Flaxseed Oil — Process & Workflow Document¶

Document ID: PROD-PROC-003
Version: 1.0
Effective Date: 2026-07-20
Product: Flaxseed Oil (Cold-Pressed & Solvent-Extracted)

1. Process Overview¶

Flaxseed oil is produced via two primary routes: Cold Press (premium, retains natural properties) and Solvent Extraction (maximum yield, lower grade). Cold-pressed oil may optionally undergo refining (degumming, neutralization, bleaching, deodorization) for specific customer requirements.

Process Flow Diagrams¶

Cold Press Flow¶

Flaxseed
    ↓
Cleaning & Drying
    ↓
  Screw Press (CCP-2)
    ↓
Crude Oil ──→ Press Cake
    ↓              ↓
  Filter         Defatted Meal
    ↓          (to powder line)
  Crude Oil Tank
    ↓
[Optional Refining]
┌───┴───┐
↓       ↓
Refined  Bottling
Oil      (Virgin)

Solvent Extraction Flow¶

Flaxseed (or Press Cake)
        ↓
  Flaking / Conditioning
        ↓
  Solvent Extractor (Hexane)
        ↓
   ┌────┴────┐
   ↓         ↓
Miscella    Spent Meal
   ↓           ↓
Evaporator   Desolventizer
   ↓           ↓
Crude Oil   Defatted Meal
   ↓        (to powder line)
Refining (full wet process)

2. Detailed Process Steps — Cold Press¶

2.1 Seed Cleaning & Drying¶

Parameter	Value / Range
Seed moisture target	6.0 – 8.0%
Foreign matter	≤0.5%
Cleaning equipment	Scalper + aspirator + destoner
Magnetic separator	Fe ≥2.0 mm removal
Drying temperature (if needed)	≤45°C (fluid bed dryer)

Quality Gate: Moisture content recorded per batch. If >8.5%, dry before pressing.
Note: Over-drying (<6%) reduces press throughput and increases oil oxidation.

2.2 Screw Press — CCP-2¶

The screw press (expeller) mechanically extracts oil from flaxseed. Temperature control is critical to preserve omega-3 fatty acids.

Parameter	Value / Range
Screw speed	15 RPM (typical range: 10–20 RPM)
Barrel temperature	<40°C (cold press)
Nozzle (choke) diameter	8 mm (range: 6–12 mm)
Motor power	15 – 30 kW
Throughput	50 – 150 kg seed/hr per press
Oil yield	70–85% of total oil (cold press)
Residual oil in cake	12–18%

Temperature Management¶

Barrel temperature is the critical parameter. Monitor with thermocouple embedded in the press barrel.
CCP-2 Critical Limit: Barrel temperature must not exceed 40°C for cold-pressed grade.
If barrel temperature approaches 38°C:
Reduce feed rate by 10%.
Check cooling jacket water flow (if equipped).
Verify screw speed is at 15 RPM.
Cooling jackets (water or glycol) should maintain barrel at 30–38°C.

Press Setup Procedure¶

Pre-heat press to 30°C by running seed at low feed rate for 10 min.
Set screw speed to 15 RPM.
Set nozzle gap to 8 mm.
Start seed feed at 50% of target rate; ramp to full rate over 5 min.
Monitor barrel temperature; stabilize before adjusting feed.
Quality Gate: Barrel temperature ≤40°C recorded every 15 min in CCP log.

2.3 Crude Oil Filtration¶

Parameter	Value / Range
Equipment	Plate-and-frame filter press
Filter media	Polypropylene filter cloth (10–20 µm)
Filtration pressure	≤4 bar
Temperature	30–40°C
Fines in filtered oil	≤0.1% w/w

Pre-coat: Diatomaceous earth (optional, for polishing).
Quality Gate: Visual clarity — clear, no visible sediment.

2.4 Crude Oil Storage (Before Refining or Bottling)¶

Parameter	Value
Tank material	SS304 or SS316
Temperature	15–20°C (cooled storage)
Headspace	Nitrogen blanket (O₂ ≤2.0%)
Light protection	Opaque tank or covered
Maximum storage duration	7 days (crude) / 30 days (refined)

3. Detailed Process Steps — Solvent Extraction¶

3.1 Flaking & Conditioning¶

Parameter	Value / Range
Flake thickness	0.2 – 0.4 mm
Flake moisture	8 – 10%
Conditioning temperature	55 – 65°C
Conditioning time	20 – 30 minutes

Purpose: Rupture cell walls for efficient hexane penetration.

3.2 Solvent Extraction¶

Parameter	Value / Range
Solvent	Hexane (food-grade, boiling range 65–70°C)
Extractor type	Rotocel or shallow-bed (De Smet / Crown)
Solvent-to-feed ratio	1:1 to 1.5:1 (w/w)
Extraction temperature	50 – 60°C
Extraction time	30 – 60 min (total cycle)
Miscella concentration	20 – 30% oil in hexane

Quality Gate: Residual oil in spent meal ≤1.0% (checked per shift).

3.3 Miscella Evaporation¶

Parameter	Value / Range
First stage evaporator	70 – 80°C, atmospheric
Second stage evaporator	90 – 100°C, vacuum (−0.6 bar)
Stripper column	100 – 110°C, steam injection
Residual hexane in oil	≤500 ppm
Recovered hexane	Recycled to extractor

3.4 Desolventizing (Spent Meal)¶

Parameter	Value / Range
Desolventizer type	DTDC (Desolventizer-Toaster-Dryer-Cooler)
Temperature	100 – 110°C (indirect steam)
Residual hexane in meal	≤500 ppm
Final meal moisture	≤10%

Output: Defatted meal → to Flaxseed Powder (Defatted) line.

4. Oil Refining (Optional — Both Cold Press & Solvent Extracted)¶

Refining is applied when a neutral, light-colored, bland oil is required. Each step is optional depending on target specification.

4.1 Degumming¶

Parameter	Value / Range
Temperature	60 – 70°C
Water addition	2 – 3% of oil weight (hot water)
Mixing time	20 – 30 min, high-shear
Centrifuge	Disc stack, 7,000 – 9,000 RPM
Phosphorus after degumming	≤20 ppm (from 200–600 ppm crude)
Hydratable gums removed	Yes (lecithin by-product)

Quality Gate: Phosphorus content ≤20 ppm.

4.2 Neutralization (Alkali Refining)¶

Parameter	Value / Range
Temperature	75 – 85°C
Alkali	NaOH solution, 16–20°Bé
Excess alkali	0.1 – 0.3% above stoichiometric
Contact time	15 – 20 min (high-speed mixer)
Centrifuge separation	Disc stack, 8,000 – 10,000 RPM
Water wash	10 – 15% hot water (90–95°C), 1–2 washes
Final FFA	≤0.05% (from 0.5–2.0% crude)
Soap content after wash	≤50 ppm

Quality Gate: FFA ≤0.05% after neutralization.

4.3 Bleaching¶

Parameter	Value / Range
Temperature	90 – 105°C
Vacuum	−0.08 to −0.09 MPa
Bleaching earth (Tonsil / Bentonite)	0.5 – 2.0% w/w
Contact time	20 – 30 min
Filtration	Vertical leaf filter or plate & frame
Color reduction	Lovibond 5.25" cell: from 30–70Y + 3–7R to ≤10Y + 1.0R

Quality Gate: Bleached oil color ≤10Y + 1.0R (Lovibond, 5.25" cell).
Note: Activated carbon (0.1–0.3%) may be added for stubborn color bodies.

4.4 Deodorization¶

Parameter	Value / Range
Temperature	200 – 230°C
Vacuum	−0.09 to −0.095 MPa (3–5 mbar absolute)
Steam sparge rate	1 – 3% of oil weight per hour
Time	60 – 120 min
Cooling	Cool to ≤40°C before breaking vacuum

Quality Gate: PV ≤1.0 meq O₂/kg; FFA ≤0.05%; odor bland.
Cold test: Must pass 24-hour cold test at 0°C (no crystallization → indicates no winterization needed for most applications).
Antioxidant addition: Add 200 ppm TBHQ or 500 ppm rosemary extract during cool-down.

5. Quality Gates (In-Process Checks)¶

Check	Frequency	Method	Acceptable Limit	Action if Out of Spec
Barrel temperature (press)	Every 15 min	Thermocouple	≤40°C	Reduce feed; check cooling
Crude oil PV	Per batch	AOCS Cd 8-53	≤2.0 meq O₂/kg	Flash to N₂; reduce storage temp
Crude oil FFA	Per batch	AOCS Ca 5a-40	≤1.5%	Refining can correct; log for refiner
Oil color (after bleaching)	Per batch	Lovibond (5.25")	≤10Y + 1.0R	Increase earth dose or re-bleach
Oil color (final)	Per batch	Lovibond (5.25")	≤5Y + 0.5R (refined)	Check bleaching step
Refined oil PV	Per batch	AOCS Cd 8-53	≤1.0 meq O₂/kg	Add antioxidant; check N₂ blanket
FFA (refined)	Per batch	AOCS Ca 5a-40	≤0.05%	Re-neutralize or blend
Cold test	Per batch	0°C / 24 hr	No crystallization	Winterize or adjust pressing conditions
Residual hexane	Per batch	GC headspace	≤500 ppm	Increase stripper temperature
Phosphorus (degummed)	Per batch	AOCS Ca 12-55	≤20 ppm	Repeat degumming

6. CCP Integration — CCP-2 (Chemical — Process Contaminants)¶

CCP Code	Hazard Type	Control Point	Critical Limit	Monitoring	Corrective Action
CCP-2	Chemical (oxidation / PAH / trans fat from overheating)	Screw press (barrel temperature)	Barrel temp ≤40°C (cold press)	Continuous thermocouple + manual check every 15 min	If temp >40°C: reduce feed rate, check cooling, hold oil for PV/FFA testing. If PV >2.0 meq/kg or FFA >1.5%, divert to refined oil stream.

Supporting Rationale: Overheating during pressing promotes: - Lipid oxidation (high PV) - Free fatty acid formation (hydrolysis) - Potential formation of processing contaminants (e.g., 3-MCPD, glycidyl esters at >200°C — relevant during deodorization, monitored separately)

Deodorization CCP (if applicable): Deodorization temperature ≥200°C ensures removal of volatile contaminants (pesticides, PAHs). Critical limit: 200–230°C for ≥60 min.

7. Troubleshooting¶

7.1 High Peroxide Value (PV > 2.0 meq/kg)¶

Possible Cause	Check	Solution
Press barrel too hot	Barrel thermocouple	Reduce feed; verify cooling jacket function
Old / rancid seed	Raw material age / PV	Use seed ≤6 months post-harvest; cold storage
High storage temperature	Tank temp log	Reduce to ≤20°C; ensure N₂ blanket
Oxygen exposure	Headspace O₂	Increase N₂ flow; minimize headspace
Metal contamination	Metal detector check	Check for wear metal from press
Light exposure	Storage vessel cover	Use opaque tanks or light-proof covers

7.2 Dark Color (Oil Too Dark)¶

Possible Cause	Check	Solution
Press temperature too high	Barrel temp log	Reduce to ≤40°C
Seed scorching	Press visual inspection	Clean press; reduce choke (larger nozzle)
High chlorophyll (immature seed)	Seed color spec	Source golden flaxseed (lower chlorophyll)
Iron contamination	Metal detector / magnet	Install magnet in seed feed line
Filtration inadequate	Filter press pressure	Replace filter cloth; add pre-coat
Over-bleaching (if refining)	Bleaching earth dosage	Reduce earth to ≤1.5%; check contact time

7.3 Poor Oil Yield (Cold Press)¶

Possible Cause	Check	Solution
Seed moisture too high (>8.5%)	Moisture analyzer	Dry seed to 6–8%
Seed moisture too low (<6%)	Moisture analyzer	Tempering — hold seed at 70% RH for 12 hr
Screw speed wrong	RPM reading	Adjust to 15 RPM
Nozzle size wrong	Nozzle diameter	Try 8 mm (smaller = higher pressure, more oil)
Worn press screw / barrel	Visual / feel	Replace worm shaft or barrel liners
Low oil content in seed	Seed spec sheet	Source seed with ≥38% oil content

7.4 Emulsion Problems (Degumming / Washing)¶

Possible Cause	Check	Solution
Water temperature too low	Thermometer	Use 90–95°C wash water
Insufficient mixing	Mixer RPM	Increase to ensure droplet dispersion
High gum content	Phosphorus in crude	Pre-degum with enzymatic degumming
Wrong centrifuge speed	Bowl RPM	Adjust to 8,000–10,000 RPM
pH imbalanced	pH of wash water	Maintain pH 6.5–7.0
Over-neutralization	Excess NaOH	Reduce excess alkali to 0.1–0.15%

7.5 Crystal Formation / Failed Cold Test¶

Possible Cause	Check	Solution
High wax content	Wax content analysis	Winterize — cool to 4°C for 24 hr, filter
High saturated fats	Seed variety	Use low-saturate flax variety
Slow cooling rate	Cooling rate	Rapid cool to 0°C for winterization
Incomplete winterization	Filtration efficiency	Use 0.5 µm filter for wax removal

7.6 High FFA in Crude Oil¶

Possible Cause	Check	Solution
Damaged / sprouted seed	Seed inspection	Reject damaged seed lots
High moisture in storage	Silo moisture meter	Maintain ≤8% moisture during storage
Long storage before pressing	Seed age	Process within 3 months of harvest
Lipase enzyme activity	FFA trend over time	Flash heat seed to 90°C / 5 min to deactivate lipase
Press temperature high	Barrel temp log	Reduce to ≤40°C

8. Line Comparison — Cold Press vs. Solvent Extraction¶

Aspect	Cold Press	Solvent Extraction
Oil yield	70–85%	97–99%
Residual oil in meal	12–18%	≤1.0%
Oil quality	Premium (virgin-grade)	Lower (requires full refining)
Omega-3 retention	High (≥55% ALA)	Moderate (∼50% ALA after refining)
Processing temperature	≤40°C	≤110°C
Solvent use	None	Hexane
Capital cost	Low–moderate	High
Operating cost	Moderate	Lower per kg of oil
Product types	Virgin + Refined	Refined only
By-product value	High (high-fat meal)	Low (defatted meal)

9. Equipment List¶

Equipment	Specification	Application
Screw press (expeller)	15–30 kW, 10–20 RPM variable	Cold press
Plate-and-frame filter	30–60 plates, polypropylene cloth	Crude oil filtration
Flaking rolls	500–1000 mm diameter, 0.2–0.4 mm gap	Solvent extraction prep
Rotary extractor (Rotocel)	Capacity: 50–500 MT/day	Solvent extraction
Falling-film evaporator	SS316L	Miscella evaporation
DTDC	Steam-heated, 100–110°C	Meal desolventizing
Degumming centrifuge	Disc stack, 7,000–9,000 RPM	Refining
Bleaching filter	Vertical leaf, pre-coated	Refining
Deodorizer	Packed column or tray design	Refining (200–230°C)
Deodorizer vacuum system	Steam ejector + vacuum pump	High vacuum

10. References¶

AOCS Cd 8-53 — Peroxide Value
AOCS Ca 5a-40 — Free Fatty Acids
AOCS Ca 12-55 — Phosphorus Content
AOCS Cc 13b-45 — Cold Test
CCP-2 Chemical Hazard Control SOP (QMS-SOP-002)
Flaxseed Oil Product Specification — PROD-SPEC-003
Cold Press Operating Manual — OPS-MAN-001
Solvent Extraction Operating Manual — OPS-MAN-002
Oil Refining Operating Manual — OPS-MAN-003

End of Document — Flaxseed Oil Process Flow