Soybeans (Glycine max)

Description

Soybeans are the mature seeds of Glycine max, a leguminous plant of the family Fabaceae. They are small, round or slightly oval, and come in various colours depending on variety: yellow, green, brown or black. Soybeans are one of the world’s most important protein crops and serve as the base for numerous foods such as tofu, soy milk, tempeh, miso, edamame, soy flour and soy protein ingredients.

Common name: Soybean seeds

Parent plant: Glycine max (L.) Merr.

Kingdom: Plantae
Clade: Angiosperms
Clade: Eudicots
Order: Fabales
Family: Fabaceae
Genus: Glycine
Species: Glycine max (L.) Merr.

Cultivation and growth conditions

Climate:
Soybean (Glycine max) thrives in warm to temperate climates with a stable, frost-free growing season. It requires long, mild summers to complete its biological cycle.

Sun exposure:
Soybean plants need full sunlight throughout the day. Insufficient light reduces flowering, pod formation, and overall yield.

Soil:
The ideal soil is deep, well-drained, medium-textured, and slightly acidic to neutral (pH 6.0–7.0). Waterlogging must be avoided, as it promotes root diseases and weakens plant development.

Irrigation:
Regular watering is essential during germination, flowering, and pod filling. Irrigation should be reduced during seed maturation to prevent pod cracking.

Temperature:
Germination occurs best between 10–20 °C. Optimal vegetative growth ranges from 20–30 °C. Temperatures below 5 °C can injure young seedlings, while heat above 35 °C during flowering can reduce pod set.

Fertilization:
Because soybean forms a symbiosis with nitrogen-fixing bacteria (Rhizobium), it requires only minimal nitrogen at planting. Phosphorus and potassium in the basal fertilization improve root strength and support flowering and seed development. In poor soils, a bacterial inoculant is beneficial.

Crop care:
Early-season weeding and light hoeing help eliminate competition and improve soil aeration. Monitoring for insects and fungal diseases is advisable, although soybean is generally resilient. Avoid soil compaction during flowering.

Harvest:
Harvest takes place when plants turn yellow and pods become brown and dry. Seeds should reach about 13% moisture before harvesting to avoid splitting. Late harvesting may lead to pod dehiscence and seed loss.

Propagation:
Soybean propagates exclusively by seed. Sowing is carried out in spring when soil temperature consistently exceeds 10 °C. Crop rotation is recommended to maintain soil fertility and prevent soilborne pests and diseases.

Indicative nutritional values per 100 g (dry seeds)

• Energy: ≈ 440–470 kcal

• Water: ≈ 8–10%

• Carbohydrates: ≈ 28–30 g

  • of which sugars: ≈ 7–8 g

• Protein: ≈ 36–40 g

• Total fat: ≈ 18–20 g

  • SFA (saturated fatty acids; should be moderated): ≈ 2–3 g

  • MUFA (monounsaturated fatty acids; generally favourable for lipid profile): ≈ 4–5 g

  • PUFA (polyunsaturated fatty acids, including omega-6 and some omega-3): ≈ 10–12 g

• Dietary fibre: ≈ 9–10 g

• Minerals: calcium, phosphorus, magnesium, potassium, iron

• Vitamins: B1, B2, B6, vitamin K, folates

Values vary with variety and processing.

Key constituents

• High-quality plant proteins

• Unsaturated fatty acids (linoleic acid and alpha-linolenic acid)

• Isoflavones (genistein, daidzein)

• Soluble and insoluble fibre

• Phytosterols, lecithins, tocopherols

• Phenolic antioxidants

Production process

Cultivation

• Annual legume requiring temperate climates and well-drained soils.

• Major producers: USA, Brazil, Argentina, China and parts of the EU.

Harvest

• Plants are harvested mechanically when pods are dry and seeds fully matured.

Post-harvest

• Drying to safe moisture levels (≈ 12–14%).

• Cleaning, calibration and storage in silos.

Further processing

• Production of soy flour, soy protein concentrate, soy protein isolate, textured vegetable protein (TVP) and soybean oil.

• Fermentation into miso, tempeh, natto, etc.

Physical properties

• Hard, round seeds with a resistant seed coat.

• Moisture content is low when dried → long shelf-life.

• Colour varies by variety (yellow most common for food).

Sensory and technological properties

• Neutral to mildly beany flavour.

• High hydration capacity; softens after soaking and cooking.

• Excellent technological functionality due to lecithin and protein structure:

  • emulsifying

  • gelling

  • thickening

  • texturising

• Suitable for plant-based beverages, tofu and meat analogues.

Food applications

• Cooked whole (soups, stews, salads).

• Tofu, tempeh, natto, miso.

• Soy milk and plant-based drinks.

• Soy flour, bakery applications.

• Textured soy protein (TVP) for plant-based meat products.

• Soybean oil for cooking and food manufacturing.

Nutrition & health

• Excellent source of complete plant protein.

• Fats mostly unsaturated, beneficial when replacing saturated fats.

• Fibre and phytochemicals support digestion and metabolic health.

• Isoflavones studied for potential effects on menopause, bone health and cardiovascular wellbeing.

• People with thyroid conditions should consult a specialist if consuming soy frequently.

Portion note

• Cooked soybeans: 80–100 g as a protein serving.

• Dry soybeans: 30–40 g (yield ≈ 90–120 g cooked).

Allergens and intolerances

• Soy is a major EU allergen.

• Reactions may be moderate to severe in sensitive individuals.

• Fermented products may be more digestible for some people.

Storage and shelf-life

• Dry seeds: up to 12 months in cool, dry, dark storage.

• Cooked soybeans: 2–3 days refrigerated.

• Soy flour and soy protein: keep sealed, away from heat and humidity.

Safety and regulatory aspects

• Must comply with limits for:

  • MRL (pesticide residues)

  • mycotoxins (especially aflatoxins)

  • heavy metals and foreign contaminants

• Production facilities must operate under GMP and HACCP standards.

• Allergen “soy” must be clearly stated on labels.

Labelling

• Name: “soybeans” / Glycine max.

• Origin.

• Lot number, best-before date, storage instructions.

• Mandatory allergen declaration.

Troubleshooting

• Rancid smell → lipid oxidation → discard.

• Seeds remain hard after soaking → product old or insufficient hydration.

• Bitter taste → oxidation or spoilage.

• Insect presence → improper storage.

Sustainability and supply chain

• High-yield crop; sustainability varies by region.

• Issues in some countries: deforestation linked to intensive agriculture.

• Availability of certified sustainable, organic, non-GMO soy.

• Soy by-products are highly valorised (oil, meal, feed, industrial uses).

Main INCI functions (cosmetics)

Cosmetic derivatives include:

• Glycine Soja Oil – emollient, nourishing.

• Glycine Soja Protein / Soy Amino Acids – conditioning agents.

• Glycine Soja Sterols – emulsifying/stabilising functions.

• Soy Isoflavone Extract – antioxidant, skin-firming.

Conclusion

Soybeans are a nutritionally rich and technologically versatile raw material, widely used in plant-based foods and functional ingredients. Their high protein content, valuable unsaturated fats and bioactive compounds make them a cornerstone in modern nutrition. Proper cultivation, processing and storage ensure quality, safety and long-term stability throughout the supply chain.

Mini-glossary

• SFA – Saturated fatty acids; should be limited due to cardiovascular risk when excessive.

• MUFA – Monounsaturated fatty acids; beneficial for lipid balance.

• PUFA – Polyunsaturated fatty acids; important for cell health and anti-inflammatory pathways.

• ALA – Alpha-linolenic acid; plant omega-3 fatty acid.

• MRL – Maximum Residue Level; legal pesticide-limit threshold.

• GMP – Good Manufacturing Practices; hygiene and quality standards.

• HACCP – Hazard Analysis and Critical Control Points; preventive food-safety system.

Studies

Soy is a rather controversial food.

On the one hand, some studies draw attention to isoflavones present in soy that help defend the cardiovascular system by regulating cellular and enzymatic functions in situations such as inflammation, thrombosis and atherosclerotic progression (1).

On the other hand, it is even assumed that it may cause damage, particularly the Alzheimer's disease, if ingested in the form of an industrial product. This study analyses the problem (2).

Infant formulae, so-called SIFs containing soybean meal, were introduced almost 100 years ago. This study analyses their safety (3).

With regard to the allergenicity of soybeans, an attempt was made to identify which proteins (representing 35-40% of the dry weight of soybeans) are at risk, in order to develop hypoallergenic soybean products for sensitive people (4).

The results of this study showed that feeding male rats with large amounts of soybeans could induce aggressive behaviour (5).

Soya beans studies

References___________________________________

(1) González Cañete N, Durán Agüero Soya Isoflavonas de soya y evidencias sobre la protección cardiovascular [Soya isoflavones and evidences on cardiovascular protection. Nutr Hosp. 2014 Jun 1;29(6):1271-82. Spanish. doi: 10.3305/nh.2014.29.6.7047. 

Abstract. Soya isoflavones represent a group of non-nutritive, bioactive compounds, of non-steroidal phenolic nature that are present in soy bean and derived foods. They share with other compounds the capacity of binding to estrogenic receptors from different cells and tissues so that they may act as phytoestrogens. The current interest in these compounds comes from the knowledge that in Asian populations with high levels of their consumption the prevalence of cancer and cardiovascular disease is lower, as compared to the Western countries populations. This cardiovascular benefit would be the result not only of the modulation of plasma lipids, which is a widely studied mechanism. This paper reviews the published evidence about the beneficial effects of soya isoflavones and the different mechanisms of action that would benefit cardiovascular health and that surpass the mechanisms traditionally approached such as the modulation of plasma lipids, and that implicate the regulation of cellular and enzymatic functions in situations such as inflammation, thrombosis, and atherosclerotic progression.

(2) Roccisano D, Henneberg M, Saniotis A. A possible cause of Alzheimer's dementia - industrial soy foods. Med Hypotheses. 2014 Mar;82(3):250-4. doi: 10.1016/j.mehy.2013.11.033. Epub 2013 Dec 7. PMID: 24440006.

(3) Vandenplas Y, Castrellon PG, Rivas R, Gutiérrez CJ, Garcia LD, Jimenez JE, Anzo A, Hegar B, Alarcon P. Safety of soya-based infant formulas in children. Br J Nutr. 2014 Apr 28;111(8):1340-60. doi: 10.1017/S0007114513003942. Epub 2014 Feb 10. PMID: 24507712.

Abstract. Soya-based infant formulas (SIF) containing soya flour were introduced almost 100 years ago. Modern soya formulas are used in allergy/intolerance to cows' milk-based formulas (CMF), post-infectious diarrhoea, lactose intolerance and galactosaemia, as a vegan human milk (HM) substitute, etc. The safety of SIF is still debated. In the present study, we reviewed the safety of SIF in relation to anthropometric growth, bone health (bone mineral content), immunity, cognition, and reproductive and endocrine functions. The present review includes cross-sectional, case-control, cohort studies or clinical trials that were carried out in children fed SIF compared with those fed other types of infant formulas and that measured safety. The databases that were searched included PubMed (1909 to July 2013), Embase (1988 to May 2013), LILACS (1990 to May 2011), ARTEMISA (13th edition, December 2012), Cochrane controlled trials register, Bandolier and DARE using the Cochrane methodology. Wherever possible, a meta-analysis was carried out. We found that the anthropometric patterns of children fed SIF were similar to those of children fed CMF or HM. Despite the high levels of phytates and aluminium in SIF, Hb, serum protein, Zn and Ca concentrations and bone mineral content were found to be similar to those of children fed CMF or HM. We also found the levels of genistein and daidzein to be higher in children fed SIF; however, we did not find strong evidence of a negative effect on reproductive and endocrine functions. Immune measurements and neurocognitive parameters were similar in all the feeding groups. In conclusion, modern SIF are evidence-based safety options to feed children requiring them. The patterns of growth, bone health and metabolic, reproductive, endocrine, immune and neurological functions are similar to those observed in children fed CMF or HM.

(4) Capriotti AL, Caruso G, Cavaliere C, Samperi R, Stampachiacchiere S, Zenezini Chiozzi R, Laganà A. Protein profile of mature soybean seeds and prepared soybean milk. J Agric Food Chem. 2014 Oct 8;62(40):9893-9. doi: 10.1021/jf5034152. Epub 2014 Sep 29. PMID: 25229310.

Abstrct. The soybean (Glycine max (L.) Merrill) is economically the most important bean in the world, providing a wide range of vegetable proteins. Soybean milk is a colloidal solution obtained as water extract from swelled and ground soybean seeds. Soybean proteins represent about 35-40% on a dry weight basis and they are receiving increasing attention with respect to their health effects. However, the soybean is a well-recognized allergenic food, and therefore, it is urgent to define its protein components responsible for the allergenicity in order to develop hypoallergenic soybean products for sensitive people. The main aim of this work was the characterization of seed and milk soybean proteome and their comparison in terms of protein content and specific proteins. Using a shotgun proteomics approach, 243 nonredundant proteins were identified in mature soybean seeds.

(5) Abdel-Aleem GA, Shafik NM, El-Magd MA, Mohamed DA. Soya bean rich diet is associated with adult male rat aggressive behavior: relation to RF amide-related peptide 3-aromatase-neuroestrogen pathway in the brain. Metab Brain Dis. 2019 Aug;34(4):1103-1115. doi: 10.1007/s11011-019-00431-2. 

Abstract. Relation between soya bean (SB) consumption and aggressive behavior has not been elucidated yet. Thus, this study was conducted to investigate the effect of large amount of SB consumption on adult male rats' aggressive behavior through investigating changes in the expression of gonadotropin-inhibitory hormone/ RF amide-related peptide 3 (GnIH/RFRP3), neuropeptide FF receptor, cytochrome P450, family 19, subfamily A, polypeptide 1 (Cyp19A1), estrogen receptors α and β and the levels of neuroestrogen, dopamine, glutamate and testosterone as well as aromatase activity in the brain. Adult male rats were divided into three equal groups: group I, control group, received standard diet; group II and group III received 25% and 50% SB of their standard diet contents, respectively, for 12 weeks. The obtained results showed that feeding male rats with large amount of SB could induce aggressive behavior in a dose dependant manner possibly through inhibition of brain GnIH/RFRP-aromatase-neuroestrogen pathway. These effects may be through decreasing aromatase activity, neuroestrogen concentration, Cyp19A1 and ER β mRNA levels and increasing ER α mRNA levels and immunostaining as well as testosterone, dopamine and glutamate levels in the brain. These findings also provide further support for the inhibitory role of RFRP3 on aggressive behavior of male rats. These data may open new avenues for the potential harmful effects of consumption large amounts of SB rich food on humans.