Affination and Melting: Preparing Raw Sugar for Refining

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 Before sugar becomes the sparkling white crystals we stir into our coffee, it goes through a fascinating transformation. The first major steps in this journey are affination and melting — two processes that clean and dissolve raw sugar to prepare it for refining. In this post, we’ll explore how these steps work, why they matter, and how modern refineries optimize them for quality and efficiency.

🧪 What Is Affination?

Affination is like giving raw sugar a deep cleanse. Raw sugar crystals are coated in molasses and other surface impurities that can interfere with refining. Affination washes these away, making the sugar easier to process and improving the final product’s clarity and purity.

Why It’s Done:

  • Removes molasses and color bodies

  • Reduces ash, starch, and dextran

  • Improves filterability and reduces turbidity

How It Works:

  1. Mixing: Raw sugar is blended with a warm, saturated syrup (called affination syrup) to loosen surface impurities.

  2. Centrifugation: The mixture is spun in a centrifugal basket to separate cleaned crystals from the syrup and wash water.

  3. Rinsing: Crystals may be rinsed with hot water or steam for extra purity.

🔥 Melting the Sugar

Once the sugar is cleaned, it’s time to melt it down. This creates a uniform sugar liquor that’s ready for clarification.

Equipment Used:

  • Melters or Dissolvers: Heated tanks with agitators

  • Steam Injection Systems: For controlled heating and mixing

  • Filtration Units: To remove undissolved solids

Key Parameters:

  • Temperature: 70–80°C to avoid caramelization

  • Brix: 60–65°Bx for ideal concentration

  • pH: Around 6.0–6.5 to prevent inversion and microbial growth

Why These Ranges Matter:

Maintaining the right temperature, Brix, and pH in the melter isn’t just about melting sugar — it’s about setting the stage for everything that comes next.

  • Temperature: Too low, and sugar may not dissolve completely; too high, and you risk caramelization, which darkens the liquor and complicates decolorization.

  • Brix: If the concentration is too low, the liquor becomes dilute and inefficient to process. Too high, and it thickens, making filtration and clarification harder.

  • pH: A pH outside the 6.0–6.5 range can lead to sugar inversion (breaking sucrose into glucose and fructose), which affects crystallization and increases color formation. It also opens the door to microbial growth.

Getting these parameters right ensures smoother clarification, better color removal, and more predictable crystallization downstream.

Water Efficiency in Melting:

Melting also plays a role in minimizing water consumption across the refinery. Instead of using fresh water, refineries often reuse "sweet water" — a lightly sugared stream recovered from other stages like crystallization or centrifugation.

This recycled sweet water helps:

  • Reduce the demand for fresh water

  • Maintain sugar concentration in the melter

  • Lower overall effluent volume

  • Increase overall sugar yield

By integrating sweet water into the melting process, refineries boost sustainability without compromising liquor quality.

⚠️ Quality Control Matters

Refineries keep a close eye on several parameters to ensure the process runs smoothly:

Parameter

Purpose

Typical Range

Moisture Content

Prevent microbial growth and clumping

< 0.1%

Ash Content

Indicates inorganic impurities

0.05–0.15%

ICUMSA Color

Guides decolorization needs

600–1200 units

Starch

Affects turbidity and filtration

< 100 ppm

Dextran

Disrupts crystallization and viscosity

< 250 ppm

Regular sampling and inline sensors help catch any issues early.

🧬 Enzymes to the Rescue

To tackle starch and dextran, refineries often use enzymes:

  • Alpha-Amylase breaks down starch into smaller sugars, improving filterability.

  • Dextranase hydrolyzes dextran chains, lowering viscosity and preventing crystallization problems.

These enzymes are added during melting or just before clarification. They help:

  • Improve sedimentation and flocculation

  • Reduce the need for chemical clarifiers

  • Enhance color removal and crystal formation

💨 Why Starch and Dextran Matter for Carbonation

If not controlled, starch and dextran can mess with the carbonation step:

  • Starch increases turbidity and interferes with calcium carbonate floc formation.

  • Dextran raises viscosity, slowing down mixing and sedimentation.

Managing these components early leads to better floc formation and clearer liquor.

🧰 Smarter Equipment and Automation

Modern systems make the process more efficient:

  • Automated feed control based on flow rates and Brix

  • Temperature sensors and steam valves

  • Inline color and turbidity meters

  • CIP systems for hygiene

🌱 Sustainability Wins

Affination and melting also offer chances to save energy and reduce waste:

  • Heat recovery using condensate or low-pressure steam

  • Water reuse in rinse cycles

  • Minimizing syrup losses to improve yield

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