Oilseed Processing Methods and Nutritional Value

Oilseed Processing Methods

Three main methods for removing oil from oilseeds:
- Screw press or expeller
- Direct solvent
- Pre-press solvent

Seeds are cracked, dried, cooked, and extruded through a die.
Temperature is closely regulated during extrusion to inactivate antinutritional factors without reducing nutritional value.
Excessive heat can reduce protein solubility and biological value through the Maillard or browning reaction.
- Feedstuffs, including forages, are susceptible to the Maillard reaction when exposed to excessive heat.
- The Maillard reaction creates linkages between carbohydrates and amino acids, reducing nutrient availability and nutritional value.
Screw-pressed oilseed meals have the highest lipid content (4-5%).

Soybeans are cracked, cooked, ground, and extracted with hexane or another solvent to remove lipids.
The process is typically performed at low temperatures.
During solvent recovery, the meal is heated to inactivate antinutritional factors.

Nutritional value varies:
- Between different oilseeds
- Within a variety of oilseed
- Between different processing methods
Oilseed meals are generally high in protein.
- Minimum crude protein content is 40% on a dry-matter basis.
- Protein content is standardized prior to marketing.
- Most of the nitrogen is in the form of true protein.
- The protein is highly digestible.
- Moderate to good biological value, but generally lower than animal protein feeds.
- Low in cystine and methionine.
- Lysine content is variable and low in all except soybean meal.
Energy value varies greatly between oilseed meals.
Mineral content:
- Low in calcium.
- High in phosphorus, but at least 50% is relatively unavailable to monogastrics.
Vitamin content:
- Low to moderate in B vitamins.
- Low in vitamin E and carotene.