Determination of mono-, di-, and triglycerides by molecular distillation and thin-layer chromatography

Analysis of mixtures of mono-, di-, and triglycerides by molecular distillation and thin-layer chromatography is described. Mono- and diglycerides undergo appreciable acyl migration through the effect of heat during molecular distillation. Nevertheless this technique may be used for the quantitative analysis of mixtures of mono-, di-, and triglycerides, provided there are no substances present which catalyze, disproportionation. Thin-layer chromatographic (TLC) analysis of mono-, di-, and triglycerides is fast and simple and can be carried out on a micro-scale with a high degree of accuracy and precision. It also is extremely sensitive, permitting the quantitative estimation of as little as 0.1% of a single component in a mixture. This research was supported by the Hormel Foundation and General Foods Corporation, Tarrytown, N.Y. Presented at fall meeting, American Oil Chemists’, Society, New York, October 17–19, 1960.     

Effect of inert atmosphere in the determination of free fatty acid or free caustic alkali and unsaponified material in soap

The conclusions to be drawn from this work can be summarized as follows:

1. Values for free fatty acid are not significantly affected by carbonation when run under the usual laboratory conditions. Under similar conditions free caustic alkali values are low (statistically significat) and, conversely, unsaponified values are high (statistically significant).
2. The magnitude of the error incurred by working under the usual laboratory conditions is so small as to be negligible unless extreme precision is required.
3. Hot alcohol apparently provides its own protective vapor barrier preventing carbon dioxide absorption. This characteristic of alcohol can be further enhanced by the judicious use of watch glasses to cover beakers and funnels during the determination

     

Three garnet compositions for bubble domain memories

The choice of magnetic garnet compositions for bubble memories is always a compromise dictated by the material requirements generated by the specifications on the memories. The three compositions reported, Y_2.62Sm_o.38Fe_3.85Ga_1.15O₁₂, Gd_2.lLu_O.9Fe_4.4Al_0.6O₁₂, and Y_l.92Sm_0.1Ca_0.98Fe_4.02Ge_0.98O₁₂, represent three examples of such a compromise. The first composition is excellent for use in circuits operating at 100 KH_z over a temperature range of -20° to 80°C. The second has a mobility up to 5000 cm/sec/0e and is capable of very high speed operation at the sacrifice of stability toward temperature. The third exhibits excellent stability toward temperature and has operated at 1 MHz but is compositionally more complex. Melt compositions for film growth and a summary of magnetic properties are presented for the three compositions. Factors to be weighed in composition selection for bubble domain memories are discussed.     

Analysis of Amadori compounds by high-performance cation exchange chromatography coupled to tandem mass spectrometry

High-performance cation exchange chromatography coupled to tandem mass spectrometry or electrochemical detection was found to be an efficient tool for analyzing Amadori compounds derived from hexose and pentose sugars. The method allows rapid separation and identification of Amadori compounds, while benefiting from the well-known advantages of mass spectrometry, such as specificity and sensitivity. Glucose- and xylose-derived Amadori compounds of several amino acids, such as glycine, alanine, valine, leucine/isoleucine, methionine, proline, phenylalanine, and glutamic acid, were separated or discriminated using this new method. The method is suitable for the analysis of both model reaction mixtures and food products. Fructosylglutamate was found to be the major Amadori compound in dried tomatoes (approximately 1.5 g/100 g) and fructosylproline in dried apricots (approximately 0.2 g/100 g). Reaction of xylose and glycine at 90 degrees C (pH 6) for 2 h showed rapid formation of xylulosylglycine (approximately 12 mol %, 15 min) followed by slow decrease over time. Analysis of pentose-derived Amadori compounds is shown for the first time, which represents a major breakthrough in studying occurrence, formation, and decomposition of these labile Maillard intermediates.     

Thermal-field forward current in GaN-based surface-barrier structures

The voltage and temperature dependences of the capacitance and forward current in surface-barrier Ni-n-GaN structures are experimentally studied. The results are compared with the Padovani-Stratton thermofield emission theory. It is established that, in a temperature range of 250–410 K, the forward current of the Ni-n-GaN surface-barrier structures (the electron density in GaN is ～10¹⁷ cm^?3) is caused by a thermofield emission of electrons, whose energy is ～0.1 eV below the potential-barrier top.     

Survival of pathogenic bacteria in pesticide solutions and on treated tomato plants

The ability of Salmonella, Escherichia coli O157:H7, Listeria monocytogenes, and Shigella to survive or grow in pesticide solutions (Ambush 240EC, Benlate T-N-G, Bravo 500, Botran 75WP, Captan 80WDG, Parasol, and Vendex 50W) used by the horticultural industry was examined. In the laboratory, individual cultures were inoculated at 4 log CFU/ml in pesticides diluted with sterile saline to the lowest recommended spray concentrations. During 21 degrees C incubation for < or =96 h, bacterial survivors in the samples and a control consisting of saline were enumerated either by agar surface plating or hydrophobic grid membrane filtration. Most formulations tested were somewhat inhibitory to the pathogenic bacteria. All inoculated bacteria survived or grew in Bravo 500. Among bacteria tested, Salmonella spp. were best able to survive and Listeria spp. were least able to survive in pesticide solutions. When the incubation temperature or pesticide concentration was increased, survival of Salmonella varied depending on the type of formulation. In the field, when a bacterial cocktail containing E. coli O157:H7 and Salmonella Enteritidis was added to Bravo 500 at 6 log CFU/ml, both organisms were recovered from leaves and fruit skins of sprayed tomato plants after the recommended 1 day-to-harvest interval. E. coli and Salmonella survived longer on tomato leaves when sprayed in saline (at least 26 and 56 days, respectively) than when sprayed in Bravo 500 (>45 h and <15 days, respectively). While Salmonella serovars Typhimurium and Heidelberg grew in the fungicide Bravo, and Enteritidis grew in the insecticide Vendex within 96 h at 21 degrees C in the laboratory, pathogen growth in other pesticide formulations did not occur. Higher temperature (< or =30 degrees C) or doubling pesticide concentrations had either no or a negative effect on Salmonella Heidelberg survival. Use of unexpired pesticide formulations may have contributed to the reduced bacterial survival and growth found in the laboratory and during the field trials with Bravo.