Flaxseed Kernel Processing — Process & Workflow Document

Document ID: PROD-KERNEL-001
Version: 1.0
Last Updated: 2026-07-20
Product: Flaxseed Kernel Products (Whole Kernel, Kernel Meal, Kernel Oil)

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1. Process Overview

The flaxseed kernel process extracts the inner kernel (cotyledon) from dehulled flaxseed, producing kernel-rich streams for oil pressing or milling. The process prioritizes kernel integrity for whole-kernel applications and controlled particle size for meal and oil applications.

1.1 Process Flow Summary

Cleaned Seed → Conditioning → Dehulling → Air Classification
    → Kernel Stream → (Oil Pressing OR Milling) → QC → Packaging

1.2 High-Level Parameters

Parameter	Target	Tolerance
Kernel purity (from classifier)	≥ 95% kernel	±2%
Kernel yield (from cleaned seed)	62–70%	±3%
Moisture (kernel meal)	≤ 7.0%	±0.5%
Oil content (kernel meal, defatted)	≤ 8%	±1%
Particle size (meal, D90)	≤ 500 µm	±50 µm

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2. Detailed Process Stages

2.1 Cleaned Seed (Input)

Purpose: Receive and hold flaxseed that has passed through CCP-1 (Cleaning). Same receiving specs as hull process — see hull-process.md §2.1.

Equipment: - Receiving hopper (2,000 kg) - Destoner (gravity table) - Magnet (CCP-1, ≥ 12,000 Gauss) - Surge bin (5,000 kg)

Parameters: - Foreign material: ≤ 0.5% (by weight) - Dockage (chaff, weed seeds): ≤ 2.0% - Moisture: 6.0–9.5% - Temperature: Ambient

Quality Check: Incoming Raw Material

Check	Frequency	Method	Target	Action Limit
Variety/identity	Per lot	COA review	Match purchase spec	Mismatch → hold for R&D
Moisture	Per lot	NIR	6.0–9.5%	> 10% → conditional acceptance with price adjustment
Oil content	Per lot	NMR	38–44%	< 36% → reject or renegotiate
Free fatty acids (FFA)	Per lot	Titration	≤ 1.0% oleic	> 1.5% → reject (rancidity risk)
Peroxide value (PV)	Per lot	Titration	≤ 2.0 meq/kg	> 3.0 → reject
Visual defects	Every 50 bags	Visual inspection	≤ 2% damaged seeds	> 5% → reject lot
Metal contamination	Continuous	CCP-1 magnet + detector	Zero detectable	Shut down; isolate 30 min product

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2.2 Conditioning

Purpose: Controlled heating and moisturizing to optimize hull separation. Kernel process conditioning may differ slightly from hull process to favor kernel intactness.

Equipment: - Horizontal paddle conditioner (steam-injected) - Tempering screw (jacketed, 10 min residence) - Steam generator (2–3 bar, culinary grade)

Parameters:

Parameter	Target	Range	Control Method
Conditioning temperature	55°C	50–60°C	Steam injection PID
Moisture after conditioning	9.0%	8.5–9.5%	Water spray + steam condensate
Residence time	15 min	12–18 min	Screw speed
Steam flow	50 kg/h	40–60 kg/h	Mass flow controller
Bed depth	20 cm	15–25 cm	Weir gate

Process Notes: - Kernel process uses lower temperature (55°C) than hull process (65°C) to preserve kernel integrity - Excessive moisture (> 9.5%) leads to kernel softening and oil exudation in dehuller - Steam quality must be culinary-grade — no boiler treatment chemicals

Quality Check: Conditioning

Check	Frequency	Method	Target	Action Limit
Temperature	Every 15 min	RTD probe	50–60°C	> 62°C → reduce steam; < 48°C → increase
Moisture	Every batch	NIR	8.5–9.5%	< 8.0% or > 10.0% → hold & adjust
Kernel firmness	Every hour	Manual squeeze test	Kernels intact, hull loose	Hull sticking → increase time or temp by 2°C

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2.3 Dehulling

Purpose: Gently separate hull from kernel while maximizing intact kernel yield.

Equipment: - Rubber-roll dehuller (differential speed, soft rolls) - Impact-free aspiration separator - Rotary sifter (for kernel/hull pre-sort)

Parameters:

Parameter	Target	Range	Control Method
Roll speed (fast roll)	1,200 rpm	1,100–1,300 rpm	VFD
Roll speed (slow roll)	600 rpm	550–650 rpm	VFD
Differential ratio	2.0:1	1.8:1–2.2:1	Fixed gear
Roll gap	0.5 mm	0.4–0.7 mm	Manual micrometer adjust
Feed rate	600 kg/h	500–700 kg/h	Screw feeder VFD
Aspiration velocity	4 m/s	3–5 m/s	Damper

Key Differences from Hull Process Dehuller: - Rubber rolls (vs. metal impact disc) — gentler on kernels - Lower speed (1,200 vs. 3,800 rpm) — reduces breakage - Narrower roll gap (0.5 vs. 0.8 mm) — compensates for lower impact force

Quality Check: Dehulling

Check	Frequency	Method	Target	Action Limit
Kernel integrity (whole)	Every hour	Hand sort (100 g)	≥ 90% whole kernels	< 85% → reduce roll speed or widen gap
Dehulling efficiency	Every hour	Sieve + hand sort	≥ 80% hull release	< 75% → increase differential speed
Fines generation	Every 2 hours	Sieve (< 1 mm)	≤ 5%	> 8% → check roll condition
Rubber roll wear	Weekly	Visual + micrometer	≥ 8 mm rubber remaining	< 5 mm → replace rolls

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2.4 Air Classification

Purpose: Separate kernel stream (heavy fraction) from hulls (light fraction). The kernel stream is the primary product for this process.

Equipment: - Two-stage aspirator classifier - Primary cyclone (kernel recovery) - Secondary cyclone (fines collection) - Rotary airlocks

Parameters:

Parameter	Target	Range	Control Method
Primary air velocity	6.0 m/s	5.5–6.5 m/s	Fan VFD
Secondary air velocity	8.0 m/s	7.5–8.5 m/s	Damper
Splitter position	60%	55–65%	Actuator (heavies bias)
Feed rate	600 kg/h	500–700 kg/h	Screw feeder

Expected Streams:

Stream	Mass Fraction	Composition	Destination
Kernel stream (heavies)	72–78%	Kernels + trace hulls	Oil press or mill
Hull stream (lights)	18–25%	Hull particles + fines	Hull process (milling)
Dust	2–4%	Fine particles	Dust collection

Quality Check: Air Classification

Check	Frequency	Method	Target	Action Limit
Kernel purity (heavies)	Every 2 hours	Density separation	≥ 95% kernel	< 92% → reduce air velocity 0.3 m/s
Hull in kernel stream	Every 2 hours	Visual + density	≤ 5% hulls	> 8% hulls → adjust classifier
Kernel loss to hull stream	Every 4 hours	Sieve + weighing	≤ 3% of total kernel	> 5% → reduce secondary air velocity

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2.5 Kernel Stream (Intermediate)

Purpose: Collect, optionally size-grade, and convey kernels to downstream processing (oil pressing or milling).

Equipment: - Surge hopper (1,000 kg) - Rotary sizer (optional, vibratory) - Metal detector (CCP-1B) - Pneumatic or mechanical conveyor

Options — Size Grading (If Required for Whole Kernel Market):

Grade	Screen Size	Typical % of Kernel	Application
Whole kernel (grade A)	> 3.5 mm	40–50%	Retail, snack, bakery topping
Split kernel (grade B)	2.0–3.5 mm	30–40%	Milling, coarse meal
Fines	< 2.0 mm	10–20%	Milling (meal), oil press

Quality Check: Kernel Stream

Check	Frequency	Method	Target	Action Limit
Kernel moisture	Every batch	NIR	8.0–9.5%	> 10% → reduce conditioning spray
Hull content	Every 2 hours	Density separation	≤ 5%	> 8% → adjust classifier
Color / visual	Every hour	Visual (Lab* reference)	Light yellow-tan	Darkening → check for overheating in conditioning

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3. Downstream Processing — Dual Path

The kernel stream can be directed to one of two parallel processing lines depending on the target product:

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Path A: Oil Pressing

Purpose: Extract flaxseed oil from kernels, producing crude oil and press cake (kernel meal).

3A.1 Kernel Pre-Heat

Equipment: Vertical stack cooker (3-tray, steam-heated)

Parameter	Target	Range
Pre-heat temperature	90°C	85–95°C
Residence time	20 min	15–25 min
Moisture after cook	5.0%	4.5–5.5%

Purpose: Reduce moisture, denature enzymes, increase oil fluidity.

3A.2 Screw Pressing

Equipment: Single-screw expeller press (e.g., Anderson Duo or equivalent)

Parameter	Target	Range	Control Method
Screw speed	25 rpm	20–30 rpm	VFD
Barrel temperature	80°C	75–85°C	Jacket heating/cooling
Choke gap	8 mm	6–10 mm	Manual adjust
Throughput	500 kg/h	400–600 kg/h	Feeder speed
Motor load	80%	70–90%	Amp meter

Expected Outputs:

Stream	Mass %	Composition
Crude oil	30–35%	Oil + meal fines
Press cake	65–70%	Meal, 8–12% residual oil

Quality Check: Pressing

Check	Frequency	Method	Target	Action Limit
Residual oil in cake	Every 2 hours	NMR	≤ 12%	> 15% → tighten choke or reduce speed
Oil temperature	Continuous	In-line RTD	≤ 50°C (exit)	> 55°C → activate cooler
Cake moisture	Every 2 hours	Halogen	≤ 7.0%	> 8.0% → reduce feed or increase cooking temp

3A.3 Oil Filtration

Equipment: Plate-and-frame filter press, polish filter

Parameter	Target	Range
Filter aid (diatomaceous earth)	0.5% w/w	0.3–0.8%
Pressure (max)	4 bar	3–5 bar
Temperature	35°C	30–40°C

Check	Frequency	Method	Target	Action Limit
Oil clarity	Every batch	Visual	Clear, no sediment	Turbid → re-filter
FFA in oil	Every batch	Titration	≤ 0.5%	> 1.0% → reprocess or downgrade
PV in oil	Every batch	Titration	≤ 1.0 meq/kg	> 2.0 → reject for human consumption
Sediment after filtration	Every batch	Centrifuge test	≤ 0.1%	> 0.2% → re-filter with tighter media

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Path B: Milling (Kernel Meal)

Purpose: Produce kernel meal (full-fat or partially defatted) for bakery, supplement, and feed applications.

3B.1 Hammer Milling

Equipment: Hammermill with DSA (dynamic screen assist)

Parameter	Target	Range	Control Method
Screen aperture	1.5 mm	1.0–2.0 mm	Screen selection
Rotor speed	3,000 rpm	2,800–3,200 rpm	VFD
Feed rate	400 kg/h	300–500 kg/h	Feeder VFD
Mill temperature	≤ 45°C	35–50°C	Cooling air

Quality Check: Milling

Check	Frequency	Method	Target	Action Limit
Particle size D90	Every 2 hours	Sieve shaker	≤ 500 µm	> 600 µm → change screen or reduce feed
Temperature out	Continuous	RTD	≤ 45°C	> 50°C → reduce feed or activate cooling
Bulk density	Daily	Scott cup	0.45–0.55 g/mL	Out of spec → adjust hammer configuration

3B.2 Optional: Defatting (Partial)

Purpose: Reduce oil content in meal for specific customer requirements.

Method: Mechanical pressing (Path A) → then press cake is milled.

Check	Frequency	Method	Target	Action Limit
Residual oil	Per batch	NMR	≤ 8% (defatted)	> 10% → re-press
Protein (defatted meal)	Per batch	Dumas	≥ 30%	< 28% → investigate kernel purity

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4. QC — Final Product Testing

4.1 Whole Kernel (Unmilled) — Final QC

Check	Frequency	Method	Target	Action Limit
Moisture	Every batch	Halogen	≤ 8.0%	> 9.0% → re-dry
Purity (kernels only)	Every batch	Hand sort	≥ 98%	< 95% → re-classify
Whole kernels	Every batch	Sieve (3.5 mm)	≥ 85%	Varies by grade
Color	Every batch	Visual (reference)	Light yellow	Dark → check conditioning
FFA (kernel oil)	Per batch	Titration	≤ 1.0%	> 1.5% → reject
PV (kernel oil)	Per batch	Titration	≤ 2.0 meq/kg	> 3.0 → reject

4.2 Kernel Meal (Milled) — Final QC

Check	Frequency	Method	Target	Action Limit
Moisture	Every batch	Halogen	≤ 7.0%	> 8.0% → re-dry
Protein	Every batch	Dumas (N×6.25)	20–24% (full-fat) / ≥ 30% (defatted)	Out → report
Fat	Every batch	NMR	38–44% (full-fat) / ≤ 8% (defatted)	Out → check upstream
Fiber	Every batch	AOAC	≤ 8%	> 10% → hull contamination
Particle size D90	Every batch	Sieve	≤ 500 µm	> 600 µm → re-mill
APC	Weekly	Petri film	≤ 10,000 CFU/g	> 50,000 → hold
Yeast & mold	Weekly	Petri film	≤ 500 CFU/g	> 1,000 → hold
Salmonella	Every 10 batches	PCR/culture	Negative/375g	Positive → quarantine + recall

4.3 Kernel Oil (Pressed) — Final QC

Check	Frequency	Method	Target	Action Limit
FFA	Every batch	AOCS Ca 5a-40	≤ 0.5%	> 1.0% → downgrade to industrial
PV	Every batch	AOCS Cd 8-53	≤ 1.0 meq/kg	> 2.0 → reject
p-Anisidine value	Every batch	AOCS Cd 18-90	≤ 5.0	> 10 → oxidation concern
ALA content	Per supplier lot	GC-FID	≥ 52%	< 48% → verify variety/ origin
Color (Lovibond)	Every batch	Lovibond tintometer	≤ 1.5R, ≤ 15Y	Out → check bleaching
Flavor score	Every batch	Sensory panel	≥ 6/10	< 5 → reprocess or blend
Cold test	Every batch	AOCS Cc 11-53	Pass (5.5 h at 0°C)	Fail → winterize

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5. CCP Integration

CCP ID	Process Stage	Hazard	Critical Limit	Monitoring	Corrective Action
CCP-1	Cleaned Seed (Receiving)	Physical — Metal	No metal > 1.0 mm Fe / 1.5 mm NFe / 2.0 mm SS	Magnet + metal detector; hourly wand test	Isolate 30 min of product; clean magnetic separator
CCP-1B	Kernel Stream (Intermediate)	Physical — Metal	Same as CCP-1	Reject mechanism; hourly test	Same as CCP-1
CCP-4	Conditioning	Biological — Pathogen survival	Product ≥ 50°C for ≥ 15 min	Continuous temp recording; manual check every 15 min	If below: extend hold or recondition
CCP-4B	Pre-Heat (Oil Press)	Biological — Pathogen reduction	Product ≥ 85°C for ≥ 10 min	Temp chart recorder; operator log	Extend residence time or raise temp
CCP-5	Packaging	Physical — Metal, Label	Metal detector functional; label match	CCP-5 checklist; 100% inspection	Reject non-conforming packs

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6. Mass Balance (Per 1,000 kg Cleaned Seed Input)

Path A: Oil Pressing

Stream	Mass (kg)	% of Input	Notes
Cleaned seed	1,000	100%	Baseline
Conditioning moisture gain	+15	+1.5%	8% → 9% MC
Dehulling loss	−10	−1.0%	Fines to dust
Hull stream (to hull milling)	−220	−22.0%	From classifier
Kernel stream to press	785	78.5%	Includes ~5% hull residue
Pre-heat moisture loss	−20	−2.0%	9% → 5% MC
Crude oil (pressed)	255	25.5%	32.5% of kernel stream
Press cake (kernel meal)	510	51.0%	65% of kernel stream
Oil filtration loss	−5	−0.5%	Filter aid + sediment
Refined oil (final)	250	25.0%
Kernel meal (final)	510	51.0%	~10% residual oil

Path B: Milling Only

Stream	Mass (kg)	% of Input	Notes
Cleaned seed	1,000	100%
Conditioning moisture gain	+15	+1.5%
Dehulling / classifier losses	−20	−2.0%	Dust, fines
Hull stream (to hull milling)	−220	−22.0%
Kernel stream to mill	775	77.5%
Mill dust loss	−15	−1.5%
Kernel meal (final)	760	76.0%	Full-fat, 38–44% oil

Yield Targets

Product	Target Yield	First-Pass Yield
Whole kernels (from seed)	40–50%	≥ 90%
Kernel meal (full-fat, from seed)	74–78%	≥ 92%
Kernel meal (defatted, from seed)	48–54%	≥ 90%
Kernel oil (from seed)	23–27%	≥ 88%

Loss Points & Recovery

Loss Point	Typical %	Recovery Method
Dehulling fines	1–2%	Sold as feed ingredient
Hull stream (kernel loss)	2–3%	Recovered by classifier adjustment
Press cake fines	0.5–1%	Blended back into meal
Oil filter sludge	0.3–0.5%	Sold for industrial use
Packaging waste	0.3–0.8%	Reprocessed as lower-grade meal

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7. Troubleshooting Guide

7.1 Conditioning & Dehulling

Problem	Possible Causes	Solutions
Low kernel recovery (< 72%)	Hulls not separating; kernels breaking	Reduce conditioning temp to 52°C; increase kernel-side classifier air velocity; check rubber roll condition
High hull in kernel stream (> 8%)	Air classifier velocity too low; splitter wrong	Increase primary air velocity by 0.5 m/s; adjust splitter toward heavies
High kernel breakage (> 15%)	Rubber rolls worn; gap too tight; feed too fast	Replace rolls (check mic); widen gap to 0.6 mm; reduce feed to 500 kg/h
Rubber roll glazing/overheating	Differential speed too low; gap too tight	Increase differential ratio; widen roll gap; ensure uniform feed distribution

7.2 Oil Pressing (Path A)

Problem	Possible Causes	Solutions
Low oil yield (< 28%)	Kernel moisture too high (> 6%); pre-heat temp low	Reduce moisture in pre-heat step; increase cooker temperature to 95°C; tighten choke gap
High residual oil in cake (> 15%)	Press choke too loose; screw speed too fast	Tighten choke 1 mm; reduce screw speed 2 rpm; check barrel wear
Dark oil color	Overheating in press; high FFA in input	Reduce barrel temperature; verify incoming FFA ≤ 1.0%; clean press barrel
Oil turbidity after filtration	Filter media worn; pressure too high	Replace filter cloth; reduce pressure to ≤ 3 bar; check pre-coat
High FFA in oil (> 1.0%)	Kernel deterioration; long hold times	Reduce kernel hold time before pressing; lower pre-heat temperature; check seed quality

7.3 Milling (Path B)

Problem	Possible Causes	Solutions
Coarse meal (D90 > 600 µm)	Screen worn or blown; hammer wear	Replace screen; reverse/replace hammers; reduce feed rate
Mill plugging	Oil-rich kernels smearing on screen; high moisture	Reduce kernel oil content (de-fat first); chill kernels to 10°C; use larger screen (2.0 mm)
Meal temperature > 50°C	Mill working too hard; screen blinding	Reduce feed; increase cooling air; clean screen with air blast
High hull content in meal (> 10%)	Air classifier not separating well; screen wear on classifier	Adjust classifier; check classifier screen integrity

7.4 Quality & Microbiological

Problem	Possible Causes	Solutions
High APC (> 50,000 CFU/g)	Sanitation lapse; warm moist conditions; long hold times	Deep clean line; reduce kernel hold time; verify CCP-4 conditions; increase product rotation
Salmonella positive	Raw material contamination; sanitation failure; cross-contamination	Quarantine batch; trace raw material; fumigate area; intensifiy cleaning frequency
Rancid odor in meal/oil	High FFA or PV; prolonged storage; light exposure	Adjust storage (25°C max, dark, N₂ blanket); reduce hold times; test incoming seed PV
ALA below spec in oil	Variety change; adulteration; oxidation	Check supplier COA; test incoming seed; verify GC method

7.5 Packaging & Metal Detection

Problem	Possible Causes	Solutions
Metal detector false rejects	Static electricity; product effect (conductivity); vibration	Install static eliminator; re-calibrate product effect phase; stabilize conveyor
Seal failure (bags)	Temperature too low/high; contaminated seal area	Adjust seal temp ±5°C; check seal jaws for residue; verify packaging material spec
Weight variation (checkweigher)	Product density variation; faulty load cell	Check bulk density (adjust mill if needed); calibrate load cell; verify free-flow

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8. Application Summary

8.1 Whole Kernel Applications

Application	Use Level	Benefit
Bakery toppings (bread, bagels)	3–8%	Crunch, visual, omega-3
Trail mixes & granola	5–15%	Nutrition, texture
Snack bars (pressed into bars)	5–12%	Binding, ALA content
Retail packaged kernels	100%	Direct consumption

8.2 Kernel Meal Applications

Application	Use Level	Benefit
Bakery — bread, muffins, pancakes	5–15% of flour	Protein & fiber boost, moist crumb
Gluten-free baking	5–20%	Structure, nutrition
Smoothie & supplement blends	10–25 g/serving	ALA omega-3, fiber, protein
Plant-based meat extenders	3–10%	Texture, water binding, protein
Pet food & animal feed	2–8%	Omega-3 enrichment, coat health
Nutritional supplements	5–15 g/serving	Ground flaxseed functionality

8.3 Kernel Oil Applications

Application	Use Level	Benefit
Dietary supplements (softgels, liquid)	1,000–3,000 mg/day	ALA omega-3 (≥ 52%)
Functional foods — dressings, dips	5–20%	Omega-3 enrichment
Personal care (creams, balms)	2–10%	Emollient, skin barrier
Paints & varnishes (industrial)	10–30%	Drying oil, renewable

8.4 Formulation Guidelines

• Whole kernels: Maximum particle size 3.5–5.0 mm; toasting at 120–150°C for 8–15 min enhances flavor.
• Kernel meal: Water-holding capacity ~2:1 (meal:water). Adjust hydration in baked goods. Store at ≤ 25°C, ≤ 60% RH. Shelf life: 6 months (full-fat), 12 months (defatted).
• Kernel oil: Sensitive to light, heat, and oxygen. Store under nitrogen in opaque containers. Refrigerate after opening. Shelf life: 12 months (unopened, refrigerated).
• Allergen status: Flaxseed is not a major allergen in most jurisdictions. Facility may process other seeds/nuts — verify per site.

8.5 Typical Nutritional Profile

Component	Whole Kernel	Kernel Meal (Full-Fat)	Kernel Oil
Energy (kcal/100g)	530–550	520–540	884
Protein (g/100g)	20–24	22–26	0
Fat (g/100g)	38–44	38–44	99.9
— ALA (g/100g)	20–24	20–24	52–60
Carbohydrates (g/100g)	5–10	5–10	0
Dietary fiber (g/100g)	6–8	7–9	0
Moisture (g/100g)	≤ 8.0	≤ 7.0	≤ 0.1

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9. Related Documents

Document ID	Title
PROD-HULL-001	Flaxseed Hull Processing Document
PROD-HACCP-001	HACCP Plan — Flaxseed Processing
PROD-CLEAN-001	Sanitation Standard Operating Procedures
QA-SPEC-FKM-001	Kernel Meal Finished Product Specification
QA-SPEC-FKO-001	Kernel Oil Finished Product Specification
QA-SPEC-WKF-001	Whole Kernel Flax — Product Specification
QA-MICRO-001	Microbiological Testing Schedule
LOG-RECEIVE-001	Raw Material Receiving & Inspection Protocol
ENG-PRESS-001	Oil Press Maintenance & Calibration Manual
ENG-MILL-001	Hammermill Maintenance & Calibration Manual

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Document owner: Process Engineering Manager
Approval required: Operations Director, QA Director
Review frequency: Annual or upon process change