Findings published in the Food Research International indicate that sucrose monopalmitate, when used in combination with a modified soy lecithin, offers an improvement in the stability of droplets in a beverage emulsion at low pH.
“This study has important consequences for the formulation of acidic beverage emulsions with improved stability and physicochemical performance,” wrote researchers led by UM’s Professor Julian McClements.
The paper follows another study by the same group and published this month in Food Hydrocolloids (Vol. 25, pp. 1413-1423), which provided an insight into the properties of the non-toxic sugar ester sucrose monopalmitate as a food grade surfactant for use in the production of colloidal dispersions (such as micro- and- nano- emulsions) with natural flavor oils.
Emulsions and emulsifiers
Emulsions – a mix of two unblendable liquids like oil and water – are stabilised by the addition of emulsifiers.
Emulsifiers work by stabilizing oil suspended in water, and this is achieved electrostatically. Part of the emulsifier is attracted to water, while another part is attracted to the oil. The isoelectric point (pI) is the pH at which the emulsifier has no electrical charge, and therefore in a food with a pH close to the pI the emulsifier can no longer stabilize the emulsion effectively.
Looking at orange oil - a widely used flavoring ingredient in food and beverages – the researchers note that many different types of emulsifiers are available emulsions made with orange oil.
Examples of such emulsifiers include surfactants, phospholipids, polysaccharides, and proteins.
“Each of these emulsifiers has its own advantages and disadvantages in terms of emulsion formation and stability,” they explain. “Some emulsifiers are highly effective at producing small droplets during homogenization, but are not particularly good at preventing particle aggregation when the emulsion is exposed to environmental stresses, e.g., some small molecule surfactants and proteins.
“On the other hand, some emulsifiers are highly effective at producing emulsions with excellent resistance to environmental stresses, but are not particularly effective at producing small droplets during homogenization, e.g., some polysaccharides.
“There is therefore a need for “label-friendly” emulsifiers that are capable of producing small droplets and providing good resistance to environmental stresses,” they added.
To explore the potential of sucrose monopalmitate to stabilize acidic beverages, the researchers formulated orange oil-in-water emulsions at pH7 stabilized by the ingredient.
The sucrose monopalmitate used in the study was provided by Compass Foods Company (Singapore), while the orange oil was provided by IFF.
Results showed that when the sucrose monopalmitate-stabilized droplets were an average of 130 nanometers in diameter, with good stability at pH7. When the pH of the emulsion was decreased to pH3, however, the particles clumped together and the even mixing of the emulsion was lost.
By incorporating an enzyme-modified soy lecithin (Solec K-EML, supplied by Solae), the stability of the droplets at low pH was “markedly improved”, said the researchers.
The study was supported financially by International Flavors and Fragrances.
Source: Food Research International
Published online ahead of print, doi: 10.1016/j.foodres.2011.07.007
“Formulation and properties of model beverage emulsions stabilized by sucrose monopalmitate: Inﬂuence of pH and lyso-lecithin addition”
Authors: S.J. Choi, E.A. Decker, L. Henson, L.M. Popplewell, H. Xiao, D.J. McClements