Sugar and Maillard

Technique:transforming sugar and onions through heat

Heating sugar to 160-170 °C: it melts, colors through five stages and develops a complex bittersweet flavor. The foundation of crème brûlée, tarte tatin and caramel ice cream: dry or wet, each with its own control.

160°C melting point of sucrose (onset of caramelization, McGee 2004)

170-185°C optimal caramel color and flavor range

110°C caramelization point of fructose (lowest sugar, Greweling 2010)

200°C burning point: above this temperature caramel becomes bitter and unusable

Requirements

Fine granulated sugar or cane sugar Heavy-bottomed pan of stainless steel or copper (NO non-stick) Sugar thermometer (up to 250 °C) Ice water bath for emergency stop Silicone spatula (heat-resistant up to 230 °C)

In brief

[DEFINITION] Definition: Caramelizing

Caramelizing is the thermal conversion of sugar by heat without the presence of nitrogen: a pyrolytic process in which sucrose breaks down into simpler sugars and new aroma compounds (diacetyl, aldehydes, furanones) form. This gives caramel its characteristic brown color, nutty flavor and bitter aftertaste at high temperatures.

Sucrose melts at 160 °C and caramelizes in stages up to 200 °C (McGee, 2004)
Dry caramelizing: faster but less controllable, risk of hotspots and uneven browning
Wet caramelizing: sugar dissolved in water (2:1 sugar-to-water), slower and more even (CIA, 2011)
Caramel vs. Maillard: caramelization = pure sugar, Maillard = sugar + amino acids (Modernist Cuisine, 2011)

Applications of caramelizing

Caramel for desserts: dry and wet

Dry caramelizing: sprinkle sugar into a heavy-bottomed pan, heat on medium without stirring until the sugar begins to melt at the edges, then gently swirl. Wet caramelizing: dissolve sugar in water (2:1) and boil to 175-185 °C. CIA (2011): wet caramelizing offers more control for beginners. Greweling (2010) describes applications: caramel ice cream, caramel cream, caramel praline, caramel sauce (crème caramel topping). Crème brûlée sugar crust: directly dry-caramelized with a blowtorch.

Caramelizing onions: Maillard reaction

Caramelizing onions is technically a combination of the Maillard reaction (amino acids + sugars) and caramelization (fructose in onions). McGee (2004): onion contains 5-8% fructose and sucrose; fructose caramelizes as low as 110 °C. Properly caramelized onions require 45-60 minutes on low to medium heat, not 10 minutes as popular recipes claim. CIA (2011): too high heat produces charred outer layers with raw interior; low and slow is the only method. Result: deep red, soft onions with concentrated umami.

Caramelized sugar for decoration

Caramelized sugar for decoration: spun sugar, praline, croquembouche and mirror caramel. Greweling (Chocolates and Confections, 2010): for decorative applications, heat dry to 155-165 °C (light amber, flexible), for praline to 175 °C (nutty) and for croquembouche sugar threads to 185-190 °C (dark, brittle). CIA (2011): add a drop of citric acid or cream of tartar to wet caramel to prevent crystallization (acidic compounds create invert sugar which inhibits sugar crystallization).

Harold McGee, On Food and Cooking (Scribner, 2004); Modernist Cuisine, Vol. 4 (The Cooking Lab, 2011); Peter Greweling, Chocolates and Confections (Wiley, 2010)

The science of caramelizing

Sugar chemistry during caramelization

Sucrose = glucose + fructose (glycosidic bond). At 160 °C the bond breaks: free glucose and fructose caramelize separately. Fructose caramelizes faster (110 °C) than glucose (150 °C). The products are hundreds of new compounds: diacetyl (buttery flavor), acetaldehyde (fruity), furanones (caramel), 5-HMF (bitterness at high temp). McGee (2004): the color deepens because the products absorb light in the visible wavelengths.

Temperature stages of caramelization

McGee (2004) and Greweling (2010): light amber 160-170 °C (soft, fruity), gold 170-180 °C (nutty, complex), dark amber 180-190 °C (intense, slightly bitter), burnt 200+ °C (too bitter, unusable). The transition is rapid: a 10 °C temperature rise changes the caramel completely. A sugar thermometer is mandatory for precise control.

Preventing crystallization

Sugar re-crystallizes when a single sugar molecule forms a crystallization nucleus: this produces a white, grainy caramel. Prevention: (1) no undissolved sugar on the pan wall (use a wet pastry brush to keep the wall clean), (2) add an inverting agent (lemon juice, glucose, cream of tartar), (3) do not stir after 110 °C. CIA (2011): copper caramel pans are superior due to even heat conduction.

Melted sugar is extremely dangerous: it reaches 150-190 °C and adheres to skin on contact, causing deep burns. Always use heat-resistant gloves and work at a safe distance. Never pour water into molten caramel: explosive steam formation. Burn treatment: cold running water for 10-20 minutes, never ice. Always use a heavy-bottomed pan: non-stick coatings deteriorate at caramelization temperatures.

Step-by-step method

1

Cut onions into rings or half-rings

Cut 1 kg of onions into half-rings of 3-5 mm thickness. Even thickness is essential for even caramelization.
2

Heat the pan with oil and butter

Heat a heavy-bottomed pan on medium-high heat. Add 2 tablespoons of olive oil and a knob of butter. Butter provides flavor, oil raises the smoke point.
3

Add onions and salt

Add all the onion and sprinkle with 1 tsp salt. Salt draws moisture from the onion: this accelerates the initial sweating phase. Stir to combine.
4

Cook slowly on low-medium heat

Reduce to low-medium heat. Stir every 3-5 minutes. The onions first become translucent (15 min), then yellow-gold (30 min), then deep brown-red (45-60 min). Patience is the only technique.
5

Check caramel color and deglaze

After 45-60 minutes the onions are deep brown and sweet. Deglaze if desired with a splash of wine or balsamic vinegar for extra depth. Season with pepper.

HACCP and safety when caramelizing

Burns from melted sugar

Melted sugar is at 150-190 °C and adheres to skin on contact: it cools more slowly than water and causes deep burns. Use heat-resistant gloves. Burn treatment: 10-20 minutes cold running water, never ice, never cream or butter. For severe burns: seek immediate medical attention (Occupational Safety guidelines).

Steam explosion when water meets hot caramel

Never pour water or cream into molten caramel above 150 °C: explosive steam formation causes spattering of 185 °C sugar. Always add liquid ingredients slowly and from the edge of the pan, or remove the pan from heat and allow 10-15 seconds of cooling before adding.

Storing caramelized products

Sugar-based caramel products are non-perishable due to low water content (water activity below 0.6). Caramel sauces with cream: treat as dairy, store at 4 °C, maximum 5 days. Caramelized onions: shelf life of 3-5 days at 4 °C, or freeze (NVWA).

Caramelization stages and applications

Temperature	Color	Flavor	Application
155-160°C	Light gold	Soft, fruity	Caramel sauce, glaze
165-170°C	Amber gold	Nutty, complex	Praline, crème caramel topping
175-185°C	Dark amber	Intense, slightly bitter	Crème brûlée, caramel praline
185-195°C	Deep brown	Strongly bitter	Bittersweet sauces, coloring agent
200°C+	Black	Burnt	Not usable

Harold McGee, On Food and Cooking (Scribner, 2004); Peter Greweling, Chocolates and Confections (Wiley, 2010)

Food cost and caramelizing

Caramelizing onions: 1 kg raw onion (0.40-0.80 euros) yields 200-250 g caramelized onion: high added value for a low purchase price
Sugar for desserts: 100 g of sugar for caramel costs less than 0.15 euros: the labor and technique are the value, not the ingredient
Caramel praline: coating nuts with caramel: almonds + sugar + a small amount of labor = praline with a selling value of 3-5x the ingredient cost
Crème brûlée: caramelizing the sugar layer with a blowtorch gives the dish its signature and justifies a higher price

Frequently asked questions

What is the difference between caramelization and the Maillard reaction?

Caramelization: purely thermal conversion of sugar without amino acids, at 110-200 °C depending on the sugar type. Maillard reaction: reaction between sugars AND amino acids at 140-165 °C, producing browning in meat, bread and coffee. Modernist Cuisine (2011): onion browning involves both: Maillard through amino acids + sugars, caramelization through fructose. Sugar caramel (dry) is pure caramelization: no amino acids present.

Why does my caramel crystallize?

Sugar crystallization occurs when: (1) the pan wall contains undissolved sugar (use a wet pastry brush to keep the wall clean), (2) stirring above 110 °C (movement creates crystallization nuclei), (3) no inverting agent is present. Solution: add 1-2 ml lemon juice or 1 tbsp glucose syrup when wet-caramelizing. Glucose syrup is non-crystallizable and prevents sugar crystallization (Greweling, 2010).

How long does it take to caramelize onions?

Properly caramelized onions require 45-60 minutes on low to medium heat. Faster via high heat produces charred outer layers with raw interior: this is frustrated Maillard, not caramelization. CIA (2011): patience is the only technique for true caramelized onions. Trick: add a pinch of baking soda (raises pH, accelerates Maillard) for 20% shorter caramelization time, but note that the onions become softer.

At what temperature is the caramel done?

Depends on the application: 155-165 °C for light caramel sauce and crème caramel topping (mild, fruity). 165-175 °C for praline and caramel ice cream (complex, nutty). 175-185 °C for crème brûlée sugar crust and dark caramel sauces (intense, slightly bitter). Above 190 °C: too bitter for most applications. Always use a sugar thermometer (McGee, 2004).

Can I make caramel without a sugar thermometer?

With visual indicators yes, but less precisely: light gold = light caramel (ready for caramel sauce), dark amber = dark caramel (for crème brûlée). Water test: a drop of caramel in cold water produces a soft ball at 155-165 °C; a hard, brittle ball at 175-185 °C. CIA (2011): for professional production a sugar thermometer is indispensable for consistent results.

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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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Sources and legal information

Harold McGee — On Food and Cooking (Scribner, 2004) — caramelization stages and sugar chemistry
Modernist Cuisine, Vol. 4 — The Cooking Lab (Nathan Myhrvold, 2011) — caramelization vs. Maillard
CIA (Culinary Institute of America) — The Professional Chef, 9th edition (Wiley, 2011)
Peter Greweling — Chocolates and Confections, 2nd edition (Wiley/CIA, 2010) — sugar temperatures and crystallization