High pressure viscosity measurement with falling body type viscometers

With the increasing number of applications of high pressure chemical and process technologies across a range of engineering fields, there is a corresponding growing interest in the need to measure accurately and reliably important rheological parameters. Of these, the measurement of good and reliable viscosity data is critical in engineering design. The ability to measure viscosity at high pressure, however, presents a number of engineering challenges and a number of innovative viscometers have consequently been devised and operated. This review considers those devices which are based on the falling body principle and considers falling ball, cylinder and needle in open and closed systems. Viscosity is determined from the rate of fall and the usual challenge is to detect its position during descent. While reliable data can be obtained from these viscometers, there is a discrepancy between theoretical values and actual values. This is the result of end effects in the form of vortices, wake oscillations and hedding. Calibration is therefore necessary in all cases. Improvements to analytical models have been attempted and computation fluid dynamics is also used to examine in more detail the flow fields around bodies to understand and appreciate better the performance of these viscometers

Experimental viscosity measurements of biodiesels at high pressure

The viscosity of biodiesels of soybean and rapeseed biodiesels blended with mineral diesel fuel were measured at pressures of up to 200 MPa. Using a falling sinker-type viscometer reproducible viscosity data were obtained based on the time taken for a sinker to descend a fixed distance down an enclosed tube under the influence of gravity. Measurements were taken using pressures which correspond to those of interest in automotive common rail diesel engines, and at temperatures of between 25oC and 80oC. In all cases, the viscosity of the biodiesel blends were found to increase exponentially for which the blends were noted as being more viscous than pure mineral fuels. A pressure-freezing effect was not observed for the blends

High pressure falling sinker liquid viscosity determination without supplementary density data : a new approach

Accurate measurement and determination of liquid viscosity data under high pressure conditions requires knowledge of liquid density data. In this study, a high pressure falling sinker-type viscometer was used to determine the viscosity of n-dodecane at elevated pressures up to 132 MPa without supplementary knowledge of liquid density. The viscometer, which involves the downward movement of a cylindrical sinker under the influence of gravity through the liquid contained within a closed tube, avoided the need for density data by repeating the sinker-timing experiments with two geometrically similar but different sized sinkers thereby allowing the liquid density in the associated formulae to be eliminated. Furthermore, it was possible to subsequently derive liquid density. Both viscosity and density data were compared to published data for which good correlation was found for viscosity. To minimize errors, it is suggested that the two sinkers for such an approach should be of sufficiently differing densities

Editorial: biodegradable materials

This Special Issue “Biodegradable Materials” features research and review papers concerning recent advances on the development, synthesis, testing and characterisation of biomaterials. These biomaterials, derived from natural and renewable sources, offer a potential alternative to existing non-biodegradable materials with application to the food and biomedical industries amongst many others. In this Special Issue, the work is expanded to include the combined use of fillers that can enhance the properties of biomaterials prepared as films. The future application of these biomaterials could have an impact not only at the economic level, but also for the improvement of the environment

Electrolyte effects on polyacrylic acid-polyvinylpyrrolidone aqueous glycol mixtures for use as de-icing fluids

Rheological and wind tunnels measurements are presented for mixtures of polymers polyacrylic acid [PAA] and polyvinylpyrrolidone [PVP] polymers dispersed in water-1,2 propylene glycol mixture to examine their use as potential aircraft de-icing fluids. PAA solutions which form the basis of de-icing fluids are known to result in undesirable gelation which may lead to undesirable and catastrophic consequences in such applications. In this study, we examine the blending of PVP with PAA blends as alternative de-icing fluid formulations that can reduce the likelihood of forming such irreversible gel deposits. Through adjustment of the electrolyte concentration, the ratio of PAA to PVP as well as the molecular weight of PVP, it is possible to achieve a required viscosity profile to that exhibited by a model de-icing fluid across a range of appropriate temperatures. Wind tunnel tests indicate that the mixtures are capable of meeting the necessary requirements for boundary layer depletion as well as having sufficient capability of retaining a stable layer required during aircraft taxiing

Lipid oxidation kinetics of ozone-processed shrimp during iced storage using peroxide value measurements

In this research, in situ generated ozone exposure/wash cycles of 1, 3, and 5 min applied to shrimp samples either before (BIS) or during iced storage (DIS) has been used to study the lipid oxidation kinetics using the peroxide values (PV). The induction period (IP) as well as PV at end of the IP (PVIP) have been obtained. The rate constants (k) as well as half-lives (t1/2) of hydroperoxides formation for different oxidation stages were calculated. The results showed that both IP and PVIP were lower with BIS (IP between 4.35±0.09 and 5.08±0.23 days; PVIP between 2.92±0.06 and 3.40±0.18 mEq kg−1) compared with DIS (IP between 5.92±0.12 and 6.14±0.09 days; PVIP between 4.49±0.17 and 4.56±0.10 mEq kg−1). The k value for DIS seemed to be the greater compared to BIS. In addition, whilst decreases and increases in t1/2 were found at propagation, respectively, for BIS and DIS, decreases and increases were only found at the induction of oxidation stage(s) for BIS. Further, the PV of ozone-processed samples would fit first order lipid oxidation kinetics independent of duration of ozone exposures. For the first time, PV measurements and fundamental kinetic principles have been used to describe how increasing ozone exposures positively affects the different oxidation stages responsible for the formation of hydroperoxides in ozone-processed shrimp

Effects of high-pressure processing (HPP) on the microbiological, physico-chemical and sensory properties of fresh cheeses: A review

High pressure processing (HPP) is an increasingly popular food processing method that offers great potential within the food industry. The drive to use HPP is to provide minimally processed foods which are safe and have extended shelf-life that rival traditional methods of food processing. HPP is currently being applied to a wide variety of food products, although to date the dairy industry has received little attention. The present paper reviews the effects of HPP on fresh rennet- and acid-coagulated cheeses.In additional to modifying physicochemical and sensory characteristics, HPP is reported to inactivate certain micro-organisms typically found in cheeses. Pathogenic microorganisms such as Listeria monocytogenes and Escherichia coli which contaminate, spoil and limit the shelf-life of cheese can be controlled by HPP. HPP can also cause changes in milk rennet coagulation properties, produce a more continuous or homogeneous protein matrix in cheese, improve cheese structure, texture and yield, aswell as reduce moisture content variations within fresh cheese blocks. Providing HPP can be operated economically, the use of pressure may be an attractive new method for the processing of cheese

Epoxysuccinyl peptide-derived cathepsin B inhibitors: Modulating membrane permeability by conjugation with the C-terminal heptapeptide segment of penetratin

Besides its physiological role in lysosomal protein breakdown, extralysosomal cathepsin B has recently been implicated in apoptotic cell death. Highly specific irreversible cathepsin B inhibitors that are readily cellpermeant should be useful tools to elucidate the effects of cathepsin B in the cytosol. We have covalently functionalised the poorly cellpermeant epoxysuccinyl based cathepsin B inhibitor [RGlyGlyLeu(2S, 3S)tEpsLeuProOH; R=OMe] with the C-terminal heptapeptide segment of penetratin (R=εAhxArg ArgNleLysTrpLysLysNH(2)). The high inhibitory potency and selectivity for cathepsin B versus cathepsin L of the parent compound was not affected by the conjugation with the penetratin heptapeptide. The conjugate was shown to efficiently penetrate into MCF-7 cells as an active inhibitor, thereby circumventing an intracellular activation step that is required by other inhibitors, such as the prodruglike epoxysuccinyl peptides E64d and CA074Me

Is high frequency ultrasound a useful process to add value to out of specification strawberries, raspberries, and blackberries industrially?

Bioactive ingredients can be extracted from surplus soft fruits to add value to them as a fortification ingredient in many new products. Ultrasound‐assisted extraction and spray drying have been heavily studied in the past, with evidence to suggest the positive uptake of these by the food industry. In this paper, strawberries, raspberries and blackberries were examined using a distilled water ‘green’ extraction method with assisted high‐frequency ultrasound and concentration through spray drying. The results showed that crop year and variety had more impact on bioactive concentration than extraction through high‐frequency ultrasound. Two different machines were examined for differences between a cold extraction of water, and a 700 and 2000 Hz industrially relevant probes. Typically, total phenolic content (TPC) was lower in strawberries and blackberries than the control for both methods, however raspberries had a higher GAE mg ml−1 for the 2000 Hz ultrasound than the control. For Radical scavenging (RS) percentage using DPPH Blackberries had higher RS % than the control, whereas strawberries and raspberries had less than the control. These results suggest that ultrasound as a singular method for extracting valuable bioactive ingredients is not suitable with water as the solvent