How to Make Shio Koji (Salt Koji) at Home | Natural Enzyme-Rich Seasoning

By: Waymond D. Wesley II

Why I Do Not Use Store-Bought Shio Koji

Basics: 

Koji Mold: (Aspergillus oryzae) non-pathogenic filamentous type of fungus used to make koji. As far back as 1300 years ago this fungus was meticulously cultured in Japan. It is the organic technology behind miso, shoyu, sake, rice vinegar, and much more. 

What is Shio Koji?: Shio koji (salt Koji) is a traditional Japanese seasoning made by combining koji rice with salt and water. Over the course of several days at room temperature, naturally occurring enzymes in the koji break down proteins and starches, producing a savory, slightly sweet seasoning base. It’s widely used in modern and traditional kitchens to enhance umami, tenderize meats, and bring depth to vegetables and grains. Despite its complexity of flavor, it’s remarkably simple to make.

You may have seen shio koji on the shelf at Japanese markets or specialty grocery stores, but I strongly recommend making your own—and here’s why.

Most commercial shio koji is adulterated with added alcohols or has been pasteurized for shelf stability. While this extends its expiration date, it comes at a serious cost: it compromises the enzymatic activity that makes shio koji valuable in the first place.

Koji rice naturally contains enzymes like amylase, protease, and lipase which break down starches, proteins, and fats into their flavorful and more digestible components. 

The Big Three

Amylase: breaks down starches into simple sugars like glucose and maltose.

Protease: breaks down proteins into savory amino acids such as glutamic acid—the foundation of umami.

Lipase: breaks down fats into flavorful esters and aromatic compounds.

Koji Use Cases

Charcuterie

Koji offers a transformative approach to traditional pepperoni curing by accelerating enzymatic activity during fermentation and enhancing umami development. In a slow-fermented, dry sausage like pepperoni, koji inoculated rice is introduced at 0.4% by weight and activated at around 86°F—the low end of its enzymatic range—over a three-day fermentation schedule inside the Koji alchemy sous vide fermentation chamber. The result is a deeper flavor profile and a shortened post-fermentation curing time. Koji’s enzymes lower the meat’s surface pH, intensifying myoglobin denaturation and contributing to both color development and microbial safety. This method pairs well with classic pepperoni ratios of pork and beef, combined with standard curing agents and spices, including star anise and Szechuan pepper for a distinctive aromatic profile. Adjustments in humidity (70–90%) and temperature throughout the fermentation and drying stages help control moisture loss and texture development. Koji’s role in charcuterie curing ultimately bridges tradition with innovation, offering a more efficient, flavorful, and technically precise method of meat preservation.

When these enzymes are denatured through heat or alcohol, shio koji loses its ability to transform food. It may still taste salty, sweet, and savory, but it no longer breaks down proteins, starches, or fats—the very reason chefs use it in the first place.

Dairy

Koji Crème Fraîche: Unlocking Buttery Depth

Crème fraîche is already a staple in many kitchens—tangy, creamy, and luxuriously rich. But when you introduce koji into the fermentation process, the result is something altogether elevated: a cultured cream with an unmistakably deeper, more buttery flavor that lingers on the palate and transforms everything it touches, from sauces to desserts.

The secret? Diacetyl.

Diacetyl is a naturally occurring aromatic compound best known for its rich, buttery aroma and flavor. It’s the same molecule responsible for the buttery notes found in certain beers, wines, and cultured dairy products. In traditional crème fraîche, trace amounts of diacetyl can emerge during fermentation. But when koji enters the equation, the enzymatic and microbial dynamics shift dramatically.

When you make shio koji at home—using clean water, quality koji, and proper technique—you’re preserving its full enzymatic potential. The result is a living, active seasoning that’s more potent, more versatile, and far more rewarding to cook with.

Bottom line: If you’re using shio koji for its functional culinary benefits—not just its flavor—skip the shelf-stable stuff and make your own.

Affiliate link to the dried koi rice I use here.