Einfluß von Futterfetten auf die Qualität tierischer Veredlungsprodukte

Effects of Feed Fats on Quality of Animal Product At the same level of energy supply intake of fats/oils do not lead to a higher fat deposition in the carcass. Additionally, fats are carrier of fat soluble vitamins A, D, E, K and improve their absorption from the intestinal tract. The fatty acid profile of fat deposited in the organism, as for example in egg yolk is influenced by the intake of fatty acids provided by feed. This especially concerns linoleic- and linolenic acid as well as lauric- and myristic acid, High contents of polyunsaturated fatty acids negatively influence oxidative stability as well as consistency of body fat and therefore quality of animal products. An improved oxidation protection can be carried out by supplementation of antioxidants. Medium-chain, saturated fatty acids reveal positive effects on both criteria.     

Effect of fatty acids and tocopherols on the oxidative stability of vegetable oils

The oxidative stability of vegetable oils is determined by their fatty acid composition and antioxidants, mainly tocopherols but also other non‐saponifiable constituents. The effect of fatty acids on stability depends mainly on their degree of unsaturation and, to a lesser degree, on the position of the unsaturated functions within the triacylglycerol molecule. Vegetable oils contain tocopherols and tocotrienols, especially α‐ and γ‐tocopherols, as their main antioxidants. The antioxidant behavior of tocopherols represents a complex phenomenon as they are efficient antioxidants at low concentrations but they gradually lose efficacy as their concentrations in the vegetable oils increase. The “loss of efficacy” of tocopherols, sometimes referred to as a “pro‐oxidant effect”, is witnessed by an increase in the rate of oxidation during the induction period, despite elongation of this phase. The phenomenon is much obvious for α‐tocopherol, but is also evident for other tocopherols. In agreement with nature's wisdom, the tocopherol levels in vegetable oils seem to be close to the optimal levels needed for the stabilization of these oils. The presence of other antioxidants in the oils, e.g. carotenoids, phenolic compounds, and Maillard reaction products, may synergize with tocopherols and minimize this loss of efficacy.     

Antioxidant activity of tocopherols,ascorbyl palmitate,and ascorbic acid and their mode of action

In the quest to use antioxidant compounds occurring in nature or related compounds, extensive studies have been made on vegetable oils, animal fats, apocarotenal, and vitamin A as substrates with ascorbyl palmitate, tocopherols, and ascorbic acid as antioxidants. Antioxidant efficiency varies with the substrate. Ascorbyl palmitate at a level of 0.01% provides a useful increase in the shelf-life of vegetable oils. Alone it is better than butylated hydroxytoluene and butylated hydroxyanisole and in combinations with other known antioxidants improves the shelf-life of all vegetable oils, as well as potato chips. Solubility problems with ascorbyl palmitate and other esters of ascorbic acid are discussed. The tocopherols have their greatest effect in protection of animal fats, carotenoids, and vitamin A. Experiments utilizing tocopherols and tocopherol combinations are presented. The activity of ascorbic acid, an excellent scavenger of oxygen, is reviewed. Quenchers of singlet oxygen do not inhibit the direct oxidation of fats and oils under the conditions used.     

Hitzestabilität der Tocopherole

Heat Stability of Tocopherole The tocopherols are very important biological and nutritive components of our food. Furthermore, they are also antioxidants. The tocopherols are not volatile substances (such as e.g. BHA and BHT) and they don't cause off-flavour (TBHQ) or colour (lecithin) at higher temperatures, therefore, they can be used for stabilisation of frying fats. They stability of tocopherols at 180°C is relatively good and it depends on the kind of fat. The heat stability of tocopherols is mostly higher in fats with higher iodine value.     

The Antioxidant Functions of Tocopherol and Tocotrienol Homologues in Oils,Fats, and Food Systems

This review paper is focused on the relative antioxidant activities of tocopherols and tocotrienols in oils and fats and certain food systems. α-Tocopherol generally showed better antioxidant activity than γ-tocopherol in fats and oils, but at higher concentrations γ-tocopherol was found to be a more active antioxidant. The results of studies on the optimum antioxidant concentrations of tocopherols in oils and fats indicated that the optimal level for α-tocopherol is usually lower than other tocopherols, meaning less α-tocopherol is needed for maximum antioxidant protection. There are comparatively very few studies related to the antioxidant activities of tocotrienols in oils and fats. It has been stated that generally γ-tocotrienol has higher antioxidant effect than α-tocotrienol, and tocotrienols may be better antioxidants than their corresponding tocopherols in certain oils and fats systems. Studies on the antioxidant activity of various tocopherols in food systems are varied and cannot be uniformly evaluated because experiments have generally focused on different foods and used various methods for the detection of antioxidant activities. Depending on the food system, in certain cases tocopherols were better antioxidants than synthetic antioxidants such as butylhydroxy toluene (BHT) or butylhydroxy anisole (BHA). However, in certain other food systems the synthetic antioxidants were more effective to increase the shelf life and the stability of foods than those containing tocopherols.     

Vitamin E und Haltbarkeit von Pflanzenölen

Vitamin E and stability of vegetable oils. The main occurrence of vitamin E basing on its synthesis and its lipophilic character are vegetable oils, seeds, nuts and cereals. The most important task of tocopherols are their antioxidative capacity in food lipids. The antioxidative potential of tocotrienols in comparison to their corresponding tocopherols is lower. According to the chemical structure γ- and δ-tocopherol are more effective than α-tocopherol. An improvement of the antioxidative capacity is possible by controlled adding to tocopherol compounds as well as by the use of synergists like ascorbylpalmitate. For this improvement the composition of fatty acids, the tocopherol content in native oil and the circumstances of the oxidation should always be considered.     

Hochdruckextraktion mit mehrstufiger fraktionierender Separation zur schonenden Gewinnung von Keimölen mit hochverdichtetem Kohlendioxid

High Pressure Extraction by Multi-Stage Fractionated Separation for Gentle Production of Corn Germ Oils with Highly Compressed Carbon Dioxide The supercritical extraction of conditioned corn germs with highly compressed carbon dioxide leads to extracts containing triglycerides and fatty accompanying substances. These are mainly water and free fatty acids but also tocopherols and sterols as well as dyestuff, flavors, and odorous substances. The quality of the corn germ oils extracted at gentle temperatures can be varied in a wide range by multi-stage separation. This is carried out either by a fractionation taking place in a multi-stage pressure cascade, or by a temporary fractionated separation, or by a combination of both processes. By means of a multi-stage high pressure extraction it is possible to yield oils nearly free from water and with a low content of free fatty acids as well as oils with a high content of tocopherols and sterols. The crude oils have the typical odor. They are light and absolutely clear and their colour ranges from a pale yellow up to a pale red. Furthermore, it is possible to fractionate the triglycerides. The process parameters pressure and temperature of the separators are of decisive importance for the fractionated separation.     

α- and γ-tocopherols as efficient antioxidants in butter oil triacylglycerols

Although tocopherols are known to be the most important natural antioxidants in fats and oils, controversial findings of their effects have been made in different model systems. The aim of the experiment was to study the effects of α- and γ-tocopherol at the levels of 2–500 μg/g on the oxidation of purified butter oil triacylglycerols (BO TAGs) at 40°C in the dark for 16 days. Both of the tocopherols were effective antioxidants. Although BO TAGs without additions began to oxidize immediately, BO TAGs with tocopherols remained in the induction period throughout the experiment. The antioxidant strength of α-tocopherol was less than that of γ-tocopherol. More hydroperoxides were formed in BO TAGs with at least 100 μg/g α-tocopherol than with less α-tocopherol at the same time being much less than in BO TAGs without tocopherols. Moreover, as the formation of secondary oxidation products in BO TAGs with tocopherols was negligible, no pro-oxidative effect of tocopherols could be found. At low concentration (≤ 10 μg/g) γ-tocopherol was slightly less stable than α-tocopherol.     

中国油脂化学工业的进展与预测

叙述了中国油脂化学工业近20年来的发展，肥皂工业经过1989年消费高峰，肥皂产量迅速下降，目前正处在产品结构调整阶段，开始有了较好的效果，油化学品一脂肪酸，脂肪醇和脂肪胺都有较大的发展，但都存在产品供大于求的困难。对此，作了分析和预测，考虑到中国植物油资源基本是以C18脂肪酸为主，对发展油脂化学工业带来了局限性，应充分利用国内外两种油脂资源。     

Current advances in sunflower oil and its applications

The fatty acid and triacylglycerol composition of a vegetable oil determine its physical, chemical and nutritional properties. The applications of a specific oil depend mainly on its fatty acid composition and the way in which fatty acids are arranged in the glycerol backbone. Minor components, e. g. tocopherols, also modify oil properties such as thermo‐oxidative resistance. Sunflower seed commodity oils predominantly contain linoleic and oleic fatty acids with lower content of palmitic and stearic acids. High‐oleic sunflower oil, which can be considered as a commodity oil, has oleic acid up to around 90%. Additionally, new sunflower varieties with different fatty acids and tocopherols compositions have been selected. Due to these modifications sunflower oils possess new properties and are better adapted for direct home consumption, for the food industry, and for non‐food applications such as biolubricants and biodiesel production.     

Single-Cell Oils as a Source of Omega-3 Fatty Acids: An Overview of Recent Advances

Omega-3 fatty acids, namely docosahexaenoic acid and eicosapentaenoic acid, have been linked to several beneficial health effects (i.e. mitigation effects of hypertension, stroke, diabetes, osteoporosis, depression, schizophrenia, asthma, macular degeneration, rheumatoid arthritis, etc.). The main source of omega-3 fatty acids is fish oil; lately however, fish oil market prices have increased significantly. This has prompted a significant amount of research on the use of single-cell oils as a source of omega-3 fatty acids. Some of the microbes reported to produce edible oil that contains omega-3 fatty acids are from the genus Schizochytrium, Thraustochytrium and Ulkenia. An advantage of a single cell oil is that it usually contains a significant amount of natural antioxidants (i.e. carotenoids and tocopherols), which can protect omega-3 fatty acids from oxidation, hence making this oil less prone to oxidation than oils derived from plants and marine animals. Production yields of single cell oils and of omega-3 fatty acids vary with the microbe used, with the fermentative growing conditions, and extractive procedures employed to recover the oil. This paper presents an overview of recent advances, reported within the last 10 years, in the production of single cell oils rich in omega-3 fatty acids.     

A review on losses and transformation mechanisms of common antioxidants

Antioxidants are considered to be one of the most effective ways to prevent and delay the rancidity of oils and fats, thus play an important role in the processing, packaging, and storage of oils, fats, and oleaginous foods. However, the losses of antioxidants inevitably occur while preventing the rancidity of oils and fats. In this work, the loss pathways and mechanisms of synthetic and natural antioxidants commonly used in oils, fats, and oleaginous foods systems during storage, use, and detection are critically reviewed. The discussion regarding the transformation of antioxidants or antioxidant models in various organic solvent systems is also covered as well as the fate, toxicities, and antioxidative activities of transformation products of antioxidants. At room temperature, antioxidants in oils and fats are mainly lost due to antioxidation with transformation products accumulated. Under thermal (heating and frying) condition, synthetic antioxidants are mainly lost due to volatilization, while natural antioxidants are mainly lost due to transformation. Under frying condition, adsorption also contributes to the losses of antioxidants. This review discusses some possible research directions regarding antioxidants applied in oils, fats and oleaginous foods, which is expected to benefit the use of antioxidants in food industry.     

Die polarographische Bestimmung von Tocopherolen und Tocopherylchinonen in Ölen und Fetten

Polarographic Determination of Tocopherols and Tocopherylquinones in Oils and Fats A method for the polarographic determination of α-, γ-, and δ-tocopherols and the corresponding tocopherylquinones in oils and fats was worked out. After saponification of the samples and extraction of unsaponifiable matter with ether, the tocopherylquinones originally present in oils and fats are directly determined polarographically. Tocopherols present in the sample are oxidized quantitatively with cerium(IV) sulfate to the corresponding tocopherylquinones and latter are then likewise polarographed. The presence of substances accompanying tocopherols in the unsaponifiable matter does not interfere with the determination of tocopherols or tocopherylquinones. The tocopherol contents of different oils and fats are given.     

Some aspects of biodiesel oxidative stability

Biodiesel, an “alternative” diesel fuel derived from vegetable oils, animals fats or used frying oils, largely consists of the mono-alkyl esters of the fatty acids comprising these feedstocks. One of the major technical issue facing biodiesel is its susceptibility to oxidation upon exposure to oxygen in ambient air. This susceptibility is due to its content of unsaturated fatty acid chains, especially those with bis-allylic methylene moieties. Oxidation of fatty acid chains is a complex process that proceeds by a variety of mechanisms. Besides the presence of air, various other factors influence the oxidation process of biodiesel including presence of light, elevated temperature, extraneous materials such as metals which may be even present in the container material, peroxides, and antioxidants, as well as the size of the surface area between biodiesel and air. Approaches to improving biodiesel oxidative stability include the deliberate addition of antioxidants or modification of the fatty ester profile. This article discusses some factors influencing biodiesel oxidative stability and their interaction. Resulting approaches to improving this property of biodiesel are related to these factors and the corresponding mechanisms.     

Der Futterwert von Fetten und Ölen aus Verarbeitungsprozessen bei Geflügel

Feeding Value of Fats and Oils from Finishing Processes for Poultry Altogether two trials with 22 different fats/oils have been carried out. In the first trial the interesterification and the digestibility of the fatty acids of seven fats and oils from the finishing processes with different contents of polymeres have been determined with broilers, aged 2–3 and 5–6 weeks as well as adult cocks. The age of the animals and the shares of the fatty acids were of high influence on the feeding value. In the second trial the fattening performance of broilers that had got ratios of 13 different frying oils, bleaching earth oils or distillation residues, was determined. The results with frying oils were successful, those with bleaching earth oils were moderate and with distillation residues extremely bad. A dependence between the content of polymeres and the feeding value of fat and oils could not be found out.     

Low trans hydrogenation of edible oils

Hydrogenation of edible oils is an important process in the food industry to produce fats and oils with desirable melting properties and an improved shelf life. However, beside the desired hydrogenation reaction trans fatty acids are formed as well. As several studies indicate a negative health effect of trans fatty acids, consumer demands will urge the food producers to lower the content of trans fatty acids in their products. This article describes the option to reduce the trans levels in the hydrogenation of an edible oil by changing process conditions and by applying alternative low trans heterogeneous catalysts.     

Physiologische Bedeutung unverseifbarer Komponenten von Nahrungsfetten

Physiological Importance of Unsaponifiable Components in Dietary Fats For evaluation of the physiological relevance of dietary fats both their fatty acid pattern and unsaponifiable components should be considered. According to fat source these components include sterols (phytosterols, cholesterol), lipopigments, fat soluble vitamins, antioxidants and different sensoric substances. In lipid metabolism the non polar fraction, mainly tocopherols and phytosterols, decrease the ratio of total-/HDL-cholesterol. In rat experiments the erythrocyte membrane-stabilizing effect of α- and γ-tocopherol was not found for β-sitosterol and ubiquinones. Tocopherols stabilize also hepatocytes by protecting the membrane fatty acids against oxidation disableing cells to maintain their physiological structure as well as function. Similar effect is to be considered also for ubiquinones. Main function of the unsaponifiable substances is their antioxidant capacity resulting from redox potentials of several components. α-and γ-tocopherol, when added in equimolar amounts, inhibit the in vitro lipid peroxidation. In this time and temperature dependent function γ-tocopherol reveals a higher potency than α-tocopherol. On the other hand, in vivo lipid peroxidation (rat liver mitochondria and testes) is less when β-tocopherol was administered compared to γ-tocopherol. Highest potency was found for mixtures with both tocopherols in combination with ubiquinones and β-sitosterol. Unsaponifiable components of dietary fats together with the fatty acid pattern are important for prevention and therapy of fat metabolism disorders. They also can regulate lipid peroxide formation in vitro and in vivo.     

Antioxidant effect of mono‐ and dihydroxyphenols in sunflower oil with different levels of naturally present tocopherols

Antioxidant properties of mono‐ and dihydroxyphenolic acids and their alkyl esters were examined, with emphasis on the relationship between their molecular structure and antioxidant activity. Test media with different tocopherol level were used for determining the oxidative stability: original refined sunflower oil (total tocopherols 149.0 mg/kg), partially tocopherol‐stripped sunflower oil (total tocopherols 8.7 mg/kg) and distilled fatty acid methyl esters (FAME) as a tocopherol‐free medium. The chemical reaction of tocopherols with diazomethane tested for the purpose to eliminate their antioxidant activity failed due to the negligible degree of methylation of hydroxyl group in the tocopherol molecule. Caffeic acid and protocatechuic acid (3,4‐dihydroxyphenolic acids) and their alkyl esters were found to be more active antioxidants than monohydroxyphenolic acid (p‐hydroxybenzoic acid), 2,5‐dihydroxyphenolic acid (gentisic acid), 3‐methoxy‐4‐hydroxyphenolic acids (vanillic and ferulic acids) and their corresponding alkyl esters. Naturally present tocopherols in refined sunflower oil proved to have a synergistic effect on gentisic acid but not on its alkyl esters. In contrast, tocopherols showed an antagonistic effect on alkyl esters of caffeic acid, because their protection factors decreased with increasing level of tocopherols in the test medium. Moreover, the antioxidant activity of these alkyl esters decreased with increasing length of their alkyl chain in conformity with the polar paradox hypothesis. Practical applications: Tocopherols as naturally present antioxidants influence considerably the antioxidant activity of other antioxidants added to plant oils used as a test medium. Distilled fatty acid methyl esters prepared from refined sunflower oil may serve as an optimal tocopherol‐free test medium. Some alkyl esters of phenolic acids were evaluated to be applicable as natural more lipophilic antioxidants in comparison with phenolic acids.     

Are natural antioxidants better – and safer – than synthetic antioxidants?

Antioxidants are necessary in the Western diet as it is rich in polyenoic fatty acids, which are easily oxidized with formation of free radicals that are harmful if present in higher amounts. Consumers prefer natural antioxidants to synthetic antioxidants, mainly for emotional reasons. The common Western daily diet contains about 1 g natural antioxidants even if no natural antioxidants have been added for lipid stabilization. Their main sources are cereals, fruits, vegetables, and beverages. Only a part of the natural antioxidants is absorbed and used as free‐radical scavengers in vivo. Natural antioxidants should be added to food in larger amounts than synthetic antioxidants as they are less active, but the actual activity depends very much on particular conditions and food composition. Nevertheless, the addition of additional antioxidants is still negligible in comparison with the dietary supply of native antioxidants. The safety limits of natural antioxidants are mostly not known, but they are hardly safer than synthetic antioxidants. The best protection would be to replace high‐polyenoic oils in the diet with high‐oleic oils, and to use alternative methods of food protection against autoxidation.     

Seed roasting improves the oxidative stability of canola (B. napus) and mustard (B. juncea) seed oils

Animal fats and partially hydrogenated vegetable oils (PHVO) have preferentially been used for deep‐frying of food because of their relatively high oxidative stability compared to natural vegetable oils. However, animal fats and PHVO are abundant sources of saturated fatty acids and trans fatty acids, respectively, both of which are detrimental to human health. Canola (Brassica napus) is the primary oilseed crop currently grown in Australia. Canola quality Indian mustard (Brassica juncea) is also being developed for cultivation in hot and low‐rainfall areas of the country where canola does not perform well. A major impediment to using these oils for deep‐frying is their relatively high susceptibility to oxidation, and so any processing interventions that would improve the oxidative stability would increase their prospects of use in commercial deep‐frying. The oxidative stability of both B. napus and B. juncea crude oils can be improved dramatically by roasting the seeds (165 °C, 5 min) prior to oil extraction. Roasting did not alter the fatty acid composition or the tocopherol content of the oils. The enhanced oxidative stability of the oil, solvent‐extracted from roasted seeds, is probably due to 2,6‐dimethoxy‐4‐vinylphenol produced by thermal decarboxylation of the sinapic acid naturally occurring in the canola seed.