What is Shio Koji?
Shio koji is an extremely amazing Japanese ingredient that I’ve read/heard of quite some time ago but only managed to get my hands on it one month ago. It can be used in marinades and in pickling agents, but so far I’ve been using it marinate, tenderise and enhance the umami flavours in food. It is made with rice koji that has been inoculated with strains of beneficial mould called Aspergillus Oryzae. If you are residing in Singapore, you can get it from Japanese supermarkets (such as Don Don Donki or Mediya). If you want to read more or make your own, you can give this recipe at Serious Eats a try.
I’ve used shio koji in pork collar (made into super delicious Garlic Butter Pork – recipe here!) and in beef steaks. I absolutely love how the tender the pork collar becomes. However, in beef steaks, we found that shio koji overpowered the natural steak flavours (as we like our steaks with just salt and a little freshly cracked black pepper). It also resulted in the steaks to burn more easily (even though I had wiped the steaks as much as possible before cooking them). If you have any tips on using shio koji in beef steaks, please let me know!
How to Use Shio Koji
For today’s recipe I experimented the shio koji on saba fish. I bought the frozen saba fish fillet online – 1/2 saba fish is just the right portion for 2 persons. The rule of thumb is to use about 10% of shio koji of the meat/seafood/vegetables’ weight – as a little goes a long way. So what I did was to place the saba fish in the ziploc bag, weigh it, then add in the amount of shio koji required. Then let time do the rest of the work. I took the easy way out and oven-grilled the saba fish so clean-up is minimal. But make sure you “air” (leave the oven door ajar) the oven overnight so that the smell of the fish doesn’t linger. If you do not have an oven, I’m sure air fryer or even pan-frying works well.
Overall, this is an incredibly easy recipe to put together and the saba fish is tender and so flavourful. Served with rice and a spinach, wakame and tofu miso soup, it’s a simple yet comforting meal. Will definitely be making this often and also trying shio koji on other types of fish fillets!
Oven-Grilled Shio Koji Saba Fish
- ½ saba fish aka mackerel (see Note 1)
- 20 grams shio koji 10% of the fish's weight
The Night Before
- Weigh your saba fish and measure 10% of the fish's weight of shio koji (e.g. 200g saba fish, 20g shio koji)
- If you have the habit of washing your fish, pat dry the saba fish with paper towels .
- Combine the saba fish and shio koji in a ziploc bag. Squeeze the air out of the ziploc bag and ensure the saba fish is coated with the shio koji on both sides. Marinate in the refrigerator overnight.
- Preheat oven to 200°C / 400°F on the fan-forced grill mode. If this function is not available, preheat oven to 215°C / 420°F in a regular oven (or 200°C / 400°F in a fan oven).
- While the oven preheats, remove the saba fish from the ziploc bag and use paper towel to wipe away the shio koji. Line a parchment paper on a tray and place the saba fish on the parchment paper, flesh-side up. Season lightly with salt. Flip the saba fish so that it is skin-side up. Cut some slits on the skin-side of the saba fish, then rub lightly with oil and season lightly with salt.
- Bake for 10 minutes in the upper-third of the oven. If the skin looks like it's burning, shift the saba fish to the lower-third of the oven. Bake for another 5 minutes until the flesh is opaque in colour and flakes away easily.
- The 1/2 saba fish that I bought weighs about 200 grams.
- Do air the oven by leaving the oven door ajar overnight after cooking so that the fish smell doesn't linger in the oven.
- If you have no oven, you can simply air-fry or pan-fry the saba fish.
- If you don't like saba fish, you can replace it with whatever fish fillets you like, but the baking times may have to be adjusted, depending on the thickness of the fish fillets.