Flaxseed Gum — Process & Workflow Document
Document ID: PROD-PROC-002
Version: 1.0
Effective Date: 2026-07-20
Product: Flaxseed Gum Powder (Water-Soluble Polysaccharides)
1. Process Overview
Flaxseed gum (also known as flaxseed mucilage) is extracted from flaxseed hulls using a hot water extraction followed by ethanol precipitation. The final product is a light-beige powder rich in water-soluble polysaccharides, used as a thickener, emulsifier, and binder in food, cosmetic, and pharmaceutical applications.
Process Flow Diagram
Flaxseed Hull
↓
Extraction Tank (Hot Water)
↓
Decanter (Solids Separation)
↓
Vacuum Concentration
↓
Ethanol Precipitation
↓
Centrifuge
↓
Spray Dry
↓
Gum Powder → QC Release
↑
Ethanol Recovery ← Still bottoms
2. Detailed Process Steps
2.1 Hull Receiving & Pre-Treatment
| Parameter |
Value / Range |
| Raw material |
Flaxseed hulls (from dehulling process) |
| Hull purity |
≥95% (≤5% kernel fragments) |
| Moisture |
≤10.0% |
| Storage |
Ambient, dry, <25°C, sealed |
| Pre-treatment |
Optional: dry milling through 20-mesh screen to increase surface area |
- Quality Gate: Visual inspection — no visible mold, insect damage, or off-odor.
- Yield factor: Hulls typically contain 8–12% extractable gum (dry basis).
| Parameter |
Value / Range |
| Water-to-hull ratio |
15:1 (15 kg water per kg hull) |
| Extraction temperature |
75°C ± 3°C |
| Extraction time |
60 minutes (from reaching target temp) |
| pH |
Neutral to slightly acidic (6.5–7.0) — no pH adjustment needed |
| Agitation |
Paddle agitator, 30–50 RPM |
| Vessel type |
Jacketed stainless steel tank with steam heating |
Procedure:
- Charge extraction tank with measured water (calculated per batch).
- Heat water to 75°C with steam jacket.
- Add hulls at 15:1 ratio.
- Maintain temperature at 75°C ± 3°C for 60 minutes with gentle agitation.
-
Record temperature every 10 minutes in batch log.
-
Quality Gate: Temperature chart review — verify 75°C ± 3°C maintained throughout.
- Optimization tip: Higher temperatures (>80°C) degrade polysaccharide chains → lower viscosity. Lower temperatures (<70°C) reduce yield.
2.3 Decanter Centrifugation (Solids Separation)
| Parameter |
Value / Range |
| Equipment |
Horizontal decanter centrifuge |
| Bowl speed |
3,000 – 4,500 RPM |
| Differential speed |
10 – 25 RPM |
| Feed rate |
500 – 2,000 L/hr |
| Solids discharge |
Hull residue (to waste or animal feed) |
| Liquid discharge (gum extract) |
Turbidity ≤ 50 NTU |
- Quality Gate: Clarified extract turbidity ≤ 50 NTU. If higher, recirculate through decanter.
- Solid residue: Contains ~80% moisture. Can be dried and sold as fiber ingredient.
2.4 Vacuum Concentration
| Parameter |
Value / Range |
| Equipment |
Falling-film evaporator under vacuum |
| Vacuum level |
−0.08 to −0.09 MPa |
| Temperature |
55 – 65°C (at vacuum) |
| Target solids content |
4 – 6% (from ~0.8% initial) |
| Evaporation ratio |
~6:1 volume reduction |
- Purpose: Reduce volume for efficient ethanol precipitation. At <3% solids, precipitation yield drops. At >8% solids, viscosity becomes too high for handling.
- Quality Gate: Refractometer check of solids content every 30 min.
- Note: Temperature kept <65°C to prevent polysaccharide degradation.
2.5 Ethanol Precipitation
| Parameter |
Value / Range |
| Ethanol concentration |
80% v/v (final mixture) |
| Ethanol grade |
Food-grade, 95% v/v (rectified) |
| Concentrated extract : Ethanol (95%) |
~1:4.75 volume ratio |
| Temperature |
15 – 25°C (ambient) |
| Mixing |
In-line static mixer or stirred precipitation tank |
| Contact time |
15 – 30 minutes (with gentle agitation) |
Mixing Calculation:
- To achieve 80% v/v final ethanol from 95% ethanol and extract:
- For 100 L of concentrated extract (assume negligible ethanol content):
- Need 475 L of 95% ethanol → total volume 575 L → ethanol % = (475 × 0.95) / 575 = 78.5% v/v
- Adjust with additional 15–20 L of 95% ethanol if needed.
Procedure:
- Transfer concentrated extract to precipitation tank.
- Slowly add 95% ethanol while stirring gently (avoid vortex).
- Continue stirring for 15–30 minutes after all ethanol added.
- White/beige flocculent precipitate forms — gum polysaccharides.
-
Allow to settle for 10–15 minutes (optional).
-
Quality Gate: Visual — distinct floc formation; supernatant should be clear to slightly cloudy.
- Ethanol Recovery: Spent ethanol (from centrifuge) is sent to the ethanol recovery system (see Section 7).
2.6 Centrifuge (Gum Recovery)
| Parameter |
Value / Range |
| Equipment |
Basket centrifuge or disc stack centrifuge |
| Bowl speed |
3,000 – 4,500 RPM |
| Wash step |
Optional: 1 volume 70% ethanol rinse |
| Recovered gum |
Wet cake, ~60–70% moisture |
| Mother liquor |
~78–80% ethanol → to recovery still |
- Quality Gate: Mother liquor clarity — should be clear or slightly hazy. Hazy = incomplete precipitation → check ethanol concentration.
- Wet gum cake: Should be off-white to light beige. Dark color indicates oxidation or contamination.
2.7 Spray Drying
| Parameter |
Value / Range |
| Inlet temperature |
160 – 180°C |
| Outlet temperature |
80 – 90°C |
| Feed solids |
4 – 6% (after resuspension of wet cake) |
| Feed temperature |
40 – 50°C |
| Atomizer type |
Rotary disc or nozzle |
| Atomizer speed |
10,000 – 15,000 RPM (rotary) |
| Air flow |
Co-current |
| Final moisture |
≤6.0% |
| Particle size |
D50 = 50 – 150 µm (agglomerated) |
Resuspension Procedure:
- Re-dissolve centrifuge cake in hot water (~60°C) to achieve 4–6% solids.
- Mix thoroughly to break clumps (high-shear mixer recommended).
-
Filter through 100-mesh screen before feeding to spray dryer.
-
Quality Gate: Outlet temperature must stay within 80–90°C range. If >90°C → risk of scorching; if <80°C → insufficient drying.
2.8 Gum Powder — Final Product
| Parameter |
Specification |
| Appearance |
Light beige to tan powder |
| Polysaccharide content |
≥80.0% (by dry weight, phenol-sulfuric method) |
| Residual ethanol |
<100 ppm |
| Moisture |
≤6.0% |
| Ash |
≤8.0% |
| Protein |
≤5.0% |
| Viscosity (1% solution, 25°C) |
≥500 cP (Brookfield, spindle #3, 20 RPM) |
| Solubility |
≥95% dispersible in cold water |
| Bulk density |
0.4 – 0.6 g/mL |
| Packaging |
Double PE-lined HDPE drums or foil bags, N₂ flushed |
3. Quality Gates (In-Process Checks)
| Check |
Frequency |
Method |
Acceptable Limit |
Action if Out of Spec |
| Extraction temperature |
Every 10 min |
RTD temperature probe |
75°C ± 3°C |
Adjust steam valve; re-check after 5 min |
| Extract turbidity |
Per batch |
Turbidity meter |
≤50 NTU |
Re-run decanter or add filter step |
| Solids after vacuum concentration |
Every 30 min |
Refractometer |
4–6% solids |
Adjust vacuum or residence time |
| Ethanol concentration (precipitation) |
Per batch |
Alcoholmeter / density |
78–82% v/v |
Adjust ethanol:extract ratio |
| Supernatant clarity |
Per batch |
Visual inspection |
Clear to slightly hazy |
Increase ethanol or contact time |
| Spray dryer outlet temp |
Continuous |
Thermocouple |
80–90°C |
Adjust feed rate or inlet temp |
| Final moisture (powder) |
Every hour |
Halogen moisture analyzer |
≤6.0% |
Reduce feed rate to spray dryer |
| Polysaccharide content |
Per batch |
Phenol-sulfuric acid assay |
≥80% |
Reject batch; investigate extraction |
| Residual ethanol |
Per batch |
GC headspace |
<100 ppm |
Extend drying or increase inlet temp |
| Viscosity (1% solution) |
Per batch |
Brookfield viscometer |
≥500 cP |
Check polysaccharide quality |
4. CCP Integration — CCP-3 (Chemical)
| CCP Code |
Hazard Type |
Control Point |
Critical Limit |
Monitoring |
Corrective Action |
| CCP-3 |
Chemical (residual ethanol) |
Spray drying outlet |
Residual ethanol <100 ppm |
GC analysis per batch |
Increase outlet temp by 5°C; re-test |
- Rationale: Ethanol is a processing aid. Residual levels must comply with food safety regulations (typically <100 ppm). The spray drying step is the CCP that removes ethanol to safe levels.
- Supporting evidence: Validation records must demonstrate that outlet temp ≥80°C and residence time ≥10 seconds consistently achieves <100 ppm residual ethanol.
5. Troubleshooting
5.1 Low Yield
| Possible Cause |
Check |
Solution |
| Low polysaccharide in hulls |
Raw material analysis |
Source hulls with ≥10% gum content |
| Extraction temp too low (<70°C) |
Batch temperature log |
Verify 75°C maintained for full 60 min |
| Water-to-hull ratio incorrect |
Batch recipe sheet |
Confirm 15:1 ratio (minimum 12:1) |
| Insufficient extraction time |
Batch timing log |
Extend to 75–90 min |
| Ethanol concentration <78% v/v |
Alcoholmeter reading |
Adjust ethanol-to-extract ratio |
| Losses in decanter |
Mass balance |
Check solids discharge for gum content |
| Poor precipitation pH |
pH meter |
Adjust to pH 6.5–7.0 (optimal) |
5.2 High Protein Content (>5%)
| Possible Cause |
Check |
Solution |
| Kernel fragments in hull |
Hull purity analysis |
Improve dehulling efficiency; target ≥95% hull purity |
| High extraction temperature |
Batch temperature log |
Reduce to 75°C (protein co-extracts at >80°C) |
| Alkaline pH |
pH meter |
Keep pH 6.5–7.0 (alkaline pH extracts protein) |
| Short precipitation time |
Process timer |
Extend ethanol contact to 30 min (selectively precipitates polysaccharides over protein) |
5.3 Low Viscosity (<500 cP at 1%)
| Possible Cause |
Check |
Solution |
| Polysaccharide degradation |
Molecular weight (intrinsic viscosity) |
Reduce extraction temp to 70–72°C |
| High shear during extraction |
Agitator speed |
Reduce to 30 RPM |
| Enzyme activity |
Raw material inspection |
Use fresh hulls or heat-treat at 90°C / 5 min before extraction |
| High spray drying temp |
Outlet temp log |
Reduce outlet to 80–85°C |
| Low polysaccharide content |
Phenol-sulfuric assay |
Optimize extraction (longer time, correct ratio) |
5.4 Poor Solubility (<95% dispersible)
| Possible Cause |
Check |
Solution |
| Over-drying |
Moisture content |
Target ≤6% but never <2% (over-drying causes hornification) |
| Large particle size |
Sieve analysis |
Mill gum powder to 100 mesh |
| High protein content |
Protein assay |
Reduce protein (see Section 5.2) |
| Ethanol not fully removed |
Residual ethanol test |
Ensure spray drying is adequate |
| Agglomeration during storage |
Storage conditions |
Keep sealed, dry, <25°C |
5.5 Dark Color (Should Be Light Beige)
| Possible Cause |
Check |
Solution |
| Maillard reaction |
Temperature logs |
Keep extraction <75°C; reduce inlet temp if needed |
| Oxidation |
PV of gum |
Add antioxidant (e.g., 0.01% ascorbic acid) |
| Iron contamination |
Metal detector / magnet |
Install magnet in hull feed line |
| Overheating in spray dryer |
Outlet temp log |
Increase feed rate to reduce residence time |
6. Ethanol Recovery System
The ethanol recovery system captures and recycles ethanol from the precipitation mother liquor, reducing operating costs and environmental impact.
Flow Diagram
Mother Liquor (78–80% ethanol)
↓
Holding Tank
↓
Rectification Column
↓
┌────┴────┐
↓ ↓
Condenser Still Bottoms
↓ ↓
95% Ethanol Water + Organic Residue
(recycled) (to wastewater treatment)
Parameters
| Parameter |
Value |
| Column type |
Packed distillation column (SS 316L) |
| Number of theoretical stages |
15–20 |
| Reflux ratio |
2:1 to 3:1 |
| Column top temperature |
78.3°C (azeotrope) |
| Column bottom temperature |
98–100°C |
| Vacuum |
None (atmospheric operation) |
| Recovered ethanol purity |
≥94% v/v (target 95%) |
| Recovery rate |
≥95% of ethanol input |
| Still bottoms |
<0.1% ethanol (sent to WWT) |
Key Operating Rules
- Never allow bottom temperature to exceed 105°C (prevents fouling).
- Check recovered ethanol concentration every 2 hours.
- If recovered ethanol purity <93%, increase reflux ratio.
- Drain still bottoms every shift — don't let solids accumulate.
- Log all recovered ethanol volumes for mass balance.
Safety Notes
- Flammable atmosphere: All electrical equipment in the ethanol recovery area must be explosion-proof (Class I, Division 1).
- Grounding: All equipment and containers must be bonded and grounded.
- Ventilation: Continuous mechanical ventilation; LEL monitor installed.
- Fire protection: Sprinkler system and fire extinguishers rated for alcohol fires.
7. Equipment List
| Equipment |
Specification |
Notes |
| Extraction tank |
Jacketed SS316L, 500–5000 L |
Steam heating, paddle agitator |
| Decanter centrifuge |
Horizontal, 3–5° cone angle |
Solids: hull residue |
| Falling-film evaporator |
SS316L, vacuum rated |
For concentration to 4–6% solids |
| Precipitation tank |
SS304, with agitator |
Ethanol-resistant seals |
| Basket centrifuge |
SS316L, 3000–4500 RPM |
For gum recovery |
| Spray dryer |
Co-current, water evaporative capacity 50–200 kg/hr |
Inlet 160–180°C |
| Ethanol distillation column |
Packed column, SS316L |
15–20 stages |
| Ethanol storage tank |
SS304, explosion-proof area |
Double-walled, grounded |
8. References
- AOCS Ba 3-38 — Determination of Polysaccharide Content
- GC Headspace Method — Residual Ethanol (QMS-TM-022)
- CCP-3 Chemical Hazard Control SOP (QMS-SOP-003)
- Flaxseed Gum Product Specification — PROD-SPEC-002
- Ethanol Recovery System Operating Manual — OPS-MAN-007
End of Document — Flaxseed Gum Process Flow