Demulsification of oil‐in‐water emulsion under freezing conditions: Effect of crystal structure modifier

Abstract

The demulsification of oil-in-water (O/W) emulsions under freezing conditions is connected to fat crystallization in the oil droplet. Therefore, demulsification can be prevented by the use of oil with a low melting point, and also by lowering the O/W ratio. However, an oil with a low melting point, such as sunflower, is rather expensive, and the O/W ratio has a significant effect on the texture of emulsions. We searched for an oil that is suitable for the production of a freeze-stable emulsion and found that soybean oil has unique characteristics. Normally, emulsions are more unstable at lower temperatures; soybean oil emulsion is unstable at −10°C and stable at −20°C. This unique characteristic results from the following two reasons. First, the solid fat content of soybean oil is almost the same at −10 and −20°C. Second, small crystals form a larger network over a period of time, and the higher temperature promotes faster restructuring. This structure formation was microscopically observed with the use of a thermostated stage. Structure formation was suppressed with the addition of a crystal structure modifier, polyglycerol fatty acid full ester, which also suppressed coalescence.

Factors governing partial coalescence in oil-in-water emulsions

“…In addition, several small-molecule surfactants can partly dissolve in the oil and may then affect the crystallisation behaviour in the globules [84,[88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103]. Small-molecules surfactants can affect nucleation, crystal growth and/or the polymorphic transitions, dependent on their miscibility in the oil [23].…”

“…Small-molecules surfactants can affect nucleation, crystal growth and/or the polymorphic transitions, dependent on their miscibility in the oil [23]. As a consequence the amount, the size, the morphology and the sintering of the crystals, the arrangement of the crystals in the globule, the fat crystal network and the SFC can depend on the type and the concentration of the surfactants and can, thereby, affect the partial coalescence stability of the emulsions [39,84,89,102,103].…”

Effects of Adding Polyglycerol Behenic Acid Esters on the Crystallization of Palm Oil

“…There are a number of reports on the effects of emulsifiers on crystal morphology (28)(29)(30)(31), and the size of the crystal is associated with the crystal form; b-form tends to produce granular crystals and b is recommended for producing small crystals. In the present study, we observed that palm oil with polyglycerol behenic acid esters added, the b -form is preferentially crystallized, and the crystal does not grow to a granular crystal.…”

Environmental Impact Analysis of Soybean Oil Production from Expelling, Hexane Extraction and Enzyme Assisted Aqueous Extraction

“…As for EAEP, water is as solvent which could mitigate the environmental impact comparing to solvent extraction. However, the demulsification has been seen as a critical step for oil recovery in aqueous extraction due to its high energy requirement especially on physical (Hagenmaier et al, 1972, Harada & Yokomizi, 2000, McClements, 2005 and chemical methods (Menon & Wasan, 1985).…”