Two Hour Tonkotsu Ramen! (part 2) / emulsified tonkotsu broth

UPDATE (7/28/2015): I have finally gotten around to repeating this recipe (new article coming soon), and can confirm that an emulsifying agent is necessary, and that egg yolks can work (ensure that the broth is at least 160 F to ensure no risk of bacteria) - just temper the egg yolks first with hot broth, then add to broth and use an immersion blender.

Continuing from last time, more on how to make a rich, creamy tonkotsu ramen broth, and the finished assembled product.

Tonkotsu Ramen Broth

Tonkotsu ramen broth can be summed up as a richly pork-flavored broth, with high gelatin content (leaves a distinctly sticky sensation on your lips), emulsified pork fat, and smoky aromatics.  Traditionally, this broth is made by boiling pork feet and chicken bones for anywhere from 6 to 10 hours, in order to break down all the collagen in bone, marrow, and other connective tissue into gelatin (gelatin is denatured collagen, or collagen protein molecules that have become unfolded).  However, as with other cuts of meat high in connective tissue, this process can be expedited using a pressure cooker.

Pressure cookers accomplish this feat by allowing you to braise meats at higher temperatures than what is otherwise possible.  Water boils when the pressure within the water to enter the vapor phase exceeds the pressure exerted on it by the air.  Under normal atmospheric conditions, water boils when it is heated to a temperature of 100^o C.  Any additional heat added to the water serves to push water into the vapor phase, rather than increasing the temperature.   However, a pressure cooker allows you to increase the pressure exerted on the water, meaning the contained water can be heated beyond 100^o C.  Since temperature is a measure of available kinetic energy, this means that on a molecular level, there is more energy available to facilitate the breaking down of bonds within collagen molecules.  What this means for a piece of meat in a pressure cooker is that it will basically see more heat energy than it would under regular boiling conditions, speeding up cooking times.

While using a pressure cooker does let you break down collagen much faster and achieve a high-gelatin broth in about 2 hours, ­­­­J. Kenji Lopez-Alt noted that what comes out of your pressure cooker is by no means a tonkotsu ramen broth – there is strong pork flavor, but it also tastes oily, as there is a layer of separated pork fat on top.  The problem is that within a pressure cooker, the water is for the most part, not boiling.  If you were to take a cross section of a pressure cooker in action, you would see that the water is totally still.  However, using the traditional cooking techniques, the water is constantly bubbling.  Over the course of several hours, the constant agitation helps to emulsify the pork fat within the watery broth.  However, this is only one way to create an emulsion.

Left: Broth strained out of the pressure cooker after 2 hours cooking.  There is a unappetizing layer of fat on the top.  Center: The equipment necessary, an immersion blender and soy lecithin powder.  Right: The fat has been emulsified into the broth.  Some light foam remains at the top, which subsides after a minute or so.

As you may know, fats and water are basically immiscible, or they do not mix well.  You can see this in some salad dressings, where the oil will separate out into a layer on top of water-based components.  To remedy this, people will either shake up the dressing before using, or they will introduce an emulsifier, like egg yolk.  Emulsifiers are molecules that can form favorable interactions with both water and fat-based molecules.  These interactions support the formation of a stable, homogeneous mix of fats and water.   By introducing a small amount of soy lecithin powder (~1.5 tsp for ~5 quarts broth), and mixing using a immersion blender, I was able to achieve a lighter broth that did not have a separated oil layer and had a taste much closer to that of a true tonkotsu ramen broth.  Fyi, lecithin is one of the main emulsifying agents in egg yolks, so I imagine this could be done with regular egg yolks. However, you would need to do this at a low enough temperature that the egg yolk wouldn’t coagulate due to heat from the broth (thanks to my research into egg boiling, I can say that the broth would need to be <148^o F).

For the condensed recipe (in part borrowed from J. Kenji Lopez-Alt, with modifications), check out my recipe pages for tonkotsu ramen broth, marinated soft boiled egg, and braised pork belly.

Pretty much every component can be made in advance and reheated as necessary.  The broth will solidify in the refrigerator (since it has high gelatin content), but can be microwaved or reheated on the stove.  

Two Hour Tonkotsu Ramen! (part 1) / eggs, noodles, pork belly

Sup suuupp so this article is written for all the ramen aficionados reading.  Anyone who’s been to enough good ramen places knows that tonkotsu broth is where all the flavor’s at.  My favorite ramen places, Ippudo NYC and Sapporo in Boston, have one thing in common: a ballin tonkotsu ramen.  The components are few: broth, noodles, pork belly, soft boiled egg, and misc other toppings (green onions, seaweed, maybe some pickled vegetables or buttery corn). When done right, you achieve a soup that is comforting and umami to the extreme.

Now, there are a few resources out there that describe fairly well how to go about making tonkotsu ramen at home (namely http://www.seriouseats.com/2012/02/how-to-make-tonkotsu-ramen-broth-at-home-recipe.html , which I borrowed from in this article).  However, most of what I’ve seen stick to the traditional & laborious 10-hour process.  With a bit of scientific understanding, I’ve crafted a few shortcuts that cut down the whole process to about 2 hours, take a look!

A sneak preview! Tonkotsu ramen broth with braised pork belly, marinated soft boiled egg, seaweed, crispy shallots and green onion

Soft boiled egg

The egg is possibly simplest component of the ramen that actually needs cooking.  Yet somehow, there’s all sorts of confusion about how to actually cook a soft-boiled egg.  I’ve heard techniques that involve putting eggs into water either before or after bringing water to a boil or simmer, then either killing the heat or maintaining a simmer or boil, lid on or off for 5-7 minutes.  

The problem with the techniques I’ve seen is that they are too vague or suffer from too much variability from kitchen to kitchen.  Since water simmers in a range of about 15 degrees, there’s not any good way of knowing what someone means by a “light simmer” unless you’re using a thermometer.  Removing pots from heat can result in totally different water temperatures depending on volume used and pot material.

My preferred technique: boil water (about 1 qt water: 2eggs, erring on the side of excess water), add ‘Large’ eggs straight from refrigerator, allow to boil for 6 minutes uncovered, remove eggs using tongs/ladle/etc and run under cold water for 60 seconds.  This technique is more reproducible between kitchens since most refrigerators are set to 35-38^oF, so the eggs will always have roughly the same starting temperature.  ‘Large’ eggs are roughly the same size and mass due to careful legal regulation. Water always boils at one temperature at a given elevation (212^o F for most of you).   Finally, using flowing water cools eggs more efficiently than eggs in an ice bath (convective and conductive transfer > conductive transfer only), keeping cooking times more consistent and precise.

Left: Large eggs boiled for 6 minutes, 5 minutes 45 seconds, and 5 minutes 30 seconds from left to right.  The 6 minute egg was significantly easier to de-shell. Right: The same eggs, halved.  The six minute egg had a more firm white, while still liquid yolk. 

Side note: I usually put a lot of trust in Serious Eats food lab articles. However, Serious Eats food lab writer J. Kenji Lopez-Alt recommends simmer eggs at 180 degrees for 6 minutes exactly.  Strangely though, in a picture in the same article, you can see that eggs BOILED for 5 minutes are underdone, and 7 minutes have set yolks.  Clearly, 6 minutes at 180 degrees is not enough.  Indeed, I tested this at home and ended up with raw egg all over my shirt after cracking the shell.  A nice model developed by Dr. Charles Williams (http://newton.ex.ac.uk/teaching/CDHW/egg/#accuracy) estimates that an average ‘Large’ egg from the refrigerator will be done at 5 minutes in boiling water (~57 gram egg with initial temperature of 4^o C will reach a yolk temperature of 65^o C, the temperature at which yolk will JUST begin to coagulate).  

A handy flash animation, courtesy of the University of Oslo, http://www.mn.uio.no/kjemi/tjenester/kunnskap/egg/..

A flash animation to help with the calculations on a variation of this formula can be found here: http://www.mn.uio.no/kjemi/tjenester/kunnskap/egg/.  However, one must keep in mind that the whites will be technically done at this point, but that only means they are opaque and slightly gelatinous, rather than firmly set.  In addition, the model makes the assumption that starting at t=0, the boundary condition of the egg is the same as the temperature of the boiling water (essentially neglecting any thermal properties of the shell).  To illustrate this inaccuracy, using the formula to calculate T_yolk at t=0 gives you a temperature of 27^o C, while the overall initial egg temperature is supposed to be 4^o C.   For the sake of getting slightly more firm whites (easier to peel, and just more appetizing to me), and to account for the need for the egg shell to heat up, I’d tack on at least an extra 30 seconds to the 5 minute estimate.  I would give a more precise correction, but couldn’t find any data on the thermal properties of egg shells.

Braised pork belly

Pork belly is notoriously difficult to cook well, in part due to its non-homogeneous composition of fat and meat and high connective tissue content.   As with any cut of meat with lots of connective tissue, the key is always “low and slow” cooking.  This would be another place where a pressure cooker would come in handy, but I’m assuming that most people out there only have one pressure cooker if any, and we’re going to need that for the broth.  Personally, I’ve found that my pork belly has had satisfactory texture with under 2 hours of simmering on the stove (1 hour, 45 minutes of simmering at 190^o F in the braising liquid resulted in pork belly that was gelatinous at the edges with moist/tender meat in the center).  The recipe on Serious Eats recommends 3-4 hours, likely because the pork belly slabs pictured were roughly double the width of mine.  The energy required to heat a piece of meat to “done-ness” is proportional to volume, but heat transfer is proportional to surface area.  Therefore, a cylinder of pork belly that has twice the width of mine, doubling the volume, only has 1.5x the surface area.  By taking a ratio of the surface area-to-volume ratios, I estimate that the larger cylinder would take 4/3 as much time, or that my cylinders would be done in ~2.25 hours. Close enough.

What’s most important is to constantly monitor the internal temperature of the meat-side of the pork belly slab.  Thinner slabs, like mine, will cook faster, and once it hits ~155^o F, it’s time to remove it from the pot.  The only disadvantages of thinner slabs is that they are a bit trickier to slice, and the ends may be slightly drier than the interior (however, these end pieces also tend to soak up more of the marinade, so no big deal).  I recommend letting your cooked pork belly rounds sit in the freezer for 15 minutes or more, and for very consistent slicing, use a mandolin.

Left: Approximately 1" pork belly slabs tied into cylinders.  Center: Uncooked pork belly rounds in marinade.  Right: Pork belly rounds after 1 hour of braising.

Ramen noodles

Ramen noodles are traditionally hand-pulled from dough that has a gluten structure that permits stretching without breaking.  I’ve given this a try for several days, and decided it’s ultimately not worth it.  Half the battle is finding the right dough formulation (lye, water, and protein content) that results in the right amount of gluten formation, and the other half is a long process of kneading, stretching and pulling.  While I’ve thought of shortcuts for the kneading and pulling process, I have no real way of knowing if I’m actually working with a proper dough formulation to begin with.  There doesn’t seem to be much in the way of improved flavor or texture through making them at home, certainly not enough to justify the days of practice it would take to master this technique.

Be sure to check out part 2 for the 2-hour tonkotsu broth!

For the condensed recipe (in part borrowed from J. Kenji Lopez-Alt, with modifications), check out my recipe pages for tonkotsu ramen broth, marinated soft boiled egg, and braised pork belly.

Pretty much every component can be made in advance and reheated as necessary.  The broth will solidify in the refrigerator (since it has high gelatin content), but can be microwaved or reheated on the stove.