Identification of adduct radiolysis products from pork fat

Mass spectrometric evidence is given to show the formation of adduct radiolysis products in pork fat. A variety of adduct radiolysis products were identified. Only the major recombination products are considered and discussed herein. These compounds consist of triglyceride dimers, propanedioldiester-triglyceride adducts, propanedioldiester dimers and branched alkyl substituted triglycerides.     

A quantitative comparison of the yields of radiolysis products in various meats and their relationship to precursors

A detailed analysis has been made of the composition of radiolysis products formed in beef, pork, ham, and chicken. The yields of the various compounds are related linearly to irradiation dose, and the fat, fatty acid and triglyceride composition of the meats.     

GC/MS analysis of some long chain esters,ketones and propanediol diesters

Identification of radiolysis products which are formed in lipids in the range of molecular weights from 400-600 has been established on the basis of gas chromatography/mass spectrometry (GC/MS) studies of long chain authentic samples of alkyl esters, ketones and propanediol diesters. This paper describes the GC/MS behavior of these compounds. Double hydrogen rearrangement was found to be the predominant ion in the spectrum of long chain saturated esters whereas in the unsaturated esters, a peak corresponding to the loss of alcohol from the molecular ion was more pronounced. On the contrary to short chain ketones, McLafferty rearrangement did not appear to be the major fragmentation in the spectrum of saturated and unsaturated long chain ketones. α-Cleavage was found to be the predominant fragmentation in the spectrum of these ketones. The “McLafferty + 1” rearrangement peak was more pronounced for the long chain ketones than those found in the spectrum of smaller ketones. Fragmentation patterns of propanediol diesters were shown to be similar to those in triglycerides, giving rise to predominant peaks corresponding to acylium ion [RCO]⁺ and parent minus acyloxy ion [R-COO]⁺.     

Measurement of oxidative interactions of cholesterol

A simple analytical technique, using a silicic acid minicolumn and capillary gas chromatography, was used for measuring the oxidative interactions of cholesterol with other compounds. When triacylglycerols were added to cholesterol before heating at 180°C, the latter oxidized faster than cholesterol heated alone, and a relatively high amount of epoxides was found. Dipahnitoylphosphatidylethanolamine and all the amino acids tested showed a protective effect, with cysteine and alanine being the most effective. The results of this study indicate that the varius compounds added not only influenced the rate of cholesterol oxidation, but also exerted different influences on its oxidative pathway.     

Identification of adduct radiolysis products from ethyl palmitate and ethyl oleate

Radiolysis induced adduct products have been separated and identi-fied from irradiated ethyl palmitate, ethyl α-d₂-palmitate and ethyl oleate. In the saturated compounds, adduct formation was observed mainly at the position α to the carbonyl group. The three major adduct products identified in irradiated ethyl palmitate were ethyl α-tetradecylpalmitate, ethyl α-pentadecylpalmitate and the α,α′- dimer of ethyl palmitate. Corresponding compounds were identified from the irradiated ethyl α-deuteropalmitate. Adduct radiolysis products formed in ethyl oleate were identified as the monoene and diene dimers.     

Identification of radiation-induced triglyceride adducts by mass spectrometry

Mass spectrometric evidence is given to show the formation of 4 types of adduct compounds induced by radiolysis of triglycerides. These are the triglyceride 2,2’ dimer, the propanedioldiester dimer (i.e., a 1,2,5,6-hexanetetraol tetraester), a 2-propanedioldiester-triglyceride adduct and an a branched alkyl substituted triglyceride. Analogous compounds have been adduced for both tributyrin and tripalmitin. Adduct formation was observed at a position α to the carbonyl group. Presented in part at the Annual Conference on Mass Spectrometry and Allied Topics, American Society for Mass Spectrometry, Seattle, WA, June 1979.     

Identification of radiolytic compounds from beef

Several previous papers have dealt with the forma-tion of radiolysis products in fats, triglycerides and fatty acids. Size excusion chromatography now pro-vides a means of separating larger, less volatile com-pounds, and its application to irradiated beef has resulted in a nearly complete analysis of the radio-lytic products formed. The components have been identified by gas chromatography/mass spectrometry (GC/MS).     

Comparison of radiolytic compounds from saturated and unsaturated triglycerides and fatty acids

Formation of certain radiolysis products from palmitic acid, oleic acid, tripalmitin and triolein has provided a means for comparing the radiolytic effects in saturated and unsaturated triglycerides and fatty acids. These substances were chosen to represent the major constituents of fat found in beef. Fractionation and concentration of radiolytic compounds from the irradiated samples was accomplished by the means of size exclusion chromatography. Quantitative and qualitative analyses were performed using a combined GC/MS computer system. In addition to the primary radiolytic compounds, recombination products of relatively high molecular weight and various propanediol diesters from the corresponding glyceryl moities were identified. Quantitative analyses indicated a greater yield of various radiolytic compounds from free fatty acids than from the corresponding triglycerides. Similarly, radiolytic compounds were produced in greater quantities from the saturated fats than the unsaturated fats. Most of the radiolytic compounds identified in this study have not been previously reported.     

Effects of various parameters on the formation of radiolysis products in model systems

Effects of various parameters on the formation of radiolysis products in triplamitin, palmitic acid, oleic acid, caprylic acid and capric acid were investigated. A greater yeild of primary and recombination products was observed in palmitic acid compared to that of oleic acid. In general, higher amounts of recombination products are formed in both acids when irradiated at room temperature than at −45 C. In the short chain acids, the yield of the hydrocarbon recombination product was enhanced in the liquid state. In contrast, the ketone recombination product was formed in greater amounts from solid capric acid than from liquid caprylic acid. In the absence of oxygen, a linear relationship was obtained between the dose and the yield of radiolysis products in tripalmitin. In the presence of oxygen, a considerable increase in the formation of γ-palmitolactone, n-3 and n-2 alkanes was observed at room temperature.     

Thermo-mechanical simulation of ultrahigh temperature ceramic composites as alternative materials for gas turbine stator blades

The efficiency of the Bryton cycle strongly depends on the maximum temperature of the cycle. However, restrictions on metallurgical problems deprive engineers from the benefit of high temperatures. Ultrahigh temperature ceramics can be considered in such cases, instead of traditional materials like M152 superalloy. In this study, SiC reinforced HfB₂ and ZrB₂ ultrahigh temperature ceramics were proposed as gas turbine stator blades. The heat transfer and stress-strain equations were solved numerically by the finite element method to obtain temperature and stress distributions. The results showed that the maximum thermal stress occurs in vicinity of the cooling ducts where the temperature gradient is maximum. The maximum displacements of 1.2 mm (for HfB₂–SiC) and 1.14 mm (for ZrB₂–SiC) occur in the upper wall. It can be noticed that the ZrB₂–SiC made blade showed lower maximum stress and displacement than those for the HfB₂–SiC made one, as a result of lower expansion coefficient of ZrB₂–SiC system. The addition of SiC to monolithic HfB₂ and ZrB₂ ceramics decreases their thermal conductivity and following that, the temperature uniformity in blades reduces. Although the thermal stresses and the probability of failure in these stator blades enhance, the ZrB₂–SiC material presented the best performance among the other investigated samples. Both Coulomb-Mohr and Von Mises failure analyses were employed. It was understood that both blades made of HfB₂–SiC and ZrB₂–SiC composites simply withstand the applied stresses with the safety factors of about 1.5.