WOW double emulsions move closer to food applications, say researchers
Writing in the journal Food Hydrocolloids, scientists from Ryerson University, Canada, developed water-in-oil-in-water (W/O/W) double emulsions, containing gelatin and sodium chloride in the inner aqueous phase, to test for its controlled release food applications.
The researchers, led by Dr Dérick Rousseau, explained that the presence of gelatin and salt “played a key role in double emulsion stability and release.”
“We designed food-grade W1/O/W2 DEs with long-term stability and desirable controlled release behaviour using a simple, reproducible approach,” said Rousseau and his team.
“All double emulsions containing both NaCl and gelatin were stable against sedimentation for the month-long study whereas control emulsions (with either no NaCl or gelatin) showed visual phase separation,” they added.
The research team said the results of the study demonstrate the synergistic action of a gelling agent and electrolyte in stabilising and modulating the release behaviour of double emulsions.
WOW challenge
Rousseau and his colleagues explained that W/O/W double emulsions have been investigated for various food applications, including the encapsulation of vitamin and minerals, to aid in the release of aroma and flavour compounds, and in production of low-calorie foods such as low-fat dressing.
The researchers said the potentially high encapsulation efficacy of double emulsions has led to the search for methods to control the encapsulation and release of ingredients:
“Due to the presence of two aqueous domains separated by an oil layer, the inner aqueous compartment offers great potential for the encapsulation and controlled release of hydrophilic bioactive ingredients,” said Rousseau and his colleagues.
However, they noted that such emulsions are more difficult to prepare and control than simple emulsions because they are usually made up of relatively large droplets that coalesce.
“Usage of W/O/W double emulsions for food applications is further limited by the lack of suitable food-grade emulsifiers and stabilizers for the inner and outer emulsions,” added the researchers.
The team notes that W/O/W emulsions have been used in cosmetics and pharmaceuticals for applications such as drug controlled release and targeted delivery, but noted that a lack of kinetic stability means that the widespread application of W/O/W double emulsions in the food industry “remains elusive.”
Study details
Rousseau and his team prepared the emulsions with water and canola oil, using polyglycerol polyricinoleate and polysorbate 80 as emulsifiers for the primary and secondary emulsion emulsions.
They reported that double emulsion stability was dependent on the presence of salt and gelatin in the inner aqueous phase, noting that that the addition of salt enhanced emulsifier properties.
“Salt-gelatin interactions also affected double emulsion stability and release behaviour,” said Rousseau and his co-workers. They explained that the amount of gelatine present altered the emulsion release behaviour.
“The double emulsions with no gelatin showed a higher release rate that was highly variable due to phase separation. Conversely, double emulsions stabilized with 10% gelatin showed a highly-reproducible lower initial release and a more delayed release profile than double emulsions stabilized with 3% gelatin," they explained.
Source: Food Hydrocolloids
Volume 27, Issue 2, Pages 316-323, doi: 10.1016/j.foodhyd.2011.10.008
“Stability and release properties of double emulsions for food applications”
Authors: L. Sapei, D. Rousseau
