Traditional mayonnaise is an oil-in-water emulsion containing 65-80% vegetable oil, 5-8% egg yolk and a spiced-water phase. The latter typically includes vinegar, mustard, salt and sugar. The oil is present as dispersed droplets with an average size ranging from 2–10 microns.
Low-fat, not low-taste
Consumers demand low-calorie products with the same taste and feel as traditional versions. But lowering the amount of oil in mayonnaise will lead to a less dense packing of the dispersed oil droplets, which means reduced viscosity and texture. Various thickening and gelling compounds can be added to the water phase to boost viscosity and texture. Starch is frequently used, but other hydrocolloids are also common.
Quality – how do consumers perceive it?
Many consumers have an opinion on what is “good quality” mayonnaise – and those opinions differ widely around the world. But it is not easy to link these opinions to measurable quality parameters. For producers, mayonnaise quality is often characterized by a combination of sensory evaluations and laboratory analyses. Mayonnaise commercials and labels often highlight texture attributes using words like as “creamy”, “smooth” and “thick”. Indeed, the texture influences the eating experience through visual appearance, handling feel and in-mouth feel.
How industry defines quality
Mayonnaise producers need to be able to control the quality of every batch. Apart from having a sensory panel of testers, who evaluate parameters such as appearance, texture and mouthfeel, laboratory analyses are also performed based on rheology. This is the study of how materials that have both solid and fluid characteristics flow and deform when subjected to a force.
One way that consumers perceive texture is the way the food is broken down in the mouth before it is swallowed. Texture is measured by using a texture analyser, where a compression technique similar to the compression performed by the mouth is applied to the mayonnaise.
- Yield stress
Place a sample of mayonnaise on a plate, and its shape will not change for several minutes if undisturbed. It behaves more like a solid than a fluid. If you then stir the mayonnaise with a spoon, it resembles a thick, viscous liquid. Yield stress is the minimum force that must be applied to the mayonnaise for it to start behaving as a liquid instead of a solid.
- Apparent viscosity
Apparent viscosity correlates to the product behaviour during pumping, mixing, chewing and pouring. It also describes some of the perceived “mouth feel” during chewing and swallowing. This parameter is measured using rheometers, where the viscosity is measured for a given shear rate.
- Droplet size
The droplet size distribution of the dispersed oil droplets is extremely important because their size influences taste, texture, viscosity, appearance and emulsion stability. Smaller droplets have larger interfacial and higher internal pressure than larger droplets, resulting in higher viscosity, yield stress and texture. Smaller oil droplets release flavours differently than larger oil droplets, reducing the intensity and delaying the flavour experience as the product is tasted. Smaller oil droplets also refract light differently than larger droplets, producing a whiter mayonnaise.
A key element in mayonnaise processing is emulsification, which includes breaking up the oil droplets. An oil droplet is broken up when the fragmenting stresses acting on it exceed the stabilizing stresses opposing droplet deformation, and do so for a certain period of time.
Tools of the trade
High-intensity mixers such as high-speed rotor-stator mixers or colloid mills are commonly used. The energy from these devices is dissipated in a relatively small product volume, which creates high levels of local energy dissipation rates and thereby small oil droplets. These mixers can be combined with, or in, mixing tanks in various ways, and the complete mixing system can be set up to operate in both batch and continuous production.
Challenges and solutions
Mayonnaise’s quality attributes are influenced not only by ingredient types and composition, but also by equipment type, processing parameters and scale of production.
- Egg yolk: Not only an emulsifier, but also a texturizer, more egg yolk means more texture and smaller droplet size. But the effect on texture depends on the type of egg yolk.
- Temperature: Higher mayonnaise textures are developed when starting the batch manufacture with cooled oil.
- Flow: Good flow in the mixer vessel allows a high oil injection rate without compromising final product quality. It also shortens overall batch mixing time and ensures trouble-free scale-up.