Does Searing Meat on High Heat Really Seal in the Juices?
― The Sizzle Is the Sound of Water Escaping
“Sear the surface on high heat first, and the juices stay locked inside.” You hear this in cookbooks and in home kitchens alike. But if you weigh meat after cooking it different ways, the seared piece has lost juice just the same. The browned crust is not a “lid”. What decides how much juice you keep is the temperature inside the meat.
You lay a steak in a hot frying pan. It lets out a loud sizzle, and white steam rises.
“First, sear the surface to seal in the flavour,” someone says, as you flip it and brown both sides.
But when you put the cooked steak on a plate, a reddish liquid seeps out around it. So where did the juice you supposedly sealed in come from?
There are only two reasons it can’t be sealed in
The seared surface is a layer of dried, shrunken meat. It has countless tiny cracks and holes, and both water and steam pass right through. The sizzle that never stops while you cook is proof that water keeps escaping.
When meat gets hot, the proteins inside shrink. Like wringing out a wet sponge, the meat itself pushes water out. How much gets squeezed out depends on how hot the centre gets.
In short, whatever you do to the surface, juice will leave once the inside gets hot. Let’s take it step by step.
Why doesn’t the crust act as a “lid”?
When the surface of meat reaches well over 100 °C, its water boils away, it dries out and turns brown. This layer looks hard, but it is not a film that holds water back, the way plastic wrap does. As it dries and shrinks, it cracks into fine pieces and leaves plenty of gaps.
Look at Figure 1. As the water inside the meat warms, it escapes through the gaps in the crust on top and through the exposed sides. On the bottom face, which touches the pan, the water that comes out turns to steam at once. That is exactly the “sizzle” you hear. If the crust really did trap the juice, the noise should die down once the surface was seared. In fact, it keeps going the whole time you cook.
The claim that “searing the surface at high heat seals in the juices” is said to have been put forward around 1850 by the German chemist Justus von Liebig. Spread through cookbooks as the view of a famous scholar, it survives today as folk wisdom. Experiments that weighed meat cooked different ways were already being done in the 1930s. They reportedly found that searing the surface did not reduce the juice lost, and sometimes the loss was even greater.
So what pushes the juice out?
Meat is a bundle of long, thin muscle fibres. Plenty of water is held in the gaps between the fibres and inside them. As meat warms, the proteins that make up the fibres change shape and shrink. This is called “denaturation”.
The shrinking proceeds roughly in stages as the temperature rises. With a centre in the 50s °C, the fibres shrink only a little. Above 60 °C, they shrink much more. The membrane around each fibre also shrinks, and is thought to squeeze the water out as if tightening from the outside.
Use the slider in Figure 2 to change the temperature at the centre of the meat. The hotter the centre gets, the more juice is squeezed out. Whether the surface was seared has almost no effect on this line.
That doesn’t mean there is no point in searing. The browned crust gives cooked meat its savoury aroma and flavour. The aim of high heat is not to “seal in the juices” but to “create a tasty brown colour”.
The most effective step is not to overheat the centre. The temperature inside keeps rising for a while even after you turn off the heat, so take the meat off a little early. Cut straight after cooking and the juice runs out easily, so letting the meat rest for a few minutes before cutting is also a common method.
Summary
Searing the surface on high heat does not seal in the juices. The crust is full of gaps, and the sizzle while you cook is the sound of water continuing to escape. What decides the amount of juice is how hot the centre gets, because meat shrunk by heat squeezes out its own juice.
The crust is for aroma, not a lid.
What protects the juice is the temperature at the centre.
How that browned aroma arises is explained in “Why do cooked foods smell so good?”, and why you rest meat after cooking is explained in “Why do you let a steak rest after cooking?”.
- Prepare two pieces of meat of the same thickness and about the same weight. Weigh each before cooking and note it down.
- Sear one on high heat on both sides first, then turn the heat down low. Cook the other from the start on about medium heat. Cook both until done through.
- When they are done, weigh only the meat, without wiping off the juice on the plate, and compare how many grams each lost.
Cooking time and thickness will change the results, but it should not happen that only the seared piece fails to lose weight. If you have a cooking thermometer, matching the centre temperature makes the comparison easier. Cook chicken and pork thoroughly all the way to the centre.
For those who want to know more ― terms, formulas and links to textbooksEach section is labelled with its level, from middle-school science to university specialist courses
- Middle schoolCovered in middle-school science
- High schoolCovered in high-school chemistry or biology
- High school+Advanced high-school material, or treated as a textbook sidebar
- UniversityNot taught in high school; university specialist courses (food science, meat science)
- ResearchNot yet taught as settled fact even at university; being investigated by researchers now
Middle schoolTerms: this phenomenon has names
- Protein denaturation: when heat or similar changes the shape of a protein. It is why meat changes colour, shrinks and turns firm.
- Change of state (evaporation): liquid water turning into water vapour. This is the sizzle and the steam over the pan.
- Maillard reaction: sugars and amino acids reacting at high temperature to give brown colour and a savoury aroma. This is the job of the crust.
Middle schoolHigh schoolChecking with a formula: how much juice leaves one steak?
Let’s estimate the juice lost when a 200-gram steak is cooked until its centre reaches 70 °C. The symbols are: W is the juice lost (grams), M is the weight of the meat (grams), w is the fraction of the meat that is water, and f is the fraction of that water which is squeezed out.
| In symbols | W ＝ M × w × f |
| In words | Juice lost ＝ weight of meat × fraction of water × fraction squeezed out |
| Where it comes from | A water balance (conservation of mass). Water in the meat does not vanish; it either stays in the meat or leaves it. f is set by the centre temperature, and whether the surface was seared does not enter into it. |
| Weight of steak M | 200 g |
| Water fraction of beef w (varies by cut; a rough guide) | about 0.7 |
| Fraction squeezed out at a 70 °C centre f (rough guide) | about 0.2 |
| Amount in one tablespoon | 15 mL (juice is nearly water, so 15 g) |
| Water in the meat | 200 × 0.7 ＝ 140 g |
| Juice squeezed out W | 140 × 0.2 ＝ 28 g |
| Fraction of the meat’s weight | 28 ÷ 200 ＝ 0.14 |
| In tablespoons | 28 ÷ 15 ≒ 1.9 tablespoons |
By this calculation, nearly two tablespoons of juice leave one steak. By weight, that is a little over 10%. If you stop at a 60 °C centre, f drops to about half by the guide in Figure 2, and the juice lost falls to about half too. Searing on high heat does not make any number in this formula smaller.
High schoolHigh school+Which proteins are doing the shrinking?
High schoolInside a muscle fibre, two kinds of protein, myosin and actin, are lined up. They are the main players in “muscle contraction” in biology class. When heated, the two denature and set at different temperatures, and the fibre shrinks.
High school+In general, myosin is said to denature at lower temperatures and actin at higher ones. Collagen, the main component of the membrane around the fibres, is also said to shrink in the 60s °C. As the centre temperature rises, more of these parts shrink, so the amount of juice released also increases in stages.
UniversityWater-holding capacity and cooking loss
In meat science, the ability of meat to hold on to its water is called water-holding capacity, and the weight lost on heating is called cooking loss. Water-holding capacity changes a great deal with the width of the gaps between myofibrils. It is also known to vary with the degree of ageing, the cut, and the acidity. The Maillard reaction that gives the brown colour proceeds only in the part of the surface that is above 100 °C, and it is a separate phenomenon from the water-holding capacity inside.
📖 Derivations and further reading: Denaturation (Wikipedia, in Japanese) ／ Maillard reaction (Wikipedia, in Japanese)
ResearchWhat is still not clear
- How we sense “juiciness”. The juicy feel in the mouth is thought to depend not only on the amount of water but also on fat and on the saliva released as we chew. How much each one contributes is still being studied.
- The fine structure of the crust. How much do the cracks and holes in the crust change the way steam escapes? Measuring how the surface dries and how the juice inside moves at the same time is hard, and detailed research continues.
- How ageing changes water-holding capacity. Aged meat is said to hold its juice better. Exactly which parts of the proteins change varies with the type of meat, and has not yet been sorted out.
So the content of this article, too, is “an explanation based on what is known now”. The line in Figure 2 and the fraction f in the formula are rough guides for seeing how the mechanism works, and they change with the type of meat and how it is cut.
Links to textbooks (by level)
| Level | Subject / unit | Where in this article |
|---|---|---|
| Middle school | Science: change of state | The sizzle is the sound of water becoming vapour |
| High school | Biology: muscle contraction / Chemistry: proteins | Heat denaturation of myosin and actin |
| High school+ | Chemistry: polymers (advanced) | More parts shrink at each higher temperature |
| University | Food science, meat science | Water-holding capacity and cooking loss |
| Research | Food physical properties, sensory evaluation | How juiciness is sensed, the effect of ageing |
| ― | Link to daily life | High heat is for aroma. To protect the juice, watch the centre temperature |
- Harold McGee, On Food and Cooking (Japanese edition: マギー キッチンサイエンス ―食材から食卓まで, Kyoritsu Shuppan)
- Ministry of Education, Culture, Sports, Science and Technology (文部科学省), Standards Tables of Food Composition in Japan (日本食品標準成分表) (water content of meats)
- Wikipedia (Japanese), “変性” (Denaturation)
- Wikipedia (Japanese), “メイラード反応” (Maillard reaction)
※This article is a general-audience science explainer. The figures given are rough guides and estimates for understanding the mechanism. Results vary with the type of meat, its thickness and how you cook it. For safe cooking temperatures, please also check information from public food-safety agencies.