Emulsification is one of the most common processes in food manufacturing. Mayonnaise, salad dressings, sauces, flavour emulsions, plant-based milks, margarine and cream liqueurs all depend on combining two liquids that do not naturally mix, and holding them together in a stable, uniform blend.
When emulsification is done well, the result is a smooth product with the right texture, appearance and shelf life. When it is done poorly, the product separates, “oils off”, or develops a coarse, grainy mouthfeel. This article explains what emulsification involves, why emulsions are inherently unstable, and how high shear mixing produces the consistent results that food production requires.
What Is an Emulsion?
An emulsion is a mixture of two immiscible liquids — most often oil and water — in which one is dispersed as fine droplets throughout the other. Oil-in-water emulsions (such as mayonnaise, milk and cream liqueurs) consist of oil droplets suspended in a water-based continuous phase; water-in-oil emulsions (such as margarine and low-fat spreads) are the reverse. Because oil and water have a natural tendency to separate, an emulsion is not a stable state on its own. Two things are needed to create and hold one: an emulsifier or stabiliser to reduce the interfacial tension between the phases, and sufficient mechanical energy to break one phase into small enough droplets to stay dispersed.
Silverson Inline Mixer
Droplet size is the key to stability. The smaller and more uniform the dispersed droplets, the slower they rise or coalesce, and the more stable and consistent the finished emulsion. Reducing droplet size also increases the total surface area of the dispersed phase, which improves texture, mouthfeel, colour and the release of flavour. Achieving a fine, narrow droplet-size distribution is precisely where the mixing method matters most.
Why Emulsification Goes Wrong
Conventional agitators and paddle mixers move liquid around a vessel but generate relatively little shear. They can blend miscible liquids, but they cannot consistently break oil into the fine droplets an emulsion needs. The typical results are a coarse, unstable emulsion with a broad droplet-size range; visible separation or creaming over time; “oiling off”, where free oil rises to the surface; and batch-to-batch inconsistency that undermines quality control. Longer mixing times are often used to compensate, but this adds cost, can entrain air, and rarely delivers the fineness required. The underlying problem is not time — it is the type of energy being applied.
How High Shear Mixing Creates Stable Emulsions
High shear mixing solves this by concentrating intense mechanical energy in a small, precisely engineered zone. At the heart of a Silverson high shear mixer is a rotor turning at high speed inside a stationary stator. The process works in three stages: the rotor draws liquid and any added ingredients into the centre of the workhead; centrifugal force drives the material outward into the fine gap between the rotor tips and the stator wall; and the product is then expelled at high velocity through the openings in the stator. It is in this fine clearance and high-velocity discharge that the oil phase is subjected to intense hydraulic and mechanical shear, tearing it into fine, uniform droplets in a fraction of the time a conventional mixer would take.
The result is a fine, stable emulsion with a narrow droplet-size distribution, produced repeatably from batch to batch. Because the workhead can also disperse and hydrate stabilisers, gums and emulsifying agents in the same operation, high shear mixing often combines several process steps — dispersing the emulsifier, incorporating the oil, and refining the emulsion — into one. Interchangeable workheads and screens allow the same machine to be tuned to the product, from general-purpose emulsifying to the very fine screens used for demanding, low-viscosity emulsions.
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Emulsification Applications in Food Manufacturing
High shear emulsification is used across the food and beverage sector wherever a stable, uniform blend of oil and water is required. Typical applications include:
- Mayonnaise, salad dressings and sauces — producing stable oil-in-water emulsions with the correct viscosity, texture and appearance.
- Flavour emulsions and cloud emulsions — fine, stable emulsions for beverages, where droplet size directly affects clarity, colour and flavour release.
- Plant-based milks and non-dairy alternatives — emulsifying oils and dispersing proteins and stabilisers for a smooth, stable product.
- Margarine and low-fat spreads — water-in-oil emulsions requiring controlled droplet size for texture and spreadability.
- Cream liqueurs and flavoured milk drinks — stabilising fat in a water-based system to prevent separation over a long shelf life.
- Ice cream mixes — hydrating stabilisers and emulsifiers and refining the mix ahead of ageing and freezing.
Many of these are dairy and beverage processes; the same hygienic high shear principles are discussed in the APS article on high shear mixing in dairy processing.
Batch or In-Line: Choosing the Right Configuration
Silverson high shear mixers are available in configurations to suit the scale and continuity of production. Batch mixers work directly in the vessel and are well suited to self-contained batches and product development. In-line mixers are installed in the pipework and process product as it passes through, making them ideal for larger volumes, continuous or semi-continuous production, and applications where an especially fine emulsion is needed in a single pass. Because a formulation developed on laboratory-scale equipment can be reproduced on production machines using the same rotor/stator principle, scale-up is predictable — an important advantage when moving a new product from trial to full production.
Consistent Emulsification with Silverson in New Zealand
Advanced Packaging Systems is the exclusive New Zealand agent for Silverson, supplying high shear mixing equipment to food, beverage and dairy manufacturers and providing local advice on mixer selection, application trials, commissioning and ongoing parts supply. If your process involves emulsification — or an emulsion that separates, oils off or varies from batch to batch — APS can advise on the right high shear configuration for your product and production scale. Contact APS to discuss your application.
