Research Progress on the Functional Properties of Fermented Soybeans

Soybeans are a highly nutritious natural crop, containing 30% to 46% protein and eight essential amino acids for the human body, which is why people often use soybeans as a substitute for animal protein. However, certain substances present in soy products are difficult for the human body to absorb, such as indigestible proteins, carbohydrates, lectins, and allergens. The use of fermentation to enhance the palatability, nutritional value, preservative properties, and medicinal characteristics of food is an ancient food processing practice. The nutritional value and functional characteristics of fermented foods may be enhanced due to molecular transformations that occur during fermentation, resulting in the formation of bioactive or bioavailable end products. Fermented soy products not only have superior quality compared to raw materials and possess unique flavors, but more importantly, they generate many bioactive compounds that the raw materials themselves do not have.

1. Antioxidant Effect

The antioxidant effect refers to the resistance against oxidative reactions in the body (such as respiration) or the oxidative attack of unstable substances—free radicals—produced by environmental influences. Excessive accumulation of free radicals can lead to aging, cancer, or other related diseases in the human body, and the production of free radicals is unavoidable. To maintain balance and protect the body, the body produces some antioxidant substances simultaneously with the generation of free radicals. Antioxidant substances can be synthesized by the body or obtained from food. Relevant studies have shown that many natural foods contain antioxidant substances, and the effective components in fermented soy products, such as antioxidant peptides, melanoidins, isoflavones, and their phenolic compounds, all have antioxidant effects. Therefore, fermented soy products can serve as natural antioxidant foods.

Soy protein breaks down to produce antioxidant soy peptides, which play a role in scavenging free radicals, reducing the incidence of related diseases, delaying aging, and lessening physiological functional diseases such as diabetes. An analysis of the isoflavone content in fermented soy-based foods found that there was no change in the total isoflavone content compared to before fermentation, but under the influence of β-glucosidase, glycosidic soy isoflavones were gradually converted into free soy isoflavones, leading to a rapid increase in the content of these isoflavones, thus significantly enhancing their antioxidant properties.

2. Blood Pressure Lowering Effect

Cardiovascular diseases are a common illness that poses a serious threat to humans, especially for middle-aged and elderly individuals over 50 years old, with hypertension being one of the main pathogenic factors. Angiotensin-converting enzyme (ACE) can convert angiotensin I into angiotensin II, which is a potent vasoconstrictor that causes vascular smooth muscle contraction, resulting in an increase in blood pressure, with ACE acting as a rate-limiting enzyme.

Wang et al. studied the composition and ACE inhibitory activity of fermented soybeans, and the results showed that the nutritional value of proteins, fats, and soluble polysaccharides increased during the fermentation process, and the ACE inhibitory activity was significant, mainly derived from the hydrolyzed protein components, with the highest ACE inhibitory activity observed in soybeans fermented for two weeks.

3. Prevention of Gastric Injury

Soybeans contain rich active components such as proteins, isoflavones, saponins, and phospholipids, and fermentation can produce more active components. Regular consumption of fermented soy products containing isoflavones can significantly reduce the incidence of gastric injury, and the saponin active components in soybeans can effectively prevent visceral injury. After gastric injury occurs, inflammation usually arises, and soy protein and soy peptides can significantly inhibit inflammation; therefore, fermented soy products are a natural functional food for preventing gastric injury.Food.

Suo et al. studied the therapeutic effects of water fermented soybeans in different containers on gastric mucosal injury induced by hydrochloric acid/ethanol in mice, finding that the gastric mucosal injury in mice treated with water fermented soybeans in glass containers had gastric juice secretion and pH values close to those of mice treated with ranitidine and normal mice, with significant alleviation of gastric mucosal injury. Liu et al. studied the effects of lactic acid bacteria fermented defatted soy milk on the integrity of gastric mucosa in rat models of gastric mucosal injury, finding that lactic acid bacteria fermented defatted soy milk reduced the gastric mucosal injury index and could prevent gastric injury.

4. Blood Sugar and Lipid Lowering

With the improvement of people's living standards, the incidence of chronic diseases such as diabetes and hyperlipidemia is also increasing, and unhealthy dietary habits are one of the main causes of chronic diseases. To prevent the occurrence of chronic diseases such as hyperlipidemia and diabetes, it is necessary to develop good dietary habits and consume foods that have preventive and therapeutic effects on chronic diseases, whilefermented soy productshave good blood sugar and lipid lowering effects.

Chen et al. isolated a bioactive component, 6-hydroxydaidzein (6-HD), from fermented soybeans, which can promote the differentiation of fat cells, improve insulin sensitivity, and enhance glucose uptake, showing potential for diabetes treatment. Du Yimei et al. found through experiments that the fermented soy product Tangke peptide can significantly lower blood sugar levels in type II diabetic rats, improve hyperlipidemia, and provide certain protective effects on the kidneys of rats.

References:

[1] Wu Yiwu, Wu Xiaogang, Jiang Xianzhi, Bai Guanhui, Zhang Zhiyong, Yu Bangwei. Research Progress on the Pharmacological Effects of Fermented Soy Products [J].

[2] Zhang Menghan, Ding Changhe. Current Status of Functional Research on Fermented Soy Foods [J]. Food Industry.

[3] Distribution, Function, and Application of Lactic Acid Bacteria in Traditional Fermented Soy Foods.

[4] Liu Yuanyuan. Health Benefits of Fermented Soy Foods on the Body [J]. Food and Fermentation Technology.

Note: This article is for informational purposes only and is not intended as medical guidance.