Microorganisms are all around us, hidden in plain sight. The most typical of these are mold, yeast, and bacteria. Though it’s called ‘rot’ when microorganisms cause food to spoil, the process is defined as ‘fermentation’ when it has a beneficial function for humans. Yogurt, alcohol, miso, and natto are examples of fermented food and drinks produced through the actions of these microorganisms. In addition to bringing out an ingredient’s aroma and umami taste, the fermentation process also helps create a better gut environment, enhancing our diets and improving our health.

Bacterial growth occurs most readily when food is neutral and decreases when food is acidic or alkaline. This can be seen when fermenting milk with lactic acid bacteria, turning it into yogurt. This produces lactic acid, which makes the milk acidic, creating a challenging environment for other bacteria, including harmful airborne bacteria, to function in. Some types of Japanese sake have lactic acid bacteria added for easier brewing, too. Doing so makes it harder for common bacteria to reproduce, creating a better environment for the required yeast to ferment.

Although some microorganisms can help preserve food, they also hold the ability to spoil it too. Improving the shelf life of food requires either creating an environment in which microorganisms cannot quickly multiply or eradicating them. Besides boiling, chilling, or keeping the food unexposed to air, another effective preservation technique reduces the moisture that microorganisms have access to. Fish and meat contain between 80 to 90 percent water content, making dehydrating or desiccating them viable. Sugaring and salting preservation methods work along the same vein. The former is comparable to using sugar for boiling fruit preserves, and the latter to curing meat with salt. Made from fermented soybeans, Miso paste is kept similarly well-preserved with its 11 to 13 percent sodium content. Using miso to preserve eggs, tofu, or other perishables can lengthen their shelf life and add even more flavor.

Definitions such as ‘rot’ and ‘fermentation’ exist thanks to the wisdom of those who discerned the growing environments and nature of microorganisms before us. Sometimes there are microorganisms like lactic acid bacteria that can survive salt preservation, and sometimes there are those like mold and yeast which can survive acidity. Natto, fermented soybeans, have robust natto bacteria, which can withstand being boiled for 15 minutes at 212°F (100°C). These natto bacteria are also well-known for producing vitamin K and nattokinase enzymes to ferment soybeans. Instead of simply killing bacteria, the fermenting process allows for food to co-exist with them, improving shelf life and making for an enjoyable meal. This is the appeal of fermented food and a testament that our predecessors’ intense research has borne fruit.

We can say salting, sugaring, and fermentation are some of the original methods of preservation knowledge humans have accumulated since ancient times. Yet with high sodium levels in foods such as miso and soy sauce, recent years have seen an increase in the use of additives and salt-reduced varieties. The preservative qualities of these food additives have become essential to our dietary habits too. What is critical is having a balanced diet in all things, and for that, I recommend miso soup. Dashi stock made from kelp and bonito contains glutamic acid and inosinic acid, and dissolving miso’s fermented soybeans in this stock will significantly enhance the umami taste. Adding vegetables, meat or fish increases the nutritional value and enriches the flavor. Since the dawn of history, fermented food has been, and will continue to be, a staple part of our dietary lives.