Ostwald Ripening Rate of Orange Oil Emulsions: Effects of Molecular Structure of Emulsifiers and Their Oil Composition

Abstract

Ostwald ripening, one of the frequently observed instability of flavor oil emulsions, can be easily prevented by adding triacylglycerols to the oil phase. The effect of interfacial characteristics of the emulsion droplets (particularly thickness) on the effectiveness of triacylglycerol inhibition of Ostwald ripening was evaluated in this study. The prepared emulsions were stabilized with emulsifiers with different‐size hydrophilic groups, which correlate to droplet interfacial thickness. Emulsions with an oil phase of pure orange oil were unstable due to Ostwald ripening. Modifying the oil phase by adding corn oil or medium‐chain triacylglycerol (MCT) effectively inhibited droplet growth. Thicker and less dense droplet surfaces in the emulsions required more triacylglycerol, regardless of its type, to resist Ostwald ripening. When the oil phase contained the same amounts of triacylglycerols, MCT was more effective at inhibiting Ostwald ripening than corn oil. Compared with corn oil, MCT more effectively inhibited Ostwald ripening of the emulsions containing micelles. Practical Applications When food and beverage industries produce food products containing flavor or essential oils vulnerable to Ostwald ripening as emulsion forms, the findings in this work could provide useful information on the interfacial engineering of emulsions and on how to modify the oil compositions of emulsions using triacylglycerols to improve the stability of these emulsions against Ostwald ripening.

Premix Membrane Emulsification: Preparation and Stability of Medium-Chain Triglyceride Emulsions with Droplet Sizes below 100 nm

“…A different way to achieve small-sized nanoemulsions with higher long-term stability is to incorporate more hydrophobic molecules than the actual lipid, so-called ultrahydrophobes [ 47 ], into the lipid phase before PME. Previous studies have shown that Ostwald ripening was decelerated after the addition of ultrahydrophobes [ 37 , 48 , 49 , 50 ]. In theory, due to the addition of the ultrahydrophobe, the osmotic pressure in the droplets rises and exceeds the Laplace pressure.…”

Inhibition of Droplet Growth in Model Beverage Emulsions Stabilized Using Poly (ethylene glycol) Alkyl Ether Surfactants Having Various Hydrophilic Head Sizes: Impact of Ester Gum

“…Strongly hydrophobic compounds can be incorporated into the oil phase of essential oil emulsions to inhibit Ostwald ripening [23,24]. Ester gum is widely used in the beverage industry as a weighting agent [1], but it may play a dual role in stabilizing beverage emulsions by also acting as a ripening inhibitor.…”

“…However, we believe that our results are better explained by the Ostwald ripening mechanism. First, since limonene, the major component (94-96%, depending on biological origin) in orange oil, could be dissolved in water to 13.8 mg/L [29], orange oil is known to be relatively polar oil [13,24], which makes it highly susceptible to Ostwald ripening. Ostwald ripening tends to occur more rapidly when the droplet size is small, which is a possible reason why Ostwald ripening occurred rapidly in our study, unlike the previous finding [28] (droplets prepared in this study were approximately 10 times smaller than those reported in the previous study).…”

Cellulose Nanocrystal-Based Emulsion of Thyme Essential Oil: Preparation and Characterisation as Sustainable Crop Protection Tool

“…Furthermore, NEs require a lower quantity of surfactants than MEs, reducing potential toxicological problems [17]. The use of surfactants and emulsifiers minimises or prevents the occurrence of Ostwald ripening, prevents coalescence, and improves the antimicrobial activity of EOs [18]. Emulsifiers are a subcategory of surfactants which prevent oil droplet aggregation, increasing colloidal stability.…”