| Tuna is a major marine food resource and has been widely consumed by humans around the world for a long time. Tuna fish oil is a by-product obtained during processing which is high in polyunsaturated fatty acid oils (PUFA), particularly w-3 fatty acids. The effect of increased dietary intake of w- 3 fatty acid oils on health has received much attention in recent years, in particular eicosapentaenoic acid (EPA, 20:5w-3) and docosahexaenoic acid (DHA, 22:6w-3), are reputed to have prophylactic properties in the reduction of cardiovascular and inflammatory diseases. However despite the presence of variable functional compounds in the fish oil it contains many different sorts of flavors which affect the quality of product. Several reports have already been published on the study of fish sauce flavors.
Conventional methods for extraction, fractionation and isolation of off-flavour from PUFA’s include the use of highly flammable or toxic solvents and energy-intensive vacuum distillation. High-temperature processing can result in degradation of thermally labile compounds. Consideration of such factors has lead investigators to apply supercritical fluid extraction (SFE) techniques to the separation of these components. The technology is of especial interest to the food and cosmetics industries because carbon dioxide, the most common supercritical fluid solvent, is non-toxic and does not leave any residue. Supercritical carbon dioxide (SC-CO2) extraction and fractionation of fish oils has been the subject of ongoing research to the extent that there already a lot of published data on fundamental measurements of solubilities and phase equilibria of polyunsaturated w-3 fatty acid fish oil compopunds in supercritical fluids. A considerable number of studies have already been conducted on fish sauce and fish oil produced by conventional treatment. However, the identification of volatile compounds is not complete. In this study the objectives were to extend the range of pressures and temperatures used in SC-CO2 extraction, to obtain the optimum processing condition for isolating flavors and to identify major compounds present in the flavours and aromas of fish oil.
A schematic diagram of the apparatus used for the supercritical fluid extraction (SFE) of off-flavor from the tuna oil is shown in Figure 69.
Table 69: Fatty acid composition of tuna oil sample
Table 30 : Volatile compounds identified in tuna fish
Table 31: Aroma active compound in fish oil
Table 32: Comparison of odor components between raw fish oil and SC-CO2 extraction
It has been shown that significant offflavors identified were 2-methyl-butene, 3-hydroxy butanal and ethylbenzene. According to the results, the removal efficiency of the odor compounds which are negatively effected on the quality of the product depends on the extraction condition. Also these results could be applied for an alternative separation process to recover fatty acids without a thermal treatment which occurs in a conventional separation technology, energy-intensive vacuum distillation. |