Stocks & broths
Bone Broth
Fond d'os · A savory liquid made by simmering animal bones — often roasted first — in water with a measured dose of acid for an extended period, until collagen-rich connective tissue converts to gelatin and minerals are extracted from the bone matrix. Distinguished from quick stock by its 12–24 hour cook time and its primary goal of gelatin extraction, not merely flavor infusion.
The formula
1 kg roasted bones : 2 L cold water : 30 ml (2 tbsp) acid (wine or vinegar)
Scale by weight of bones. Increase water only slightly — a concentrated broth is the goal. The acid is non-negotiable for proper mineral and gelatin extraction.
Identity
- Collagen converts to gelatin — broth sets firmly when chilled (true test)
- Acidified cold water started — ensures maximum extraction from bone matrix
- Roasted bones — Maillard compounds give depth, color, and savoriness
- Never boiled — a bare simmer (85–90 °C) yields a clear, clean result
- Long cook — 12 h minimum for poultry, 18–24 h for beef/pork bones
- No seasoning added during cook — finished broth seasoned to taste at service
Ingredients
| Base | Animal bones (beef, pork, veal, poultry, or fish) | Knuckle, femur, and marrow bones preferred for collagen and fat content. 1–2 kg for a 2 L batch. |
| Liquid | Cold water | Enough to cover bones by 2–3 cm. Hard tap water is acceptable; filtered water minimizes off-flavors. |
| Acid | Wine (red or white) or distilled white vinegar | 30 ml per kg of bones. Lowers pH to ~4.5–5, demineralizing bone matrix and enabling collagen solubilization. More is not better — excess acid toughens protein. |
| Aromatics | Onion, carrot, celery (mirepoix) | Optional but traditional. Use raw or roasted alongside bones. Do not overwhelm the mineral-savory backbone. |
| Aromatics | Bay leaf, thyme, parsley stems | Classical bouquet garni. Added after skimming phase, removed before final straining. |
| Seasoning | Coarse salt | Added only at the table or at final service. Never during the cook — salt impedes collagen extraction and produces a bitter, flat broth. |
Method
- 1Roast raw bones at 200 °C (400 °F) for 30–45 min, turning once, until deeply browned.The Maillard reaction between amino acids and reducing sugars on the bone surface creates hundreds of flavor compounds (pyrazines, furans, thiazoles) that infuse the broth with savory depth. Unroasted bones yield a pale, one-dimensional liquid.
- 2Place roasted bones in a stockpot or heavy Dutch oven. Cover with cold water and add acid. Do not add salt.Cold water ensures slow, even heating as the pot comes to a simmer, maximizing extraction time. Acid begins the demineralization of the bone matrix. Salt during cooking causes protein to denature prematurely and produces bitter notes.
- 3Bring to a full boil over high heat, then immediately reduce to a bare simmer (85–90 °C). Skim the grey foam that rises for the first 15–20 minutes.Boiling momentarily coagulates serum proteins into visible foam; immediate skimming removes them before they disperse into the liquid. Once the simmer stabilizes, the broth remains clear.
- 4Add aromatics (mirepoix, bouquet garni) after the skimming phase. Maintain a bare simmer, partially covered, for 12–24 hours depending on bone type.Poultry bones require 12–15 h; beef and pork require 18–24 h. The extended exposure at sub-boiling temperature allows collagen Type I to hydrolyze into gelatin — a process requiring sustained warmth but destroyed by boiling.
- 5Strain through a fine-mesh sieve lined with damp cheesecloth. Do not press the solids.Pressing extracts bitter compounds from the bone solids and cloudiness from any debris. Cheesecloth catches fine particulate while letting gelatin pass freely.
- 6Cool rapidly in an ice bath or by transferring to shallow containers. Refrigerate. Optionally defat the surface layer before reheating.Rapid cooling inhibits bacterial growth in the danger zone. Removing the congealed fat layer improves flavor purity and extends refrigerated shelf life.
Techniques that matter
Maillard reaction
Roasting bones before simmering generates savory, complex aroma compounds (pyrazines, heterocyclic amines) that dissolve into the broth and define its depth.
Collagen hydrolysis
Sustained low-temperature cooking (65–85 °C) over 12–24 hours allows collagen Type I to gradually denature and convert to gelatin — the protein that gives the finished broth its body, viscosity, and characteristic silky mouthfeel.
Acid-aided demineralization
Dilute acid lowers the pH of the cooking water, partially dissolving the calcium phosphate matrix of bone. This exposes more collagen surface area to the water and enables extraction of minerals (calcium, magnesium, phosphorus, amino acids) that contribute to the nutritional profile.
Bare simmer (not boil)
Boiling (100 °C) agitates protein coagulants into suspension, clouding the broth. A bare simmer at 85–90 °C maintains clarity while keeping extraction active. A pot of water at a true simmer shows occasional small bubbles, not a rolling boil.
Degreasing
Rendered fat from marrow bones rises and congeals on cooling. Removing it prevents rancidity during storage, improves flavor, and allows the broth to be used in low-fat applications.
Variations & derivatives
Blonde bone brothFrench classical
Bones are not roasted but blanched first to remove impurities, then simmered. Produces a pale, delicate-flavored broth used in fine sauces and clear soups. Less gelatinous and savory than the roasted version.
Brown stock (Fond brun)French classical
Bones are roasted at higher heat (220 °C) with tomato paste added for the last 20 minutes, deepening color and umami. Longer aromatics roster. The classic base for demi-glace.
Poultry bone brothUniversal
Uses chicken or turkey carcasses. Shorter cook time (8–12 h) sufficient for lighter bones. Traditionally finished with a small amount of dissolved arrowroot for clarity in clear soups.
Fish bone broth (Fumet)French classical
Fish bones (sole, turbot, or other white fish) simmered 30–45 min only. Acidulated water with lemon juice. No mirepoix — only fennel or a hint of white wine. Used as the base for maritime sauces and chowders.
Pho bone brothVietnamese
Beef bones roasted until charred, then simmered 12–18 h with charred onion, ginger, and spices (star anise, cinnamon, clove, coriander). Fish sauce and rock sugar added in final 30 minutes. Served over rice noodles with sliced beef.
Used in these dishes
Substitutions
- Bone broth → Quick chicken or beef stock — Simmer bones 45–60 min with aromatics. Lacks gelatin body and mineral depth. Use only when time is unavailable — the result is a flavored liquid, not bone broth.changes result
- Bone broth → Purchased commercial broth — Commercially sterilized broths have been boiled and homogenized, destroying gelatin and most volatile aromatics. Serviceable for braising but not as a foundation for soups or sauces requiring body.changes result
- Acid (vinegar) → Lemon juice or wine — Either works; wine adds flavor compounds beyond pure acidity. White wine is neutral; red wine adds color and tannins; lemon juice adds brightness. All perform the demineralization function.
- Fresh bones → Frozen bones — Frozen then thawed bones are actually preferable — the freeze-thaw cycle fractures bone cell walls, improving both mineral and gelatin extraction.
Troubleshooting
Broth is cloudy and opaque
Boiling during cooking (agitates protein coagulants into suspension) or insufficient skimming during the first 20 minutes → Next batch: maintain a bare simmer, never a rolling boil. For the current batch, fine-strain through cheesecloth — cloudiness cannot be fully removed but can be reduced.
Broth does not set to a gel when chilled
Insufficient collagen extraction — bones were too old (depleted of collagen), cook time was too short, or acid was omitted or insufficient → Extend cooking time to the full range for the bone type. Add 15 ml more vinegar and simmer 4–6 additional hours. Use younger, fresher bones with visible cartilage and joint surfaces.
Grease layer difficult to remove; broth tastes fatty or rancid
Fat wasn't removed before refrigeration, or broth was stored too long → Skim the congealed fat layer with a spoon or spider after refrigeration. For future batches, defat immediately after straining using a wide-mouth ladle or fat separator.
Bitter or astringent flavor
Salt added during cooking, excessive acid (> 60 ml per kg bones), or over-reduction of the broth → Add water to dilute and reheat for service. Reduce acid to 30 ml per kg bones maximum. Never add salt until the broth is finished and tasted.