Freezing Characteristics and Storage Stability of Broccoli (Brassica oleracea L. var. botrytis L.) Under Osmodehydrofreezing and Ultrasound-Assisted Osmodehydrofreezing Treatments

Freezing characteristics (freezing time, latent heat of fusion of ice, and freezable water content) and quality parameters (drip loss, color, firmness, and l-ascorbic acid content) of broccoli (osmodehydrofrozen and ultrasound-assisted osmodehydrofrozen) during frozen storage were investigated. Freezing time, latent heat of fusion of ice, and freezable water content of osmodehydrated samples decreased significantly compared to samples which were not under osmotic dehydration. The changes of drip loss, color, firmness, and l-ascorbic acid content of osmodehydrofrozen and ultrasound-assisted osmodehydrofrozen broccoli during frozen storage were inhibited markedly compared to samples which were not submitted to osmotic dehydration before freezing. Compared to osmotic dehydration, the ultrasound-assisted osmotic dehydration shortened the needed dehydration time and better preserved the firmness and l-ascorbic acid content after osmotic dehydration pretreatment. In addition, the ultrasound-assisted osmotic dehydration minimized the drip loss and loss of l-ascorbic acid content and better maintained the color and firmness when stored at ?25 °C for 6 months. These findings indicate that it is promising to apply ultrasound-assisted osmodehydrofreezing in freezing and frozen storage of food.     

Effect of Power Ultrasound and Pulsed Vacuum Treatments on the Dehydration Kinetics,Distribution, and Status of Water in Osmotically Dehydrated Strawberry: a Combined NMR and DSC Study

The effect of power ultrasound and pulsed vacuum (PV) treatments on the dehydration kinetics and the status of water during osmotic dehydration of strawberries was investigated. Low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) were used to determine the spatial distribution and status of water within the cellular and intercellular spaces. Differential scanning calorimetry (DSC) was used to determine the freezing point depression and the amount of frozen water. Osmotic treatment was performed by immersing the samples in 25 and 50 % (w/w) sucrose solutions at 40 °C for 3 h. Water loss and solid gain of strawberry samples were measured and the data were fitted by Peleg’s model. The Peleg’s model fitted the experimental water loss and solid gain kinetics data well (R ²?>?0.98). At a given sucrose concentration, the highest water loss and the highest decrease in firmness occurred while using ultrasound treatment, while the highest solid gain and the highest firmness values were achieved by pulsed vacuum treatment. LF-NMR signals were able to quantify the effect of water-osmotic solute exchange on the cell compartments (vacuole, cytoplasm plus intercellular space, and cell wall). The LF-NMR data showed that the relative space occupied by the vacuole decreased and the relative space occupied by the cytoplasm and intercellular space were increased due to these osmotic treatments. MRI results indicated that a bright “water strip” appeared in the periphery of all the osmotically dehydrated samples. DSC results showed that the decrease in water content and the increase in the osmotic solutes depressed the initial freezing point and the freezable water content in osmotically dehydrated strawberry.     

Modelling thermal fluctuations in non-ideal fluids with the lattice Boltzmann method

Recently, we proposed a theoretical framework to include thermal fluctuations into the Lattice Boltzmann (LB) method for non-ideal fluids. Here, we apply a variant thereof to a certain class of force-based non-ideal fluid LB models. We find that ideal-gas-like noise is an exact result of the fluctuation-dissipation theorem in the hydrodynamic regime. It is shown that satisfactory equilibration of the density and fluid momentum can be obtained in a simulation over a wide range of length scales.     

Hexafluorozirconic acid based surface pretreatments: Characterization and performance assessment

A new phosphate-free pretreatment from Henkel Corp. named TecTalis^®, was investigated. The treatment bath is composed of dilute hexafluorozirconic acid with small quantities of non-hazardous components containing Si and Cu. The corrosion resistance of treated steel was compared to samples treated in a phosphate conversion coating bath, in simple hexafluorozirconic acid and in TecTalis without the addition of the Cu-containing component. Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) were used to characterize the coating surface morphology, structure and composition. A Quartz Crystal Microbalance (QCM) was used for studying film growth kinetics on thin films of pure Fe, Al and Zn. Electrochemical Impedance Spectroscopy (EIS) was performed on treated and painted steel for studying long-term corrosion performance of the coatings. The phosphate-free coating provided long-term corrosion performance comparable to that of phosphate conversion coatings. The coatings uniformly cover the surface in the form of 10–20 nm sized nodules and clusters of these features up to 500 nm in size. The coatings are usually about 20–30 nm thick and are mostly composed of Zr and O with enrichment of copper at randomly distributed locations and clusters.     

Spray Drying of Skim Milk Mixed with Milk Permeate: Effect on Drying Behavior,Physicochemical Properties,and Storage Stability of Powder

The possibility of using milk permeate (MP) to lower the protein level of skim milk powder (SMP) in producing powders of 34% and lower protein is explored. Skim milk suspensions with various levels of MP were prepared by mixing SMP and MP powder (MPP) at the ratios of 1:0, 7:3, 3:7, and 0:1: from 34 to 5.3% protein. The suspensions were dried in a spray dryer with inlet and outlet temperatures of 180 and 80°C, respectively. Increasing permeate concentration in the mixture showed a greater tendency to stickiness manifested by lowered the cyclone recovery of the powder as more powder stuck on the wall of the dryer. Increasing permeate concentration in the resultant powder did not significantly affect the bulk density but led to a reduction in the particle size and also made the powder slight green and yellowish in color. It also found to lower the glass transition temperature (T_g ) of the skim milk powder (SMP) and induce crystallization of lactose at lower water activity (a_w  ≥ 0.328 for SMP:MPP of 3:7 and 0:1 compared to a_w  ≥ 0.0.432 for SMP:MPP of 1:0 and 3:7). Addition of MP in SMP lowered the T_g values of the resulting powders. The permeate fraction in spray-dried SMP/MPP mixtures found to lower the critical a_w and moisture content, suggesting the SMP mixed with MPP is more likely to become sticky than SMP alone (at 34% protein) when stored at a similar water activity and moisture content.     

Interphase of polyoctenamer-single-wall carbon nanotubes by thermogravimetric analysis in air

Non-isothermal thermogravimetric analysis in air, of polyoctenamer-single wall carbon nanotubes (PO-SWNTs), loaded by various amounts of SWNTs up to 10% wt., at different heating rates (ranging from 5 to 40°C/min) is reported. The thermal degradation in the air of PO_SWNTs is dominated by a main single sigmoidal dependence, assigned to the polymer and eventually polymer-nanofiller interphase, over which a weaker sigmoid assigned to the thermo-oxidative degradation of the nanofiller is superimposed at higher temperatures. The temperature at which the nanocomposite's residual mass fraction reaches x% wt. of the initial mass, T_x%, is reported (for x = 5, 50, and 85). The dependence of T_x% on the heating rate and the loading by nanotubes is analyzed. The temperature derivative of the thermograms defines new parameters (inflection residual mass fraction and inflection temperature) and (degradation) width. Their dependence on the loading by SWNTs was reported. Estimation of the interphase in polymer-based nanocomposites is based on the postulate that the dependence of the inflection temperature on the composition of the nanocomposite obeys a Fox-like dependence, where the bulk polymer and the polymer trapped within the interphase are considered as a blend of two miscible polymers. Complementary Raman, x-ray diffraction, and differential scanning calorimetry support these results.     

Short communication: Dairy bedding type affects survival of Prototheca in vitro

Protothecae are algal pathogens, capable of causing bovine mastitis, that are unresponsive to treatment; they are believed to have an environmental reservoir. The role of bedding management in control of protothecal mastitis has not been studied. The purpose of this study was to evaluate the growth of either environmental or mastitis-associated Prototheca genotypes in dairy bedding materials that are commonly used in Maine. Prototheca zopfii genotypes 1 and 2 (gt1 and gt2) were inoculated into sterile broth only (control ), kiln-dried spruce shavings, “green” hemlock sawdust, sand, or processed manure-pack beddings with broth, and incubated for 2 d. Fifty microliters of each isolate was then cultured onto plates and the resulting colonies counted at 24 and 48 h postinoculation. Shavings were associated with significantly less total Prototheca growth than other bedding types. Growth of P. zopfii gt1 was significantly higher than that of gt2 in the manure-pack bedding material. Spruce shavings, compared with manure, sand, or sawdust, may be a good bedding type to prevent growth of Prototheca. Based on these in vitro findings, bedding type may affect Prototheca infection of cattle in vivo.     

Effect of flaxseed meal on the dynamic mechanical properties of starch-based films

Starch (S)–flaxseed meal (FM) biofilms were prepared from potato and maize starch by incorporating FM up to 15% (dry solid basis) and using glycerol as plasticizer. The dynamic mechanical properties, tensile properties and water vapor permeability (WVP) of these films were measured. The storage modulus of both the starch (control) and starch–FM films decreased as temperature increased. Tan δ increased initially in all the films with increase in temperature until a peak value was reached which allowed the determination of glass transition temperature (T_g). Both tensile strength and Young’s modulus of the starch–FM films increased with increase in the FM content. The WVP of the potato starch–FM films first increased to 2.261 (×10⁵ g m⁻² h⁻¹ Pa⁻¹) when FM content increased to 5% and decreased down to 1.832 (×10⁵ g m⁻² h⁻¹ Pa⁻¹) with further increase in the FM content to 15%. While the WVP values of the cornstarch and corn starch–FM films were not significantly (p > 0.05) different. The incorporation of FM increased the tensile strength, decreased the % elongation at break and increased the T_g.     

Hydrostatic pressure effects on the structural properties of condensed whey protein/lactose systems

Hydrostatic pressure effects on whey protein/lactose mixtures were recorded with subsequent analysis of their structural, molecular and glass transition properties in comparison to thermal effects at atmospheric pressure. Experimental techniques used were small deformation dynamic oscillation in shear, modulated differential scanning calorimetry, Fourier transform infrared spectroscopy, and theoretical modelling of glass transition phenomena. Levels of solids ranged from 30 to 80% (w/w) in formulations with a protein/co-solute ratio of four-to-one. Addition of lactose protects the secondary conformation of the protein under application of high hydrostatic pressure. Nevertheless, pressurized protein systems are able to form three-dimensional structures due to the reduction in polymeric free volume and the development of an efficient friction coefficient amongst tightly packed particles. Systems can be seen as developing a “molten globular state”, where the structural knots of pressure-treated networks remain in the native conformation but achieve intermolecular cross-linking owing to frictional contact. Furthermore, pressure treated assemblies of condensed whey protein preparations could match the viscoelasticity of the thermally treated counterparts upon cooling below ambient temperatures. That allowed examination of the physical state and morphology of a condensed preparation at 80% solids by the combined framework of reduced variables and free volume theory thus affording derivation of glass transition temperatures for pressurized and atmospheric samples.