White sugar is one of the most common sweeteners in daily life, and its source and production process have undergone long-term development and optimization. The following is a detailed introduction from the aspects of source and production process:

I. The Source of White Sugar

The main raw materials for white sugar are sugarcane and sugar beets. Both dominate global white sugar production, with regional differences in raw material selection due to climate and resource conditions:

· Sugarcane: A tropical and subtropical crop that thrives in high-temperature and rainy regions (such as Guangxi, Yunnan, Guangdong in southern China, as well as Brazil, India, etc.). Sugarcane has a high sucrose content, accounting for about 12%-18% of its fresh weight. It is the primary raw material for global white sugar, contributing over 70% of total production.

· Sugar Beets: A temperate crop suitable for cool climates with large day-night temperature differences (such as Northeast China, Xinjiang, and European countries like France and Germany). Sugar beets have a sucrose content of approximately 15%-20% and are the main raw material for white sugar production in northern regions, accounting for about 30% of global white sugar output.

Whether from sugarcane or sugar beets, the core component is sucrose. The production of white sugar essentially involves extracting, purifying, and crystallizing sucrose from the raw materials.

II. The Production Process of White Sugar

The production process of white sugar varies slightly depending on the raw material, but the core steps are similar, including raw material pretreatment, juice extraction, purification, evaporation, crystallization, centrifugation, and drying. Below are the typical processes for sugarcane and sugar beet sugar production:

(I) Sugarcane Sugar Production Process

1. Raw Material Pretreatment

· Cleaning: Remove，impurities, and residual leaves from the sugarcane surface.

· Crushing and Pressing: Cut sugarcane into small segments, then use presses (e.g., three-roll presses) to repeatedly squeeze, breaking down sugarcane cells and releasing cane juice. In traditional processes, the pressed bagasse (fibrous residue) can be used as fuel or papermaking raw material.

2. Juice Extraction

· The juice obtained from pressing, called "mixed juice," contains sucrose, water, cellulose, proteins, minerals, pigments, and other impurities, requiring further processing.

3. Purification

· The goal is to remove non-sucrose impurities (e.g., colloids, pigments, ash) to improve sucrose purity. Common methods include:

· Lime Method: Add lime milk (calcium hydroxide) to the cane juice to neutralize acidity and coagulate impurities, then remove precipitates through filtration to obtain "clear juice."

· Carbonation Method: On the basis of the lime method, introduce carbon dioxide gas to react with excess lime, forming calcium carbonate precipitates that adsorb more impurities. After filtration, the clear juice has higher purity (often used for high-quality white sugar production).

· Sulfitation Method: Add sulfurous acid or sulfites to bleach, preserve, and assist in impurity precipitation, suitable for small and medium-sized sugar factories.

4. Evaporation and Concentration

· The clear juice is sent to evaporators (multi-effect evaporation systems) and heated under vacuum to evaporate water, concentrating the cane juice into "syrup" (with a concentration of about 60%-65%), reducing energy consumption for subsequent crystallization.

5. Crystallization

· The concentrated syrup is transferred to crystallizers, where further evaporation occurs under vacuum. Small "seed crystals" (fine sucrose crystals) are added as nucleation sites. Sucrose molecules gradually grow around the seeds, forming larger crystals—a process called "sugar boiling." Multiple boiling stages (first, second, and third massecuites) are usually performed to improve sucrose recovery.

6. Centrifugation

· The crystallized mixture (massecuite, a blend of crystals and residual syrup) is spun in centrifuges. Centrifugal force separates the residual syrup (molasses) from the crystal surface. Molasses can be used for subsequent crystallization or to produce brown sugar or yellow sugar.

7. Drying and Sieving

· Wet crystals are dried in hot air dryers to reduce residual moisture (to below 0.5%), then sieved by particle size using sieving machines to obtain finished white sugar.

(II) Sugar Beet Sugar Production Process

Compared to sugarcane sugar production, the pretreatment and juice extraction steps for sugar beets differ significantly, while subsequent purification, evaporation, and crystallization steps are similar:

1. Raw Material Pretreatment

· Cleaning and Peeling: Beets are washed to remove soil, then peeled using peelers or cutters (since the skin contains more impurities).

· Shredding: Beets are cut into thin "cossettes" (to increase surface area for efficient juice extraction).

2. Juice Extraction (Diffusion Method)

· Cossettes are fed into diffusers, where hot water (70-80°C) is used in countercurrent leaching to dissolve sucrose from beets into water, producing "diffusion juice." The leftover beet pulp (pommace) can be used as animal feed.

3. Purification

· Beet diffusion juice contains more non-sugar organic substances (e.g., betaine) than cane juice, so purification focuses on removing these impurities. The carbonation method is commonly used: first, lime milk is added for neutralization, then carbon dioxide is introduced to precipitate impurities. After filtration and decolorization (e.g., with activated carbon), clear juice is obtained.

4. Subsequent Steps: Same as sugarcane sugar production, including evaporation, crystallization, centrifugation, drying, and sieving, resulting in finished white sugar.

(III) Refined Sugar Process (High-End White Sugar Production)

For refined white sugar with higher purity requirements (e.g., fine granulated sugar, soft sugar), an additional refining stage is added to the above processes:

· Raw sugar is dissolved into syrup, then deeply decolorized and desalted using ion exchange resins or activated carbon to remove trace impurities.

· Crystallization, centrifugation, and drying are repeated to obtain highly pure (sucrose content ≥99.8%) and whiter refined white sugar.

III. Classification and Characteristics of White Sugar

Based on production processes and purity, white sugar can be classified as:

· Granulated White Sugar: Large, uniform granules with ≥99.5% sucrose content, white in color, widely used in baking and beverages.

· Soft White Sugar: Fine, soft granules with slightly lower sucrose content than granulated sugar (due to added invert syrup for better texture). It has a sweeter taste and is suitable for direct consumption (e.g., in cold dishes, drinks).

The production process of white sugar not only affects its purity and taste but also relates to production costs and environmental impact. Modern sugar factories generally adopt automated equipment and energy-saving technologies to improve sucrose recovery while reducing wastewater and waste residue pollution.