Most people use soy sauce when cooking. It not only adds color to dishes but also enhances their flavor.
There is a distinction between cooking soy sauce and table soy sauce, but many people don't pay much attention to this when purchasing. It's common to have only one type at home, using it for everything from stir-fries to cold dishes, which can easily pose health risks.
Cooking soy sauce is generally divided into two types: flavor-oriented and health-oriented. The former includes varieties like wheat-scented soy sauce, aged soy sauce, and Beijing light soy sauce. The latter includes no-salt soy sauce (which contains no sodium but has a certain saltiness, suitable for kidney disease patients), iron-fortified soy sauce, and iodized soy sauce. It is almost inevitable that these types of soy sauce can become contaminated during production, storage, transportation, and sales due to poor hygiene conditions, and may even mix with pathogenic bacteria that cause intestinal infectious diseases. Furthermore, the requirements for microbial indicators during testing are relatively low, so it's not uncommon for a qualified bottle of soy sauce to contain a small amount of bacteria.
Experiments have shown that Shigella bacteria can survive in soy sauce for 2 days, while Paratyphoid bacteria, Salmonella, and pathogenic E. coli can survive for 23 days. Typhoid bacteria can survive for 29 days. Other research has found a type of halophilic bacteria in soy sauce that can generally survive for 47 days. Once a person consumes soy sauce containing this halophilic bacteria, they may experience symptoms such as nausea, vomiting, abdominal pain, and diarrhea. In severe cases, it can lead to dehydration, shock, and even be life-threatening. Although this is relatively rare, for safety reasons, it is best to cook soy sauce before consumption, as heating will generally kill these bacteria.
If you want to make cold dishes, it is best to choose table soy sauce. The microbial standards for table soy sauce are stricter than for cooking soy sauce. National standards stipulate that for table and cold dishes, the total number of bacterial colonies detected per milliliter of soy sauce must not exceed 30,000, so it is not harmful to health even when consumed raw.
Although soy sauce is highly nutritious, containing up to 17 amino acids, various B vitamins, and a certain amount of calcium, phosphorus, iron, and other minerals, its salt content is relatively high, so it is best not to consume too much of it. The salt content in soy sauce can be as high as 18%—20%, meaning that about 1 gram of salt is contained in every 5 milliliters of soy sauce. Besides for seasoning, this is mainly added to prevent the soy sauce from spoiling. People with conditions such as hypertension, kidney disease, pregnancy-related edema, cirrhosis with ascites, or heart failure should be especially cautious when consuming it, as it can worsen their condition.
In clinical practice, people often ask whether eating soy sauce after a skin injury will cause the wound to darken and leave a scar. In fact, this concern is completely unnecessary. Whether a skin scar is left mainly depends on the depth of the injury, the degree of bacterial infection, and individual differences. The main component of soy sauce is glutamic acid, which has no direct relationship with tissue repair. The pigments in it are food colorants and are not transported to the skin after being ingested. Therefore, people with injuries or who have undergone cosmetic surgery do not need to avoid eating soy sauce.