Hydrogenation of linolenate. XI. Nuclear magnetic resonance investigation

Nuclear magnetic resonance (NMR) spectra have been obtained during the hydrogenation of methyl linolenate with platinum, nickel and sulfur-poisoned-nickel catalysts and during the reduction of linolenic acid with hydrazine. Structural changes have been studied by “proton counting” techniques and include those for the total unsaturation (olefinic protons), 15,16-double bond (β-olefinic methyl protons), 1,4-pentadienes (di-α-olefinic methylene protons) and allylic methylene (α-olefinic methylene protons). The number of olefinic protons is inversely related to the degree of saturation as determined by iodine value, GLC and hydrogen absorption. Amounts of double bonds in the 15,16-position and in the 1,4-pentadiene structures decrease linearly with increasing saturation, but the slopes of lines differ for specific catalysts. Sulfur-poisoned pickel has the most negative slope, followed by electrolytic nickel, and then platinum and hydrazine. Amounts of α-olefinic structures with increasing saturation are roughly constant for hydrazine and platinum during reduction with the first mole of hydrogen; they fall to zero at complete saturation. For the two nickel catalysts, the α-olefinic structures increase during absorption of the first mole and a half of hydrogen before dropping to zero. The possibility of substituting NMR measurements for iodine value, alkali-isomerization spectrophotometric determination and other structural analyses is discussed. Presented at AOCS Meeting in Minneapolis, 1963. A laboratory of the No. Utiliz. Res. & Dev. Div., ARS, USDA.     

Search for new industrial oils. IV

Summary Chemical screening of seed oils continues to reveal nature's diversity. This work provides leads to numerous species which warrant further research to investigate their oil and meal in greater detail, to appraise their crop potential, and to assess their practical value for providing new oilseeds. This is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture. Agricultural Research Service, U. S. Department of Agriculture.     

Antagonistic effect of fat on the antibotulinal activity of food preservatives and fatty acids

The effect of fat on the antibotulinal activity of 11 food preservatives, 12 free fatty acids, and nine lots of enzyme-modified cheese (EMC) was evaluated in a media system. Anhydrous milkfat or soybean oil was added to tubes of Trypticase–peptone–glucose–yeast extract medium (TPGY) supplemented with the additives (final pH adjusted to 5.9). Treatments were inoculated with 3-log₁₀ proteolytic Clostridium botulinum spores/ml (10-strain mixture of serotypes A and B) and incubated anaerobically at 30°C for up to 14 days. For the preservative and fatty acids studies, growth of C. botulinum was determined by measuring optical changes at OD_{640 nm}. Botulinal toxin production was determined in EMC-treatments using the mouse bioassay. Data revealed that the antibotulinal effects of nisin, and free fatty acids caprylic, capric, lauric, myristic, oleic, and linoleic acids were each significantly reduced in treatments supplemented with 20% fat (P<0.05). Similar trends were observed in TPGY supplemented with 20% fat and potassium sorbate, sorbic acid, monolaurin, polyphosphate emulsifier, or EDTA–lysozyme, but the differences were reduced. Fat was also antagonistic to the antibotulinal activity of five EMC-treatments. This study suggests that fat may reduce the efficacy of some antimicrobials added to or found naturally in foods.     

Antibotulinal activity of process cheese ingredients

Ingredients used in the manufacture of reduced-fat process cheese products were screened for their ability to inhibit growth of Clostridium botulinum serotypes A and B in media. Reinforced clostridial medium (RCM) supplemented with 0, 0.5, 1, 2, 3, 5, or 10% (wt/vol) of various ingredients, including a carbohydrate-based fat replacer, an enzyme-modified cheese (EMC) derived from a Blue cheese, sweet whey, modified whey protein, or whey protein concentrate, did not inhibit botulinal growth and toxin production when stored at 30 degrees C for 1 week. In contrast, RCM supplemented with 10% soy-based flavor enhancer, 10% Parmesan EMC, or 5 or 10% Cheddar EMC inhibited botulinal toxin production in media for at least 6 weeks of storage at 30 degrees C. Subsequent trials revealed that the antibotulinal effect varied significantly among 13 lots of EMC and that the antimicrobial effect was not correlated with the pH or water activity of the EMC.     

Consensus categorization of cheese based on water activity and pH—A rational approach to systemizing cheese diversity

Development of science-based interventions in raw milk cheese production is challenging due to the large diversity of production procedures and final products. Without an agreed upon categorization scheme, science-based food safety evaluations and validation of preventive controls would have to be completed separately on each individual cheese product, which is not feasible considering the large diversity of products and the typically small scale of production. Thus, a need exists to systematically group raw milk cheeses into logically agreed upon categories to be used for food safety evaluations. This paper proposes and outlines one such categorization scheme that provides for 30 general categories of cheese. As a base for this systematization and categorization of raw milk cheese, we used Table B of the US Food and Drug Administration’s 2013 Food Code, which represents the interaction of pH and water activity for control of vegetative cells and spores in non-heat-treated food. Building on this table, we defined a set of more granular pH and water activity categories to better represent the pH and water activity range of different raw milk cheeses. The resulting categorization scheme was effectively validated using pH and water activity values determined for 273 different cheese samples collected in the marketplace throughout New York State, indicating the distribution of commercially available cheeses among the categories proposed here. This consensus categorization of cheese provides a foundation for a feasible approach to developing science-based solutions to assure compliance of the cheese processors with food safety regulations, such as those required by the US Food Safety Modernization Act. The key purpose of the cheese categorization proposed here is to facilitate product assessment for food safety risks and provide scientifically validated guidance on effective interventions for general cheese categories. Once preventive controls for a given category have been defined, these categories would represent safe havens for cheesemakers, which would allow cheesemakers to safely and legally produce raw milk cheeses that meet appropriate science-based safety requirements (e.g., risk to human health equivalent to pasteurized milk cheeses).     

Independent testing and validation of prototype hydrogen sensors

In this article, the independent testing and validation of a packaged, electrochemical prototype hydrogen sensor at the National Renewable Energy Laboratory (NREL) is reported. Custom electronics were developed to be compatible with the data acquisition system at NREL. The specialized hydrogen sensor-testing laboratory at NREL used a variety of standardized test protocols to assess sensor performance. The system controlled and monitored humidity, pressure, and hydrogen gas concentration and introduced interference gases such as methane, carbon dioxide, carbon monoxide and ammonia.     

The Effect of Fibre Medullation on Laserscan Diameter Measurement

The effect of wool fibre medullation on diameter measurement in the expanding beam Laserscan has been investigated. A range of single fibres of diameter from 10 to 75 µm was uaed to investigate differences in the Laserscan optical response to normal and medullated wool. The concept of mean 'Fresnel diameter' is introduced to account for the variation in diameter along the fibre axis. Measurements on unmedullated and highly medullated wool fibres show no discernable systematic differences, and are in good agreement with Fresnel diffraction theory.     

Adaptive compliant motion control of manipulators without velocity measurements

This article presents two adaptive schemes for compliant motion control of uncertain manipulators. The first strategy is developed using an adaptive impedance control approach and is appropriate for tasks in which the dynamic character of the end-effector/environment interaction must be controlled, while the second scheme is an adaptive position/force controller and is useful for those applications which require independent control of end-effector position and contact force. The proposed controllers are very general and computationally efficient, require virtually no information regarding the manipulator dynamic model or the environment, and are implementable without velocity measurements. It is shown that the schemes ensure semiglobal boundedness of all signals in the presence of bounded disturbances, and that the ultimate size of the system errors can be made arbitrarily small. The capabilities of the proposed control strategies are illustrated through both computer simulations and laboratory experiments with a 6 degree-of-freedom (DOF) IMI Zebra Zero manipulator. ©1997 John Wiley & Sons, Inc.