Key Takeaways
  • Katsuobushi (bonito flakes) and niboshi (dried sardines) can accumulate oxidized lipids and smoke-derived residues during production and storage, so pay attention to their origin, manufacturing methods, and how you store them.
  • While MSG (often labeled as "seasoning (amino acids, etc.)") is considered safe by many organizations, sensitive individuals may experience headaches or fatigue, so be mindful of your intake.
  • Powdered and granulated dashi often contain hidden salt, sugar, and yeast extract. We recommend learning how to read labels and combining them with homemade dashi.
  • How to choose safe and flavorful options: Utilize high-quality domestic kombu, dried shiitake mushrooms, honkarebushi (premium fermented bonito flakes), and frozen homemade dashi.

Introduction — Japanese Dashi and Its "Hidden Risks"

Dashi, the cornerstone of Japanese cuisine, has long gently supported our dining tables. Here at the geefee team, we make almost all of our everyday miso soups and simmered dishes using homemade dashi. However, when we take a closer look at the "convenient granulated dashi" and cheap katsuobushi used at home, we realized that there are health concerns hidden behind their flavor and low cost. In this article, we will clearly explain the risks that vary depending on ingredients, manufacturing methods, and storage, as well as the safe ways to choose and make dashi that we have actually tried and loved.

Main Risks Hidden in Dashi Ingredients

Katsuobushi and Niboshi: Oxidation and Smoke-Derived Residues

Katsuobushi develops its flavor during the process of drying and aging with smoke, but there is a possibility that benzopyrene, a type of polycyclic aromatic hydrocarbon (PAH) derived from that smoke, may adhere to it. With evaluations by the International Agency for Research on Cancer (IARC) and movements toward import regulations, manufacturing methods and quality control are crucial. Additionally, the unsaturated fatty acids in fish fat are prone to oxidation, and lipid peroxides can increase during drying and long-term storage, potentially leading to oxidative stress. It is essential to seal them tightly in the refrigerator after opening and use them up quickly.

Hidden Ingredients in Powdered Dashi and Seasoning Labels

Ingredients like "seasoning (amino acids, etc.)," "yeast extract," and "protein hydrolysate" provide a strong umami flavor, but they are highly processed and may contain large amounts of salt and sugar. You can feel secure by checking the label for "salt equivalent" and "ingredients," and choosing products clearly marked as having no added salt or chemical seasonings.

A Proper Understanding of MSG (Monosodium Glutamate)

There has long been debate surrounding MSG. While it is true that some people report headaches and fatigue, often referred to as "Chinese restaurant syndrome," organizations like the U.S. Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA) evaluate it as safe in normal dietary amounts. On the other hand, sensitive individuals may experience symptoms, so if you are concerned, we recommend avoiding "seasoning (amino acids, etc.)" and combining the natural umami of kombu, shiitake mushrooms, and katsuobushi. When we reduced our MSG intake and started keeping kombu water on hand, our satisfaction with the taste didn't drop, and we felt less thirsty the next morning.

How to Read Labels and Identify Them in Daily Life

  • Check the ingredients list: Products with "salt," "sugar," or "yeast extract" at the beginning tend to be high in salt and sugar.
  • Look for "additive-free" or "no chemical seasonings used" as a guide. However, keep in mind that even "additive-free" products contain naturally occurring sodium from the ingredients.
  • Origin and manufacturing method: Honkarebushi, kombu with a clearly stated origin, and domestic dried shiitake mushrooms have clear manufacturing methods, so you can expect good quality control.
  • Storage methods: Katsuobushi easily deteriorates from moisture and oxygen, so store it in an airtight container in the refrigerator. Powdered dashi should also be used up quickly after opening.

How to Make Safe, Delicious Dashi and Alternatives

Easy and Deep Umami with Kombu Water + Dried Shiitake

Simply adding domestic dried shiitake mushrooms to "kombu water"—made by soaking high-quality kombu in water overnight—creates a gentle umami base. Thanks to the synergistic effect of glutamic acid (kombu) and guanylic acid (shiitake), you can feel satisfied even with less salt. We also noticed the difference in taste by adopting a routine of preparing it at night to use in the morning.

Tips for Using Honkarebushi

If you prioritize flavor, the key is to choose honkarebushi katsuobushi with a clear manufacturing method and extract its aroma in a short time. Boiling it at a high temperature for a long time will bring out off-flavors, so adding it at the very end or turning off the heat before adding the bonito flakes will result in a clear dashi.

How to Incorporate Bone Broth and Points to Note

Bone broth is rich in collagen and minerals, but there are reports of the accumulation of trace metals (e.g., lead) derived from bones. It is wise to avoid consuming it excessively every day and to combine it with other types of dashi. When simmering for a long time, adjust the flavor by frequently skimming off the scum.

Storage and Stocking Techniques

It is convenient to freeze homemade dashi in ice cube trays and store it in small portions. You can melt just the amount you need, which also helps preserve the flavor.

Conclusion

Japanese dashi can produce an amazingly deep flavor through the combination of ingredients, but depending on the processed products and storage conditions, risks of oxidation and additives can arise. The important thing is "what" you choose and use, and "how" you do it. First, check the labels, and try incorporating homemade dashi a few times a week, based on reliable ingredients like domestic kombu, dried shiitake mushrooms, and honkarebushi. In two to three weeks, your sense of taste will reset, and you should be able to feel the natural umami of the ingredients more strongly. Even the small tweaks we actually tried (keeping kombu water on hand, freezing dashi stock) increased the satisfaction at our family's dining table. Let's review how we choose our dashi, taking it one step at a time without overexerting ourselves.

Disclaimer: The information in this article is for general informational purposes only and does not constitute medical advice. Please consult a qualified healthcare professional before making any health-related decisions.