Processing fish oils

Bimbo, A.P. Crowther, J.B. Fish oils Processing beyond crude oil. Infofish Int. 1991, 6, 20-25. 

Apphcations include ka olin clay dewatering, separation of fish oils from press Hquor, starch and gluten concentration, clarification of wet-process phosphoric acid, tar sands, and concentrations of yeast, bacteria, and fungi from growth media in protein synthesis (14). 

Dietary polyunsaturated fatty acids (PUFAs), especially the n-3 series that are found in marine fish oils, modulate a variety of normal and disease processes, and consequently affect human health. PUFAs are classified based on the position of double bonds in their lipid structure and include the n-3 and n-6 series. Dietary n-3 PUFAs include a-linolenic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) whereas the most common n-6 PUFAs are linoleic acid, y-linolenic acid, and arachidonic acid (AA). AA is the primary precursor of eicosanoids, which includes the prostaglandins, leukotrienes, and thromboxanes. Collectively, these AA-derived mediators can exert profound effects on immune and inflammatory processes. Mammals can neither synthesize n-3 and n-6 PUFAs nor convert one variety to the other as they do not possess the appropriate enzymes. PUFAs are required for membrane formation and function... 

Figure 8.1-8. Return on Investment (ROI) for the compressor process of fish-oil fractionation at different solvent/feed ratios, depending on variable benefits per kg of product.

Fish oil is also converted to hard fat by a similar process and the resultant fat is used in the manufacture of soap. 

The promise shown by supercritical fluid extraction led to the development of the Solexol process for the purification and separation of vegetable and fish oils. This process concentrated the polyunsaturated triglycerides in vegetable oils and the so-called vitamin A values from fish oils using propane as a selective solvent [5]. 

There are a number of minor oils, all of high value, most of which are marketed mainly either for medical purposes or for their flavour. Olive, evening primrose, borage, fish oils and cocoa butter are described elsewhere. Others include hazelnut, walnut, macadamia, almond, apricot, pumpkin, poppy-seed and rice bran oils. The process of testing for authenticity of these oils should be approached in the same way as for the bulk oils above, i.e. fatty acid profile, sterols, tocopherols and triglyceride composition. However, there is little generally available published material on the ranges of values to be expected... 

Enzymatic process is one of the effective techniques for purification of DHAEE from fish oil, such as tuna oil. The first step for purifying DHAEE is conversion of tuna oil to FA ethyl esters (FAEEs) (Fig. 2.6). Of course, a chemical reaction with an alkaline catalyst can convert tuna oil to the mixture of FAEEs containing DFIAEE, but an enzymatic process under mild conditions is preferable because heating under alkaline conditions often results in the isomerization of DFIA. Therefore, stepwise alcoholysis, which was established in production of BDF from vegetable oil, was applied to ethanolysis of tuna oil. 

Belarbi, E. H., Molina, E., and Chisti, Y. 2000. A process for high yield and scaleable recovery of high purity eicosapentaenoic acid esters from microalgae and fish oil. Proc. Biochem.,35, 951-969. 

Raw materials for producing fish oils include (1) pelagic-type (surface feeding) fish pursued for reduction to meal and oil (2) waste products produced at facilities that process edible fish and occasionally (3) by-catch species also netted with the primary catch. The type of processing used depends on geographic location, species of fish normally taken in the area, and whether done at an on-... 

Suggested rough flow diagram showing extraction process for fish-oil recovery. (Details are not included and changes may be necessary.)... 

Cho, Y.H., Shim, H.K., and Park, J. (2003). Encapsulation of fish oil by an enzymatic gelation process using transglutaminase cross-linked proteins. J. FoodSci. 68, TlYl-212 i. 

Heinzelmann, K., Franke, K., Velasco, J., and Marquez-Ruiz, G. (2000). Micro-encapsulation of fish oil by freeze-drying techniques and influence of process parameters on oxidative stability during storage. Fur. Food Res. Technol. 211,234 239. 

The presence of photosensltlzers In fish oils depends on the method of processing and the source of fish used for rendering. Some species of fish, such as menhaden, which are primarily phytoplankton feeders, can easily contribute residual chlorophyll from their stomach contents when oils are rendered. Fish liver oils have a likelihood of containing residual heme compounds, and thus both oils would be generally more vulnerable to singlet oxygen autoxldatlon than oils recovered from dressed fish. 

Vitamin E, or a-tocopheroi, is a natural antioxidant found in fish oil, almonds, hazelnuts, and leafy greens. Although the molecular details of its function remain obscure, it is thought that vitamin E traps radicals, thus preventing the unwanted oxidation of unsaturated fatty acid residues in cell membranes. In this way, vitamin E helps retard the aging process. In Chapter 15 we learn about radical reactions and the role of vitamin E and other antioxidants in inhibiting radical processes. 

Gas chromatography-olfactometery (GC-O) provides a sensory profile of odor active compounds present in an aroma extract by sniffing the GC effluent. Several techniques have been developed to collect and process GC-O data and to estimate the sensory contribution of individual odor active compounds, including dilution analysis (29, 30), time intensity (31), and detection frequency (32) methods. GC-O has successfully been used to evaluate the odor active compounds of olive oil (33), soybean oil (34), and fish oil enriched mayonnaise (35). 

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