Musard Oil Processing

Cold-Pressing Process for Mustard Seeds

Definition of Cold-Pressing: The process involves no roasting or steaming of the seeds; the oil extraction temperature remains ≤60°C, preserving myrosinase, the pungent flavor, and Vitamin E. Oil yield is lower than in hot-pressing, and the crude oil appears cloudy, requiring settling and filtration. Mustard seeds contain 35–46% oil; actual cold-pressed yield is approximately 28–34%.
Safety Warning: Homemade "artisanal" oil is unrefined, and the breakdown products of glucosinolates can be irritating; long-term, large-scale consumption of the raw oil (e.g., in cold dishes) is not recommended. It is best to heat the oil slightly before consumption. Small-scale home pressing equipment often struggles to meet full safety standards, posing higher risks compared to commercial oils.

Complete Process Flow

 Raw Material Cleaning (Crucial Step)
1. Air separation/Sieving: Remove dust, shriveled seeds, and stalk debris; use magnetic separation to remove iron filings; manually pick out stones and moldy or blackened seeds (bad seeds cause the oil to quickly go rancid/develop an off-flavor).
2. Drying and Moisture Adjustment: Optimal moisture content for cold-pressing is 6%–8%.
Traditional test method: Press a fingernail into the seed; it should crack open and leave an oil trace without sticking to the finger or crumbling into powder.
Excessive moisture → Cloudy oil and sticky press cake (poor oil flow); too dry → Significant drop in oil yield.
Air-dry or sun-dry at low temperatures; strictly avoid intense sun exposure or high-temperature roasting, which would turn the process into hot-pressing.
Do not wash with water; it is difficult to dry thoroughly afterward, making the seeds highly susceptible to mold and rancidity.
Pressing (Core of Cold-Pressing)
1. Equipment: Small household cold-press screw oil press or hydraulic cold press; disable the heating function and control the press chamber temperature to <60°C (ideally 40–50°C).
2. Direct feeding: No roasting or steaming; press the raw seeds directly.
Two-pass pressing: Extract oil in the first pass, then crush the press cake and feed it back into the machine for a second press to increase the total oil yield.
The resulting product is crude oil: dark yellow in color with a distinct, pungent mustard aroma. 3. Filtration and Sedimentation (Essential Steps)
1. Coarse filtration: Filter the freshly extracted crude oil through food-grade cotton cloth or cheesecloth to remove large seed particles.
2. Static sedimentation: Let the oil settle in a cool, dark place for 7–15 days; "foots" (sediment consisting of proteins and fine seed powder) will accumulate at the bottom.
3. Collect the clear oil from the top layer; do not consume the bottom sediment directly—it can be re-filtered or used as animal feed.
Avoid using simple filter paper for rapid filtration; cold-pressed crude oil contains high levels of colloids, so rapid filtration fails to remove impurities thoroughly, making the oil prone to rancidity during storage.

Cold-Pressed Mustard Seed Oil

Pre-treated raw seeds are pressed directly without roasting; oil extraction temperature is <60°C. Flavor is pungent and spicy.
Strong mustard aroma; lower oil yield (28–34%). Shorter shelf life; prone to oxidation.

Hot-Pressed Mustard Seed Oil

Seed roasting: 110–140°C
Oil extraction temperature: 100–120°C. Rich, toasted aroma; reduced pungency.
High oil yield: 34–40%. Long shelf life.