In case you hadn’t noticed, we like meat around here. Don’t get me wrong, we like our vegetables, too, but we do have a penchant for animal protein.
A standing rib roast is an expensive treat we might enjoy once a year, so I try to get it right. Our butchers always have beautiful rib roasts around special holidays, so I assume that it’s a tradition for many families.
Since I have been experimenting with koji, and its effect on proteins, I decided try koji aging a rib roast. The idea here is that the enzyme-rich koji produces a similar effect to dry aging.
I’ve gotten pretty good at growing and producing koji rice. Excess can be frozen for later use. In this case, I made a fresh batch of koji rice just for this project, but frozen or purchased packages of koji rice or even shio koji can be substituted. If using shio koji, I wouldn’t add more salt as the ship koji already contains salt. Control of the salt content here is one reason I used koji rice.
Dry aged beef tastes “beefier” than fresh beef. The reason for this is two-fold. First, dry aging, as the name implies, causes the beef to lose water content. Typically a 10-15% loss of water in the meat, dry aging will concentrate flavor. Second, meat contains natural enzymes which will serve to break down protein and fat to increase tenderness and enhance flavor. Dry aged beef normally grows some mold which will slow moisture loss and also contribute enzyme activity.
Aging beef with koji does not result in the same level of moisture loss, but instead relies on the high enzyme levels in koji to break down protein and fats, and to yield metabolic byproducts of the enzymatic reaction which contribute to the umami flavors in the beef. Put more simply, koji aging will make the beef flavor beefier. In this regard, the effect is similar to dry aging.
Unlike dry aging, which must use larger cuts of meat or primals, koji aging can be done with even a steak or any smaller cut.
For our koji aged rib roast, trim the roast, rinse and pat dry. Take 1-2 cups of koji rice and place in a blender with just enough water to create a thick paste. Coat the paste on the roast. Place the roast on a rack in a pan to catch any drips, and refrigerate.
There are methods to actually grow koji spores on meat, but this requires a high degree of sanitation, and controlled temperature and humidity. For a single roast, this slurry method in the refrigerator works quite well.
Leave the roast uncovered on the rack in the pan for five days. After that, rinse the koji from the meat with cool water. You will notice the meat has deepened in color, and it will be very tender. Your fingers may sink into the flesh as you rinse it, so handle with care.
Pat the roast dry, and return to the fridge on the rack. Leave for at least 24 hours. I left mine for 3 days.
To cook, remove the membrane from the ribs. Trim away any discolored spots. I like to rub the roast with olive oil, then coat generously with coarse salt and black pepper. Place in a roast pan with no rack. A small amount of water in the roast pan with carrot, shallot, garlic, and herbs.
I used convection roast to create a good crust at 500F, then reduce the temperature and continue to convection roast at 325-350F until a probe thermometer reads 130F. Remove from oven and rest 30 minutes before carving. The temperature continues to rise during the rest, so make sure to remove from the oven 5 degrees before your desired temperature.
Make a sauce by deglazing the pan and add reduced wine or port, and finish with a knob of butter.