Quality of wheat germ oil extracted by liquid and supercritical carbon dioxide

The extraction of wheat germ oil by liquid and supercritical CO₂ is described from the point of view of both operative method and pretreatment of raw material. The best conditions for wheat germ oil extraction are: pressure, 150 bar; temperature, 40°C; and solvent flow rate, 1.5 L/min at standard temperature and pressure. The yields and fatty acid compositions obtained are very similar to those resulting from the conventional extraction process using hexane as solvent (8.0 wt%), although a higher-quality oil is obtained by using CO₂ as solvent (free fatty acids, 12.4%; tocopherol content, 416.7 mg tocopherol/g wheat germ oil). These factors lead to the conclusion that the extraction process using CO₂ could be economically competitive with the conventional process, since it considerably simplifies the oil refinement stages and completely eliminates the solvent distillation stage, which are the most costly processing steps in terms of energy consumption.     

Determination of peroxide value by fourier transform near-infrared spectroscopy

A Fourier transform-near infrared (FT-NIR) method originally designed to determine the peroxide value (PV) of triacylglycerols at levels of 10–100 PV was improved upon to allow for the analysis of PV between 0 and 10 PV, a range of interest to the edible oil industry. The FT-NIR method uses convenient disposable glass vials for sample handling, and PV is determined by spectroscopically measuring the conversion of triphenylphosphine (TPP) to triphenylphosphine oxide (TPPO) when reacted with hydroperoxides. A partial-leastsquares calibration was developed for 8 mm o.d. vials by preparing randomized mixtures of TPP and TPPO in a zero-PV oil. The method was validated with samples prepared by gravimetric dilution of oxidized oil with a zero-PV oil. It was shown that the American Oil Chemists’ Society primary reference method was quite reproducible (±0.5 PV), but relatively insensitive to PV differences at lower (0–2) PV. The FT-NIR method on the other hand was shown to be more accurate overall in tracking PV, but slightly less reproducible (0.9 PV) due to working close to the limit of detection. The sensitivity and reproducibility of the FT-NIR method could be improved upon through the use of larger-diameter vials combined with a detector having a wider dynamic range. The proposed FT-NIR PV method is simple to calibrate and implement and can be automated to allow for routine quality control analysis of edible fats and oils.     

The preparation of flat H–Si(111) surfaces in 40% NH4F revisited

The reasons why ideally flat H–Si(111) surface can be prepared by NH₄F etching are investigated from correlation between AFM observations and experimental conditions used for etching. It is shown that pitting may be completely suppressed if a one side polished wafer is immersed in an oxygen free solution. An analytical electrochemical study of the (111) and rough face of the same n-Si wafer is presented to yield insight into observations.     

Changes in serum lipids in rats treated with oral cooper

Disturbances in lipid metabolism during copper deficiency in rats are well recognized. Copper deficiency is associated with the spontaneous retention of hepatic iron. Previous studies have reported that hypercholesterolemia and hypertriglyceridemia are associated with elevated hepatic iron concentrations in copper deficient rats. There was a direct relationship between the magnitude of blood lipids and the concentration of hepatic iron. Based on these data, it has been hypothesized that iron was responsible for the development of lipemia of copper deficiency. In this study was determined the effect of increasing doses of Cu(10, 20 and 50 ppm) in the diet, on the serum total lipids, total cholesterol, triglycerides (triacylglicerols), phospholipids, non-esterified fatty acids (NEFA) and liver iron and zinc concentrations in normal rats. The results were compared with normal rats that received a balanced diet containing 0.6 and 6 ppm of Cu, respectively. The results show that Cu-supplement diminished the cholesterol and triglyceride serum levels, increased the level of phospholipids, NEFA and concomitantly decreased the hepatic concentrations of Fe and Zn. There was a statistically significant (p < 0.05) simple correlation between triglycerides and liver Fe (r = 0.917; R2 = 64.03%), cholesterol and liver Zn (r = 0.872; R2 = 76.07%), cholesterol and liver Fe (r = 0.995; R2 = 99.10%), liver Fe and liver Cu (r = -0.612), liver Fe and liver Zn (r = 0.837), liver Cu and liver Zn (r = -0.612), and serum triglycerides and liver Zn (r = 0.967). The mechanism(s) by which Fe and Zn determine these changes is not known; none of the enzymes that act in cholesterol and triglyceride metabolism and biosynthesis require Fe and/or Zn. The increase of NEFA is due to changes in the process of lipolysis and re-esterification of the fatty acids in blood. However, additional studies are needed for the precise mechanisms of this interrelationships to be clarified.     

Enzymatic modification of the functional, nutritional and sensorial properties of soybeans for special feeding

Production of new protein-based products for special nutrition such as hypoallergenic infant formulas, fortified beverages and nutraceutics, require ideal ingredients. Protein ingredients were developed by enzymatic hydrolysis and methionine synthesis of soy protein. Hydrolysis was done at 4% (w/v) using porcine pancreatic enzymes (4% w/w), 50 degrees C, 6 h and pH 8. After drying powder was resuspended (20% w/v) and incubated with 7.6% (w/w) methionine methyl-ester, 1% (w/w) chymotrypsin and 3 M glycerol, 37 degrees C, 3 h and pH 7. Hydrolysates were fractionated by ultrafiltration (UF) before and after enrichment (E): FI > 10, 10 > FII > 3 and 3 > FIII > 1 kDa. Functional properties, amino acid content, anti-physiological factor activities and antigenicity were assayed for all the UF fractions and the soybean meal. Protein quality bioassay and sensorial test of an non-enriched fraction and an enriched fraction were performed. Functional properties were positively modified by hydrolysis and synthesis by using a minimum time and methionine added for the last reaction. After UF all the fractions under 10 kDa showed 100% solubility (pH 4 and 7), good clarity, acceptable foam capacity and negligible antigenicity and antiphysiological activities. Additionally, methionine enrichment enhanced their nutritional value, upgrading sulfur amino acid requirements for infants and adults. Because functionality and nutritional value FIII-E could be used for hypoallergenic infant formulas, FII-E for fortified soluble formulas and nutraceutics and FI-E for a semi-solid baby food.     

Comparative proximal and mineral analysis of iguana,poultry and beef meats

Raw meat samples from iguana, poultry and beef cattle specimens were used to compare proximal (g/100 g) and mineral (mg/100 g) composition. Iguana meat was obtained by dissecting whole specimens (Iguana iguana) captured at a ranch (n = 20). Thighs and breasts were separated from broiler (either chilled or frozen) carcasses (n = 20), and deboned to represent chicken meat samples, whereas 2.5-cm-thick longissimus (ribeyes) steaks were removed from carcasses and frozen to represent beef of several breed types (n = 20). The one-way analysis of variance performed by the least squares method (LS Means) showed specie affected significantly (p > 0.05) all composition variables under study. Moisture content did not differ between iguana and chicken meats (74.7 y 74.9%, respectively) whereas beef samples had the lowest water content (73%) (p < 0.01). LS means for protein content showed beef samples (22.3%) were highest (p < 0.05) in this nutrient, iguana meat being intermediate (20.8%). Chicken meat presented the highest amount of total lipids (7.75 +/- 0.20 g/100 g) (p < 0.01) followed by iguana (3.49 +/- 0.12 g/100 g) and beef (2.57 +/- 0.20 g/100 g). Ash and most individual minerals were more concentrated in iguana meat, except for K and Zn that were more abundant in beef samples. Non-significant differences in Mg, Na, Cu or Mn contents were detected between chicken and beef samples. It was concluded that iguana meat could be an alternate source of protein and minerals as compared to those of traditional meat species.     

Dislocations at Prismatic Fracture Surfaces in Sapphire

Single-crystal sapphire exhibits a highly anisotropic fracture behavior. The surfaces of specimens fractured along prismatic planes are wavy, with fractographic features appearing as small areas of contrast under an optical microscope. Optical microscopy, atomic force microscopy, X-ray topography, and confocal microscopy are used to demonstrate a correlation between the areas of contrast and dislocations penetrating the sample surface. The surface features are argued to be a consequence of the stress field surrounding the dislocations, which deflect the crack approximately 10 nm normal to the surface as the crack cuts the dislocations. The lateral extent of measurable surface deflection is of the order of 5 μm. These images can be compared directly to show the equivalence of the position of the dislocations observed by X-ray topography and the surface contrast observed optically.     

Evidence for the involvement of tyrosine-69 in the control of stereospecificity of porcine pancreatic phospholipase A2

We have studied the role of Tyr-69 of porcine pancreatic phospholipaseA₂ in catalysis and substrate binding, using site-directed mutagenesis.A mutant was constructed containing Phe at position 69. Kineticcharacterization revealed that the Phe-69 mutant has retainedenzymatic activity on monomeric and micellar substrates, andthat the mutation has only minor effects on k_cat and K_m. Thisshows that Tyr-69 plays no role in the true catalytic eventsduring substrate hydrolysis. In contrast, the mutation has aprofound influence on the stereospecificity of the enzyme. Whereasthe wild-type phospholipase A₂ is only able to catalyse thedegradation of sn-3 phospholipids, the Phe-69 mutant hydrolysesboth the sn-3 isomers and, at a low (1–2%) rate, the sn-1isomers. Despite the fact that the stereospecificity of themutant phospholipase has been altered, Phe-69 phospholipasestill requires Ca²⁺ ions as a cofactor and also retains itsspecificity for the sn-2 ester bond. Our data suggest that inporcine pancreatic phospholipase A₂ the hydroxyl group of Tyr-69serves to fix and orient the phosphate group of phospholipidmonomers by hydrogen bonding. Because no such interaction canoccur between the Phe-69 side-chain and the phosphate moietyof the substrate monomer, the mutant enzyme loses part of itsstereospecificity but not its positional specificity.     

Nucleation in ZBLAN Glasses

Nucleation rates were measured in a ZrF₄–BaF₂–NaF–LaF₃–AlF₃ glass (ZBLAN) using an optical technique. The results were compared with a similar glass having a slightly different composition. The difference in the nucleation rate is explained by classical nucleation theory using calculated free-energy differences between the ZBLAN liquid and the BaZrF₆ crystal, which is found as the precipitating phase.     

A Convenient Method for the Accurate Determination of Phosphorous in Fish Oils

The phosphorous content of fish oil was determined by acid hydrolysis for 168 h (one week) in 2 M hydrochloric acid at 120°C in glass tubes, followed by filtration and molybdenum blue colour development in an aliquot of the filtrate. The method is regarded as a convenient routine laboratory procedure, and the results obtained by the method are in good agreement with those obtained with the ashing procedure of the American Oil Chemists' Society. The determination has been satisfactorily applied to the analysis of many South African fish oils.