1. How the First Pork Cutlet at Renkatei in Ginza Was Served with Vegetables and Sauce
The Ginza Western-style restaurant Renkatei is said to have opened in 1895 (Meiji 28). Its signature "pork cutlet" was based on the French dish *côtelette* [1]. While it is often viewed as the ancestor of today’s tonkatsu, the exact origin is debated, with several theories existing [3][3]. The most surprising difference was the plate itself. Originally, it was a Western-style dish served with cooked vegetables and poured over with demi-glace sauce. Shredded cabbage was not yet the main accompaniment [3].
There are also competing stories about the origin of the shredded cabbage. One theory suggests that the first owner of Renkatei invented the style of serving shredded cabbage with sauce, making it the original tonkatsu [3]. Another explanation, featured in a TV program, claims that when the restaurant was short-staffed, they switched to shredded cabbage because it required less boiling time and paired well with the sauce. However, this account has not been verified as historical fact [2]. Regardless of which story is true, the dish started in Western-style restaurants. So, what changed to turn that meat into "tonkatsu"?
2. Three Changes That Turned Pork Cutlet into Tonkatsu: Thicker Meat, More Oil, and Chopstick-Friendly Cuts
The transformation involved three main shifts: cutting the meat thicker, deep-frying it in abundant oil, and cutting it so it could be eaten with chopsticks. This direction of change is described in historical accounts [3]. The first two changes happened gradually. It is said that by 1899 (Meiji 32), Renkatei was using pork instead of beef and frying it like tempura in lots of oil, rather than sautéing it. Note that the founding year (1895) and this menu change (1899) are separate events, and dates vary by source [3].
The decisive change in thickness occurred in the Showa era. In 1929 (Showa 4), a cook named Shinjiro Shimada at the Western restaurant Ponchiken in Okachimachi is said to have devised a method to cook thick slices of 2.5–3 cm (about 1 inch) meat thoroughly. This is considered close to the current form. While Shimada is sometimes called the "inventor," identifying the exact origin is difficult; there is also a theory pointing to the restaurant "Oroji" in Shinjuku in 1921 [3]. In Ueno, thick-cut tonkatsu became a staple Western dish in the early Showa period. The store Isenshin, founded in 1930 (Showa 5), continued to serve "soft tonkatsu that can be cut with chopsticks," while Horaiya, founded in 1914 (Taisho 3), is said to have started double-frying [4]. Deep-frying in plenty of oil is said to result in less moisture evaporation, creating a moist and soft texture [3]. So, what happens to thick meat when heated?
Safety note: When cooking at home, ensure the meat is cooked through completely. Always handle hot oil with adult supervision.
3. Why Cooks Cut Incisions in Thick Pork Before Frying
Pork is an ingredient that tends to shrink and curl when heated. Therefore, when making tonkatsu, incisions are made with a knife into the tough connective tissue between the fat and the red meat. This process is called making cuts in the tough connective tissue (*suji-kiri*) [5]. Another method is pounding the meat to loosen the fibers. This is said to even out the thickness, make heat penetrate more easily, and soften the meat [3]. Since thick cuts take time to cook, ensuring uniform thickness helps reduce uneven cooking. Explanations for the depth and spacing of the cuts vary by source. Once the meat’s shape is prepared, the next question arises: what is the standard for "cooked through"?
4. How Cooks Decide Pork Is Cooked Through: The 63°C Heating Standard
For vendors selling food made with pork to general consumers, regulations require heating the center to 63°C (145°F) for at least 30 minutes, or using an equivalent sterilization method (such as 75°C/167°F for at least 1 minute). Since June 12, 2015 (Heisei 27), serving raw pork for consumption has also been prohibited [6]. Comparing these numbers, raising the temperature by 12°C (about 22°F) reduces the required time from 30 minutes to 1 minute. To get heat to the center of thick meat, one approach is to heat longer, another is to use a higher temperature. However, these are hygiene standards for businesses, not standards for taste or home obligations. When frying at home, it is still important to cook the inside thoroughly, and frying oil should be handled with an adult.
Safety note: Always cook pork thoroughly at home and handle hot frying oil with an adult.
5. The Breading Order for Tonkatsu and How Panko Differs from Other Breadcrumbs
The standard order in home recipes is flour, then beaten egg, then panko (breadcrumbs) [3]. The frying oil temperature is generally around 170°C (338°F). A key tip is not to touch the meat for about 20 seconds after putting it in the oil; touching it can cause the coating to fall off. For example, Japan Self-Defense Forces school lunches use 160–170°C (320–338°F). These temperature figures are guidelines, not fixed values [3]. There are two types of panko: fresh (raw) and dried. Fresh panko has more moisture and larger granules, said to create a voluminous, crispy texture. Dried panko is finer and results in a crunchier finish [9]. However, this description comes from one source, and moisture levels vary by product. Recipes commonly use this order. How does the breaded meat behave in the oil?
Safety note: Frying oil should be around 170°C (338°F), and do not touch the food for about 20 seconds after adding it to the oil.
6. What the Breading and Moisture Do Inside the Frying Oil
Experiments have investigated the relationship between moisture and oil. When a model food made of flour and water was fried in 150°C (302°F) oil, the authors inferred that while moisture was evaporating, the pressure of the steam prevented oil from entering. For samples with 80% moisture, oil absorption remained low during frying but increased sharply during cooling [7]. The authors note that much of the explanation regarding gelatinization is speculative. This experiment used a flour-and-water model, not tonkatsu breading itself. However, the idea that oil has difficulty entering while moisture is leaving aligns with the earlier explanation that deep-frying reduces moisture evaporation, keeping the meat moist. Breading also protects the oil. Another study suggested that breaded frying results in less discoloration and off-flavors in the oil compared to plain frying, inferring that the coating suppresses the leaching of components into the oil [8]. A single piece of tonkatsu combines tendon cutting to prevent curling, preparation to even out thickness, heat penetration to the center, and the relationship between breading and oil. How can we observe this ourselves?
7. How to Check Tonkatsu's Thickness and Breading Grains by Looking at the Cut Surface
When eating tonkatsu, look at the cut surface from the side. If you have a ruler, measure the thickness. How does the restaurant’s thickness compare to the 2.5–3 cm (about 1 inch) said to be devised by Shinjiro Shimada? Try cutting it with chopsticks to see if it works. If you have panko at home, check the package label to see if it is fresh or dried. Pour the grains onto your palm and compare them; the sizes may differ. Because frying involves splashing oil, always cook with an adult. Among the sources used, Wikipedia’s "Tonkatsu" entry lists references such as Satoshi Okada’s *The Birth of Tonkatsu*. You can read the original articles on restaurant history and oil experiments via the links. The existence of multiple theories about the origin suggests that new materials may still be discovered.
Safety note: Because frying uses high-temperature oil, always cook with an adult.