Icebox Time Machine: Koji 'Dry Aged' Steak in 2 Days!

This is your guide to achieving that 'Dry Aged' steak flavor in 48-72 hours utilizing Koji powder while requiring significantly less patience and equipment than traditional Dry Aging.

Ahhh yes, the Koji Aging Trick. Utilizing Koji Powder to emulate the taste and texture of a proper dry-aged cut of beef has been trending pretty well the past couple of years with references that appear to originally point to a Bon Appetit article published in the Spring of 2016.  Koji can be purchased from Asian specialty markets locally or right here on Amazon.com. Effectively it is a rice grain that has a live culture (Aspergillus oryzae) growing on it. This culture is utilized in the fermentation of items such as sweet sake, soy sauce, and miso paste.  This culture, when rubbed onto meat products, appears to accelerate the natural breakdown of the protein thus providing a simulated 'dry aging' and verified tasty impact upon the final product.

sirloin rubbed with koji powder

We happened to source our Koji from a local home chef who maintains their own living supply.  We sourced thick cuts of top sirloin from our favorite local butcher so we knew we were working with a product that we were familiar with from a taste perspective.  Our Koji was already in a rough powder form so we opted to just crush it down a bit with a heavy glass.  If purchased in the form of whole grain it would certainly not hurt to give it a quick mill in the Vitamix or similar.  

We placed the sirloins on a wire rack, generously coated them with the Koji powder, and placed them into the fridge to hang out in open air for a while.  In our case, we did this for 64 hours but recommendations fall into the range of 48-72 hours.  This provides a good buffer to accommodate your cooking process and dining schedule. We flipped them over once during this process to equalize the drying process.

sirloin rubbed with koji powder 64 hours

Once removed from the refrigerator you will note that your once dry and frosty Koji powder will have absorbed some moisture from the beef and transitioned in many areas to more of a dull moist coating.  We scraped the coating off gently with the back of a butter knife and then thoroughly rinsed off the steaks in cold water.  Don't be alarmed if after rinsing you have some dull grey areas - this should quickly resolve itself.  Once rinsed the steaks were patted dry and given a light dry brine with kosher salt and returned to the rack in the fridge to finish drying out for 2 hours or so.

koji rubbed sirloin after rinse and dry brine

At this point, we had two delicious looking cuts of beef.  There were a couple excessively dry areas around the corners that we trimmed up just slightly with a boning knife.  They probably would have cooked up just fine but it didn't take much time to trim the small bits.

koji rubbed sirloin ready for cast iron skillet

This party is easy.  Hit the steaks with a bit of salt and pepper or final seasoning of your choice.  Next up prepare them using any method you desire such as a reverse sear on the charcoal grill, sous vide, or cast iron. You can't go wrong.

koji rubbed sirloin cast iron butter basted

We opted for a standard cast iron preparation, melting a couple tablespoons of butter in the pan over the stovetop. We seared the steaks while basting occasionally with butter for 3 minutes or so on each side. We then dropped the pan into a 400˚ oven and finished to our desired internal temperature of 132˚ as indicated by our trusty ThermoWorks Thermapen.

finished cast iron butter seared koji rubbed sirloin

We ended up with two delicious sirloins that were without a doubt more flavorful than nearly identical cuts from the same source that we have prepared using identical preparation techniques.  They without a doubt had a more complex flavor and presence of umami that we have not experienced previously, especially with a standard thick cut top sirloin.  We would agree with anyone who has described the flavor of steak prepared in this manner to be nutty and carrying a more concentrated and desirable beef flavor.  All the thumbs up.

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