# Oil Press-Cakes and Meals Valorization through Circular Economy Approaches: A Review
## 3 Oilseed Production Process and by-Products Physiochemical Properties  
Oilseeds are cleaned, dehulled, grinded, cooked (destruction of microorganism and oil cell, enzymes inactivation, coagulation of proteins), and then are subjected to oil extraction. Each phase of the process generates waste with residual bioactive compounds that can be recovered: steams, leaves, pods, and broken grain in the cleaning steps and in the dehulling phase, hulls [16; 18]. The two traditional methods to extract oil involve either the use of a mechanical press (hot and cold pressing) or a solvent. When the process is mechanical the oilseeds are heated (100 degrees) and the oil is extracted with a screw-press. Alternately, in cold pressing, the temperature of heating is kept at 50-60 degrees. The use of a solvent helps to maximize the oil recovery. The differences in chemical compositions between the cold-pressed and expeller cakes were in crude protein, fat, and crude fiber content. The protein content of the cold-extracted cakes was lower in comparison to that extracted at high temperatures. Regarding the fat content, the mechanical expeller cakes have 6-7% and the solvent extracted ones have \(<\)1%. The product resulting directly from the expeller is called a cake, and when it has undergone an additional solvent de-oiling process the term meal is used. This conventional oil extraction method can be replaced by modern/green techniques (pressurized liquid, pulsed electric field, high hydrostatic pressure, and high voltage electrical discharges) because they are more rapid and less solvent consuming [19; 20; 21; 22; 23]. After the extraction of oil from seeds, the principal by-product obtained is oil cake/meal. Oilcakes/meals are classified into two categories--edible and non-edible. Edible oil cake (soybean, groundnut, rapeseed, sunflower, coconut, cottonseed, safflower, flaxseed) have a high nutritional value and can be used in animal and human consumption as processed ingredients (protein concentrate, isolate, hydrolysate), a substrate (in the production of bioactive compounds, surfactants, enzymes, antibiotics, vitamins, pigments, flavors, and amino acids) and source of antioxidants. The defatted edible cakes can be used in the diet of undernourished people by incorporating them in bakery, infant products, and multipurpose supplements. Non-edible oilseed cake/meal (castor, neem, mauha, karanja and linseed) are used as manure due to the presence of toxic compounds [22]. According to the U.S. Department of Agriculture (USDA), the world production of oilseeds in 2018/2019 was 600.47 million metric tons, hence a large amount of press cakes and residues are available. The use of these by-products and residues from the oil industries is a sustainable alternative to reduce waste disposal and also contributes to the development at low cost, of new products rich in nutrients [17]. Oilcakes/meals composition depends on variety, extraction method, and growing condition. Taste and smell are characteristics to the initial raw materials without musty, mold, pro-rancid, and foreign smells. Walnut oilcakes are yellow to light brown, and sweetish. The color of pumpkin seeds oilcake is brown to brownish green with an insipid and a sweetish flavor. Sesame oilcake color varies from cream to light brown and has sweetish, insipid taste. Oilcake from flaxseeds have different shades of brown with a neutral and insipid taste [24]. As shown in Table 1, the highest content in proteins was found in groundnut cake then soybean, almond, chia, rapeseed, sunflower, cottonseed, pumpkin, hemp, safflower, sesame, coconut, flaxseed, and olive oilcakes. The oil content in sunflower and rapeseed is over 40%, 15-25% in soybean and cotton, another major source is peanut (56%) [18]. Despite the fact that oilcakes are low-processed materials they are safe. Improper storage and handling can cause rancidity (unpleasant taste and smell). During four months of storage, [PERSON] et al. [25] observed that the water activity remains stable inhibiting bacterial and mold growth.