An oil mill is a grinding mill designed to crush or bruise oil-bearing seeds, such as linseed or peanuts, or other oil-rich vegetable material, such as olives or the fruit of the oil palm, which can then be pressed to extract vegetable oils, which may be used as foods or for cooking, as oleochemical feedstocks, as lubricants, or as biofuels. The pomace or press cake – the remaining solid material from which the oil has been extracted – may also be used as a food or fertilizer.
Oil-rich vegetable materials have been processed mechanically to extract the valuable oils for thousands of years, typically using vertical millstones moving around a central post (edge runner stones or kollergangs in an edge mill) to crush or bruise the seeds or fruit which can then be stamped or pressed to extract the oil. A treadmill, windmill or watermill was later used to drive the milling and pressing machinery, replaced in modern times with steam and later other power sources. Bullock or horse driven oil mills, such as the traditional ghani in Bangladesh, have increasingly been replaced by power-driven steel oil mills. [1]
In some areas, watermills may be "double" water mills, with machinery for grinding wheat on one side of the watercourse and machinery for extracting oils on the other side.
Historical wind-driven oil mills could process between 100 and 200 tons of raw materials per year.
Modern mechanical oil mills can process up to 4,000 tons per day in hot pressing processes, and up to 25 tons per day cold pressed. Industrial oil pressing methods usually use a screw to crush the raw materials in a continuous process, before extraction of the oil from the press cake using a centrifuge or a solvent such as hexane.
Edible oils may be extracted for culinary purposes. Non-edible oils can be used in the manufacture of soaps saponification, biodisel production biodiesel, paints and varnishes, or as fuel for oil lamps. Important feed stocks include soybeans, rapeseed (canola), sunflower seeds, cottonseed, and maize (corn), as well as peanuts, olives, various nuts, sesame seeds, safflower, grape seeds, flaxseed (linseed), and Mustard oil which is a secondary product of the Sarin production. Palm oil is extracted from the pulp of the oil palm fruit, palm kernel oil from the kernel of the oil palm, and coconut oil from the kernel of the coconut.
Olive oil is a liquid fat obtained by pressing whole olives, the fruit of Olea europaea, a traditional tree crop of the Mediterranean Basin, and extracting the oil.
Palm oil is an edible vegetable oil derived from the mesocarp of the fruit of oil palms. The oil is used in food manufacturing, in beauty products, and as biofuel. Palm oil accounted for about 36% of global oils produced from oil crops in 2014. Palm oils are easier to stabilize and maintain quality of flavor and consistency in ultra-processed foods, so they are frequently favored by food manufacturers. Globally, humans consumed an average of 7.7 kg (17 lb) of palm oil per person in 2015. Demand has also increased for other uses, such as cosmetics and biofuels, encouraging the growth of palm oil plantations in tropical countries.
Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of edible plants. Like animal fats, vegetable fats are mixtures of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or fats from seeds. Olive oil, palm oil, and rice bran oil are examples of fats from other parts of plants. In common usage, vegetable oil may refer exclusively to vegetable fats which are liquid at room temperature. Vegetable oils are usually edible.
Coconut oil is an edible oil derived from the kernels, meat, and milk of the coconut palm fruit. Coconut oil is a white solid fat below around 25 °C (77 °F), and a clear thin liquid oil at higher temperatures. Unrefined varieties have a distinct coconut aroma. Coconut oil is used as a food oil, and in industrial applications for cosmetics and detergent production. The oil is rich in medium-chain fatty acids.
Cottonseed oil is cooking oil from the seeds of cotton plants of various species, mainly Gossypium hirsutum and Gossypium herbaceum, that are grown for cotton fiber, animal feed, and oil.
Sesame oil is an edible vegetable oil derived from sesame seeds. The oil is one of the earliest-known crop-based oils. Worldwide mass modern production is limited due to the inefficient manual harvesting process required to extract the oil. Oil made from raw seeds, which may or may not be cold-pressed, is used as a cooking oil. Oil made from toasted seeds is used for its distinctive nutty aroma and taste, although it may be unsuitable for frying, which makes it taste burnt and bitter.
Expeller pressing is a mechanical method for extracting oil from raw materials. The raw materials are squeezed under high pressure in a single step. When used for the extraction of food oils, typical raw materials are nuts, seeds and algae, which are supplied to the press in a continuous feed. As the raw material is pressed, friction causes it to heat. In the case of harder nuts the material can exceed temperatures of 120 °F (49 °C).
Olive oil extraction is the process of extracting the olive oil present in olive drupes. Olive oil is produced in the mesocarp cells, and stored in a particular type of vacuole called a lipo vacuole, i.e., every cell contains a tiny olive oil droplet. Olive oil extraction is the process of separating the oil from the other fruit contents. It is possible to attain this separation by physical means alone, i.e., oil and water do not mix, so they are relatively easy to separate. This contrasts with other oils that are extracted with chemical solvents, generally hexane. The first operation when extracting olive oil is washing the olives, to reduce the presence of contaminants, especially soil which can create a particular flavor effect called "soil taste".
Sunflower oil is the non-volatile oil pressed from the seeds of the sunflower. Sunflower oil is commonly used in food as a frying oil, and in cosmetic formulations as an emollient.
Cottonseed is the seed of the cotton plant.
A stamp mill is a type of mill machine that crushes material by pounding rather than grinding, either for further processing or for extraction of metallic ores. Breaking material down is a type of unit operation.
Fragrance extraction refers to the separation process of aromatic compounds from raw materials, using methods such as distillation, solvent extraction, expression, sieving, or enfleurage. The results of the extracts are either essential oils, absolutes, concretes, or butters, depending on the amount of waxes in the extracted product.
Plant oils or vegetable oils are oils derived from plant sources, as opposed to animal fats or petroleum. There are three primary types of plant oil, differing both the means of extracting the relevant parts of the plant, and in the nature of the resulting oil:
Mango oil, mango kernel fat, or mango butter, is an oil fraction obtained during the processing of mango butter. Mango oil is a seed oil extracted from the stone of the mango, the fruit of the Mangifera indica tree. The oil is semi-solid at room temperatures, but melts on contact with warm skin, making it appealing for baby creams, suncare balms, hair products, and other moisturizing products. The oil is a soft yellow color with a melting point of 32–42 °C (90–108 °F).
Tamanu oil is pressed from nuts of either Calophyllum inophyllum (usually) or Calophyllum tacamahaca (ati), tropical trees belonging to the Calophyllaceae family. The oil originates in Polynesia, where it continues to play an important cultural role.
A finishing oil is a vegetable oil used for wood finishing.
Vateria indica oil is extracted from the seeds of the Vateria indica plant, a species in the family Dipterocarpaceae. The Vateria indica plant is indigenous to the Western Ghats, Kerala and Tamil Nadu regions of India. It thrives in the evergreen forests, surviving up to 800 meters above sea level. Oil from the seeds of the plant is extracted through a chemical refining process which makes the plant edible.
An oilseed press is a machine that lies at the center of vegetable oil extraction. This is due to the fact that this technology is designed to release oil from oilseeds. Multiple oilseed press layouts have been developed over time to complete this process, with each having its own distinct set of advantages and disadvantages. Moreover, the products that are created by oilseed presses, namely oil and oilseed meal, possess great nutritive benefits for humans and livestock respectively. The oilseed press, being at the center of the oil-extraction process, is joined with various other pieces of equipment and procedures that form a pre- and post-extraction system.
Cooking oil is a plant or animal liquid fat used in frying, baking, and other types of cooking. Oil allows higher cooking temperatures than water, making cooking faster and more flavorful, while likewise distributing heat, reducing burning and uneven cooking. It sometimes imparts its own flavor. Cooking oil is also used in food preparation and flavoring not involving heat, such as salad dressings and bread dips.
