Generally speaking, soybeans can be cold-pressed directly without roasting, but there are obvious drawbacks in oil yield, oil quality and machine operation.
Raw soybeans have high moisture and protein content. Direct cold pressing without heating will lead to a much lower oil extraction rate. Most raw soybeans only achieve an oil yield of 12%–16%, while properly roasted soybeans can reach 18%–22%. Besides low oil output, unroasted soybean crude oil contains more lipoxygenase, which easily causes oxidation, resulting in strong beany flavor, dark oil color and short shelf life.
In terms of equipment operation, raw soybeans are tough and elastic. Feeding unprocessed soybeans into a screw oil press will increase machine load, cause excessive residue discharge, accelerate wear of the press shaft and press cage, and even lead to blockage and shutdown.
If you insist on direct cold pressing for organic raw soybean oil production, you must pre-dry soybeans first to reduce moisture to 7%–9%. Slow feeding and low pressing pressure are required during operation to avoid equipment damage. It is also necessary to equip an oil filter machine to remove protein residues and improve oil clarity.
For most small oil mills and commercial production, moderate low-temperature roasting is still recommended. Low-temperature heating can retain most nutritional substances of soybean oil, greatly reduce beany odor, improve oil yield and extend oil storage time, balancing product quality and production efficiency.
Our automatic screw oil press supports both hot pressing and cold pressing of soybeans. We also provide matched soybean roaster and oil filter machine to help you get higher oil yield and premium refined soybean oil. Contact us to get the best production configuration for your soybean oil mill.
