Essential oils are a key ingredient in foods, beverages, and personal- and home-care products due to their flavors, scents, and various biological activities. This study investigates the capacity of polysorbate 60 (PS60) micelles to solubilize eight essential oils classified into two groups based on their composition. The first group (tea tree, rose, lavender, and melissa oils) contains more than 40% polar aliphatic or alicyclic alcohols or aldehydes, whereas the oils from the second group (chamomile, yarrow, lemon, and orange oils) contain less than 20% of these compounds. The efficient solubilization of the studied essential oils within PS60 micelles is proposed to occur via a mechanism involving two steps: (1) the formation of mixed micelles between PS60 molecules and the polar alcohol or aldehyde constituents of the essential oils, and (2) the dehydration of PS60 ethoxy groups in the presence of highly water-soluble additives (such as citric acid and sodium citrate), which is suggested to decrease the hydrophilic barrier of the micellar corona, thereby facilitating the mass transfer of hydrophobic oil molecules into the micellar core. Stable, transparent microemulsions form only with the first group of essential oils in a certain concentration range. The second step in the proposed mechanism leads to the unexpected finding that reducing the concentration of water-soluble additives, such as citric acid and sodium citrate, impairs solubilization by allowing the micellar corona to rehydrate.

Polysorbates are hydrophilic, nonionic surfactants widely used in food, cosmetic, and pharmaceutical products. Often, these emulsifiers are used in combination with different preservatives, and it is essential to conduct an in-depth study of the influence of such additives on the properties of Polysorbate 60 solutions. In the current study, we investigated the effect of various food additives: citric acid, sodium benzoate, potassium sorbate, a mixture of citric acid and sodium citrate, and propylene glycol on the stability and micellar properties of Polysorbate 60 by using different experimental methods such as GC, DSC, SAXS, DLS, optical observations in polarised light, and NMR. When stored at room temperature without additives, solutions of Polysorbate 60 slowly undergo phase separation over time. Our results show that citric acid, a mixture of citric acid and sodium citrate, and propylene glycol increase the rate of this phase separation. In contrast, sodium benzoate and potassium sorbate are incorporated into the mixed micelles. They localize within the palisade layer, a region of the micelle where the surfactant tails begin, effectively preventing the phase separation. As a result, Polysorbate 60 solutions with these specific additives remain transparent and stable for over a year

Alkyl sarcosinates are amino acid-based anionic surfactants commonly used as primary surfactants in sulfate-free personal care products. The major aim of this study is to identify the key factors influencing the rheological behaviour of sodium sarcosinate solutions and their mixtures with nonionic, zwitterionic, and cationic co-surfactants. To achieve this, we examined the effects of salt type and concentration for alkyl sarosinates with different chain lengths (dodecyl, tetradecyl, and cocoyl) across concentration range of 2–20 wt%. Experimental results reveal two distinct regions in the salt curve for the three studied sarcosinates. At low electrolyte concentrations, viscosity remains constant until reaching the critical electrolyte concentration, C1, beyond which viscosity increases logarithmically with salt concentration. Further electrolyte addition leads to phase separated solutions at the critical precipitation concentration, CTR. Both C1 and CTR decrease as the hydrocarbon chain length increases from dodecyl to tetradecyl. However, the presence of shorter chain molecules in cocoyl sarocisinate significantly increases both C1 and CTR due to the formation of spherical micelles. A theoretical expression for predicting viscosity dependence on salt concentration is derived and successfully applied to describe the experimental data. The adsorption energy of sodium and potassium to alkyl sacrosinate micelle surfaces is found to be much smaller than that to sodium lauroyl ether sulfate surfactants (1 vs. 3 kBT for Na+ and 0.8 vs. 3.8 kBT for K+). No significant effect of amphoteric co-surfactants, including cocoamidopropyl betaine, sulfobetaine, or decylamine oxide, is observed. NMR analysis confirms that cocoamidopropyl betaine and sodium dodecyl sarcosinate form mixed micelles that are structurally similar to sarcosinate micelles, as carboxyl groups remain exposed on the micelle surfaces in both cases. When using amine oxide and sulfobetaine, the increase in viscosity is attributed to the elongation of mixed micelles, though steric hindrance from side methyl groups limits their growth. The practical significance of this study lies in the finding that longer-chain alkyl sarcosinates (such as tetradecyl, as investigated here) can attain significantly higher viscosities at lower salt concentrations compared to shorter-chain analogs or surfactant mixtures. The scientific significance stems from the development of a theoretical model capable of predicting the viscosity of alkyl sarcosinate solutions across various surfactant and salt concentrations.

High-pressure homogenizers, typically used for producing nanoemulsions at the industrial scale, are energy and maintenance intensive, and limited to produce only dilute, low viscosity nanoemulsions. We propose an alternative approach to produce dilute to concentrated food-grade nanoemulsions with droplet size ranging between 100 and 500 nm using rotor-stator homogenization. Gum Arabic (GA) or modified starch (MS) was used as both viscosity modifier and emulsion stabilizer. GA and MS have relatively low surface activity compared to the common low-molecular-mass surfactants used typically for nanoemulsion preparation. The main differences between GA and MS are the lower viscosity of the GA solutions, compared to MS solutions, and the faster adsorption of MS, as compared to GA. The obtained results show that stable nanoemulsions are formed by rotor-stator homogenization when the rapidly adsorbing MS is used as emulsifier. Much larger drops are formed during emulsification with GA, which is due to significant drop-drop coalescence in the respective emulsions. The experimental results for the nanoemulsions prepared with MS are well-described by the theoretical expression for emulsification in turbulent viscous regime, after proper account for the effects of temperature and drop-drop interactions in the sheared emulsions.