Ramen broth-making is not merely a matter of a chef’s intuition — it is a continuous series of precise chemical reactions. Simmering bones for hours is, at the molecular level, nothing other than the work of efficiently “extracting” umami compounds and lipids from bones and meat into water, then “binding” (emulsifying) them together.
Why does switching from a conventional stockpot (boiling point 100°C) to a commercial pressure cooker (boiling point 120°C+) so dramatically increase broth umami and create a smoother mouthfeel? Here we unravel that secret from the perspectives of thermodynamics and food science.
The Critical Difference Between 100°C and 120°C: An Explosive Change in Molecular Motion
No matter how powerful the heat source, water in an ordinary kitchen at atmospheric pressure will not rise above 100°C. However, by sealing the interior of a commercial pressure cooker and raising the internal pressure to its limit, it becomes possible to push water’s boiling point above 120°C. A mere 20-degree gap — yet the impact at the molecular level is dramatic.
Thermodynamics: “Molecular Collision Frequency” Skyrockets
Temperature is a measure of the intensity of thermal motion within a substance’s molecules. As temperature rises from 100°C to 120°C, the speed (kinetic energy) of water molecules increases explosively.
Enhanced Penetration: Rapidly moving water molecules instantly penetrate even the deepest micro-structures within pork bones and chicken carcasses.
Increased Destructive Force: Water molecules colliding with the cell walls and tissues of bones at extreme speed are able to physically break down and decompose internal bone structures that conventional stockpots could not destroy even after several hours.
Science-Proven Ultra-Fast, High-Concentration Extraction of Umami Compounds
At the heart of what makes ramen broth delicious are amino acid “glutamate” and nucleotide “inosinate” released from meat and bones. A 120°C environment maximizes the extraction efficiency of these components.
Maximizing “Umami Synergy” in a Short Time
In food science, it is well known that when glutamate (found in kombu and vegetables) and inosinate (from pork, chicken, and seafood) meet in a broth, an “umami synergy effect” occurs — the perceived umami intensity is several to more than ten times stronger than either compound alone.
The “Time-Saving” Advantage That Protects Glutamate from Heat Destruction
In fact, glutamate — the very source of umami — has a weakness: it is sensitive to heat. When simmered slowly for 10–15 hours in a conventional pot, the glutamate that has been extracted gradually breaks down (heat degradation) over time.
With 120°C pressure cooking, all compounds are drawn out at once in a short time (1.5–2 hours) before heat degradation can occur, so the components remain intact and the overall glutamate concentration in the broth is maintained at a very high level.
Pushing Inosinate from Bone Marrow to Its Absolute Limit
The marrow at the center of pork knuckles is packed with inosinate and lipids that form the base of rich, deep flavor. In a conventional 100°C stockpot, it takes enormous time for heat to penetrate through the bone’s hard calcium layer to reach the marrow. In a 120°C high-pressure environment, the bone is literally “pulverized,” allowing every last drop of marrow umami to dissolve into the broth in an instant.
The Mechanism of Collagen “Gelation” and “Auto-Emulsification”
The signature viscosity and creaminess of rich-style ramen — tonkotsu and chicken paitan — are also the product of chemical changes brought about by 120°C high temperature and pressure.
Ultra-Fast Conversion of Hard Collagen into Supple “Gelatin”
Collagen — abundantly found in pig trotters, pig skin, and chicken carcasses — has a rigid triple-helix structure that does not dissolve in water naturally. Converting it into the water-soluble polymer “gelatin” (hydrolysis) requires a large amount of thermal energy.
At 100°C, this decomposition takes an almost unimaginable amount of time. But once 120°C is reached, the collagen structure rapidly undergoes thermal dissociation and dissolves into the broth before your eyes. This gives the broth overwhelming body (thickness) and the supreme, lip-coating viscosity that defines great ramen.
Auto-Emulsification: Miraculously Merging Water and Oil
By nature, water and oil (pork lard, chicken fat) do not mix. To create a creamy, smooth paitan broth, you need to achieve “emulsification” — a state in which oil is dispersed as minute particles throughout water.
The Limits of “Physical Agitation” in a Conventional Stockpot
In a conventional stockpot, chefs forcibly break up bones with a rod and boil the stock vigorously on high heat for hours, using that physical energy to force emulsification. This is exhausting labor, and the moment the heat is reduced, water and oil tend to separate again — an unstable emulsion.
The “Ultra-High-Density Natural Emulsification” Created by 120°C Pressure
Inside a pressure cooker, gelatin (which acts as a natural emulsifier) dissolves out in large, concentrated quantities under 120°C heat. Furthermore, when pressure is suddenly released or when the soup passes through a dedicated valve during transfer, a powerful shear force acts within the broth. As a result, oil particles are broken down to their absolute limit and firmly bonded with gelatin, producing an extremely fine, high-density emulsified broth that never separates — completely automatically, with no human intervention required.
Side Benefits of 120°C Cooking: Eliminating Bitterness and Off-Odors
“Won’t cooking at high temperatures for a short time also bring out unpleasant bitterness and off-odors from the bones?” is a concern shared by many professionals. But from the perspective of food hygiene science, the result is actually the opposite.
High-Temperature Sterilization Cleanses Unwanted Flavors
Small amounts of blood and organic matter remaining on bone surfaces oxidize with prolonged heating, becoming the source of characteristic fishiness or bitterness. The 120°C high-temperature, high-pressure environment instantly thermally decomposes and denatures these odor-causing compounds. At the same time, the powerful sterilization effect of 120°C prevents off-flavors from oxidation before they can develop, resulting in a smooth broth in which only the ingredient’s own pure, clean umami comes to the fore.
Summary: Broth-Making with Thermodynamics on Your Side
A broth simmered with great care for 10 hours is delicious — but not because “time” itself worked any magic. It is simply the result of chemical changes — extraction of compounds and emulsification — that took all that time to finally achieve.
The environment of “120°C and high pressure” realized by a commercial pressure cooker is the scientifically optimal solution for reproducing those chemical changes at the ideal speed and highest concentration. By harnessing thermodynamics — the laws of physics — broth quality improves dramatically and consistently.
If you would like to actually taste a broth that has evolved scientifically, please visit Kitchen Techno’s test kitchen. You can experience for yourself the overwhelming umami concentration that 120°C brings — something that conventional stockpots simply cannot achieve.