Caffeine content in coffee as influenced by grinding and brewing techniques

The caffeine content of coffee as influenced by various coffee preparation methods was investigated. The variables studied included the coffee solids to water volume ratio, the volume of coffee prepared, home versus store grinding, and drip/filtered versus boiling. Caffeine contents per 177 ml (6 oz) of coffee ranged from 50 to 143 mg, depending upon the mode of preparation. As expected, more coffee solids and larger extents of grinding led to significantly higher caffeine contents in filtered coffee. Larger volumes of coffee prepared at a constant coffee solids to water ratio also yielded significantly higher caffeine contents. Homegrinding yielded caffeine contents similar to that of store-ground coffee. Boiled coffee had caffeine contents equal to or greater than filtered coffee, depending upon the length of boiling time. The variable caffeine contents in coffee resulting from the mode of preparation should be recognized and addressed by both food composition data bases and epidemiologists.     

A stochastic approach for integrating strain variability in modeling Salmonella enterica growth as a function of pH and water activity

Strain variability of the growth behavior of foodborne pathogens has been acknowledged as an important issue in food safety management. A stochastic model providing predictions of the maximum specific growth rate (μ_max) of Salmonella enterica as a function of pH and water activity (a_w) and integrating intra-species variability data was developed. For this purpose, growth kinetic data of 60 S. enterica isolates, generated during monitoring of growth in tryptone soy broth of different pH (4.0-7.0) and a_w (0.964-0.992) values, were used. The effects of the environmental parameters on μ_max were modeled for each tested S. enterica strain using cardinal type and gamma concept models for pH and a_w, respectively. A multiplicative without interaction-type model, combining the models for pH and a_w, was used to describe the combined effect of these two environmental parameters on μ_max. The strain variability of the growth behavior of S. enterica was incorporated in the modeling procedure by using the cumulative probability distributions of the values of pH_min, pH_opt and a_wmin as inputs to the growth model. The cumulative probability distribution of the observed μ_max values corresponding to growth at pH 7.0-a_w 0.992 was introduced in the place of the model's parameter μ_opt. The introduction of the above distributions into the growth model resulted, using Monte Carlo simulation, in a stochastic model with its predictions being distributions of μ_max values characterizing the strain variability. The developed model was further validated using independent growth kinetic data (μ_max values) generated for the 60 strains of the pathogen at pH 5.0-a_w 0.977, and exhibited a satisfactory performance. The mean, standard deviation, and the 5th and 95th percentiles of the predicted μ_max distribution were 0.83, 0.08, and 0.69 and 0.96 h^− 1, respectively, while the corresponding values of the observed distribution were 0.73, 0.09, and 0.61 and 0.85 h^− 1. The stochastic modeling approach developed in this study can be useful in describing and integrating the strain variability of S. enterica growth kinetic behavior in quantitative microbiology and microbial risk assessment.     

One-step colloidal synthesis of biocompatible water-soluble ZnS quantum dot/chitosan nanoconjugates

Quantum dots (QDs) are luminescent semiconductor nanocrystals with great prospective for use in biomedical and environmental applications. Nonetheless, eliminating the potential cytotoxicity of the QDs made with heavy metals is still a challenge facing the research community. Thus, the aim of this work was to develop a novel facile route for synthesising biocompatible QDs employing carbohydrate ligands in aqueous colloidal chemistry with optical properties tuned by pH. The synthesis of ZnS QDs capped by chitosan was performed using a single-step aqueous colloidal process at room temperature. The nanobioconjugates were extensively characterised by several techniques, and the results demonstrated that the average size of ZnS nanocrystals and their fluorescent properties were influenced by the pH during the synthesis. Hence, novel ''cadmium-free’ biofunctionalised systems based on ZnS QDs capped by chitosan were successfully developed exhibiting luminescent activity that may be used in a large number of possible applications, such as probes in biology, medicine and pharmacy.     

Hydrogen production via solar‐aided water splitting thermochemical cycles with nickel ferrite: Experiments and modeling

Water splitting — thermal reduction cyclic studies with NiFe₂O₄ redox materials were performed in a differential fixed‐bed laboratory reactor in the temperature range 700–1,400^°C to quantify the effects of operation temperatures and steam mole fraction on hydrogen and oxygen yields. Hydrogen yield increased drastically by an increase of the water splitting temperature from 800 to 1,000^°C reaching a plateau at 1,100^°C. In parallel, a simple mathematical model was formulated describing the water splitting process via the heterogeneous surface reactions of water vapor with the redox powder material, from which, in conjunction to the aforementioned experiments, the kinetic parameters of the water splitting and thermal reduction reactions were extracted. The water splitting kinetic constants exhibited weak temperature dependence between 700 and 1,100^°C suggesting the existence on the redox material of more than one type of oxygen storage sites with respect to ease of exposure and accessibility to the gas phase. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1213–1225, 2013     

Energetic Effects of Substitution of La–Nd and Si–Ge Oxyapatite‐Type Materials

A series of lanthanide oxyapatites, neodymium silicates (Nd_9.33?xM_3x/2(SiO₄)₆O₂; x = 0.0 and 2.0 and M = Ca, Sr, and Ba), and lanthanum germanate (La₁₀(GeO₄)₆O₃) were prepared by a variety of heat treatments and characterized. High‐temperature oxide melt solution calorimetry in molten 2PbO–B₂O₃ solvent at 1078 K was performed to determine their enthalpies of formation from constituent oxides at room temperature. The energetics of these materials is discussed in terms of the effects of doping on two crystallographic sites, the lanthanide and tetrahedral sites. The enthalpy of formation from oxides becomes less exothermic by substituting La with Nd throughout the whole series, in both doped and undoped compositions, reflecting the smaller radius and lower basicity of Nd compared with La. Cation stoichiometric lanthanum germanate apatite (La₁₀(GeO₄)₆O₃) shows a more endothermic enthalpy of formation than the corresponding silicate, reflecting the larger radius and lower acidity of Ge than Si.     

Effects of pre‐emulsifying fat/oil on meat batter stability,texture and microstructure

The effects of pre‐emulsified beef fat and canola oil (CO) (25%) with Tween 80 (T‐80) or sodium caseinate (SC) were studied in beef meat batters prepared at three protein levels (9%, 12% and 15%). Raising meat protein level to 15% resulted in low emulsion stability of products prepared with CO. Using pre‐emulsified beef fat with Tween 80 (BF‐T80) showed significantly higher fat and water losses at all protein levels. There were no differences in fat and water losses between pre‐emulsified beef fat and CO when SC was used at the 9% and 12% protein levels compared to the controls (non pre‐emulsification). Light microscopy revealed fat globule coalescence in the CO meat batters prepared with 15% protein and BF‐T8 treatments, as well as formation of fat channels and more protein aggregation; both resulted in lower emulsion stability. Using SC to emulsify fat/oil produced a finer dispersion of fat globules compared to all the other treatments.     

Cryopreservation of Mesenchymal Stem Cells Using Medical Grade Ice Nucleation Inducer

Mesenchymal stem cells (MSCs) can differentiate into multiple different tissue lineages and have favourable immunogenic potential making them an attractive prospect for regenerative medicine. As an essential part of the manufacturing process, preservation of these cells whilst maintaining potential is of critical importance. An uncontrolled area of storage remains the rate of change of temperature during freezing and thawing. Controlled-rate freezers attempted to rectify this; however, the change of phase from liquid to solid introduces two extreme phenomena; a rapid rise and a rapid fall in temperature in addition to the intended cooling rate (normally −1 °C/min) as a part of the supercooling event in cryopreservation. Nucleation events are well known to initiate the freezing transition although their active use in the form of ice nucleation devices (IND) are in their infancy in cryopreservation. This study sought to better understand the effects of ice nucleation and its active instigation with the use of an IND in both a standard cryotube with MSCs in suspension and a high-throughput adhered MSC 96-well plate set-up. A potential threshold nucleation temperature for best recovery of dental pulp MSCs may occur around −10 °C and for larger volume cell storage, IND and fast thaw creates the most stable process. For adhered cells, an IND with a slow thaw enables greatest metabolic activity post-thaw. This demonstrates a necessity for a medical grade IND to be used in future regenerative medicine manufacturing with the parameters discussed in this study to create stable products for clinical cellular therapies.     

Melting temperature measurement of refractory oxide ceramics as a function of oxygen fugacity using containerless methods

An aerodynamic conical nozzle levitator (CNL) has been used to measure the melting temperatures of refractory ceramics. The well-established method of cooling traces has been adapted to allow measurements for air-sensitive samples using a controlled atmosphere, where the oxygen partial pressure can be adjusted and monitored in real time. In this study, we explain the details of a system that we developed for use at the Spallation Neutron Source (Oak Ridge National Laboratory). Measurements of the melting behavior of (Fe,Cr,Al)₃O₄ spinels were made between log (P_O2 (atm)) of −0.7 and −5. The melting temperature of hercynite is found to be oxygen potential dependent, ranging between 1692 and 1767°C at log (P_O2) values from −4.42 to −0.70.     

Explicit model predictive control of gas–liquid separation plant via orthogonal search tree partitioning

Solutions to constrained linear model predictive control (MPC) problems can be pre-computed off-line in an explicit form as a piecewise linear (PWL) state feedback defined on a polyhedral partition of the state space. This admits implementation at high sampling frequencies in real-time systems with high reliability and low software complexity. Recently, algorithms that determine an approximate explicit PWL state feedback solution by imposing an orthogonal search tree structure on the partition, have been developed, and it has been shown that they may offer computational advantages. This paper considers the application of an approximate approach to the design of an explicit model predictive controller for a two-input two-output laboratory gas–liquid separation plant, including experimental evaluation. The approximate explicit MPC controller achieves performance close to that of the conventional MPC, but requires only a fraction of the real-time computational machinery, thus leading to fast and reliable computations.