Die Veränderungen von Nahrungsfetten bei höheren Temperaturen

Alterations of Edible Fats and Oils at Elevated Temperatures Refining of vegetable fats and oils has no deleterious effect upon their composition as far as desliming, neutralization or bleaching is concerned. However, during deodorization or physical refining small amounts of dimeric triglycerides and of trans fatty acids are formed depending on temperature and duration. The amounts of these by products are insignificant provided that the usual process conditions are applied. In the kitchen the various cooking methods can have quite different effects upon the quality of the fats and oils. Whereas boiling and baking have no effects and short-term shallow frying show only minor changes in quality, deep-fat frying can cause serious alterations especially if the oil is used far too long. Numerous investigations tried to identify these chemical reactions which are predominatly isomerizations as well as polymerization and oxidation reactions. The German Society for Fat Science and Federal Health Authorities in Germany issued recommendations for the assessment of fat deterioration basing on sensory evaluation in combination with some analytical data. Since 60 years and with considerable effort more or less systematic investigations have been performed to answer the question if heated fats are detrimental to human health. Fats and oils were heated under the conditions of good commercial practice and then fed to test animals. In some cases the heated fats were separated into various fractions and these were fed individually. The results of the most significant long-term feeding trials are reported and critically evaluated.     

Veränderungen der Hornschicht bei Feuchtigkeitsschwankungen in vivo

Variations of the Horny Layer by Humidity Fluctuations in vivo In its origin and formation at the periphery of the body the horny layer (HS) acts first of all as a natural water barrier. The healthy HS is equipped with sufficient effective defense mechanisms against the influence of water under normal conditions. Under the conditions of an experimental irritation by mechanical and chemical influences, especially solvent contacts, structural and functional variations in-HS-structure can be proved. Their objectification allows first conclusions about the individual - occupational - maximum stress of the skin surface and about direct external protective measures.     

Veränderungen der Fette unter Fritierbedingungen und deren analytische Erfassung Chemische Veränderungen der Fette beim Fritieren

Alterations of Fats Under Conditions of Deep-Frying and Their Analytical Detection: Artefacts Formation in Frying Fats During Deep-Frying During deep-frying the fats decompose with the formation of volatile, monomeric and polymeric compounds. Their amount and chemical structure depends on the fat blend, the temperature, the frying time, the frying good, and in a high degree on the accessibility of oxygen. As we have shown a quantitative determination of polymeric material in frying fats is possible using gel permeation chromatography. However, gel permeation chromatography determines the size of the molecules only and does not destinguish between various degrees of oxidation. For his purpose we apply liquid chromatography on silica gel which separates various fractions according to their polarity. In combination with a “moving wire” and flame ionisation detector a semi-quantitative evaluation of the amount of polar material in heated fats in possible. Liquid chromatography is applicable for preparative purposes and enables the non-destructive isolation of sufficient material for feeding experiments.     

Die Veränderungen des Lipoidstoffwechsels beim Herzinfarkt

Change of Lipid Metabolism in Cardiac Infarction The authors investigated the alterations of various lipid fractions at different stages of cardiac infarction of 111 patients. A statistically significant increase in the level of β-lipoproteins, free fatty acids and saturated esters of cholesterol was observed at the beginning of the disease. A striking rise in triglyceride content occurred in the sixth week. The proportion of α-lipoproteins and cholesteryl linoleate decreased during the entire period of ailment. The content of free fatty acids sank from the second collection (4th till 10th day) of blood onwards.     

Zur Bildung von Ketonen und Aldehyden während der Oxydation gesättigter Triglyceride bei hohen Temperaturen

Formation of Ketones and Aldehydes During the Oxidation of Saturated Triglycerides at High Temperatures Ketones and aldehydes which are formed during the oxidation of tricaprin and tripalmitin were isolated as 2,4-dinitrophenylhydrazones, separated by thin-layer chromatography and quantitatively analysed by UV-spectrometry.     

Veränderungen im Plasma-Lipid-Muster bei Patienten mit Neurodermitis - Beeinflussung durch Applikation ungesättigter Fettsäuren

Influence of Polyunsaturated Fatty Acids on the Plasma Phospholipids of Atopic Patients Patients with atopic eczema and a control group received evening primrose oil (EPO) for 4 weeks. In the group with atopic eczema a statistically significant improvement was observed. The baseline fatty acid composition of plasma phospholipids from the patients with atopic eczema did not differ significantly from that in the healthy subjects. After treatment the content of dihomo-γ-linolenic acid was significantly higher in the group with atopic eczema. Skin roughness decreased after treatment with EPO. Roughness was assessed by use of a stylus instrument.     

Veränderung der Sterine durch industrielle Verarbeitungsprozesse von Fetten und Ölen II: Veränderungsprodukte bei der Behandlung von Cholesterin mit Bleicherden

Alteration of Sterols by Industrial Processing of Fats and Oils II: Alteration Products Formed by Treatment of Cholesterol with Bleaching Earths A part of the derivatives formed by the action of Tonsil on cholesterol could be isolated by preparative thin-layer chromatography and identified using synthetic standards. Depending upon experimental conditions, various amounts of dicholesteryl ether, Δ3,5-cholestadiene, isomeric cholestenes (mainly Δ2-cholestene) and Δ2,4,6-cholestatriene were formed. Disteroids were formed under extreme experimental conditions. Small amounts of oxidized sterols are formed from non-polar sterol derivatives by a subsequent reaction. Chromatographic properties of these substances were studied, in order to find their eventual interference in the analysis of sterols.     

Veränderungen von Sameninhaltsstoffen verschiedener Rapssorten unter kontrollierten Bedingungen

Changes in Seed Ingredients of Various Rape-Seed Varieties Under Controlled Climate Conditions By phytotron tests with winter and summer rape-seed varieties the influence of temperature, photoperiod and atmospheric humidity on various ingredients was investigated. Fat and protein contents are very significantly influenced by the vegetation temperature, as the increase in temperature lowers the fat content and increases the protein content. Considering the influence of climate conditions on the fatty acid distribution it is to he differentiated between old varieties with high or new varieties with low erucic acid content.     

Über die Veränderung der Sterine in Fetten und Ölen bei der industriellen Bearbeitung derselben II

Alteration of Sterols in Fats and Oils During the Industrial Processing Nonpolar steroids are formed by the action of bleaching earth on cholesterol, β-sitosterol, stigmasterol and brassicasterol in the presence of hexane. The hydrocarbons formed were isolated and investigated by column chromatography and preparative thin-layer chromatography. The hydrocarbons formed by the action of activated bleaching earth on cholesterol were repeatedly crystallized from ethyl alcohol and identified as Δ^3,5-cholestadiene.     

Über die Veränderung der Sterine in Fetten und Ölen bei der industriellen Bearbeitung derselben I

Changes in Sterols During the Industrial Processing of Fats and Oils I The investigations of the authors have shown that 7-hydroxy sterols are formed when soybean oil containing sterols is heated in the presence of oxygen. Hydrocarbons and disteryl ethers are formed by bleaching earth treatment of cholesterol, β-sitosterol, stigmasterol and brassicasterol. Treatment of 7-hydroxy sterol with bleaching earth leads to the formation of hydrocarbons and keto-steroids. The sterols are partly oxidized during deodorization under inadequate vacuum. Freshly extracted rapeseed oil does not contain any disteryl ether. However, these substances could be detected in commercial fat samples. In experiments on rats, no carcinogenic properties of dicholesteryl ether could be found.