Analytical techniques in food emulsifiers

After reviewing some problems arising in the analysis of food emulsifiers, we describe an analytical technique to detect most of them. The analytical method is based on the following procedure: (a) extraction of total lipids from food with a mixture of chloroform-methanol; (b) removal of nonpolar lipids from the lipidic extract by column chromatography with an elution media based on petroleum ether-ethyl ether mixtures; (c) thin layer chromatographic identification of the polar lipids extracted from foods. The validity of the method has been practically checked on some emulsifier-based foods, i.e., chocolates, toppings, ice creams, and whippable creams.     

Occurrence of cyclic fatty acid monomers in frying oils used for fast foods

Cyclic fatty acid monomers were analyzed by gas chromatography in commercial frying oils, obtained in this country and in the Middle East. Samples were obtained from food outlets in California and Illinois after varying periods of usage. The samples from Egypt and Israel were collected from street vendors frying vegetable patties (known as “fallafel”) in open-air stands. The United States samples ranged from 0.1 to 0.5% cyclic monomers, and from 1 to 8% polar +noneluted thermal oxidation materials. The Middle Eastern samples showed significantly more heat abuse, with values for cyclic monomers from 0.2 to 0.7% and polar materials ranging from 2 to 22%.     

驱油用水溶性乳化剂乳化性能的评价

结合改进后的水溶性乳化剂乳化力的测定方法以及现有乳化稳定性的评价方法,分别测定了驱油常用的磺酸盐类(阴离子型乳化剂)、甜菜碱类(两性离子型乳化剂)、聚氧乙烯烷基苯酚醚类(OP型,非离子型乳化剂)3类乳化剂的乳化力和乳化稳定性,并计算了乳化剂的乳化强度综合指数。探究了乳化剂类型与碳链长度对乳化剂乳化性能的影响,并着重分析了乳化剂浓度对其乳化性能的影响。结果表明,乳化剂疏水链中碳原子数相近时,甜菜碱类(两性离子型)乳化京-11原油的能力要优于磺酸盐类乳化剂(阴离子型)。当乳化剂疏水基含碳原子数与原油等效烷烃碳数相近时,同类型乳化剂的乳化性能随疏水链中碳原子数的增加而变弱;当两者相差较大时,乳化剂的乳化性能较差。其次,乳化剂的浓度越高,3种类型乳化剂的乳化稳定性均越强;当乳化剂浓度高于其CMC值时,乳化剂浓度对乳化剂的乳化力影响较小。     

驱油用水溶性乳化剂乳化性能的评价

结合改进后的水溶性乳化剂乳化力的测定方法以及现有乳化稳定性的评价方法,分别测定了驱油常用的磺酸盐类(阴离子型乳化剂)、甜菜碱类(两性离子型乳化剂)、聚氧乙烯烷基苯酚醚类(OP型,非离子型乳化剂)3类乳化剂的乳化力和乳化稳定性,并计算了乳化剂的乳化强度综合指数。探究了乳化剂类型与碳链长度对乳化剂乳化性能的影响,并着重分析了乳化剂浓度对其乳化性能的影响。结果表明,乳化剂疏水链中碳原子数相近时,甜菜碱类(两性离子型)乳化京-11原油的能力要优于磺酸盐类乳化剂(阴离子型)。当乳化剂疏水基含碳原子数与原油等效烷烃碳数相近时,同类型乳化剂的乳化性能随疏水链中碳原子数的增加而变弱;当两者相差较大时,乳化剂的乳化性能较差。其次,乳化剂的浓度越高,3种类型乳化剂的乳化稳定性均越强;当乳化剂浓度高于其CMC值时,乳化剂浓度对乳化剂的乳化力影响较小。     

Technology for rerefining used lube oils applied in Europe: a review

The European oil rerefining industry is comprised of 28 plants treating waste oil, which represent one‐third in volume of the total European market for lubricants. The biggest European rerefineries with capacity greater than 40 000 tons/year apply various technologies for recycling of used oils from different sources. Used oil recycling technology has undergone significant changes over the past decade. With the newly developed rerefining technologies it is possible to produce higher quality base oil compared with the traditional and old acid clay methods. Currently in Europe the following re‐refining methods are widely used: solvent extraction (N‐methyl‐2‐pyrrolidone (Germany), Interline process (United Kingdom, Spain)); combined vacuum distillation and solvent extraction (Vaxon process (Denmark, Spain); hydroprocessing (Hylube process (Germany)); combined thin film evaporation and hydrofinishing (CEP process (Finland)); combined thermal de‐asphalting and hydrofinishing (Revivoil process (Italy, Poland, and Spain)). The majority of applied technologies in Europe is appropriate for rerefining of synthetic lubricating oils, which currently are replacing the conventional mineral lube oils due to their enhanced performance characteristics. However, for the rerefining technologies applying alkaline treatment (CEP, Vaxon) and hydrofinishing step (Cyclon, Snamprogetti, Revivoil) the amount of synthetic or semi‐synthetic oils based on esters in the feedstock should be eliminated, since these oils are less stable under alkali and hydrofinishing conditions. © 2013 Society of Chemical Industry     

Design methodology for bio-based processing: Biodiesel and fatty alcohol production

A systematic design methodology is developed for producing multiple main products plus side products starting with one or more bio-based renewable source. A superstructure that includes all possible reaction and separation operations is generated through thermodynamic insights and available data. The number of alternative processes is systematically reduced through a screening procedure until only feasible alternatives are obtained. As part of the methodology, process intensification involving reaction–separation tasks is also considered to improve the design by shifting the equilibrium reactions. Economic analysis and net present value are determined to find the best economically and operationally feasible process. The application of the methodology is presented through a case study involving biodiesel and fatty alcohol productions.     

Trans fatty acids: foods and effects on health

Trans fatty acids can be found in foods derived from ruminant animals and foods that contain partially hydrogenated fat such as fast foods. The consumption of trans fatty acids is larger in the United States, Canada, and some European countries than in Japan and Mediterranean countries. The incidence of coronary heart diseases is higher in countries where the consumption of trans fatty is high. Studies show that trans fatty acids can contribute to increase LDL and lipoprotein [a], and to reduce the levels of HDL. In addition, trans isomeric seems to inhibit the action of desaturase enzymes of essential fatty acids (A5- and A6-desaturase) by holding back the biosynthesis of important fatty acids such as arachidonic acid and docosahexaenoic acid (DHA). With respect to pregnant women's and infant's health, concentrations of trans fatty acids ingested by the mother are associated to concentrations found in the maternal milk. Besides the milk, the trans fatty acids can be transferred to the newly born through the placenta. Studies suggest that trans fatty acids can affect intrauterine growth due to the inhibition of the conversion of essential fatty acids by desaturase enzymes. The inhibition of DHA can also cause early atherosclerosis lesion. However, studies on the effects of trans fatty acids on health are still inconclusive and there are no current recommendations on their consumption. Additionally, in Brazil, studies to determine the composition of trans isomeric in foods are still incipient, which indicates a great need of research in this area.     

Analytical critique of hexitols used as a cooking medium

Analysis by differential scanning calorimetry and gas liquid chromatography of hexitol blends used as a roasting medium for peanuts demonstrated that there was no significant deterioration of the hexitol components due to prolonged repetitive heating. Small decreases in the hexitol content of the roasting medium, which were found after 72 hr at a temperature of 330 F, closely corresponded to the increases in the hexitan content. Furthermore no evidence could be found of any significant oxidative degradation products in any of the polyol samples analyzed.     

Interaction of dyes used for foods with food packaging polyamides

The effect of pH, temperature, dye concentration, and additives on the adsorption of the dyes FD & C (Food, Drugs & Cosmetics) Blue 1 and Blue 2 upon the polyamides nylon 4–7,9, and 10–12 was studied and a correlation between these parameters and the dye uptake was found. The adsorption kinetics of the dyes on the polyamides were studied and a mechanism based on the interaction of the acid groups of the dyes and the positively charged groups of the polyamides was suggested. © 1993 John Wiley & Sons, Inc.     

Lipid conversion factors for calculating fatty acid contents of foods

The U.S. Department of Agriculture is searching the world literature published since 1960 for data on food lipids and their fatty acid composition. These data are being used to update and expand the national tables of food composition and to establish a computerized nutrient data bank. Customarily, investigators report fatty acid data in terms of weight percent of total methyl esters. For the benefit of users of nutrient tables, relative amounts of com-ponent fatty acid esters should be converted to grams fatty acid (as free acid) per 100 grams food. For this purpose, conversion factors, defined as the weight of fatty acids in 1 gram of fat, were derived for various food products. Derivation of, and basis for, factors and their application are described for selected food products. Variables affecting factors are also dis-cussed. Investigators should include, in reports on fatty acid composition of foods, information on total lipid content and on the fatty acid content of the lipid. The latter values are readily obtained by a saponification procedure, complete acid hydrolysis, or if desired, by lipid class analysis. Presented at the AOCS Meeting in Cincinnati, September 1975.     

Analytical methodology for linear alkylbenzene sulfonate (LAS) in waters and wastes

Analytical methodology has been developed for the measurement of linear alkylbenzene sulfonate (LAS) in a broad spectrum of water and wastewater samples. In addition to providing the homolog-isomer composition of LAS, the gas chromatographic procedure has been quantified by incorporation of an internal standard to provide a specific measurement of LAS. The applicability and sensitivity of the standard, but non-specific, methylene blue active substances (MBAS) method have been increased by concentration and clean-up steps that eliminate many of the known interferences. The gas chromatographic procedure has provided specific, as well as significant, information relative to the removal of LAS in the waste treatment process.     

Fatty acid components of fried foods and fats used for frying

Oxidation of fat is accelerated at temp as high as those used for frying. The extent of this oxida-tion has been studied by frying two kinds of foods (chicken or potatoes) in cottonseed oil and in lard. Fat samples, taken prior to use and follow-ing 5 and 10 hr of frying (both for chicken and potatoes) were esterified. Subsequent quantita-tive assays of methyl esters by gas chromatogra-phy showed that the linoleic acid content had decreased from 57-49% after cottonseed oil had been used 10 hr for frying. This decrease was present regardless of whether chicken or potatoes were fried. There was no change in the linoleic acid content of lard after chicken was fried, but a decrease from 11.3-5.8% was noted when pota-toes were fried for 10 hr. The fatty acid content of the fat extracted from the potatoes and the fat used to fry them, was the same when sampled at 5 hr. However, at the end of the 10-hr frying period, fat ex-tracted from the potatoes had a lower linoleic acid content than fat used to fry them. Results were the same for both cottonseed oil and lard. Fatty acid components of the fat extracted from the chicken seemed to be affected as much by the fatty acid composition of the chicken itself as by fat used for frying. Whether the chicken was cooked in fat used 5 or 10 hr made little differ-ence. Journal Paper No. 1130, Mississippi Agricultural Experiment Station. A portion of the work in this paper is taken from a thesis sub-mitted in partial fulfillment of the requirements for the Master of Sci-ence degree at Mississippi State University in January, 1963.     

Interaction of dyes used for foods with food packaging polyester fibers

The effect of pH, temperature, dye concentration, and additives on the absorption of the dyes FD & C (Food, Drugs and Cosmetics) Blue 1 and Blue 2 upon poly(ethylene terephalate) (PET) and poly(butylene terephthalate) (PBT) subjected to different draw ratios (and, thus, resulting in different percentage crystallinities determined with DSC and wide-angle X-ray diffraction patterns) was investigated and a correlation between these parameters and the dye uptake was suggested. The absorption kinetics of the dyes on the polyesters were studied and a mechanism based upon the development of hydrogen bonds between the dyes and the end groups (? COOH,? OH) of the polyesters and the swelling of the network was proposed. Finally, an indirect measurement of the T_g values of the polyesters was suggested based upon the different dyeing diffusion rates. © 1994 John Wiley & Sons, Inc.     

Oxidative stability of polyunsaturated fatty acids and soybean oil in an aqueous solution with emulsifiers

The oxidative stability of polyunsaturated fatty acids (PUFA) and soybean oil homogenized with emulsifiers was investigated. Model emulsions were prepared from PUFA, including linoleic acid (LA), arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), and from soybean oil emulsified with different emulsifiers: three Tween emulsifiers (Tween 20, Tween 60, Tween 80) and two sucrose esters (S-1170 and S-1570) were used. The results showed that the emulsions prepared from LA and the various emulsifiers, oxidized at 40°C, were unstable. However, the corresponding AA, EPA, and DHA emulsions were stable, indicating that PUFA with a higher degree of unsaturation were more stable with emulsifiers than without the emulsifiers. In the soybean oil-in-water model system, the oxidation of soybean oil with various emulsifiers was less than without the emulsifiers.     

Proteins as emulsifiers: Methods for assessing the role

The objective of this review is to present a variety of surface and colloid chemical methodologies, in brief, with which one may study the role of proteins as emulsifiers and co-emulsifiers. The techniques range from microtechniques aimed at single interfaces (film balance) and double interfaces (tensiolaminometry) to macrotechniques aimed at the gross emulsion (microcalorimetry, electrophoresis, pulsed, nuclear magnetic resonance, microwaves). Equipment, procedures, typical results, and interpretation of the data are reviewed. Some results with commercially available proteinaceous materials are presented. A link between emulsion formation and stability theory, experimental methods, and food applications is made through the examples of a salad dressing emulsion and a foamable emulsion.     

碳纤维类材料用于电芬顿体系电极的研究现状

电芬顿技术作为先进氧化技术的一种,基于电化学原理间接性地产生·OH自由基,可以高效快速地去除水中的有机污染物。碳纤维类材料因其比表面积大、密度低、耐腐蚀等优点而被常用作电芬顿体系的电极材料。本文首先介绍了电芬顿技术的基本原理,对近年来碳纤维类材料用于电芬顿电极的研究现状进行了归纳总结,分析了碳纤维材料用于电芬顿电极时的改性手段及应用方式。着重分析了其用于电芬顿阴极时的改性机理与改性方式,并指出了其应用优势与局限性。同时也对碳纤维类材料在电芬顿阳极的应用进行了总结。最后,针对碳纤维类材料用于电芬顿体系时的产业化问题、能耗问题、电极的多功能化等问题进行了分析和展望,为碳纤维类材料应用于电芬顿体系的深入研究提供参考。     

A simple method for determining light transmittance of polymer films used for packaging foods

Sensitive components of food may undergo degradation reactions when subjected to light. The packaging of the food may slow down such reactions by absorbing and reflecting a fraction of the incident light. Riboflavin is a light‐sensitive vitamin and undergoes first‐order degradation when subjected to visible light. Rate constants of this reaction were evaluated under 20 W coolwhite light at pH = 9.0 at 25 °C, with no light shielding or by shielding the light with methylcellulose films. Based on this photodegradation reaction, a new model was proposed to define percentage light transmittance of methylcellulose films. Depending on composition, the percentage transmittance was in the range 66–96%. Variation of light transmittance was explained in terms of solubility and crystallinity. © 2001 Society of Chemical Industry     

High performance liquid chromatography of fatty methyl esters: Analytical separations

Fatty methyl esters are separated on the basis of unsaturation and chain length on an analytical scale by high performance liquid chromatography with a C18/Corasil column and aqueous acetonitrile solvent. Analysis by this method includes polymerized and oxidized esters which may not be detected by gas chromatography.     

Substitution of trans fatty acids in foods on the Danish market

Three surveys of the content of trans fatty acids (TFA) in foods on the Danish market were carried out before and after the Danish regulation was introduced in January 2004 restricting the use of industrially produced (IP)‐TFA to a maximum of 2 g per 100 g fat in any food product. For this purpose, food samples were collected in 2002–3, 2004–5, and 2006–7. Of these, 60 paired samples (defined as samples included in two of the three investigations and with higher levels of IP‐TFA in the first determination than in the second) were identified. Comparisons of the fatty acid profiles showed that, in 68% of the products (e.g. sweets, cakes and cookies as well as fast food such as pie and tortilla), IP‐TFA were mainly substituted with saturated fatty acids (SFA). In some cases, the SFA source was coconut fat, whereas in other products, palm oil was added instead of partially hydrogenated oils. However, in important cases like frying fats, healthier fat substitutes with monounsaturated fatty acids were used. The surveys showed that the IP‐TFA content has been reduced or removed from most products with originally high IP‐TFA content, like French fries, microwave oven popcorn and various bakery products, so that IP‐TFA are now insignificant for the intake of TFA in Denmark.