The encyclopaedia of gravy
Collagen in bones and connective tissue dissolves into gelatin during long simmering. Gelatin gives stock its body, gloss and lip-sticking texture — and it is the one thing a stock cube cannot supply.
Collagen to gelatin¶
Connective tissue — the stuff that holds muscle to bone and bone to bone — is mostly collagen, a protein whose molecules are triple helices of three intertwined chains.
Heat plus water plus time unwinds those helices. The chains separate, dissolve into the liquid, and become gelatin. The conversion needs sustained temperatures above roughly 70 °C and is slow: hours rather than minutes. This is exactly why stock is simmered for four hours and not boiled for twenty minutes.
What gelatin does in gravy¶
Body. Gelatin molecules are long and they tangle, resisting flow. A stock rich in gelatin is noticeably viscous even without starch.
Mouthfeel. Gelatin coats the tongue and palate in a way starch does not — the distinctive lip-sticking quality of a good jus or a properly reduced stock.
Gloss. Gelatin at the surface gives the shine that professional sauces have.
Emulsion stability. Gelatin helps keep fat droplets suspended, so a gelatinous gravy is less prone to separating. See emulsification in gravy.
The jelly test¶
Chill a stock. If it sets — even softly — it is rich in gelatin and will make an excellent gravy. If it stays liquid, it will taste fine but feel thin, and you will need more flour to compensate.
Where to get it¶
| Source | Gelatin |
|---|---|
| Chicken feet | Exceptional |
| Pork trotters | Exceptional |
| Beef knuckle, shin, oxtail | Very high |
| Chicken wings and necks | High |
| Marrow bones alone | Low — flavour, but little collagen |
| Rib bones | Low |
| Stock cube | None |
See beef stock and chicken stock.
Why cube gravy is different¶
A stock cube supplies salt and flavour compounds but no protein structure. The result tastes savoury but feels thin, which is why cube gravies need more flour to seem substantial — and why they still never feel quite the same. The flour thickens; it does not coat. See stock cubes.
Why slow-cooked meat makes such good gravy¶
A shoulder of lamb or a beef shin braised for hours releases large amounts of gelatin into the cooking liquid. That liquid, skimmed and reduced, often needs no flour at all. See reducing stock.