What is an oil mill?

An oil mill is a processing unit for raw materials containing oil. It combines an oil press - usually a screw press - with seed cleaning, storage, filters and bottling. The goal: to press high-quality vegetable oil from seeds such as rapeseed, sunflower, linseed or nuts. Classic mills worked with stone grinding and hydraulic presses, modern oil mills like those in the oelwerk series use Screw presses with s-inox stainless steel.

History: from oil stone to screw press

Oil pressing is one of the oldest processing techniques: as early as 4,000 BC. In the Mediterranean region, olive paste was pressed using stone mills. Impact mills dominated Central Europe in the Middle Ages, the hydraulic press dominated in the 19th century, and the continuous screw press became established from the 1950s onwards. Today it is standard for all classes - from farms to industrial plants.

Cold vs. hot pressing

Cold pressing: The seeds are pressed without any external heat supply; the oil outlet temperature remains below 40–60 °C (depending on the variety). Advantages: high retention of aromas, vitamin E, tocopherols, polyphenols - the end product is marketable as a "virgin oil".
Hot pressing: Pre- or heat treatment increases the yield (often 5-15% higher), but costs quality. Industrially often used to maximize yield, then refining.
Extraction (solvent process): Non-mechanical, with hexane - not enough for oelwerk mills; we produce exclusively mechanically.

Processable seeds

With a modern screw press, over 50 oil-containing raw materials can be processed:

• Very oil-rich (40–55% oil): Rapeseed, mustard, sunflower, hemp, sesame, poppy seeds
• Medium-oily (30–40%): Linseed, pumpkin seed, soy, Walnut
• Specialties: Black cumin, thistle, safflower, poppy, rosehip seed, grape seed
• Non-seeds: Avocado (pulp), olives, coconut

Each seed requires its own pressure, temperature and speed configuration. oelwerk machines can be adapted to the seeds by changing the press spindle and temperature sensors.

Oil yield – what influences it?

The actual yield depends on many factors:

• Seed moisture: Optimum 6–10% — too dry: seeds form dust; too moist: screw slips
• Pressing pressure: 800–1,500 bar usual
• Spindle throughput: low throughput = higher yield
• Seed maturity: fully ripe produces more oil than unripe
• Storage conditions: low temperature, dry, dark
• Pre-treatment: Peeling (e.g. sunflower) significantly increases the yield

For rapeseed, the mechanical yield is approx. 30-35 % of the initial weight, for sunflower seeds it is 35-40%.

Quality criteria

A natural vegetable oil is evaluated according to three axes:

• Chemical: Acid number (FFA) < 1 mg KOH/g, peroxide number < 5 meq/kg, anisidine number < 4
• Sensory: Smell and taste without burnt notes, without rancid overtones, pure
• Visual: Free of trub after filtration; Color typical of the variety (rapeseed yellow-green, linseed gold, sesame dark-amber)

Size classes - from hobby to industry

The choice of oil mill is based on the annual amount of seed:

• Hobby: < 50 kg of seed/day - e.g. B. Stamp presses
• Direct marketers: 50–200 kg/day — OW 100 s-inox / OW 400 w-inox
• Manufactory: 200–1,000 kg/day — OW 500/510 s-inox
• Industry: 1–10 t/day — OW 5500 / OW 7500 s-inox
• Large industry: > 10 t/day — Premium lines

Market & direct marketing

According to UFOP, there are around 800 decentralized oil mills in Germany and over 3,000 decentralized locations across the EU. Direct marketing is constantly growing - consumers are increasingly asking for regional, cold-pressed oils. For direct marketers, an oil mill is both a value creation and marketing tool: the end product is a publicly visible, regional premium food.

Law & Hygiene

An oil mill for food pressing must comply with the following standards: EU Regulation 852/2004 (food hygiene), HACCP concept, optional certifications IFS Food, BRCGS, Organic (EC-Öko-VO 2018/848). oelwerk machines are manufactured exclusively from food-grade stainless steel 1.4301/1.4404 (s-inox) and are designed to be CIP-capable.

Investment & support

There are often support programs for agricultural businesses: AFP (agricultural investment support), Diversification bonuses, regional economic development. The investment costs for a complete oil mill range from the low five-figure range (small farm mill) to the seven-figure range (industrial plant). Exact investment planning on request - we calculate quantity requirements, energy requirements and amortization on a project-specific basis.

Delivery, commissioning & maintenance

oelwerk delivers worldwide. Delivery time per system depends on configuration and factory utilization — typical ranges from a few weeks for standard presses to several months for individual industrial lines. Training of the operators takes place online or on site (OW introductory training). Maintenance recommendation: daily cleaning of the press spindle, annual service check - the machines will last over 20 years if well cared for.