Isolates oilseed processing

FIGURE 4.8 Membrane-based process for canola protein isolation. (From Jones, J. D. and Holme, J. 1979. Oilseed processing. US Patent 4,158,656 Diosady, L. L., Xu, L. and Chen, B. K. 2005. Production of high-quality protein isolates from defatted meals of Brassica seeds. US Patent 6,905,713. With permission.)... 

Initially, gossypol is in the free state, but in the course of the heat treatments involved in conventional oilseed processing it binds irreversibly with protein. The situation can be appreciated by observing the effect of heat and/or added gossypol (G) on the digestibility of prepared protein isolates (see Table 1). 

Seed-Meal Concentrates and Isolates. Seed-meal protein products include flours, concentrates, and isolates, particularly soy protein products. These can be used as extenders for meat, seafood, poultry, eggs, or cheese (see Soybeans and other oilseeds). Detailed information on soybean and other seed-meal production processes is available (13,14,18). 

Use of some oilseed proteins in foods is limited by flavor, color, and flatus effects. Raw soybeans, for example, taste grassy, beany, and bitter. Even after processing, residues of these flavors may limit the amounts of soybean proteins that can be added to a given food (87). The use of cottonseed and sunflower seed flours is restricted by the color imparted by gossypol and phenoHc acids, respectively. Flatus production by defatted soy flours has been attributed to raffinose and stachyose, which are removed by processing the flours into concentrates and isolates (88). 

Whole oilseeds and legumes and their derivatives (defatted flours, and protein concentrates and isolates) are used in traditional foods as sources of protein and for their texture-modifying functions. This article reviews, on a comparative basis, processes for preparation of vegetable food proteins, compositions and characteristics of the resulting food ingredients, and their functionalities and uses in traditional foods. 

A flowsheet for preparation of glandless cottonseed full-fat kernels and subsequent processing of defatted flours and concentrates and isolates is shown in Figure 1. This scheme, with specialized adaptations depending upon oilseed species, is typical for processing of all oilseeds. 

Shahidi, F., Wanasundra, U., and Amarowicz, R. 1995. Isolation and partial characterization of oilseed phenolics and evaluation of their antioxidant activity. In Food Flavors Generation, Analysis and Process Infleunce (G. Charalambous, ed.), Elsevier Science. 

An alternative method of producing hydrocarbon fuels from biomass uses oils that are produced in certain plant seeds, such as rape seed, sunflowers, or oil pahns, or from aquatic plants (see Soybeans and other oilseeds). Certain aquatic plants produce oils that can be extracted and upgraded to produce diesel fuel. The primary processing requirement is to isolate the hydrocarbon portion of the carbon chain that closely matches diesel fuel and modify its combustion characteristics by chemical processing. 

Aqueous enzymatic oil extraction is another ecofriendly extraction procedure. It is based on simultaneous isolation of oil and protein from oilseed by dispersing finely ground seed in water and separating the dispersion by centrifugation into oil, solid, and aqueous phases. The presence of certain enzymes during extraction enhances oil recovery by breaking cell walls and oil bodies (22). For peanuts, a multistep aqueous extraction process has been described with a recovery of about 98% (23). More recently, the relatively new technique of enzyme-assisted aqueous extraction has been applied to peanuts with a reported oil recovery of 86-92% (24). 

The sohds remaining after fat removal are generally rich in protein and find a ready market in animal feeds. Some oilseed solids, especially soybean, go into human foods as flours, concentrates, textured particles, or protein isolates. Some oilseed sohds contain toxins or allergens that make them unfit for animal feeds tung nut and castor bean, for example. Unless treated, these solid residues go into fertilizers. Various processes have been developed to remove or chemically destroy undesirable compounds (10). One process developed at Texas A M University for UNIDO (11, 12) uses a chemical additive and extrusion to detoxify and deallergenate castor meal making it suitable for animal feed. 

Several processes for the manufacture of protein concentrates or isolates for aquaculture have also been developed. These technologies yield nondenatured proteins with better digestibility for fish nutrition. Membrane separation techniques are used to separate oilseed components, remove antinutritional factors, and fractionate protein for fish feed production. 

However, various technologies have been developed that utilise extractions from oilseed meals and pulses as the raw material for the production of flours, protein isolates and protein concentrates. These technologies are mainly used in the processing of soybeans and, to a lesser extent, in the processing of peanuts, cotton, lupine and other oilseed meals. Additional sources of protein are whey, fishmeal and others. The final products can be various mixtures rich in proteins (often enriched by minerals and vitamins), which are mainly used in less-developed countries. 

The lipid extraction processes commonly used to explore the potential of various oilseeds are hot and cold extraction by hydraulic/mechanical pressing solid-liquid extractions using petroleum ether, hexane, ethanol, methanol, and chloroform among other reagents isolated or combined and extractions using supercritical fluids, such as ethanol, propanol, n-pentane, ammonia, and carbon dioxide (CO )- However, research on the interactions between methods of extraction and their effect on the quality and the thermal and oxidative behavior of these oilseeds has so far been scanty [1-3]. 

During the development of oilseed rape embryos starch accumulates transiently during the early stages of oil accumulation (P. da Silva and A.M. Smith, pers. comm.). Both starch and fatty acids are synthesized in the plastids and these processes are dependent upon the import of cytosolic metabolites in non-photosynthetic cells. Plastids have been isolated from several nonphotosynthetic tissues and characterized with respect to their enzyme capacities and utilization of exogenous substrates to support starch and fatty acid synthesis in vivo. These studies have revealed that the glycolytic pathway is present although the activities of some of the enzymes in the lower half of the pathway can be low. Pyruvate dehydrogenase is also present in these plastids. 

Hassanien FR, Mukheijee KD. Isolation of lipase from germinating oilseeds for biotechnological processes. J Am Oil Chem Soc 1986 63 893-897. 

Combination of immersion and percolation extractors has also been used for oil extraction from oilseed. This process involves partial extraction of the oil in a percolation extractor (until there is 10-15% residual oil in the seeds) followed by wet flaking of the partially defatted seed as it comes out of the percolation extractor. This operation is carried out in a special solvent-tight flaker operating in a solvent vapor-saturated atmosphere. Finally, flaked seeds are extracted in an immersion-type extractor. The advantage of this process is that seeds are extracted at a low temperature (maximum 50 °C) and the subsequent meal desolventizing is carried out lower than 105 °C, producing a meal suitable for protein concentrates and isolates manufacturing (Bemardini, 1976). 

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