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Oil seed processing

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13. Introduction: Present Status And Future Prospects of oil seeds

14. Physical Properties of oilseeds

15. Nutritional value in oil seeds

16. Anti nutritional compounds in oil seeds

18. Introduction to post harvest technology of oil seeds

19. Introduction to oil seed milling

20. Unit operations involved in oil seed processing (decortications, cleaning, grading , pretreatments before oil extraction , storage of oil seeds)

21. Oil extraction by ghanis, advantages and disadvantages

22. working mechanism of hydraulic press , advantages and disadvantages 23. Screw press oil expellers working mechanism, its advantages and disadvantages

24. Solvent extraction method for oil seeds

25. Oil refining-degumming, neutralization , bleaching, filtration, deodorizatio

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• Dietary fat includes all the lipids in plant and animal tissues that are eaten as food.
• Dietary fat –Visible and Invisible fat.
• Plant derived dietary lipids –Vegetable fats/oils (Visible fat).
• Vegetable oils are obtained by mechanical expelling or solvent extraction of oleaginous seeds (soybeans, rapeseed, sunflower, etc.) or oleaginous fruit like palm and olive
• The most common vegetable fats (solid at room temperature) or oils (liquid at room temperature) are essentially composed of triacylglycerol (TG/TAG); glycerolipids(Otherwise called fatty acid esters of glycerol), which constitutes 90 -98%.

Dietary fat

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• In addition, they contain minor amounts of phospholipids, mono & diglycerides.
• Non-triglyceride fraction of 2 -10% contains various bioactive molecules, including sterols, tocopherols, waxes, carotenoids, flavor compounds, etc.
• Some of them such as diglycerides, vitamins, phytosterols, tocopherols, and polyphenols have important health benefits in humansnd therefore they should not be removed during processing.
• Other compounds known for their negative effect on the quality and stability of oils, include free fatty acids, unsaponifiable matters, waxes, pigments, solid impurities (mainly fibers), oxidation products (peroxides, aldehydes, ketones, alcohols, and oxidized fatty acids)

Cont…

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• Refined vegetable oil means any vegetable oil which is obtained by expression or solvent extraction of vegetable oil bearing materials, deacidified with alkali and/or physical refining and/ or by miscell are fining using permitted food grade solvents followed by bleaching with absorbent earth and /or carbon and deodourised with steam. No other chemical agent shall be used.

Refined vegetable oil

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Methods

• Mechanical Extraction
• Ghani
• Power Ghani
• Screw press
• Hydraulic press
• Solvent (Hexane) extraction
• determine the upper limit of available oil from the oilseeds
• screen the best oilseed species
• Super critical fluid extraction
• Cold press
• To determine optimal conditions for oil extraction
• Evaluate economic feasibility of cold press
• Novel continuous extrusion extraction
• combine high shear extrusion and high efficient solvents
• Evaluate economic feasibility of extrusion method

ASE System

For oil extraction

RotoVap System

Separates Oil and solvent mixture

Accelerated Solvent Extraction (ASE)

• Run with 10 g of sample
• About 15 min oil extraction time
• 16 ml. solvent consumption

Cold press for oil extraction

Continuous Extrusion-Solvent Extraction

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• Combine high shear extrusion and high efficient solvents to efficiently extracting oils from different oilseeds for further conversion into aviation fuels.
• Using a single screw extruder to determine the upper limit of available oil from the oilseeds
• Combine with solvent extraction
• Quality analysis of the extracted oils
• Equipment: Single-screw extruder (Brabender, Plasti-Corder (PL 2000)

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• Degumming is a crucial step in the refining process of vegetable oils.
• It allows the elimination of “gums” or “mucilage,” composed mainly of phospholipids from the crude oil as well as compounds such as carbohydrates, proteins, and trace of metals
• There are four types of degumming processes,
1. Water degumming,
2. Acid degumming,
3. Dry degumming, and
4. Enzymatic degumming.
• Enzymatic refining is a kind of biotechnological process in which a phospholipase, especially the phospholipase C, converts nonhydratable phospholipids into lysophospholipids

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Degumming

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• Free fatty acids content is expressed in g/100 g of oleic acid except for some oils such as palm oil where it is reckoned in g/100 g of palmitic acid, and coconut and palm kernel oils, where it is in g/100 g of lauric acid. Acidity depends on the nature of the oil, which, in turn, depends upon its geographical origin, harvesting, seed crushing conditions, and storage duration
• Many methods for fatty acids elimination have been developed to improve the value of degraded vegetable oils. Some include chemical refining with caustic soda neutralization and physical refining based on steam distillation
• In chemical refining, the oil is treated with an alkali solution (caustic soda) that reacts with the free fatty acids (FFA) present

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Neutralization

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• This operation eliminates alkaline substances present in the oil from coming out of the neutralization turbine (caustic soda and excess soap) as well as last metallic and phospholipids traces and other impurities.
• The oil, free of gums, traces of soapstock, and other impurities, is pumped through a plate heat exchanger where it is heated by steam. It is then sent to the centrifugal mixer to be combined with water and further centrifuged in a centrifuge for water washing.
• After this treatment, water-washed oil is dried with a vacuum dryer until the moisture level of the oil falls below 0.1%. This stage will be followed by bleaching.

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Washing and Drying

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1. The bleaching is a critical step in the refining process of oils, preceded generally by degumming, neutralization, and drying processes.
2. Bleaching is a complex physical and chemical process employed in the refining of vegetable oils.
3. The objective of bleaching (or decolorizing) is to reduce the levels of colored pigments (carotenoids and chlorophylls).
4. It also further removes residue traces of phosphatide, soap, phospholipid contaminants, lipid peroxidation products, and other impurities.
5. Finally, it indirectly impacts the deodorized oil color.
6. To perform bleaching, adsorption bleaching clays, activated carbon, special silica, or a combination of these are used .

Bleaching

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• Waxes are esters of long-chain primary alcohols and long fatty acids.
• These acids have low solubility in oils, are high melting, and usually crystalline during the winter season at low and room temperature.
• The wax generally does not negatively affect the functionality of the vegetable oil.
• The presence of wax affects the quality aspect of the oil, which gives it a cloudy appearance especially during the winter season.
• Its hazy appearance is due to the precipitation of dissolved waxes.
• The dewaxing process is also called winterization.
• The term “winterization” appears as during winter when the temperature is low, waxes present in the oil crystallize, thereby giving a hazy appearance to the oil.

Dewaxing or Winterization

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• The dewaxing process includes three main processing steps.
• In the first one, the bleached oil should be heated to 328°K (55°C) to make sure the oil is completely liquid.
• Secondly, the oil is cooled slowly to 283–288 K (10–15°C). Ideally, the chilled oil is held for several hours at this temperature.
• In the third step, after finishing the crystallization, the cooled oil is pumped into a filter machine to separate the wax from vegetable oil.
• The filtration yields a clear liquid oil and the by-product waxes.

Cont…

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• The last stage in refining involves high temperature and requires a great care. A deodorized oil is devoid of any taste, even pleasant ones.
• Deodorization is a simple distillation process.
• This operation allows for the elimination of free fatty acids and removes odors, different off-flavor components, contaminants (pesticides, light polycyclic aromatic hydrocarbons, and other volatile components)

Deodorization

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Physiochemical properties of oil