Soybean oil: classification, properties and applications

Soybean oil is a liquid vegetable product obtained from soybean seeds (Glycine max) by pressing or extraction. It is one of the most mass-produced and versatile vegetable oils in the world, occupying leading positions in terms of production and consumption. Soybean oil is not only an important food product but also a strategic raw material for the production of biodiesel, technical lubricants, paints, varnishes and lecithin.

Chemical Nature and Fatty Acid Composition

Soybean oil is characterised by a high content of unsaturated fatty acids. The fatty acid composition depends on the soybean variety and growing conditions. A typical ratio of the main acids is: linoleic (omega-6) — 50–60%, oleic (omega-9) — 20–30%, linolenic (omega-3) — 5–10%, palmitic — 8–12%, stearic — 3–5%. It is the high content of linoleic acid that provides good nutritional properties but at the same time makes the oil prone to oxidation and rancidity.

Soybean oil contains phospholipids (lecithin), tocopherols (vitamin E), phytosterols and trace amounts of isoflavones. Lecithin, obtained as a by-product of refining, is a valuable emulsifier widely used in the food and pharmaceutical industries.

Classification, Grades and Standards

In Russia and CIS countries, requirements for soybean oil are established by GOST 31760-2012 "Soybean oil. Specifications". The standard applies to oil intended for food and industrial purposes. Depending on the processing method and quality level, soybean oil is divided into the following types:

• Unrefined — oil that has undergone only mechanical cleaning (filtration). It retains the maximum of accompanying substances (phospholipids, tocopherols) but has a limited shelf life and a characteristic odour.

• Hydrated — oil treated with water to remove phospholipids. It is more resistant to oxidation and has less tendency to form sediment.

• Refined non-deodorised — oil that has undergone alkaline neutralisation, bleaching and washing but retains its characteristic odour.

• Refined deodorised — oil that has undergone complete purification, including deodorisation (removal of volatile compounds). It is used for direct human consumption and in the food industry.

Key physicochemical quality indicators include: acid value (not more than 0.30 mg KOH/g for refined deodorised oil and not more than 6.0 mg KOH/g for unrefined), mass fraction of phosphorus-containing substances, mass fraction of non-fatty impurities, colour and anisidine value. The content of pesticides, toxic elements, radionuclides and aflatoxin B1 must not exceed the levels established by sanitary norms.

Production Technology

Soybean oil production includes several stages. Soybeans are cleaned, crushed and subjected to moisture-heat treatment (to inactivate anti-nutritional factors such as trypsin inhibitors). The oil is then extracted by two main methods: pressing (cold or hot) and extraction using organic solvents (usually hexane). After extraction, the oil undergoes refining stages: hydration (removal of phospholipids), neutralisation (removal of free fatty acids), bleaching (removal of pigments) and deodorisation (removal of volatile compounds that impart odour).

By-products of processing are soybean meal (after extraction, contains up to 50% protein) and soybean cake (after pressing, contains more residual oil and less protein). Both products are valuable feed components, and meal is the main source of plant protein in global livestock farming.

Applications

Food consumption. Refined deodorised soybean oil is used for direct human consumption and as an ingredient for the production of margarines, mayonnaise, sauces, confectionery and bakery products. Due to its high smoke point, it is suitable for frying and deep-frying.

Biodiesel production. Soybean oil is one of the main feedstocks for biodiesel production (fatty acid methyl esters) in the USA, Brazil and Argentina. A significant part of the soybean crop is directed to these purposes.

Feed production. Soybean meal serves as the main protein component of compound feeds for pigs, poultry and cattle. Soybean oil is also added to feed to increase its energy value.

Technical and industrial purposes. Soybean oil is used for the production of lubricants, hydraulic fluids, soap, paints, varnishes and bioplastics. Lecithin is used as an emulsifier in the food, pharmaceutical and cosmetic industries.

Safety and Storage

Soybean oil is a food product. Refined oil is stored in closed, darkened rooms at a temperature not exceeding 25 °C and a relative humidity of not more than 75%. Unrefined oil has a shorter shelf life due to its tendency to oxidise and become rancid. Oil is a combustible material, so fire safety measures must be observed during storage.

Market and Trends

The global soybean oil market demonstrates steady dynamics. The largest producers of soybean oil are China, the USA, Brazil, Argentina and India. The USA and Brazil are the leading exporters, while China and India are the largest importers. A significant part of soybean oil in the USA and Brazil is directed to biodiesel production, which affects the balance of food and technical consumption.

Key industry trends include: growing demand for high-oleic soybean oil (as more resistant to oxidation and healthier), expansion of biodiesel production, and increased soybean processing within producing countries. Producers with access to quality raw materials and modern refining capacities occupy stable competitive positions.

Conclusion

Soybean oil remains a strategically important product of the global agro-industrial complex, combining the functions of a food product, feedstock for biodiesel and a feed component. Understanding the classification according to GOST 31760-2012, the fatty acid composition (including differences between traditional and high-oleic varieties), refining technologies and applications is the basis for competent selection of oil for specific purposes.