Why Does Soy Sauce Contain Gluten?

In my journey of unglutening, I was surprised to find out that soy sauce contains gluten. This made a lot of sense because I would get bloating and stomach aches after eating a meal full of soy sauce and dark sauce.

While the name might suggest a simple fermented soy product, more than 95% of store bought soy sauce actually contain wheat, making it unsuitable for those with celiac disease or gluten sensitivities. But why is there gluten in soy sauce, and what alternatives are available?

The Traditional Fermentation Process

Soy sauce originated in China over 2,000 years ago and spread across Asia, evolving into different regional varieties. The earliest forms of soy sauce were actually fermented soybean pastes (known as jiàng 酱) and were typically made using only soybeans and salt, especially in southern China, where wheat was not as commonly available.

The use of wheat in soy sauce became more widespread later, particularly in northern China, where wheat was a staple crop. As soy sauce production evolved and influenced Japanese-style brewing, the practice of adding wheat became more widespread.

Today, the most common type of soy sauce is brewed using a combination of cooked soybeans, roasted wheat, water, and salt. The mold from the roasted wheat enables the fermentation process, allowing natural enzymes to break down proteins and starches into flavorful amino acids and sugars. This process creates the deep, umami-rich taste that makes soy sauce a staple in many cuisines.

The Role of Wheat in Soy Sauce

Wheat plays a crucial role in developing the flavor and texture of soy sauce. During fermentation, wheat helps produce:

• A more complex and slightly sweet taste, balancing the natural bitterness of soybeans.

• A thinner, more pourable consistency, since wheat starches contribute to the liquid’s texture.

• A darker color and richer aroma, as the Maillard reaction occurs between wheat proteins and sugars.

  
  

Since wheat is a primary ingredient in modern soy sauce production, most traditional soy sauces contain gluten, making them unsuitable for gluten-free diets.

Cost Considerations in Commercial Soy Sauce

In modern commercial soy sauce production, wheat is often used not just for flavor but also to reduce costs. Wheat is generally cheaper than soybeans, and many mass-produced soy sauces use a higher proportion of wheat to soybeans to make production more cost-effective. Additionally, some commercial brands accelerate the process by using acid hydrolysis instead of traditional fermentation. This chemical process breaks down proteins in a matter of days rather than months, producing a soy sauce-like product that is significantly cheaper to manufacture but often lacks the depth of flavor of traditionally brewed soy sauce.

Gluten-Free Soy Sauce

Fortunately, you can buy gluten-free soy sauce off the supermarket shelves easily these days. The colour of gluten-free soy sauce is lighter and does not produce a deep hue when cooked unlike standard soy sauce. However, the taste is more intense and I find myself using less of it as compared to standard soy sauce. It also does not leave a stinging, thirst-inducing aftertaste unlike soy sauce made with wheat.

My go-to brand is Lee Kum Kee’s Gluten Free Soy Sauce. You can buy it for around $5.70 per bottle (500ml) at NTUC, Sheng Siong and Cold Storage. While it is about 3.5 times more expensive than the cheapest soya sauce, the quality in taste and health benefits are not comparable. If you compare it with better quality soy sauces (less sodium, less wheat), the price difference is less than double. And since you don’t have to use as much in terms of quantity when cooking with the gluten-free soy sauce, it is well worth the price to ungluten your pantry.

(Insert picture of lee Kumkee)

Tamari Shoyu Soy Sauce

Another alternative is Tamari Shoyu. This is a Japanese-style soy sauce that is typically brewed with little or no wheat, making it a great gluten-free option. Unlike typical gluten-free soy sauce, Tamari Shoyu is slightly darker and thicker. I find it great when paired with sushi and for making Japanese stews (nimono 煮物).

Reading Labels is Key

If you are avoiding gluten, always check ingredient lists carefully. Some soy sauce brands may contain hidden sources of gluten, and cross-contamination can be a concern in manufacturing processes. Look for products labeled “gluten-free” to be sure.

Final Thoughts

The presence of gluten in soy sauce is a result of the evolution of fermentation methods that incorporated wheat to enhance flavor, color, and texture. While ancient Chinese soy sauces may have contained little or no wheat, especially in southern China, modern commercial soy sauces typically include a 50:50 ratio of wheat to soybeans, sometimes even more in mass production to reduce costs. However, with increasing awareness of gluten sensitivities, there are now excellent alternatives available. Whether you choose tamari, coconut aminos, or specially formulated gluten-free soy sauce, you can still enjoy the rich umami taste without compromising your dietary needs.