EFFECT OF PARTICLE SIZE AND SAMPLE SIZE ON LIPID STABILITY OF MILLED FLAXSEED (Linum usitatissimum L.)

Experiments were conducted to determine the effect of sample size and particle size on lipid oxidation of milled flaxseed. An initial experiment showed that most of the lipid oxidation detected in milled flaxseed samples occurred on the surface that was exposed to the air during storage. In a subsequent experiment, milled flaxseed at 100, 200 and 300 g were stored in the dark in rectangular pans for 8, 24 and 48 days at 50C. Lipid oxidation, as determined by surface lipid content, peroxide value and α-linolenic acid content, was lower in the 300 g samples than in the 100 g samples of milled flaxseed. Large versus small samples had less apparent lipid oxidation because of their inherently lower surface to volume ratio. In a third experiment, oxidation was lower in lipid extracted from coarse ( > 600 µm) than fine particles ( < 600 µm), after 48 days of storage.

PRACTICAL APPLICATIONS

This research has practical applications to the flaxseed milling and food industries. These results show that assessment of lipid oxidation in milled flaxseed needs to consider sample size (collection). Milled flaxseed oxidized predominantly at the sample surface where a polymerized layer of flaxseed particles formed over time. Relatively little oxidation occurred in the interior of the sample. Thus, sampling from the surface or interior of a milled flaxseed sample will end in different results and conclusions. Similarly, results will vary with surface : interior ratio of milled flaxseed. Food manufacturers may want to discard the top layer of milled flaxseed that has been exposed to air. Lipid oxidation was less with coarse than fine particles. Thus it would be prudent not to use milled flaxseed with a finer particle size than is necessary for acceptable end-use quality.     

NiN4/Cr修饰的石墨烯电化学固氮电极

工业上应用哈伯工艺法合成氨过程要求严苛, 需要消耗大量能源且二氧化碳排放量大。因此, 开发在常规环境条件下通过电催化氮还原反应的清洁技术, 对未来可持续的能源转化进程具有重要意义。本研究采用密度泛函理论计算方法, 对TM₁N₄/TM₂嵌入石墨烯的氮还原反应进行了全面研究。在充分考虑活性和稳定性的情况下, 研究结果表明, NiN₄/Cr锚定石墨烯通过酶促反应途径表现出最佳的催化活性, 其中第一次加氢为电位决定步骤, 起始电位为0.57 V, 优于商业Ru基材料。此外, 与单一的Cr原子修饰的石墨烯相比, 引入NiN₄官能团降低了ΔG_max并提高了电催化性能。根据Mulliken电荷分析, 催化剂的催化活性主要来源于载体和反应中间体之间的电子转移。上述结果为高效合成氨提供了电极候选材料, 进一步深化了相应的电催化机理。     

1H-NMR study of bovine myoglobin autoxidation. Influence of muscle type and time post mortem

¹H NMR spectroscopy was used to determine first order rate constants at four temperatures (300, 304, 308, 312 K) and activation energies of the autoxidation reaction for oxymyoglobin. the haeminic pigment was purified from two bovine muscles with different colour stabilities ( psoas major (PM) and longissimus lumborum (LL)) at 2h (day 0) and 192 h (day 8) post mortem. to characterize this autoxidation reaction, we have focused attention on the time-temperature dependent disappearance of the Val-E11 methyl group signal. This study showed that, whatever the time post mortem , although the myoglobin autoxidation rate was greater for PM than for LL muscle, the activation energies were similar. It was also worth noting that, in the range 300–312 K, the average ratio of autoxidation rate constants between day 8 and day 0 was near 1.6 for the two muscles studied. It is reasonable to think that oxidative processes developed during 8 days meat storage have led to a structural change within the cavity of the heme pocket of the myoglobins. Moreover, only one orientation of the porphyrin within the heme pocket was noted for the two muscles studied.     

EFFECT OF IMMATURE AND OFF-COLORED SEEDS ON THE LIPID QUALITY OF MILLED FLAXSEED

The effect of visibly inferior flaxseed ( Linum usitatissimum L.) on the lipid quality of milled flaxseed was investigated. Flaxseed was aspirated and separated into low-, medium- and high-density fractions. All density fractions contained ≤ 0.1% broken seed, ≤ 0.4% contrasting seed and ≤ 0.25% extraneous material. The low-density fraction contained the most immature (2.8%) and off-colored seed (4.1%). Immature seed had a lipid content of 40.8%, a peroxide value (PV) of 2.69 meq/kg and a free fatty acid (FFA) content of 1.06%. The off-colored seed had a lipid content of 38.1%, a PV of 5.79 meq/kg, and a FFA content of 1.89%. Hand-cleaned seed (averaged across fraction density) had a lipid content of 41.4%, a PV of 0.41 meq/kg and FFA content of 0.37%. The removal of seed defects improved flaxseed quality and improved lipid quality in the low-density fraction.

PRACTICAL APPLICATIONS

Lipid oxidation is a major concern when using milled flaxseed as a food ingredient. These results indicate the importance of removing off-colored and immature flaxseed. Seed lots that contain immature and off-colored seed likely will have poor lipid quality and, when milled, be more susceptible to lipid oxidation during storage than will seed lots free of immature and off-colored seed.     

Atomic force microscope (AFM) combined with the ultramicrotome: a novel device for the serial section tomography and AFM/TEM complementary structural analysis of biological and polymer samples

A new device (NTEGRA Tomo) that is based on the integration of the scanning probe microscope (SPM) (NT‐MDT NTEGRA SPM) and the Ultramicrotome (Leica UC6NT) is presented. This integration enables the direct monitoring of a block face surface immediately following each sectioning cycle of ultramicrotome sectioning procedure. Consequently, this device can be applied for a serial section tomography of the wide range of biological and polymer materials. The automation of the sectioning/scanning cycle allows one to acquire up to 10 consecutive sectioned layer images per hour. It also permits to build a 3‐D nanotomography image reconstructed from several tens of layer images within one measurement session. The thickness of the layers can be varied from 20 to 2000 nm, and can be controlled directly by its interference colour in water. Additionally, the NTEGRA Tomo with its nanometer resolution is a valid instrument narrowing and highlighting an area of special interest within volume of the sample. For embedded biological objects the ultimate resolution of SPM mostly depends on the quality of macromolecular preservation of the biomaterial during sample preparation procedure. For most polymer materials it is comparable to transmission electron microscopy (TEM). The NTEGRA Tomo can routinely collect complementary AFM and TEM images. The block face of biological or polymer sample is investigated by AFM, whereas the last ultrathin section is analyzed with TEM after a staining procedure. Using the combination of both of these ultrastructural methods for the analysis of the same particular organelle or polymer constituent leads to a breakthrough in AFM/TEM image interpretation. Finally, new complementary aspects of the object's ultrastructure can be revealed.     

Routine patch testing with the preservative system Kathon CG

Of 1620 patients routinely patch tested with Kathon CG 100 p.p.m. aqua for suspected allergic contact dermatitis, 81 (5.0%) had a positive reaction. Sixty-two reactions (3.8%) were relevant for the dermatitis for which the patient consulted the dermatologist. Most patients were females who presented with dermatitis of the hands and/or face. Forty-six per cent of the patients had become sensitized by using cosmetic products on healthy skin. The other 54% had pre-existing dermatitis, especially atopic dermatitis and irritant dermatitis. Most reactions were caused by moisturizing creams.     

Antimicrobial coatings — obtaining and characterization

In this paper, we present inorganic–organic hybrid coatings with polymer matrix (water soluble) that contain silver nanoparticles (AgNPs). The structure and morphology of coating materials were determined by infrared spectroscopy (FT–IR) and scanning electron microscopy (SEM). Therefore, the antimicrobial activities and mechanisms of coatings for several pathogenic bacteria (Bacilius cereus and Staphylococcus aureus) were investigated. It was demonstrated that the obtained material with silver nanoparticles keep their antimicrobial effect even if they are subjected to several cycles of washing with water and detergent.     

Biosorption of Rare Earth Elements

Abstract

By using X-ray microanalysis, the mechanism of sorption of rare earth elements (REE) and their localization in cells of Candida utilis were found to depend on the metal ion speciation in solution, the permeability of the cytoplasmic membrane (CPM), and elemental composition of cells. Sorption capacity of the yeast cells increased with the increase in the pH of solution, which is connected with the extent of metal hydrolysis. Cells with native permeability of CPM did not sorb either scandium at pH values below 4.5 or lanthanum and samarium at pH values below 5.0. Such cells accumulate rare earth elements on surface structures. Only the cells with impaired CPM could sorb REE from the acid solutions. In this case, REE were accumulated inside the cells due to the interaction with phosphorus-containing compounds; the amount of sorbed REE depended on the content of phosphorus in the yeast cells. The yeast cells were shown to have extremely high affinity to scandium which thus can be selectively sorbed from solutions containing other REE, iron, and aluminum.     

Composition, Solubility and Emulsifying Properties of Granules and Plasma of Egg Yolk

Yolk was fractionated by a low speed centrifugation into granules and plasma. The composition, solubility and emulsifying properties of granules and plasma were compared to those of industrial spray-dried yolk. Granules contained about half the lipids and cholesterol and about double the proteins of yolk and plasma. Yolk and granules required an ionic strength ≥ 0.3M sodium chloride to become solubilized at pH 7.0, whereas plasma was solubilized at any ionic strength. At about 80% solubility, yolk, granules and plasma had similar emulsifying activities and granules had the best emulsion stabilization. Results suggest that granules could be used as stabilizers in food emulsions.     

BISPECTRAL ANALYSIS OF THE CUTTING PROCESS

A higher order spectral analysis of the cutting process is presented with the purpose of indicating the chatter. First, the information contents of the cutting force components are compared using a bicoherence estimator. The analysis reveals that all three components are equally informative. Additionally, the magnitude bispectrum's and the bicoherence's estimator efficiency in identifying chatter is studied with respect to three different cutting regimes. In two of the regimes, which are denoted as strong and weak chatter, several interactions between spectral components in both the magnitude bispectra and bicoherence estimators are outstanding. This suggests the presence of quadratic-type non-linearities in the dynamics of chatter. In the third chatter-free regime of cutting, the magnitude bispectrum and bicoherence estimators reflect almost insignificant interactions between spectral components. It is shown that both magnitude bispectrum and bicoherence estimators identify this reduction in the quadratic-type non-linearities. However, using the magnitude bispectrum is numerically slightly more efficient when compared to the bicoherence estimator, since calculating the magnitude bispectrum is numerically less demanding. Since only short time series of data are available for on-line characterization, the amount of averaging is often insufficient when calculating estimators. This leads to unreliable values of the estimators. In the present work we try to overcome this problem by utilising a combination of a standard segment and additional inner triangle averaging. This approach decreases the sensitivity of the estimator values to the small changes of input parameters. The presented combination is then applied in the bicoherence analysis of the cutting process.