The texturing process of shortening and margarine is a highly controlled engineering and crystallization procedure. It transforms liquid vegetable oils and fats into smooth, functional, semi-solid products with exact melting points and plastic properties.
While both follow a similar mechanical path, their starting formulations differ: shortening is 100% fat, whereas margarine is a water-in-oil emulsion containing roughly 80% fat and 16–20% water.
1. Raw Material Blending and Emulsification
The process begins by heating the oil and fat blend to 60–70°C to achieve a fully melted, homogeneous liquid.
- For Shortening: Fat-soluble ingredients and emulsifiers (like mono- and diglycerides) are blended directly into the bulk oil. No water phase is added.
- For Margarine: An aqueous phase (water, salt, milk solids, and water-soluble flavors) is prepared separately and mixed into the fat phase under high-speed industrial blending. This creates a stable, uniform water-in-oil emulsion.
2. Rapid Subcooling (Scraped Surface Heat Exchanger)
The hot liquid mixture is pumped under high pressure into a Scraped Surface Heat Exchanger (SSHE), often commercially known as a Votator or Polaron unit.
- Supercooling: The jacketed cooling tubes drop the temperature drastically down to 10–28°C within seconds. This rapid cooling supercools the liquid, forcing fat crystals to initiate nucleation (start forming) quickly.
- Scraping: Internal rotating blades continuously scrape the crystallizing fat off the inner freezing tube walls. This prevents massive crystal growth and keeps the cooling efficient.
3. Kneading and Working (Pin Rotor / Pin Worker Units)
As crystallization begins, the viscosity of the blend rapidly rises. The thick, semi-solid mass then exits the SSHE and passes into a pin rotor machine (or "B-unit").
- Inside this cylinder, a concentric shaft equipped with rotating pins intermeshes with rows of fixed pins.
- The intense mechanical shearing actively breaks up forming crystal agglomerates.
- This mechanical agitation promotes the formation of desirable, tiny β' (beta-prime) crystals. β' crystals are essential because they give the fat its smooth, creamy, non-grainy texture and high plasticity.
4. Resting and Extrusion
Depending on the final product type, the fat may pass through a resting tube to build mechanical strength (vital for structured pastry/puff margarines) or be extruded directly into packaging lines as a semifluid plastic fat. Gas injection (such as nitrogen) is often utilized during texturing to yield a whiter, more whipped opacity and creamier volume.
5. Maturation and Tempering
The packaged product cannot be shipped or used immediately because crystallization continues over the next several hours. The final step requires tempering in a temperature-controlled resting room.
- Shortening: Usually tempered around 25–30°C for 24–48 hours to stabilize the crystal matrix so it won't melt or alter hardness during storage.
- Margarine: Soft tub margarines are typically tempered at 5–7°C to lock in spreadability, whereas industrial baking/pastry margarines are tempered at slightly higher temperatures to develop ideal elasticity and structure.
If you are looking into industrial texturing machinery or troubleshooting a batch, let GEASB know:
- Are you focusing on commercial factory equipment design or small-scale laboratory production?
- What is the intended application? (e.g., table spreads, puff pastry lamination, or general baking shortening)
- Are you dealing with specific texture issues like graininess or oil-bleeding?
