Fatty Acid Soaps Research Articles

Biodegradability and cytotoxicity of choline soaps on human cell lines: effects of chain length and the cation

Using choline as a counterion in fatty acid surfactants substantially increases their water solubility as compared to classical sodium and potassium soaps, and thereby enables the application of desirable longer-chain derivatives at ambient temperature. Since choline can be decomposed both physiologically and environmentally, corresponding fatty acid soaps are considered to be highly biocompatible. Recent toxicity and biodegradability studies of choline ionic liquids, including anions such as short- and middle-chain alkanoates, have verified the expected low toxic impact. However, according to the European Cosmetic Directive 76/768/EEC, all salts of choline are forbidden in cosmetic products, mainly just due to its classification as a quaternary ammonium ion. In order to facilitate their application in the future, we have investigated the biodegradability of choline soaps (ChCm) with alkyl chain lengths of m = 12–18 according to the OCDE 301F standard. Further, the cytotoxicity of ChCm surfactants with m = 8–16 was determined, both for odd- and even-numbered fatty acids. Studies were carried out using two different human cell lines, namely cervix carcinoma cells (HeLa) and keratinocytes (SK-Mel-28). For a better comparability to common soaps and to shed light on the influence of the cation, sodium and potassium homologues were also investigated. Results reveal an unexpected non-linear relationship between the hydrophobic chain length and the IC50 value. Most importantly, the presented data show that IC50 values of ChCm surfactants coincide with those of the widely applied sodium and potassium soaps. This demonstrates that choline carboxylate surfactants are harmless and thus strongly supports their applicability in customer end products.

Studies on fatty oil derivatives of Pithcellobrium dulce and Buchanania lanzan: possible industrial application

Amide derivative prepared from the fatty oil of Pithcellobrium dulce has been found to disperse calcium and magnesium ions. The property can be used in removing the limitation of fatty acid soaps (usually sodium salt) which are good surface active agents but precipitate in hard water. In the preparation of amide derivative, no solvent has been used, thus a green approach has been attempted. The prepared derivative has been identified by IR, NMR and HPLC. In the second part of the study, preparation of a wood adhesive using natural source – Buchanania lanzan flour, has been tried due to high cost and environmental concerns of petroleum based phenol – formaldehyde and urea – formaldehyde resins. The method is economical and ecofriendly. Pithcellobrium dulce (Leguminosae) 1 is a cultivated tree, distributed in Central Madhya Pradesh. Two saponins from P. salman 2 , a triterpenoid glycoside from P.arboreum and P cubense 3 and chemical composition of P. multiforum 4 have been reported. The linoleic –oleic acid rich oil has been analysed in our Laboratory 5 Soaps precipitate with calcium and magnesium, which are present in hard water. To overcome this difficulty, dispersing agents are used alongwith soap based detergents. For preparation of these dispersing agents large amount of organic solvents are used. 6-8 In the present study, solvent has not been used. Buchanania lanzan (Anacardiaceae) 9 is a middle sized tree, distributed in dry hot forests of Bundelkhand 10. Kernels 11 and bark 12 have been worked out. Fatty oil analysis has been carried in our Laboratory. 13 The flour in presence of phenol and formaldehyde has been evaluated in the present study – to know its performance as a

Impact of Hydrolysis at High Temperatures on the Apparent Viscosity of Carboxybetaine Viscoelastic Surfactant-Based Acid: Experimental and Molecular Dynamics Simulation Studies

Summary Carboxybetaine viscoelastic surfactants have been applied in acid diversion and fracturing treatments in which high temperatures and low pH are usually involved. These surfactants are subjected to hydrolysis under such conditions because of the existence of a peptide group (-CO-NH-) in their molecules, leading to changes in the rheological properties of the acid. The objective of this paper is to study the impact of hydrolysis at high temperatures on the apparent viscosity of carboxybetaine viscoelastic surfactant-based acids, and propose the mechanism of viscosity changes by molecular dynamics (MD) simulations. Surfactant-acid solutions with different compositions (surfactant concentration varied from 4 to 8 wt%) were incubated at 190°F for 1 to 6 hours. Solutions were then partially spent by CaCO3 until the sample pH was 4.5, and the apparent viscosity was measured using a high-temperature/high-pressure (HT/HP) viscometer. To understand the mechanism for viscosity changes on the molecular level, MD simulations were carried out on spent surfactant-acid aqueous systems using the Materials Studio 5.0 Package. It was found that short-time hydrolysis at high temperatures (for example, 1 to 2 hours at 190°F) led to a significant increase in surfactant-acid viscosity. However, after incubation for 3 hours, phase separation occurred and the acid lost its viscosity. Simulation results showed that viscosity changes of amido-carboxybetaine surfactant acid by hydrolysis at high temperatures may be caused by different micellar structures formed by carboxybetaine and fatty acid soap, its hydrolysis product. The optimum molar ratio of amido-carboxybetaine and fatty acid soap to form wormlike micelles was found to be nearly 3:1 from our simulations. Our results indicate that hydrolysis at high temperatures has a great impact on surfactant-acid rheological properties. Short time viscosity build-up and effective gel breakdown can be achieved if surfactant-acid treatments are carefully designed; otherwise, unexpected viscosity reduction and phase separation may occur, which will affect the outcome of acid treatments.

Lipids in the Diet and the Fatty Acid Profile in Beef: A Review and Recent Patents on the Topic

The objective of this review is to report how the use of lipid sources in diets for ruminants can affect the fatty acid profile of beef. In addition, recent patents that can be utilized to alter the fatty acid profile in the meat, or which concern the synthesis of conjugated fatty acids will be reviewed. The industrial production of conjugated linoleic acid (CLA) has already started and the commercial products present isomers cis-9, trans-11; trans-9, cis-11; and trans-10, cis-12. Patents on the biological synthesis of isomer C18:2 cis-9, trans-11 from the linoleic acid have also been published. However, the economic production of CLA in industrial scale is a difficult process. Most of the patents published for CLA production utilize bacteria of the genera Bifidobacterium sp. and Propionibacterium sp. Lipid supplementation, with the objective to improve the fatty acid profile of beef, can be done through the use of patented products, such as genetically modified oilseeds and calcium soaps of fatty acids.

Surface‐Enhanced Raman Spectroscopy of Tribochemically Formed Boundary Films of Refined and Unrefined Canola Oils

AbstractThe paper reports the investigation of tribochemically formed boundary films of canola oils using surface‐enhanced Raman spectroscopy. This is the first time that metallic surfaces lubricated by plant oils have been studied using this technique. The results of this work provided strong evidence that fatty acids were liberated from the triglyceride structure during sliding to form a fatty acid soap layer on the silver surface. The study also revealed that the fatty acid chains of the unrefined canola oil were more disordered and most likely in a gauche conformation, while that of the refined canola oil were tightly packed and oriented perpendicular to the surface. It is believed that the greater presence of polar minor components in the unrefined oil, such as phospholipids, interfered with the ability of free fatty acids to form a tightly packed monolayer on the silver surface.

Formation of wormlike micelles with natural-sourced ingredients (sucrose fatty acid ester and fatty acid) and a viscosity-boosting effect induced by fatty acid soap

We have investigated the formation of a viscoelastic wormlike micellar solution with natural-sourced materials such as sucrose monopalmitate (C16SE) and fatty acid (FA). Zero-shear viscosity of 10wt% aqueous solutions of C16SE and lauric acid (LA) increased with the increase in the C16SE fraction to a certain level but it decreased after a maximum value. Viscous solutions having almost maximum zero-shear viscosity showed non-Newtonian behavior and had Maxwell-type mechanical properties. When a small fraction of LA of the water/C16SE/LA system was substituted with sodium laurate (SL), the maximum zero-shear viscosity increased by nearly one order of magnitude from the original system due to a decrease in the diffusion constant of the wormlike micelles. With further substitutions of LA with SL, the zero-shear viscosity decreased because the highly hydrophilic fatty acid soap makes elongated micelles shorter.

Enzymatic deinking of secondary fibers: cellulases/hemicellulases versus laccase-mediator system

The use of enzymes has been suggested as an environmentally friendly alternative to complement conventional chemical deinking in the recycling of recovered paper. This study compares the use of cellulases/hemicellulases versus the laccase-mediator system for deinking printed fibers from newspapers and magazines. For this purpose, two commercial enzyme preparations with endoglucanase and endoxylanase activities (Viscozyme Wheat from Aspergillus oryzae and Ultraflo L from Humicola insolens, Novozymes) and a commercial laccase (NS51002 from Trametes villosa, Novozymes), the latter in the presence of synthetic or natural (lignin-related) mediators, were evaluated. The enzymatic treatments were studied at the laboratory scale using a standard chemical deinking sequence consisting of a pulping stage; an alkaline stage using NaOH, sodium silicate and fatty acid soap; and a bleaching stage using hydrogen peroxide. The handsheets were then prepared and their brightness, residual ink concentration, and strength properties were measured. Among the different enzymatic treatments assayed, both carbohydrate hydrolases were found to deink the secondary fibers more efficiently. Brightness increased up to 3-4% ISO on newspaper fibers, being Ultraflo 20% more efficient in the ink removal. Up to 2.5% ISO brightness increase was obtained when magazine fibers were used, being Viscozyme 9% more efficient in the ink removal. Regarding the laccase-mediator system, alone or in combination with carbohydrate hydrolases, it was ineffective in deinking both newspaper and magazine fibers, resulting in pulps with worse brightness and residual ink concentration values. However, pulp deinking by the laccase-mediator system was displayed when secondary fibers from printed cardboard were used, obtaining up to 3% ISO brightness increase and lower residual ink concentrations.

Surface nanostructure of Hevea brasiliensis natural rubber latex particles

Natural rubber (NR) from the Hevea brasiliensis tree is the main commercial feedstock for rubber and latex dipping industries. NR latex particles in a matured commercial latex concentrate are stabilized by charged groups derived from proteins, long-chain fatty acid soaps and polypeptides adsorbed on the particle surface. The colloidal stability of the latex is extremely sensitive to pH as well as to the ionic environment of the dispersing medium. Previous work on particle microelectrophoresis has shown that the charge on the particle surface is derived mainly from carboxylic groups of long chain fatty acids ( ca. 86%). Freshly collected field latex from the tree, on the other hand, is believed to be stabilized by proteins and phospholipids before hydrolysis sets in upon leaving the tree. The exact arrangement of the adsorbed proteins and phospholipids and the thickness of this adsorbed layer have yet to be successfully determined. The present study has been focused on unraveling the arrangement of these proteins and phospholipids on the particle surface of a freshly tapped NR latex. In order to visualize these molecules, they were imaged using phase contrast atomic force microscopy (AFM). Moreover, the molecules in the particle were labeled with fluorescent Rhodamine B (RB) and uncharged fluorescein-5(6)-isothiocyanate (FITC), and monitored by confocal laser scanning microscopy (CLSM) thereby permitting an in situ observation of their locations on and inside the particles. The selective labeling of the proteins and phospholipids with RB and FITC in protein-free as well as in protein-and-lipid-free latex particles permitted an unequivocal determination of their presence both on the surface and in the interior of the particles. An indentation study of the surface layer of the original untreated NR particle was also carried out to confirm the hypothesis of a core–shell structure with a mixed layer of proteins and phospholipids surrounding the hydrophobic core of polyisoprene particles. According to the obtained results, the surface of the particles in freshly tapped latex is distinctly different from that of a matured latex concentrate.

Thermotropic Phase Behavior of Choline Soaps

Choline carboxylates (ChCm with m = 12-18) are simple biocompatible anionic surfactants with very low Krafft temperatures, possessing a rich aqueous phase behavior. In the present work, we have investigated the thermotropic mesomorphism of anhydrous ChCm salts for m = 12-18. Transition temperatures and enthalpies determined by differential scanning calorimetry reveal that all investigated compounds exhibit three different phases between -20 and 95 °C. The phases were further characterized by optical polarizing microscopy, NMR spin-spin relaxation, and X-ray scattering measurements. The nature of the phases was identified with increasing temperature as crystalline, semicrystalline, and liquid-crystalline lamellar. Even long-chain choline carboxylates (m = 18) were found to melt into a lamellar liquid-crystalline phase below 100 °C. Accordingly, with choline as counterion in simple fatty acid soaps, not only the water solubility is considerably enhanced but also the melting points are substantially reduced, hence facilitating thermotropic mesomorphism at temperatures between 35 and 95 °C. Thus, simple choline soaps with m = 12-18 may be classified as ionic liquids.

Effect of Calcium on the Phase Distribution of Resin and Fatty Acids in Pitch Emulsions

Resin and fatty acids (RFAs) play a key role in deinking processes of recycled fiber after precipitation by calcium. The distribution of RFAs between the lipophilic/colloidal phase and the water phase, here called pKlw, was determined by gas chromatography for different emulsions of TMP pitch and fatty acid soaps in the presence of calcium ions. Resin acids were at least partially dissolved at alkaline conditions even at high calcium ion concentrations, while fatty acids were only slightly soluble. The structure of the component was an important factor, along with the calcium content present which made fatty acids practically insoluble.

Precipitation of a Poorly Soluble Model Drug during In Vitro Lipolysis: Characterization and Dissolution of the Precipitate

Precipitation of cinnarizine during in vitro lipolysis of a self-microemulsifying drug delivery system (SMEDDS) was characterized to gain a better understanding of the mechanisms behind the precipitation. During in vitro lipolysis of the SMEDDS with or without cinnarizine, samples were taken at several timepoints and ultracentrifuged. Cinnarizine content in the pellet increased from 4% to 59% during lipolysis. The precipitation of cinnarizine during in vitro lipolysis correlated well with the degree of lipid digestion, determined by sodium hydroxide addition. The pellet from the endpoint of lipolysis was isolated and subjected to dissolution in biorelevant media. Dissolution rate of cinnarizine from pellets containing precipitated cinnarizine was initially 10-fold higher than dissolution from blank pellet spiked with crystalline cinnarizine, reaching more than 50% drug dissolved in the first minute. Pellets were further characterized by X-ray powder diffraction (XRPD) and polarized light microscopy (PLM). Both methods indicated the presence of liquid crystalline phases of calcium fatty acid soaps, but no presence of crystalline cinnarizine in the pellet. Overall, dissolution studies along with XRPD and PLM analysis indicate that cinnarizine precipitating during in vitro lipolysis of this SMEDDS is not crystalline, suggesting an either amorphous form or a molecular dispersion.

Comparative Study of Jhamarkotra Soap Emulsion and Tall Oil Soap Emulsion as Flotation Collectors

Soaps of mixed fatty acid origin or soap-light diesel oil (LDO) emulsion are used as collectors in the froth flotation of salt type minerals (for example – apatite, fluorite, dolomite, etc.). Detergents are sometimes used along with soaps to reduce the consumption of soap and also to improve the process efficiency. In the present investigations effect of different reagent regimes on flotation of a siliceous phosphate ore was studied. Flotation tests were carried out using mixed fatty acid soap and tall oil. Both the reagents were used as emulsions with light diesel oil in the ratio of 1:1.2. Tests were also carried out with promoters (Alfa Olefin Sulfonate [AOS], Linear Alkyl Benzene Sulfonate [LABS] and Urea) along with these reagents to evaluate the process efficiency. While AOS and LABS are detergents, urea is a polar non electrolyte reagent known to act as hydrotrope. It is noted that mixed fatty acid soap-LDO emulsion (SL emulsion) shows better process efficiency than tall oil-LDO emulsion (TL emulsion). The highest recoveries (>90%) were achieved when mixed fatty acid was used in conjunction with promoters. The experiments with promoters yielded higher recoveries rather than mixed fatty acid or tall oil used alone.

Dissolution Study of Salt of Long Chain Fatty Acids (Soap Scum) in Surfactant Solutions. Part II: Kinetics of Dissolution

AbstractA study of the dissolution kinetics of soap scum, calcium octadecanoate (Ca(C18)2), by aqueous solutions was carried out by measuring the rate of dissolution of Ca(C18)2 using a flow cell apparatus. These solutions contained three different types of surfactants: dimethyldodecylamine oxide (DDAO), sodium dodecyl sulfate (SDS), or octyl polyglycoside (C8APG), in the presence of a chelating agent, disodium ethylenediaminetetraacetate (Na2EDTA). The resulting rate of dissolution corresponds well with the equilibrium solubility obtained in the part I of this series even though the dissolution is rate limited (far from equilibrium). High rates of Ca(C18)2 dissolution are achieved in solutions of zwitterionic DDAO or nonionic C8APG with Na2EDTA at high pH. From rate analysis, the Ca(C18)2 dissolution was found to be surface‐reaction limited rather than limited by solution processes or wettability.

Lipophilic Extractives in Populus × euramericana “Guariento” Stemwood and Bark

The lipophilic extractives in stemwood and bark from three different heights of Populus × euramericana “Guariento” were analyzed. The bark samples, especially from 4 and 8 meters height, contained much more extractives than the stemwood samples. The lipophilic extractives identified by Gas Chromatography–Mass Spectroscopy (GC-MS) were composed of five component groups (i.e. triglycerides, steryl esters, free fatty acids, sterols, and free fatty alcohols both in the stemwood and bark). Besides ferulic acid esters, α-amyrin and its esters, 4-hydroxycinnamic acid esters of fatty alcohols were also identified in the stemwood and bark. Small amounts of alkanes and oligomeric or polymeric material with higher molar mass than triglycerides were present only in the bark. Glycerides, mainly triglycerides, were the largest component group of the lipophilic extractives. The high proportion of short-chain fatty acids released after alkaline hydrolysis are beneficial when removing pitch particles or fatty acid soaps by dispersing and washing during pulping and papermaking.

Rapid, colorimetric quantification of lipid from algal cultures

Algae have significant potential as a source of biomass for the production of biofuels, due to their high growth rates and high cellular lipid content. Studies that address the use of algae as biofuels often require the frequent measurement of algal lipid content. Traditional methods for the quantification of lipid are, however, costly if sub-contracted, or involve the use of expensive analytical equipment that is not available in many labs. This study describes a simple, colorimetric method for the quantification of algal lipid from small amounts of culture. The technique is derived from a method for the quantification of fatty acids dissolved in chloroform. Algal lipids are saponified to fatty acids and then mixed with a copper reagent. Chloroform-extractable copper soaps of long-chain fatty acids are then colorimetrically measured by the addition of diethyldithiocarbamate to develop a yellow colored product. Linear responses for fatty acids in the range of C10:0 to C16:0 were observed for a concentration range between 0.025 and 1 μmol of fatty acid per 200 μL of sample. Fatty acids with chain lengths of less than twelve carbons produced significantly reduced signal. Decenoic acid yielded a slightly, but significantly lower signal than decanoic acid indicating that the assay underestimates the presence of unsaturated fatty acids. Lipid contents of Phaeodactylum tricornutum and Chlorella vulgaris CM2 were monitored for eight days during exponential growth to demonstrate the feasibility of the technique as a monitoring methodology. Overall, the method allowed reliable detection and quantification of fatty acid content from 1 to 2 mL of algal culture. Adaptation of the technique to micro-centrifuge format allows assaying 30 samples in less than 2 h. Considering reagents and time, the total cost per assay was estimated at less than $5, representing a significant cost savings over traditional lipid quantification procedures.

Synthesis and surfactant properties of N-acylation compounds derived from hydrolysis degradation products of N-(\beta-cianoethyl)-\epsilon-caprolactam

N-acyl amino acids can be used as active surface agents in the detergents industry, as well as in the pharmaceutical industry and cosmetics. Properties of these compounds are superior to those of fatty acids soaps and they are not toxic to the environment and have low Kraft points, because of peptide bonds (CO-NH). Acylation at the nitrogen atom can be performed with good yields without catalysts, for strong nucleophilic derivatives. The synthesis of some derivatives of 4-azasebacic acid, which are hydrolysis degradation products from N-(\beta -cianoethyl)-\epsilon -caprolactam, has been described and the N-acylation processes for these compounds are also presented. The obtained products have been characterized using various methods: IR, UV-VIS, ^1H-NMR, ^{13}C-NMR, elemental analysis, TLC, m.p. (Boethius), and in some cases refractive index. The most important surfactant properties of these N-acylated products were investigated using the surface tension method. The related thermodynamic parameters were also calculated.

Insuffisance pancréatique exocrine de l’enfant : diagnostic positif et étiologique

Lipid digestion is critical for infant development, and yet, the interconnection between lipid digestion and the microbiota is largely understudied. This review focuses on digestion of the human milk fat globule and summarizes the current understanding of the mechanisms underlying this process in infants. We first discuss the partial hydrolysis of milk fat in the stomach, which leads to rearrangement of lipid droplets, creating a lipid-water interface necessary for duodenal lipolysis. In the first few months of life, secretion of pancreatic triglyceride lipase, phospholipase A2, and bile salts is immature. The dominant lipases aiding fat digestion in the newborn small intestine are therefore pancreatic lipase-related protein 2 and bile salt–stimulated lipase from both the exocrine pancreas and milk. We summarize the interaction between ionic fatty acids and cations to form insoluble fatty acid soaps and how it is influenced by various factors, including cation availability, pH, and bile salt concentration, as well as saturation and chain length of fatty acids. We further argue that the formation of the soap complex does not contribute to lipid bioavailability. Next, the possible roles that the gut microbiota plays in lipid digestion and absorption are discussed. Finally, we provide a perspective on how the manufacturing process of infant formula and dairy products may alter the physical properties and structure of lipid droplets, thereby altering the rate of lipolysis.

Milk production, peripartal liver triglyceride concentration and plasma metabolites of dairy cows fed diets supplemented with calcium soaps or hydrogenated triglycerides of palm oil

The aim of the study was to test the effect of rumen-inert fat supplements of different chemical forms or containing different unsaturated/saturated (U/S) fatty acid contents on milk production, milk composition and liver and blood metabolic variables of high-yielding dairy cows in the peripartal period. Thirty Holstein-Friesian dairy cows were divided into three equal groups and fed a corn silage-based diet, without fat supplementation (control) or supplemented with 11.75 MJ NEl per day of calcium soaps of palm oil fatty acids (CAS; U/S=61/39) or with 11.75 MJ NEl per day of hydrogenated palm oil triglyceride (HTG; U/S=6/94). Each diet was fed from 25+/-2 d prior to the expected calving to 100+/-5 d post partum. Compared with the control, both CAS and HTG supplementation resulted in an increase of the average milk yield. Milk fat content and fat-corrected milk yield were higher in the HTG group but lower in the CAS group than in the control group. In all groups liver triglyceride concentrations (TGL) increased from 15 d prepartum to 5 d post partum, and then decreased thereafter. At 5 d TGL was lower in the HTG group than control or CAS cows. No significant differences were detected in TGL among dietary treatments at 15 d prepartum and 25 d post partum. Higher plasma glucose and insulin and lower non-esterified fatty acids and beta-hydroxybutyrate concentrations and aspartate aminotransferase activity were measured in the HTG group than in the control or CAS groups at 5 d or 25 d post partum. Our results show that HTG may provide a better energy supply for high-yielding dairy cows in negative energy balance than CAS around calving.

Separation of sericin from fatty acids towards its recovery from silk degumming wastewaters

Sericin is a valuable protein, which is currently discarded as a waste in silk industry. Silk degumming wastewaters (SDW) are abundant sources of sericin, however, they contain impurities such as salts of fatty acids (soap) in conventional degumming processes. In this study, a process consisting of centrifugation (CFG), low temperature crystallization (LTC) and ultrafiltration (UF) was developed to separate sericin from fatty acids towards its recovery from conventional SDW. Complete removal of fatty acids was achieved by CFG + LTC, where CFG possibly accelerated crystal formation and separation processes. In CFG + UF (20 kDa), sericin rejection increased as pH was reduced from alkaline to acidic levels, possibly due to decreased solubility of sericin and increased amounts of undissociated fatty acids. Fatty acids were partly retained, leading to inadequate separation. Despite very high flux declines, cakes formed by the combined foulants were removable at both pH conditions. In CFG + LTC + UF (5 kDa), sericin was rejected by 92%. Although solution pH did not affect rejection performance, flux decline decreased from 85% to 61% at alkaline pH. Different fouling mechanisms were observed for different foulant types. Only cake formation occured with combined foulant (sericin + fatty acids). The cake surfaces were irregular, with denser and more heterogeneous structure at acidic pH. However, smooth cake formation plus pore narrowing occured with sericin alone at alkaline pH. Additional pore clogging occured at acidic pH, possibly due to decreased solubility of sericin. Chemical cleaning was less effective at acidic pH due to adsorption and pore clogging. Sericin recovery from conventional SDW was achieved in a three-stage process; CFG + LTC for complete separation of sericin from fatty acids and UF for recovering sericin.

Binary coalescence of gas bubbles in the presence of a non-ionic surfactant

The coalescence behavior of air bubbles in a dilute aqueous surfactant solution of a polyglycerol fatty acid ester (PGE), a commercial non-ionic surfactant, is investigated in a binary coalescence experiment. The focus is on the influence of the ionic strength of the solution on the rate of coalescence. Results are compared with the adsorption kinetics and surface shear/dilatational rheological properties of the surfactant. Experiments show that the coalescence frequency is significantly lower at low ionic strength, and that bubble stability increases with increasing aging time. Stabilization occurs via surfactant adsorption and a resulting electrostatic and/or steric repulsive force. The electrostatic force presumably originates from small amounts of anionic fatty acid soaps, which are residues from the industrial synthesis. The steric force can be related to the adsorption of visco-elastic layers of PGE at the air–water interface.