Tough Cuts Made Tender.
At 90 °C a shank is tender in four hours and gives up a third of its juice. At 70 °C it takes half a day and keeps more. Both are right; they are different dishes.
Tough cuts become tender in one way: their collagen, the sheaths and tendons that make them chewy, shrinks above about 60 °C and then slowly dissolves into gelatin (VI.6). The dissolving is a reaction with a steep temperature dependence, so it takes most of a day at 65–70 °C, about half a day at 75 °C, three or four hours near 90 °C and a couple at the boil (XVI.4). Meanwhile the muscle fibres have long since passed every temperature at which they tighten, so they lose juice according to how hot they are (XVIII.3).
That is the trade-off. A traditional braise at a bare simmer (90–95 °C) is quick and loses about a third of the meat's weight; the gelatin, the rendered fat and the sauce make it succulent anyway. A low oven (around 80 °C) or a water bath at 65–75 °C (XVI.7, XXXIII.6) takes much longer and keeps the meat juicier and more like a steak in texture. The cut matters too: pork belly, half fat, stays moist whatever you do; shank, lean and full of collagen, needs care. The workshop sets the temperature.
Below: hours for 90 % of the collagen to turn to gelatin (course kinetics), and the juice the fibres lose (course loss curve), at the temperature you choose, for the cut you choose with its fat content.
- Explain how collagen makes tough cuts tender.
- Weigh time against juiciness.
- Choose a cut for a braise.
- Cook 红烧肉 and other belly dishes.
Hot and quick, or cool and slow
In the course kinetics, 90 % of the collagen dissolves in about 13 hours at 70 °C, 7 at 80 °C, 3.8 at 90 °C and 2.2 at 100 °C; the fibres lose about 24 % of their weight at 70 °C and 35 % at 90 °C. Pork belly is about 53 % fat and shank 4 %: the belly's rendered fat coats every fibre and it tastes rich and moist at any of these temperatures, while a shank braised hard is better sliced thin and served in its gelatinous liquid.
Practical braising (XVI.4): brown the meat for flavour (VIII), add liquid to come part way up, cover, and keep it at a bare simmer on the hob or in a 140–150 °C oven (the liquid settles near 90–95 °C). Test with a fork: done when it slides in without resistance. Cool it in its liquid so it reabsorbs some juice and the fat can be lifted off cold. 红烧肉 and 东坡肉 are belly braises of exactly this kind: blanched, browned in caramel, simmered for one to three hours in soy, wine and sugar until the fat is trembling and the skin is gelatinous. For a steak-like shoulder or short rib, cook it sous vide at 60–70 °C for one to three days.
Braise two pieces of shin: one at a bare simmer for four hours, one in an 80 °C oven overnight (covered with liquid, starting from a boil). Compare tenderness and juiciness.
Terms
- Braise
- Cooking slowly in a little liquid, covered.
- Gelatin
- Dissolved collagen; it makes braises succulent and sets when cold.
- Low and slow
- Long cooking at moderate temperature for tough cuts.
- Fork-tender
- Soft enough for a fork to slide in without resistance.
Sources
- A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.
- D. E. Baldwin, A Practical Guide to Sous Vide Cooking (2008–2012) and "Sous vide cooking: a review", Int. J. Gastron. Food Sci. 1, 2012.
- USDA FoodData Central, SR Legacy (April 2018), public domain.
- H. McGee, On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed., Scribner, 2004.