Given:
Taste preferences for cooked meat aside: Could one theoretically just wash a raw steak with soap and water, and then not have to worry about foodborne illness?
No, you can't. Your assumptions are both wrong.
The inside of a steak is sterile and the bacteria are only on the outside
This isn't true. Bacteria enjoy eating stuff wherever they find it. There are more of them on the surface, but the inside is certainly not sterile! They go in through microscopic lesions - after all, they are microscopic too.
After handling raw steak, one typically washes hands with soap and washes knives with dishwashing liquid and a sponge, which seems to be enough to remove bacteria
This is enough to remove the whole medium in which bacteria can thrive - that is, raw meat juices. After it, your knives can sit in the drawer at room temperature, and any leftover bacteria trying to start a colony will starve and dehydrate. The bacteria left on your hands will not be able to outcompete your own commensals. If you wash steak, you won't be able to remove the food for the bacteria, they eat the steak itself - and cling to it for dear life, so you won't be able to remove them all, just reduce them.
The "reduce them" part is what has lead people to start washing in the hope of cooking meat with less bacteria on it, but it turns out that in practice, it's counterproductive, because of the cross contamination risk.
Desinfecting meat is a thing, but it's done on a commercial scale, e.g. when producing hamburger patties, and not done with soap. They then have to continue treating the meat to remove the stink of the disinfectant. Also, it achieves a longer shelf-life in high-risk environments (such as when mixing the meat of thousands of cows in a single batch), but certainly doesn't make the meat safe for raw consumption.
Meat of a healthy animal is, by definition, sterile. That is why it is so important to get the intestinal tract out undamaged. So healthy meat is not contaminated from the start.
Of course, in the meat industry, especially of certain nasty jurisdictions, there is little hygiene, and the animals are often sick or fed antibiotics, or both (due to breeding resistant bacteria). Often, it could not even be sold without prior disinfection.
And of course, if you take it out, it will instantly get contaminated on the outside in any non-fully-sterile environment. (Including the skin and intestine!) The question is just how much?.
And that depends on the temperature, humidity and amount of light, as well as porosity and damage (rips along the cutting surface), but meat has blood vessels, lymphatic vessels, pores (esp. chicken), and other means to get into it. Also, the bacteria of certain environments can handle lower temperatures. (This is why fish needs be colder than fridge temperatures: Their natural environment is often already that cold.)
So the bacteria will, over time, get in there. And the more they can eat in there, the more gaps there will be for more bacteria.
Now of course, if you wash it hard enough, you can theoretically wash those bacteria out there again too. But as you can imagine, over time that has to get closer and closer to just destroying the meat really quickly. Like … hours. (Imagine your meat being marinated in soapy water, then washed out, and repeat. If it then still tastes of anything, it will taste of soap. :)
(To be precise, some things aren’t soluble in water nor fat, and therefore can’t be cleaned with soapy water. But this is such an exception for anything living, that I think it it is negligible for this situation.)
In any case, if the butcher is actually serious about food hygiene, and the farmer is actually serious about keeping their animals healthy, almost any meat can be eaten raw for a certain time after. (Bats being a critical exception, since their immune system is so extreme that they just aren’t affected by most pathogens, and carry them happily.)
This is common practice in may countries. Japan has sushi (raw fish). France as steak tartare (raw minced beef). Germany has Mettbrötchen (raw minced pork). In Germany, meat cannot even be sold if a veterinarian doesn’t give their approval before and after butchering. So even minced meat is sold for raw consumption on the same day, and consumed (on bread) a lot, as a breakfast or snack.
So my real answer would be, that washing it is unnecessary, and based on assumptions stemming from already bad (and here in Germany illegal) practice by those who sold that meat.
This was a major conflict during “free trade” negotiations between the EU and USA, for example.
I think this has already been done for a long time. Not all pathogens are destroyed by the pH of lemon, but many are and enough to render them safe. Soap would destroy better, but taste worse and might not be as safe even after rinsing.
from https://en.wikipedia.org/wiki/Ceviche
Ceviche[1][2] (Spanish pronunciation: [seˈβitʃe]) is a Hispanic America dish typically made from fresh raw fish cured in fresh citrus juices, most commonly lime or lemon.
https://www.youtube.com/watch?v=h-DpNvYkDt0
Transcript:
0:09 now the water we'll be using came from a
0:11 pond and it's been sitting stagnant for
0:12 weeks as you can see it's completely
0:14 infested with some kind of rod-shaped
0:16 bacteria I added the lemon juice here
0:18 and you can see it take effect almost
0:20 immediately as it washes over the little
0:22 rods and they all stop moving lemon
0:24 juice is around 90 water with the
0:26 remaining 10 percent being natural acid
0:28 sugars vitamins flavonoids and terpenes
0:31 typically four to six percent of that 10
0:33 percent is citric acid which is doing
0:35 most of the heavy lifting and getting
0:37 rid of these germs here since it's such
0:39 a low PH citric acid can penetrate the
0:41 bacterial cell membrane and cause
0:43 important intracellular components to
0:45 leak out resulting in the death of the
0:46 bacteria it also contains other
0:48 antibacterial compounds like limonene
0:51 pinene and citrol which are kinds of
0:53 terpenes that can inhibit the growth of
0:55 bacteria by disrupting their cell
0:56 membrane and metabolism
