The study, published in Food Research International, investigated the influence of fat content and thickener type on the texture rheology, structure, stability, in-vivo aroma release and sensory perception of a lemon flavoured oil/water emulsion.
The researchers, from the Instituto de Agroquímica y Tecnología de Alimentos (CSIC) in Spain, and Unilever R&D, Netherlands, prepared six formulations of the lemon emulsion, in which the oil content varied between 5 and 30 per cent and the matrix composition was switched between thickeners (carboxymethyl cellulose, modified starch, or thickener).
The authors found that changes in fat content and matrix type affected the rheological behaviour, structural properties, physical stability, and perceived flavour of the emulsions.
“Despite their stabilising effect on o/w emulsions, the addition of different hydrocolloids modify not only their rheological behaviour but also flavour release and sensory perception mechanisms in different ways,” said the researchers, led by Sara Bayarri.
The authors noted that emulsions represent an important category of food products, including ice creams, margarines, sauces, spreads or some dairy drinks.
“Emulsions are normally composed by two immiscible liquids, usually oil and water, with one of them being dispersed in the other one as small spherical droplets,” they said.
However, one of the greatest problems is that emulsions are thermodynamically unstable and tend to break during certain processing operations (such as heat treatment, mechanical deformation, freezing, etc.) or during storage.
The use of biopolymers, especially proteins and hydrocolloids represents one of the most common strategies used to stabilize food emulsions. However, changes to emulsion composition by varying fat and stabilizer, both in type and concentration, can lead to emulsions with different physical and sensory properties, which in turn may influence consumers’ acceptance.
Type and concentration of fat modify the physical properties of foods and have been reported to influence the perception of flavour both in terms of flavour release and textural changes.
“Fat has an effect on aroma release, modifying the qualitative, quantitative and temporal flavour profile of foods … Fat has also an influence on the emulsion texture, impacting on creaminess, smoothness or fattiness perception which may modify how flavour is perceived in emulsions during their oral processing,” said Bayarri and co-workers.
They noted that it is generally assumed that increasing viscosity through the addition of thickeners, results in a decrease in flavour and taste intensity. However, the decrease seems to be dependent on thickener type.
“In this context the objective of this work was to study the influence of fat content and thickener type on rheological behaviour, structure, stability, in-vivo aroma release and sensory perception in lemon flavoured oil/water model emulsions,” said the authors.
Bayarri and colleagues reported that the effect of the interaction between fat content and matrix type was significant on most flow and viscoelastic parameters, but not on flow index or loss modulus values.
They noted significant differences in the creaming index based on oil content and thickener type, adding that higher emulsion stability was obtained with starch-based emulsions.
“Besides the different rheological behaviour observed among samples, fat content and matrix type also affected the structural properties and physical stability of oil/water emulsions,” said the researchers.
Fat content and matrix type were both found to create differences in perceived flavour and texture attributes.
Both thickeners types were found to influence the aroma release profiles, whilst fat content had a variable effect on aroma perception, with large a large impact on the most lipophilic aroma compound (linalool) but no affect on least lipophilic compound (cis-3-hexen-1-ol).
Source: Food Research International
Published online ahead of print, doi: 10.1016/j.foodres.2011.04.049
“Flavour release and sensory characteristics of o/w emulsions. Influence of composition, microstructure and rheological behaviour”
Authors: C. Arancibia, L. Jublot, E. Costell, S. Bayarri