Extraction Methods fats and oils food tech
Download as PPTX, PDF0 likes144 views
The document discusses the extraction methods for vegetable oils and fats, highlighting the significance of extraction as the first step in refining. It details various methods including cold pressing, rendering, mechanical pressing, and solvent extraction, emphasizing modern extraction techniques that combine different processes for efficiency. Additionally, it describes the handling and preparation of raw materials, showcasing the importance of storage and processing to minimize deterioration.
Extraction Methods fats and oils food tech
- 1. 1 EXTRACTION METHODS Dr. Muhammad Asim Shabbir
- 2. 2 Introduction ■ Extraction is the first step in the refining process of vegetable oils and fats. ■ Oils and fats are extracted from their original source (the seeds, fruits or other oil-bearing raw materials) using a variety of methods. ■ For crude or virgin oils, the oil is extracted directly from the fruit by means of a simple mechanical press and used without the need for any further processing. This process is known as cold pressing. ■ Modern oil mills extract oil using a combination of pressing, cooking and solvent extraction techniques.
- 3. 3 Cont… ■ A typical extraction system consists of: i. Handling and storage of raw materials ii. Cleaning to remove tramp iron, dirt, foreign weed seeds, and stones iii. Removing hulls or cortex in cracking, aspirating, or screening operations iv. Cracking or rough grinding the kernels, meats, or prepressed cake v. Steaming (rendering, tempering or cooking) of the meats vi. Flaking the small pieces between smooth flaking rolls vii. Extracting the oil with or without solvent vii. Separating the meal, from residual oil through solvent extraction viii.Removing the solvent from oil-solvent miscella to obtain oil.
- 4. 4 Handling and preparation of oil bearing raw material ■ The handling and control of the raw materials for the oil seed industry can be primarily characterized by: 1. Short harvest season 2. Necessity to move them into protected storage in minimum time 3. Required care before they can be processed ■ The raw materials can be treated and stored successfully with minimal deterioration long enough to allow the processing industry to operate throughout the year.
- 5. 5 Cont… ■ Storage ■ Bulk storage in warehouses on flat floors has the advantage of easy control of oil seeds, like cottonseeds, sunflower seeds, corn germ and meals etc. ■ To prevent self heating or autocombustion of the seeds, recycling by horizontal and vertical transportation means are recomended.
- 6. 6 Types of extraction methods ■ Fats and oils may be recovered from oil-bearing animal or plant sources by three general methods, with varying degrees of mechanical simplicity: 1. Rendering 2. Pressing with mechanical presses 3. Extracting with volatile solvents
- 7. 7 Essential steps in the extracting and refining of edible oil from oilseeds.
- 8. 8 Rendering ■ Rendering of Animal fats ■ The rendering process is applied on a large scale to the production of animal fats such as tallow, lard, bone fat, and whale oil. ■ It consists of cutting or chopping the fatty tissue into small pieces that are boiled in open vats or cooked in steam digesters. ■ The fat, gradually liberated from the cells, floats to the surface of the water, where it is collected by skimming. ■ The membranous matter (greaves) is separated from the aqueous (gluey) phase by pressing in hydraulic or screw presses, additional fat is thereby obtained.
- 9. 9 Cont.. ■ Rendering of Vegetable Oils ■ The crudest method of rendering oil from oleaginous fruits, still practiced in some countries consists of: • Heaping them in piles • Exposing them to the sun • Extracting the oil that remains in dried leftovers ■ This process is used in the preparation of palm oil, fresh palm fruits are boiled in water, and the oil is skimmed from the surface. ■ Such processes can be used only with seeds or fruits (such as olive and palm) that contain large quantities of easily released fatty matter.
- 10. 10 Mechanical pressing ■ With many oil-bearing seeds and nuts, rendering will not liberate the oil from the cellular structures in which it is held. ■ In these cases the cell walls are broken by grinding, flaking, rolling, or pressing under high pressures to liberate the oil. ■ The general sequence of modern operations in pressing oilseeds and nuts is as follows: i. The seeds are passed over magnetic separators to remove any stray bits of metal. ii. If necessary, the shells or hulls are removed. iii. The kernels are converted to coarse meal by grinding them between grooved rollers or with special types of hammer mills. iv. They are pressed in hydraulic or screw presses with or without preliminary heating, depending on the type of oil-bearing material and the quality of oil desired.
- 11. 11 Pressing machines ■ Many different mechanical devices have been used for pressing. ■ The Romans developed a screw press, for the production of olive oil centuries ago ■ The Chinese employed the same series of operations followed in modern pressing mills which include: 1. Bruising or grinding the seeds in stone mills, 2. Heating the meal in open pans 3. Pressing out the oil in a press
- 12. 12 Cont… ■ The yield of oil from the hydraulic press is considerably higher than that from earlier processing methods because of the much higher applied pressures. ■ In open presses, the ground seed material was confined in cloths of human hair or, less commonly, camel hair. Pressures on the cake varied from approximately 70 to 140 kilograms per square centimeter (1,000 to 2,000 pounds per square inch) ■ Closed-type press were later introduced in which the oil-containing material was confined in a strong perforated steel cage during the pressing operation. Pressures of approximately 400 kilograms per square centimeter or more were attained.
- 13. 13 Cont… ■ The modern screw press replaced many of the hydraulic presses because of following benefits: 1. Continuous process 2. Greater capacity 3. Requires less labor 4. Remove more oil. Screw Press
- 15. 15 Solvent extraction ■ Cakes obtained by pressing operations still retain 3 to 15 percent of residual oil ■ When the value of the oil is considerably greater as oil than as a part of the meal, it is desirable to obtain more complete extraction with solvents. ■ Modern commercial methods of solvent extraction use volatile purified hydrocarbons, especially the various grades of petroleum benzene. ■ In large-scale operations, solvent extraction is a more economical means of recovering oil than is mechanical pressing. Example of Solvent extractor (Soxhlet’s apparatus)
- 16. Cont…. Through the screw conveyor, the pre-pressed cake from the pre-pressing workshop is sent to the extraction workshop. Through the bucket elevator, the cake is lifted to the overhead screw elevator and enters the extraction tank. ■ When the temperature reaches 45-50 , the solvent (n-Hexane) enters the tank ℃ extractor through the spraying pipe. ■ After immersion for 40-60 minutes, oil is separated from pre-pressed cake and this mixture of solvent + oil is known as miscella. ■ The miscella is pumped into storage tank, and fresh solvent is pumped into the extraction tank to immerse again for 40 minutes. ■ The miscella is then transferred to distillation tank where solvent is removed, and crude oil is separated and collected which can be further refined.
- 18. Cont.. Essential Oils ■ Soxhlet’s apparatus is most commonly used in laboratory for solvent extraction. ■ However, the industrial method employs food grade solvents like hexane and ethanol to isolate essential oils from plant material. It is best suited for plant materials that yield low amounts of essential oil. ■ Through this process, the non-volatile plant material such as waxes and pigments, are also extracted and sometimes removed through other processes. ■ Once the plant material has been treated with the solvent, it produces a waxy aromatic compound called a “concrete”. When this concrete substance is mixed with alcohol, the oil particles are released. ■ The chemicals and waxes used in the process are then removed by various techniques of heating and distillation and the oil is collected after the alcohol is removed from the mixture.