The present invention relates to a new process for preparing stabilised edible oil-in-water emulsion, especially mayonnaise or dressing, without using food additives.
An emulsion is a mixture of two (or more) immiscible liquids: a dispersed phase which is dispersed in a continuous phase. The boundary between these phases is called the interface. An oil-in-water (o/w) emulsion designates an emulsion in which oil is dispersed in water.
Main problem encountered with emulsions is their instability. Emulsions do indeed not form spontaneously. Energy input through shaking, stirring, homogenizing, or spray processes are needed to initially form an emulsion. Over time, emulsions tend to revert to the stable state of the phases comprising the emulsion. Such instability may be due to various factors among which improper process control, bad choice of emulsifier or wrong quantity of it, environmental influences during the production, stockpiling or use during the shelf life recommendation.
An example of this instability can be seen in the separation of the oil and vinegar components of vinaigrette, an unstable emulsion that will quickly separate unless shaken continuously.
Difference should be made between physical, microbiological and chemical stability. Physical stability of an emulsion indicates its resistance to changes in the dispersed state. An emulsion is said to be “physically stable” when its size distribution is independent from the time and place. This means that the droplets of the emulsion should not be subject to sedimentation, aggregation or coalescence. In principle, the following mechanisms may lead to the physical instability of an emulsion.
Sedimentation/Creaming
There is usually a difference of density between the continuous phase and the disperse phase of an emulsion which can lead to sedimentation or “creaming” of the droplets without impacting the droplet distribution of the disperse phase. Such process is reversible and the initial distribution of state can be restored, for example by shaking or gentle stirring.
Aggregation
The existence of attractive forces between the drops can lead to droplet aggregation (agglomeration, grapes etc . . . ). The drops remain separate in the aggregates by a thin film of continuous phase which makes the droplet size distribution changing only in appearance. This process is reversible and the initial distribution of state can be restored, for example by shaking or gentle stirring.
Coalescence
An insufficient contact with droplets of the dispersed phase may stabilize the phase boundary to the tearing of the film located between the drops and lead to the confluence (“coalescence”) of the drops. In the extreme case, this can lead to a complete phase separation of the system generally designated by “breaking” of the emulsion. Coalescence results in a “real” change of the droplets size distribution of the dispersed phase and is reversible only by a renewed comminution step/reduction of the size of droplets.
Ostwald Ripening
Differences in capillary pressures may grow larger droplets at the expense of smaller ones.
These physical processes can occur separately or together, one of the above processes being generally at the origin of another one, or strengthening it. For example, the formation of bunches or the coalescence generally increases the speed of sedimentation. Conversely, the sedimentation favours the aggregate coalescence.
Oil-in-water emulsions are commonly used in the food industry for preparing various food products (or foodstuffs) such as mayonnaise or emulsified sauce among which Hollandaise sauce, Béarnaise sauce or dressing. The most important characteristic of such edible oil-in-water emulsion is its stability. For example, an insufficient short-term stability will lead to the breaking of the emulsion and will significantly impact the quality (texture, mouthfeel etc . . . ) of the product. It is therefore necessary to provide highly stable edible oil-in-water emulsions for preparing food products such as mayonnaise or emulsified sauce among which Hollandaise sauce, Béarnaise sauce or dressing.
The quality of an emulsion is generally characterised by the average oil droplets size and the distribution of said oil droplets. For example, for high fat mayonnaise, mean oil droplets diameter should be of from 6 to 12 μm.
Various food additives such as emulsifier and stabiliser or thickener are generally used improve the stability of edible oil-in-water emulsions.
Emulsifier is an ambiphilic surface-active substance possessing a hydrophilic and a lipophilic moiety. An emulsifier stabilizes an emulsion by increasing its kinetic stability. Various emulsifiers can be used for preparing edible oil-in-water emulsions among which lecithin, monoglycerides, diglycerides or proteins.
Stabiliser (or thickener) is a macro-molecule increasing the viscosity of the continuous phase which reduces the mobility of the plug and slows the sedimentation or creaming. Various stabilisers can be used for preparing edible oil-in-water emulsions among which starch, pectin, gelatine, xanthan gum, guar gum or local bean gum.
To regulate these food additives, and to inform consumers, each of these additives is assigned a unique number, termed as “E-number”. An “E-number” designates a code for food additive that has been assessed for use within the European Union (the “E” prefix stands for “Europe”). They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority.
Nevertheless, several drawbacks are associated to the use of such “E-number” additives for preparing stable edible oil-in water emulsions.
First, it is commonly known that, in the mind of consumers (and in casual language in the UK), “E-number” is perceived as a pejorative term designating artificial, chemical and/or non-natural food additives
In addition, the use of such E-number additives for stabilising edible oil-in-water emulsions can impact significantly the quality of the food product (such as mayonnaise or dressing which can be too sticky, can have a bad mouthfeel (characterized by various criteria used in sensory profiles such as melting behaviour, flowing, film, dense, sticky or raw) and/or can become off-flavoured after pasteurisation.
Subsequently, the use of such E-number additives has an impact on the price of the food product since their production is generally expensive.
Finally, the use of E-number food additives may have a mid- or long-term impact on the health of the consumers.
Accordingly, there exists a strong need for providing food products such as mayonnaise or dressing that are “free of E-number additives” while maintaining their quality.
International patent application WO-A-2005/039316 discloses edible emulsion containing insoluble natural fibres and a process for making the same. The insoluble natural fibres are used for preparing reduced-fat products without decreasing their taste and mouthfeel in comparison to full-fat products. Nevertheless, the process disclosed in this application for preparing said emulsions does not allow preparing a stable emulsion free of food additives.