Stability of anthocyanins in frozen and freeze-dried raspberries during long-term storage: in relation to glass transition

Abstract: Anthocyanins, natural plant pigments in the flavonoid group, are responsible for the red color and some of the nutraceutical benefits of raspberries. This study explores anthocyanin degradation in frozen and freeze‐dried raspberries during storage in relation to glass transition temperatures. Frozen raspberries were stored at ?80, ?35, and ?20 °C, while freeze‐dried raspberries were stored at selected water activity (a_w) values ranging from 0.05 to 0.75 at room temperature (23 °C) for more than a year. The characteristic glass transition temperatures (T′_g) of raspberries with high water content and glass transition temperature (T_g) of raspberries with small water content were determined using a differential scanning calorimeter. The pH differential method was used to determine the quantity of anthocyanins in frozen and freeze‐dried raspberries at selected time intervals. The total anthocyanins in raspberries fluctuated during 378 d of storage at ?20 and ?35, and ?80 °C. Anthocyanin degradation in freeze‐dried raspberries ranged from 27% to 32% and 78% to 89% at a_w values of 0.05 to 0.07 and 0.11 to 0.43, respectively, after 1 y. Anthocyanins were not detectable in freeze‐dried raspberries stored at a_w values of 0.53 to 0.75 after 270 d. First order and Weibull equations were used to fit the anthocyanin degradation in freeze‐dried raspberries. The 1^st‐order rate constant (k) of anthocyanin degradation ranged from 0.003 to 0.023 days^?1 at the selected water activities. Significant anthocyanin degradation occurred in both the glassy and rubbery states of freeze‐dried raspberries during long‐term storage. However, the rate of anthocyanin degradation in freeze‐dried raspberries stored in the glassy state was significantly smaller than the rate of anthocyanin degradation in the rubbery state.     

Natural convection heat transfer from upward-facing plates in saline water

Saltwater or brackish water is used as a coolant in most industries. Therefore, understanding the heat transfer processes and hydrodynamics during the natural convection in saline water is crucial for enhancing the efficiency of a heat exchanger. This study elaborates on the natural convection heat transfer in saline water under atmospheric conditions. A DC power supply is used to regulate the power given to the heater in a liquid pool for thermal analysis. The pool liquid comprises solutions with varying salinity from 0%, 0.2%, 0.5%, and 2%. The effect of varying salinity on the heat transfer coefficient and the thermal aspects encountered during the desalination process is analyzed. The temperature distribution across the surface of the heater is monitored using an infrared camera. It is studied for the solution of different salinities. The heat transfer coefficient and Nusselt number are investigated during natural convection for normal water and salt solution of different concentrations. It is inferred from the study that in the regime of natural convection, there is no significant difference in the Nusselt number for normal water and saltwater for the lower value of temperature difference between the plate and pool. The heat transfer coefficient in 0.2% saline water is higher as compared to the other solutions.     

The interconnected CaCO3 coated SnO2 nanocrystalline dye-sensitized solar cell with superior performance

Design, Development, fabrication and investigation of the I–V characteristics of the DSSC based on interconnected 15 nm SnO₂ nanoparticles covered with a nano-scale thin layer of CaCO₃ are described. The presence of CaCO₃ has been confirmed by its characteristic XRD pattern and EDX plots. The thickness of the protective layer can be conveniently controlled by the molar ratio of SnO₂:CaCO₃ used in the preparation of the thin film and the optimum conditions for best performance of the DSSC are presented together with possible explanations for the variations observed when the molar ratio is changed. An optimum light-to-electricity conversion efficiency of 5.4% in the presence of a layer of CaCO₃ has been obtained which is 3.2 times enhancement over the cell prepared without CaCO₃. The characterization of the surface using different techniques is explained.     

Hydrogenation effect on structural,electrical and optical properties of CdS thin films for solar cell

Adsorption effects would be expected to be of considerable importance with thin films because of the changes in electron location accompanying adsorption. The effects of hydrogenation on structural, optical and electrical properties of the CdS thin films have been reported. GIXRD patterns shows that films have polycrystalline nature with a hexagonal structure. The optical band gap increased after hydrogenation of the film. The variation of conductivity of CdS films have been investigated depending upon the applied voltage at room temperature. The resistivity increased after hydrogenation of the films. Hydrogenated thin films can be used in solar cells because hydrogen plays an important role to modify the physical properties.     

Non-destructive determination of acid–brix ratio of tomato juice using near infrared spectroscopy

Consumer's acceptance of tomato juice depends on its sourness to sweetness ratio and measuring this is important for quality control and marketing. Traditional methods destroy the samples, are time consuming and cannot be used in continuous packing or bottling systems. A non‐destructive method of quality evaluation, using near infrared (NIR) techniques, was tested, by using a portable NIR measuring unit. Spectra of tomato juice of known acid and brix values were determined and, in the wavelength range 703–1124 nm (NIR), a calibration model for acid–brix ratio (ABR) was developed, by using unscrambler software. When used to predict ABR of tomato juice statistical analysis showed minimal standard error (0.009) and satisfactorily high correlation coefficients (0.92) over the wavelength range 1059.5–1124.8 nm, for both calibration and prediction. These values were hardly different from analytical results and the NIR model has potential for non‐destructive prediction of ABR of tomato juice.     

Growth of undoped and Te doped InSb crystals by vertical directional solidification technique

We have successfully grown high mobility undoped and Te doped InSb crystals of size 10–12 mm dia. and 60 mm length under inert argon atmosphere in closed quartz ampoules, by vertical directional solidification (VDS) technique. The crystals showed predominantly (220) orientation along the growth axis. The surface defects, such as voids were reduced drastically by selecting proper lowering rate, rotational speed and cone angle of the ampoule. The high mobility and quality crystals were obtained with the ampoule conical angle less than 20°, lowering rate 5mm/h, and rotational speed 10 rpm.     

Elastic anisotropy and micro-damage processes in polycrystalline ice Part I: Theoretical formulation

A microstructural damage model is developed for polycrystalline ice deforming at the high end of the quasi-static domain of loading. The formation (nucleation) of microcracks is attributed to the extension of grain boundary precursors under the influence of the applied stresses and microstructural stresses resulting from the elastic anisotropy mechanism. In a compressive stress field, a growing population of stable cracks leads to progressive damage in the material. Nucleation, and hence damage accumulation, is influenced by three random variables-the precursor orientation, the basal plane orientation of the grains adjoining the precursor of interest, and the grain size. Model predictions consist of the following steps: (a) computation of microstructural stresses using a first-order approximation of the Eshelby procedure, (b) analysis of nucleation using a mixed-mode fracture criterion, and (c) computation of the elastic compliance using the self-consistent method. When coupled to a creep model, the relative contribution of microcracking and creep to the total deformation can be delineated.     

A MODEL FOR THE COMBINED EFFECTS OF STRESS RATIO AND GRAIN SIZE ON THE LEFM FATIGUE THRESHOLD CONDITION

A long-crack, fatigue-threshold model which explains and predicts the commonly observed effects of stress ratio, R, and grain size, d, on δK₀, is proposed. The inclusion of a grain-size-effect is an extension of a recently proposed model that examined the effect of the R ratio. The extended model is based on the hypothesis that near-threshold, crack growth involves two micro-mechanical processes of fracture; K_max-controlled submicroscopic cleavage, which predominates when the defect concentration is small, and δK-controlled reversed shear which predominates when the defect concentration is large, both processes occurring in a critically stressed volume, V_c, ahead of the crack tip. Defect concentration in V_c is reduced by a low value of R and a coarse grain size and is increased by a high value of R and a fine grain size. Good agreement is shown to exist between predicted and experimental curves of δK₀ versus R and δK₀ versus grain size for several steels and aluminium alloys. In particular, δK₀ is shown to have an upper and a lower bound value for a material. The model may be used as an alternative procedure for obtaining quick, approximate but conservative estimates of δK₀ for practical design applications.