Cooled, ultrahigh Q, sapphire dielectric resonators for low-noise, microwave signal generation

Ultra-high Q, X-band resonators, used in a frequency discriminator for stabilization of a low-noise signal generator, can provide a means of obtaining significant reduction in phase noise levels. Resonator unloaded Qs on the order of 500 K can be obtained in sapphire dielectric resonator (DR) operating on a low-order (i.e. TE(01)) mode at 77 K and employing high-temperature superconducting (HTS) films installed in the DR enclosure covers. Rigorous analysis for the determination of resonator frequency, modes, and unloaded Q have been carried out using mode matching techniques. Trade-off studies have been performed to select resonator dimensions for the optimum mode yielding highest unloaded Q and widest spurious mode separation. Field distributions within the resonator have been computed to enable practical excitation of the required mode. The results of both analysis and prototype device evaluation experiments are compared for resonators fabricated using enclosures consisting of conventional, metal sidewalls and covers employing HTS films as a function of cover conductivity.     

Sulfur content of crude rapesseed oil from aqueous extraction

Dry heating of rapeseed before grinding increased the sulphur content of the crude rapeseed oil. Boiling the seeds in H₂O before grinding caused a slight decrease in the sulphur level of the oil. Control of pH during boiling of the ground rapeseed increased the sulphur content of the oil from ca. 2 ppm at pH 3.1 to ca. 10 ppm at pH 7.6.     

Label-free determination of picogram quantities of DNA by stripping voltammetry with solid copper amalgam or mercury electrodes in the presence of copper

Highly sensitive label-free techniques of DNA determination are particularly interesting in relation to the present development of the DNA sensors. We show that subnanomolar concentrations (related to monomer content) of unlabeled DNA can be determined using copper solid amalgam electrodes or hanging mercury drop electrodes in the presence of copper. DNA is first treated with acid (e.g., 0.5 M perchloric acid), and the acid-released purine bases are directly determined by the cathodic stripping voltammetry. Volumes of 5-3 microL of acid-treated DNA can easily be analyzed, thus making possible the determination of picogram and subpicogram amounts of DNA corresponding to attomole and subattomole quantities of 1000-base pair DNA. Application of this determination in DNA hybridization detection is demonstrated using surface H for the hybridization (superparamagnetic beads with covalently attached DNA probe) and the mercury electrodes only for the determination of DNA selectively captured at surface H.     

Application of avidin-biotin technology and adsorptive transfer stripping square-wave voltammetry for detection of DNA hybridization and avidin in transgenic avidin maize

The proteins streptavidin and avidin were electrochemically detected in solution by adsorptive transfer stripping square wave voltammetry (AdTS SWV) at a carbon paste electrode (CPE). AdTS SWV was used to quantify biotinylated oligonucleotides, DNA hybridizations, and avidin in extracts of transgenic avidin maize. The detection limits of denatured and native streptavidin were 6 pM and 120 nM, respectively. The results demonstrated that streptavidin/avidin AdTS SWV is a sensitive and specific method for quantifying DNA and proteins in biological samples such as foods and tissue extracts, including genetically modified crops (avidin maize) and other plants in neighboring fields.     

Acrylamide formation in low-fat potato snacks and its correlation with colour development.

A recipe and technological process for the production of low-fat potato snacks (7% fat) was developed at the Institute of Food Technology of Plant Origin (Agricultural University of Poznan) using a combination of extrusion and a roasting process. Due to the character of the product, the level of acrylamide was analysed. At the same time, the influence of temperature and time of heating on acrylamide levels were monitored, as well as the correlation between colour development and acrylamide content. The level of acrylamide in low-fat potato snacks was 489 +/- 26 microg kg(-1), which is comparable to French fries, crackers and cookies but almost three times less than in potato chips, as analysed by other authors. It was also shown that temperature and heating time have a significant influence on acrylamide formation, with temperature having a stronger effect than time. Measurement of colour and acrylamide content at different temperatures and roasting times showed that there is a substantial correlation between lightness (L*), redness (a*), yellowness (b*) and acrylamide concentration as a function of time: r(2) = -0.995, r(2) = 0.996, r(2) = 0.998, respectively. Graduated increases in roasting temperature showed a correlation between lightness (L*) or redness (a*) and acrylamide concentration: r(2) = -0.947 and r(2) = 0.968. Yellowness (b*) was not correlated with acrylamide content as a function of temperature.     

High pressure microfluidization treatment of heat denatured whey proteins for improved functionality

Solutions (5% protein) of a whey protein concentrate (WPC) in fresh acid whey or in water, as well as the fresh whey alone, were adjusted to pH 5.8, 4.8 or 3.8, heat treated at 90 °C for 10 min and further exposed to high pressure (150 MPa) microfluidization treatment. The volumes of sediment after centrifugation were recorded as a measure of the degree of insolubility of the proteins. Microfluidization disrupted the heat-induced aggregates into non-sedimenting whey protein polymers so that in some cases, especially at pH 3.8, the products studied were almost completely resistant to sedimentation after the microfluidization treatments. Heat denatured/microfluidized whey proteins reaggregated upon subsequent heating, with the pH having a major impact on the amount of sediment produced. Microfluidization of aqueous WPC solutions heat-treated before spray- or freeze-drying substantially increased the solubility of the powders upon reconstitution. Heat-induced viscoelastic gels were produced from freeze-dried microfluidized samples processed at pH 3.8 and reconstituted to solutions containing 12% (w/w) protein.     

Effect of filtration on virgin olive oil stability during storage

The effect of filtration and dehydration on the stability and quality of virgin olive oil during storage at room temperature (25 °C) and under accelerated conditions (40 °C) was studied. Different types of monovarietal olive oil, namely unfiltered (UF), filtered (F) and filtered‐dehydrated (FD), were obtained from Arbequina, Colombaia, Cornicabra, Picual and Taggiasca cultivars. Results showed that filtration and dehydration decreased the rate of hydrolysis of the triacylglycerol matrix, especially at the higher temperature and in oils with a higher initial free acidity (e.g. free acidity of 0.82% and 0.63% in UF and FD Colombaia samples, respectively, after 8 months of storage), and delayed the appearance of rancid defects (e.g. UF and FD Arbequina samples lost extra‐virgin grade after 10 and 12 months of storage, respectively). The formation of simple phenols due to the hydrolysis rate of their secoiridoid derivatives was also greater in unfiltered olive oils (e.g. 174 μmol/kg and 137 μmol/kg in UF and FD Picual samples, respectively, after 8 months of storage). Thus, filtration and especially dehydration could help to prolong the shelf life of high‐quality and less stable olive oils like those obtained from the Arbequina and Colombaia varieties.     

The effects of breed,sex, intramuscular fat and ultimate pH on pork tenderness

A study was conducted to evaluate the influence of breed and sex of animals on tenderness of pork. For evaluation, carcasses of pure breed barrows and gilts of Large White, Czech pig meat, Landrace and Duroc were used. For laboratory investigations, the samples of musculus longissimus lumborum et thoracis (20 mm thick) were taken from the same place, at the first cruciate vertebra 48 h post mortem. Seven days post mortem, the texture of heat-processed meat was measured objectively by the shear method on Instron equipped with Warner–Bratzler shear device. Meat tenderness and juiciness were also evaluated sensorially. It was observed that the tenderness of cooked meat is influenced by breed (the tenderest meat was from Duroc breed). The sex of animals has significant effect on meat tenderness too. At the same time, the effects of pH 45 minutes (pH₄₅) and 24 hours (pH₂₄) post mortem and intramuscular fat content on meat tenderness were evaluated. Correlations were found between shear force (tenderness) and intramuscular fat content and also between shear force and pH value 45 min post mortem. The shear force decreased with increasing intramuscular fat content and with increasing pH₄₅ value. Sensory evaluation of tenderness confirmed the objectively measured data.