pulse voltammetry (DPV), at a signal-noise ratio of 3, was 6.0 × 10(-8) M. The electrochemical catalysis of DA was proven to be a surface process with an electron transfer coefficient (α) of 0.478 and a rate constant (k(s)) of 1.456 s(-1). It correlates well with the conventional UV-vis spectrophotometric approach (R = 0.9973) but with more than thrice the dynamic range (up to 4.5 mM). The sensor also exhibited good stability and capability to detect DA in beef samples, and thus is a promising candidate for simple and inexpensive sub-nanomolar detection of DA, especially in the presence of UV-absorbing compounds.     

Voltammetric behavior of nicotine at pencil graphite electrode and its enhancement determination in the presence of anionic surfactant

The electrochemical oxidation of nicotine was studied in aqueous as well as micellar media at a pencil graphite electrode using cyclic, differential pulse and square-wave voltammetric techniques. The compound was oxidized irreversibly at low positive potentials in one (in acidic and neutral media) or two (in alkaline media) oxidation steps. The response was evaluated with respect to pH, scan rate, addition of surfactant and other variables. For analytical purposes, very resolved voltammetric peaks at +0.84 V (versus Ag/AgCl) were obtained in phosphate buffer at pH 7.0 containing 2 mM sodium dodecylsulfate using square-wave mode. The process could be used to determine nicotine concentrations in the range of 7.6–107.5 μM with a detection limit of 2.0 μM (0.33 mg L⁻¹). The proposed method was applied to the determination of nicotine in different brands of commercial cigarettes.     

Electrochemical behavior of dopamine in the presence of citrate: Reaction mechanism

The electrochemical behavior at a mercury electrode of dopamine (DA) in the presence of citrate was investigated in aqueous solution, using cyclic voltammetry and alternating current polarography. The influence of the composition of the supporting electrolyte, citrate concentration and pH was evaluated. At potentials more positive than 250 mV DA and Hg are oxidized yielding, in the presence of citrate, dopaminoquinone (DQ) and Hg(II). Hg(II) reacts with the DA forming DQ, leucodopaminochrome (LDC) and dopaminochrome (DC). DQ undergoes further reduction at 200 mV. Citrate, in the form of Cit³⁻, stabilizes the DC formed and this new electroactive compound suffers further reduction at −250 mV. This reaction pathway inhibits the formation of polymerized films on the surface of solid state electrodes and allows the determination of DA using the mercury electrode.     

Preparation and characterization of the dopamine film electrochemically deposited on a gold template and its applications for dopamine sensing in aqueous solution

A dopamine polymer film was electrogenerated on the bare gold template from a 5 × 10⁻³ M dopamine solution in phosphate buffer at pH 7 and next subjected to overoxidation in 0.1 M sodium hydroxide solution. The overoxidized dopamine polymer film obtained shows good permeability to cationic species and was used for quantitative determination of dopamine. A linear relationship between dopamine concentration and current response was obtained in the range of 1 × 10⁻⁶ M to 6 × 10⁻⁴ M with the detection limit 2 × 10⁻⁷ M. The results have shown that using the overoxidized dopamine film it is possible to perform electrochemical analysis of dopamine without interference of ascorbic and uric acids, which is the major limitation in dopamine determination. The modified electrode shows good selectivity, sensitivity, reproducibility and high stability.     

Voltammetric determination of bisoprolol fumarate in pharmaceutical formulations and urine using single-wall carbon nanotubes modified glassy carbon electrode

The electrochemistry of bisoprolol fumarate (BF) has been investigated by differential pulse voltammetry at a single-wall carbon nanotubes (SWNTs) modified glassy carbon electrode (GCE). The prepared electrode showed an excellent electrocatalytic activity towards the oxidation of BF leading to a marked improvement in sensitivity as compared to bare glassy carbon electrode where electrochemical activity for the analyte cannot be observed. The SWNTs-modified GCE exhibited a sharp anodic peak at a potential of ∼950 mV for the oxidation of BF. Under optimum conditions linear calibration curve was obtained over the BF concentration range 0.01-0.1 mM in 0.5 M phosphate buffer solution (pH 7.2) with a correlation coefficient of 0.9789 and detection limit of 8.27 × 10⁻⁷ M. The modified electrode has been applied for the drug determination in human urine with no prior extraction and in commercial tablets. The proposed method has also been validated.