Such processes can be used only with seeds or fruits such as olive and palm that contain large quantities of easily released fatty matter. 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. The residue is used for animal feed or fertilizer. Several centrifugal separation processes were developed in the s. Cells of the fatty tissues are ruptured in special disintegrators under close temperature control. The protein tissue is separated from the liquid phase in a desludging type of centrifuge, following which a second centrifuge separates the fat from the aqueous protein layer.
Compared with conventional rendering, the centrifugal methods provide a higher yield of better-quality fat, and the separated protein has potential as an edible meat product. Fat and oil processing. Article Media. Info Print Print. Table Of Contents. Submit Feedback. Thank you for your feedback.
Introduction General methods of extraction Rendering Fruits and seeds Animal fats Pressing Pressing processes Pressing machines Solvent extraction Processes Extractors Processing of extracted oil Refining Alkali refining Water refining Bleaching Destearinating or winterizing Hydrogenation Hydrogenation reactions Isomerization reactions Deodorization. Written By: Marvin W.
Formo R. Paul Singh A. Richard Baldwin.
Oils and Fats | IFST
See Article History. Facts Matter. Start Your Free Trial Today. Load Next Page. More About. Free fatty acids are generated from the hydrolysis of triglycerides or phospholipids. They are usually eliminated during deodorization and physical refining processes due to their impacts on foaming and the smoke point of oils. However, their contents are higher when oils have high mono- and diglyceride percentages.
Free fatty acids with a low HLB value of approximately 1. Most fatty acids of natural origin have an alkyl chain comprising between 4 C4 and 22 C22 carbon atoms. The most common unsaturated fatty acids are C16 and C Short or medium chain fatty acids are normally recognized below these lengths whereas fatty acid chains with more than 18 carbons are often deemed to be long chain fatty acids [ 19 ]. Apart from the very low content of cholesterol in vegetable oils, plant sterols, namely phytosterols, are not only some of the important minor compounds with considerable biological activities [ 20 , 21 ], but also the predominant compounds in the unsaponifiable fraction of vegetable oils.
Phytosterols are affected by several oil refining processes, in which deodorization can significantly reduce the total sterols due to distillations and esterifications of free sterols [ 11 ].
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Since phytosterols are rather hydrophobic and poorly soluble in fats, they are usually esterified to make them liposoluble for easily processing handling in the food industries [ 23 ]. Tocopherols and tocotrienols are well-known vitamin E compounds, which are vital for enhancing the oxidative stability of vegetable oils because of their strong inhibitory effects against lipid oxidation [ 24 , 25 ].
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Naturally, tocopherols are presented as free alcohols while tocotrienols are in esterified forms [ 26 ]. The content of tocopherols and tocotrienols in different types is dependent on the oil type, which may also be influenced by their unintentional removal during the oil refining, especially in the deodorization [ 27 , 28 ].
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A water content of less than 0. Since water is known for its immiscibility with oils, it can probably provide oil-water interfaces in vegetable oils where endogenous or exogenous surface active compounds with low HLB values migrate, preferably concentrate to form and to stabilize association colloids such as reverse micelles and lamellar structures [ 30 ]. These energetically preferential structures enable the coexistence of both hydrophilic and lipophilic compounds, which may inspire a novel solution for the extraction of water-soluble compounds in vegetable oils. A wide range of phenolic compounds were reported at varying levels in vegetable oils particularly in olive oils depending on the oil type, ripeness, storage and processing conditions [ 31 ].
These polar compounds possessing free radical scavenging activity are important for the oxidative stability of the polyunsaturated fatty acids in vegetable oils. They tend to stay in the polar region of association colloids. Squalene is a triterpenoid hydrocarbon of thirty carbons, which presents in vegetable oils at a very low level [ 32 ].
Fat and oil processing
It can be used in healthy foods and its hydrogenated form can be applied as a moisturizing agent in cosmetics. Pigments such as carotenoids in most virgin oils appear as a conjugated system with alternated double bonds in a long chain of forty carbons. They can be classified in nonpolar e. Chlorophylls usually mask the colour of carotenoids in freshly pressed virgin oils, whose variable contents are determined by the oilseed maturity and the oil extraction method.
Furthermore, the presence of proteins and peptides has also been investigated as minor components in virgin oils, which has attracted increasing concerns on the stability and the allergenicity of oils [ 33 , 34 ]. Besides, trace quantities of other components such as metals, hydrocarbons and amphiphilic lipid oxidation products are deleterious to oil quality so that they should be reduced to the minimum [ 22 ]. Although no official standards exist so far for the alternatives to petroleum-based solvents, the ideal properties of a green solvent to minimize environmental impacts during its complete life cycle have been summarized [ 35 ].
These bio-sourced or agro-based solvents should be non-volatile, safe, easy to regenerate and economically viable. Most importantly, they must have considerable dissolving power and selectivity. Hence, vegetable oils may have the potential of being a green alternative solvent due to their good consistency with ideal solvent properties.
Empirical infusion or maceration of medicinal and aromatic plants in vegetable oils as solvents dates back to ancient civilizations as already mentioned. In recent years, edible commercial vegetable oils have been successfully enriched or aromatized with bioactive compounds from herbs, spices or other plant materials in order to improve their nutritional values and organoleptic qualities, and to prolong shelf-life as well.
As the consumption of these products has drawn more interest due to their particular capacities for the prevention of diseases through a healthy diet, their versatility, convenience, and wide range of tastes have made them diffuse rapidly among traditional and non-traditional consumers across many countries in the world.
Therefore, it is meaningful to explore more on their characteristics and applications as they are gaining an increasing popularity in diets, which can help to establish a sound labelling standard for strict regulations [ 36 ]. Nowadays, various enriched or aromatized oils are available in the market as seasonings.
Moreover, considering that the solvent is often the major ingredient of a formulation, a reaction, or an extraction [ 37 ], vegetable oils are excellent alternatives for the substitution of petroleum solvents, such as hexane, in the extraction of bioactive compounds, and finally, they allow a better integration in the formulation of products.
Table 1 shows different applications of various vegetable oils as solvents in natural product extractions, enriched oil preparations, and the formulation of products with applications in food and cosmetic industries. As summarized above, most laboratory studies have proved the good dissolving power of vegetable oils, as well as better organoleptic quality and oxidative stability of their enriched forms. Since using vegetable oils as solvents in the direct extraction of carotenoids from shrimp by-products and microalgae has been successfully applied in several studies [ 38 , 45 , 48 , 49 , 50 , 53 ], vegetable oils have proved their effectiveness in retaining high concentration of carotenoids under optimal conditions without any loss or degradation of carotenoids, or changes in the fatty acid profiles of the oil.
Moreover, vegetable oils are usually enriched or flavoured with antioxidants or aromatic extracts from plants or by-products, which are obtained by means of traditional infusion, one-step solvent extraction, etc. This is consistent with a previously reported finding indicating that vegetable oil was a remarkably good solvent for a wide variety of food aroma compounds [ 67 , 68 ]. Although these organic solvents have been evaporated afterwards in enriched oils, it has also drawn an increasing concern on their safety in food-related applications and environment.
In addition, the selectivity of vegetable oils is dependent on their types and components inside, resulting in variable extraction efficiency and enrichment factors. For vegetable oil solvents targeting to six major aroma extracts i. Notwithstanding, such sunflower oil was not the optimal in the extraction of phenolic compounds from olive leaves as compared to its virgin form and several other vegetable oils like avocado, flaxseed and castor oils [ 69 ].
The extraction yield of total phenolic compounds was found to be more related to the type of vegetable oils and endogenous amphiphilic minor compounds rather than the polyunsaturated degree of vegetable oil triglycerides.
gueternece.tk These compounds play an important role in great number of unit operations in chemistry and chemical engineering. In fact, nowadays there is no production process in perfume, cosmetic, pharmaceutical, food ingredients, nutraceuticals, biofuel or fine chemicals industries without a solvation step [ 71 ].
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Solvents can be used as diluents or additives in paints and inks, as cleaning agents or solvents for syntheses and extractions. From a macroscopic point of view, a solvent is a continuum characterized by physical constants e. The problem with most commonly used solvents is their negative impacts on health, safety and environment HSE as most solvents currently available in the world market come from the petrochemical industry and are volatile organic compounds VOCs , such as the example of hexane used for oil extraction.
With the geopolitical environment increased oil prices and decrease of reserves , societal demand for more sustainable products and the arrival of the new regulations and guidelines e. In other words, alternatives to petrochemical solvents have to fulfill the principles of Green Chemistry. Replacing one solvent by another does not necessarily mean eliminating all the hazards and issues related to the implementation of a process. Indeed, the modification of a process is generally associated with new risks.
Precautions should therefore be taken into account in the selection of an alternative solvent as for physicochemical, environmental or sanitary criteria, the eco-compatibility of the process and the price of the solvent, but also techno-economic criteria related to the properties of the solvent like dissolving power and energy consumption [ 74 ]. On the other hand, pharmaceutical companies such as GSK [ 75 ], Sanofi [ 76 ], AstraZeneca [ 77 , 78 ] and Pfizer [ 79 ] developed their own solvent selection guides that provide technical data and clear instructions for the development of more sustainable processes.
This allows the involvement and commitment of industries in the investigation on greener alternative solvents and proves their concern for the integration of sustainable development approaches. To sum up, an ideal alternative solvent must fulfill the following requirements: a does not emit VOC; b be of low toxicity for humans; c have a limited impact on environment be eco-friendly ; d be obtained from renewable resources; e have a high dissolving power; f be easy to recover; and g does not change the process set-up significantly.
To this end, new technologies such as solvent-free methods, aqueous formulations or alternative solvents, appear to be good candidates. Among these solutions the use of greener solvents, such as bio-based solvents, constitutes one of the most important alternative routes for the substitution of petrochemical solvents. It is worth noticing that the greenness of some solvents is questionable with regard to toxicity e.