Rapeseed Oil Refining Yield (Crude Oil → Refined Finished Oil, by mass percentage)
Definition: Refining Yield = Quantity of refined finished oil ÷ Quantity of crude oil entering the refinery × 100%
Sources of loss: Degumming sludge (foots), alkali-refining soapstock, oil retained by bleaching earth, deodorizer distillate (free fatty acids + volatiles), and filtration residue.
1. Conventional hot-pressed crude oil → Grade 1 rapeseed oil (chemical alkali refining; the mainstream industrial method)
Yield: 94%–96% (95% is the most common industry figure)
Loss: 4%–6%; higher crude oil acid values and gum content result in greater losses.
If crude oil quality is excellent (fresh "double-low" rapeseed, acid value < 1.5), the yield can reach 96%; with aged rapeseed or high-acid crude oil, it may drop to 93% or lower.
2. Hot-pressed crude oil → Grade 1 rapeseed oil (physical refining; no alkali refining)
Yield: 96.5%–97.8%
Physical refining does not produce large amounts of soapstock, resulting in a significantly higher yield than alkali refining; however, it imposes strict requirements on crude oil pretreatment and acid values.
3. Cold-pressed rapeseed oil (Key focus, given your previous research on cold-pressing lines)
Cold-pressed crude oil has low phospholipid content and generally low free fatty acid levels, making it suitable for mild, low-temperature refining (degumming + low-temperature adsorption bleaching only; no high-temperature deodorization; preserves nutrients; high-end cold-pressed oil). Low-temperature simplified refining (premium cold-pressed product, no high-temperature deodorization): Yield 97%–98.5%
Uses only plate-and-frame filtration + centrifugal degumming and low-temperature adsorption (activated carbon/bleaching earth); losses are minimal.
If cold-pressed crude oil undergoes the full high-temperature Grade 1 refining process (degumming + alkali refining + bleaching + high-temperature deodorization), the yield drops to 94%–96% and significant Vitamin E is lost; high-end cold-pressing projects generally do not use this method.
4. Simple Filtration (Small-scale oil mills: crude oil undergoes only plate-and-frame filtration without full refining)
This process removes only meal residue and does not constitute standard refining. While the yield is high (98.5%–99.2%), the product cannot be labeled as "Grade 1 refined oil"; it fails to meet standards for acid value and phospholipid content, resulting in a short shelf life.
Key Influencing Factors
1. Crude oil acid value (FFA) is the primary variable: Higher free fatty acid levels lead to greater refining losses (as alkali refining soapstock carries away significant amounts of oil).
2. Raw material freshness: Crude oil pressed from moldy rapeseed exhibits high acid and peroxide values, causing refining losses to rise significantly.
3. Process selection: Alkali refining incurs much higher losses than physical refining; alkali refining should be avoided for high-end cold-pressed products.
4. Bleaching earth dosage: Bleaching earth adsorbs oil; the more earth used, the lower the yield.
Distinguishing between two easily confused concepts
Oil pressing yield: Rapeseed → Crude oil (approx. 32% for cold pressing; 37–39% for hot pressing)
Refining yield: Crude oil → Refined oil
