Refined white sugar is 99.9% sucrose by weight. Getting from sugarcane or sugar beets to that product involves a multi-stage industrial process that removes everything except the sucrose crystal. Understanding refining is understanding what “white sugar” means chemically.

The Two Raw Materials

About 80% of the world’s sugar comes from sugarcane (Saccharum officinarum), a tropical grass. The rest comes primarily from sugar beets (Beta vulgaris). Both contain sucrose in roughly similar concentrations, sugarcane stalks are 12-18% sucrose by weight; sugar beets 14-21%.

The refining process differs slightly between them but converges on the same product.

Cane Sugar Refining: Step by Step

1. Harvesting and milling. Harvested cane is shredded and crushed between heavy rollers. The juice extracted, called cane juice, is about 15% sucrose, 80% water, and 5% impurities including wax, protein, and fiber.

2. Clarification. Lime (calcium hydroxide) is added to the juice, raising pH to about 7. This precipitates many impurities, phosphates, proteins, fine particles, which settle to the bottom or float to the top as scum. The clarified juice is filtered.

3. Evaporation. The clarified juice goes through a series of evaporators that reduce water content. The result is a thick syrup, roughly 60% sucrose.

4. Crystallization. The syrup is seeded with small sucrose crystals in a vacuum pan (lower pressure means lower boiling point, preventing caramelization). Sucrose crystallizes around the seed crystals over several hours.

5. Centrifugation. The crystal-syrup mixture spins in a centrifuge at 1,000+ rpm. Crystals stay; the remaining liquid (molasses) is flung outward and collected. Multiple centrifuge cycles at increasing speed produce progressively purer crystal.

The product at this stage is raw sugar: golden-brown crystals still coated in a thin film of molasses. Raw sugar is 96-98% sucrose.

6. Further refining. Raw sugar is dissolved again in hot water, treated with carbon (to decolorize), filtered through diatomaceous earth or ion exchange resin, then recrystallized and centrifuged again. White sugar reaches 99.9%+ sucrose purity.

What Molasses Contains

Molasses is everything removed from the cane juice during refining. It contains iron, calcium, potassium, magnesium, and B vitamins. The nutrients in sugarcane that refining eliminates.

Blackstrap molasses (from the third and final centrifuge pass) is most mineral-rich:

  • 1 tablespoon: 20% DV iron, 10% DV calcium, 18% DV manganese, 15% DV potassium

This is why people comparing “raw” and “refined” sugars focus on molasses. Raw sugars like turbinado, demerara, and muscovado retain varying amounts of molasses — and therefore trace minerals. But at the quantities used in cooking, the nutritional difference is minimal.

Beet Sugar Refining

Beet sugar is refined in a single location, not two. Beet juice is extracted with hot water (diffusion), clarified with lime and CO₂ (carbonatation rather than the phosphatation used for cane), then evaporated and crystallized. Beet molasses is less palatable than cane molasses and is typically used for animal feed or industrial fermentation.

Chemically, beet white sugar and cane white sugar are identical, both 99.9%+ sucrose. Some bakers claim they’re not interchangeable in certain applications, but controlled tastings don’t support this.

What “Raw Sugar” Actually Means

The term “raw sugar” on consumer packaging doesn’t mean unprocessed. In the U.S., the FDA prohibits selling genuinely raw sugar for direct consumption because raw sugar can contain soil, microbes, and cane debris. Retail “raw sugars” (turbinado, demerara) have been partially processed — centrifuged once but not fully refined. They are 96-98% sucrose with a residue of molasses.

Historical Note

Before mechanical refining, sugar was purified manually by repeatedly dissolving, boiling, and forming into loaf-shaped molds. A labor-intensive process done at refineries in consuming countries, not at production sites. The shift to industrial centrifugal refining in the 1850s-1880s collapsed the cost of refined white sugar and drove the enormous growth in sugar consumption through the late 19th and early 20th centuries.

Sources:

  • Asadi M. Beet-Sugar Handbook. Wiley 2007, detailed technical reference on industrial refining
  • McGee H. On Food and Cooking. Scribner 2004 — chapter on sugar covers refining history and chemistry accessibly
  • USDA Economic Research Service sugar supply and use data: ers.usda.gov