Blanching
From spinach to tomatoes, from broccoli to fresh pasta. Blanching is the technique that locks in colour, halts enzymes and controls texture.
In brief
[DEFINITION] Blanching is the brief immersion of food in boiling water (100°C), followed by immediate shocking in ice water. The purpose is to halt enzymes that would otherwise cause loss of colour, flavour and nutritional value. (Larousse Gastronomique; Escoffier, Le Guide Culinaire, 1903; Harold McGee, On Food and Cooking, 2004)
- Enzyme inactivation: peroxidase and catalase are the primary enzymes responsible for colour loss and flavour deterioration. Heating above 70°C denatures these enzymes. (Harold McGee, On Food and Cooking, 2004)
- HACCP cooling protocol mandatory: from 100°C to below 7°C within 2 hours (EU Regulation 852/2004, Article 4)
- Salt in cooking water: 10-20g per litre improves osmotic balance and preserves chlorophyll in green vegetables. (CIA The Professional Chef, 9th ed., 2011)
Why blanch — 6 reasons
Halt enzyme activity
Peroxidase, catalase and lipoxygenase cause browning, flavour loss and quality deterioration in vegetables. Blanching denatures these enzymes at temperatures above 70°C. Essential before freezing vegetables — without blanching, frozen vegetables degrade in quality even at -18°C. (CIA The Professional Chef, 2011)
Lock in colour
Chlorophyll in green vegetables retains its vivid green colour with rapid heating followed by immediate shocking. Prolonged heat converts chlorophyll to pheophytin — a dull olive green. (Harold McGee, On Food and Cooking, 2004)
Loosen skins
Tomatoes, peaches and almonds: 30-60 seconds in boiling water loosens the skin from the flesh without cooking the product. The heat breaks the bond between skin and flesh. (Larousse Gastronomique)
Remove bitter compounds
Fresh pasta, chicory and certain nuts: brief blanching removes water-soluble bitter compounds that remain in the cooking water. The product becomes milder in flavour without losing texture or colour. (Escoffier, 1903)
Texture preparation
Soften vegetables for faster finish cooking in the pan or oven, without fully cooking them. A blanched carrot has a shorter cooking time in an oven preparation. (CIA Professional Chef, 2011)
Freezer readiness
EU Regulation 852/2004 stipulates that vegetables must be enzymatically inactivated before freezing. Unblanched frozen vegetables lose colour, flavour and texture even at correct freezer temperatures.
Step-by-step method
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1
Prepare the ice bath
Prepare a large bowl with equal parts ice and cold water. Target temperature: 0-4°C. This is step 1, not step 8: the ice bath must be ready before blanching begins.
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2
Bring plenty of water to a boil
Use at least 5 litres of water per kilogram of product to be blanched. Sufficient water ensures the temperature does not drop too far when the product is added.
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3
Add salt
Add 10 to 20 grams of salt per litre. Salt improves osmotic balance and stabilises chlorophyll in green vegetables. (CIA The Professional Chef, 2011)
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4
Cut the product to uniform size
Uniform pieces cook uniformly. Uneven pieces result in some parts overcooked and others undercooked, which becomes visible after shocking.
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5
Add the product to the boiling water
Add the product. The water will briefly lose its boil: check that it returns to a boil quickly. Adding too much product at once drops the temperature excessively.
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6
Cook for exactly the required time
Use the time table and set a timer. Spinach: 30 to 60 seconds. Broccoli: 2 to 3 minutes. Green beans: 3 to 4 minutes. (CIA The Professional Chef, 2011)
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7
Check the colour
Vivid green in green vegetables is the doneness signal. The chlorophyll has reached its brightest colour but has not yet degraded to the dull pheophytin.
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8
Transfer immediately to the ice bath
Every second of delay costs colour. The cooking process only stops when the core temperature drops below 7°C. Move the product into the ice bath immediately.
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9
Agitate the product in the ice bath
Move the product regularly for even and rapid cooling. Still water around the product slows heat transfer.
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10
Check the core temperature
The core temperature must be below 7°C. This is a requirement of EU Regulation 852/2004, Article 4. Use a probe thermometer to verify with larger products.
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11
Pat thoroughly dry
Dry the product thoroughly before further use. Surface moisture causes splattering when pan-frying or sauteing and dilutes flavour when used in a sauce.
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12
Use immediately or store correctly
Use the product immediately or store it covered at a maximum of 4°C. Maximum shelf life after blanching: 24 hours. Always label with product name and date.
HACCP cooling protocol
EU Regulation 852/2004, Article 4 — mandatory for every food service establishment. From boiling point to safe.
⏱ Cooling rule
- From 100°C to <7°C within 2 hours. This is not recommended: this is a legal requirement (EU Regulation 852/2004, Article 4).
EU Regulation 852/2004, Article 4
Ice bath standard
- Minimum 1 part ice to 1 part water. Measure the temperature of the ice bath before use: target is 0-4°C. A warm ice bath = insufficient shocking.
Water renewal
- Renew blanching water after 3-4 batches. Bacterial load and enzymatic breakdown products increase with reuse of cooking water.
Storage
- Store blanched product at <4°C, maximum 24 hours. Always label with product name, preparation date and time for HACCP traceability.
Never re-blanch
- Never reheat and re-blanch. The product loses texture, colour and nutritional value without any food safety benefit. Process prepared products once only.
Blanching times per product
| Product | Blanching time | Purpose |
|---|---|---|
| Spinach | 30-60 sec | Colour fixation, wilting |
| Peas | 1-2 min | Colour, texture |
| Broccoli | 2-3 min | Colour, enzyme halt |
| Asparagus | 2-3 min | Colour, texture |
| Green beans | 3-4 min | Colour, texture |
| Cauliflower | 3-4 min | Colour, softening |
| Carrots | 3-4 min | Softening |
| Tomato (peeling) | 30 sec | Skin removal |
Source: Culinary Institute of America, The Professional Chef (9th ed., 2011) and Larousse Gastronomique
Frequently asked questions
What is the difference between blanching and poaching?
Why must you shock immediately after blanching?
Do you always need to add salt to the blanching water?
Can you freeze blanched vegetables?
How do you know when vegetables are done blanching?
Why do you blanch tomatoes?
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Informational disclaimer
The information on this page is intended solely for educational and informational purposes for hospitality professionals. KitchenNmbrs B.V. strives for accuracy and timeliness but cannot guarantee that all information is fully correct, complete or up-to-date at all times. Culinary techniques, scientific insights and food safety guidelines may change.
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Applying the techniques described requires professional expertise and training. KitchenNmbrs is not liable for damage, injury, illness or loss resulting from the application of information from this website without adequate professional guidance or verification. Every kitchen, every product and every environment is different: always apply your own professional judgement.
Food safety & HACCP
The HACCP guidelines, temperatures and storage advice on this page are based on Codex Alimentarius (WHO/FAO) as the global baseline standard and EU Regulation 852/2004. Local laws and regulations may differ. Always consult your national food safety authority for the applicable standards in your region:
- Netherlands: NVWA (nvwa.nl)
- Belgium: FAVV (favv-afsca.be)
- Germany: BfR (bfr.bund.de)
- United Kingdom: FSA (food.gov.uk)
- United States: FDA (fda.gov) — FDA Food Code
- EU general: EU Regulation (EC) 852/2004 on food hygiene
- International: Codex Alimentarius CAC/RCP 1-1969 (revised 2020)
Allergens & dietary information
Allergen information is indicative. When in doubt about allergens in preparations, always contact the supplier or a certified allergological adviser. KitchenNmbrs accepts no liability for allergic reactions or diet-related harm.
Copyright & sources
All sources mentioned (Escoffier, McGee, CIA Professional Chef, etc.) are the property of their respective publishers and authors. KitchenNmbrs cites these works in accordance with fair use for informational purposes. The source attribution at the bottom of each technique page is not a complete bibliography but an indication of primary sources consulted.
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- CIA Professional Chef (Wiley, 9th ed. 2011)
- Harold McGee — On Food and Cooking (Scribner, 2004)
- Larousse Gastronomique (Larousse, 2009)
- EU Regulation 852/2004, Article 4 — cooling protocol
