Avaliação do processamento a baixas temperaturas do óleo de fígado de Alaska pollock (Theragra chalcogramma)

The demand for edible fish oils is growing. In Alaska, USA, large quantities of fishery byproducts are being used as raw materials, amongst which, Alaska pollock (Theragra chalcogramma) livers are of particular interest due to their high lipid contents. The temperature normally used for the extraction of fish oils is high and potentially incompatible with lipid stability. The goal of this research was to evaluate the processing of Alaska pollock liver oil, processed at low temperatures. As expected, the raw material obtained in the spring (40%) had significantly less lipids than that obtained in the autumn (50%). The liver oils were rendered five times for each of four combinations of time (15 and 30 minutes) and temperature (50 and 60 oC). Two batches of liver and viscera pollock oils produced on a processing ship were analyzed. The process yields were similar (~52%), and in general, the liver oils produced were lighter and more yellowish in colour than those produced from the pollock viscera in the autumn. The free fatty acid levels were similar for the viscera and liver oils produced in both seasons, reaching a maximum of 0.4%, while the peroxide values, anisidine values and thiobarbituric acid values determined for all the oils were 2-14 meq.kg-1, 20-26 and 0.4-0.6 mg malonic dialdehyde.kg-1, respectively. All the oils investigated were composed mainly of triacylglycerols (88-100%), with the phosphorus content not exceeding, on average, 15 ppm.