Production of High-Quality Fish Oil from Herring By-products

Isabel Aidos,

Food and Bioprocess Engineering Group, Wageningen University, the Netherlands. October 2002.

The thesis was based on 8 papers, of which 3 are published, 2 are in press, and 3 are submitted.

Isabel is well known among several of the Lipidforum members, and has also participated in Lipidforum seminars, last in May 2002 in Trondheim; By-products in Marine Processing Industry, - a Lipid Source for Fish Feed and Food. At this meeting she had the contribution “Upgrading of by-products from the herring processing industry into fish oil”.

She was born in Portugal, where she also graduated from the University of Aveiro. For her PhD study at the University of Wageningen, the Netherlands, she had work placement at the Netherlands Institute for Fisheries Research (RIVO) in Ijmuiden. During this period she also completed a postgraduate program at Institute for Nutrition, Directorate of Fisheries, Bergen, Norway.

Outline of the thesis:

The upgrading of herring by-products into high-quality crude oil was discussed and evaluated. The influence of the variability of the raw material quality was discussed and explained (1, 2, 3). Subsequently, the seasonal variation (1), the use of salted raw material (2), and a comparison between different extracted oils evaluated chemically and sensorial (3) were discussed. The processing of raw material into high-quality crude fish oil was described (4, 5, 6). The effect of storage of herring by-products at two different temperatures up to 72 hours was evaluated (4). The sorting of by-products was presented (5), and the optimization of the fish oil pilot plant was assessed and discussed (6). The oil product quality was evaluated as well (7, 8). The first question addressed was until which extent storage temperature of the oil affected oil’s quality. Therefore, the oil extracted from fresh herring by-products was stored at three different temperatures (7). Volatiles that developed in the oil during storage were followed and evaluated (8). Final considerations, including a general discussion, was given in the last chapter of the thesis. Attention was also given to the content of dioxins and PCB’s present in the oil (given in Appendix 1). Finally, a comparison was made between the extracted crude and refined herring oil and the commercially available menhaden oil.

Concluding remarks

The feasibility of producing high-quality fish oil from herring by-products was evaluated in various ways in this work. Thus a contribution was made to a more efficient usage of natural resources yielding a high-quality product. Crude oil extracted from herring by-products is relatively rich in essential n-3 PUFA’s such as EPA and DHA, and is relatively stable during storage. In most cases, the level of FFA increased over time. However, since it is crude oil, the off-odors, flavours and oxidation products were eliminated again during the refining process. This refining procedure could be a compromise between removing “undesirable” compounds, and keeping beneficial components that might improve the oil quality, such as α-tocopherol. The currently obtained knowledge of fish oil extracted from herring by-products iis a first step towards the valorization of by-products from different fatty fish species into production of fish oil, thereby contributing to a better utilization of the marine resources that are available.

Publications:

• Aidos I, van der Padt A, Luten JB, Boom RM. Seasonal changes in crude and lipid composition of herring fillets, by-products, and respective produced oils. J Agr Food Chem, (2002) 50: 4589-4599
• Aidos I, van der Padt A, Luten JB, Boom RM. Upgrading of maatjes herring by-products: production of crude fish oil. J Agr Food Chem, (2001) 49: 3697-3704
• Aidos I, Schelvis –Smit R, Veldman M, Luten JB, van der Padt A, Boom RM. Chemical and sensory evaluation of crude oil extracted from herring by-products from different processing operations. Submitted publication (2002)
• Aidos I, van der Padt A, Boom RM, Luten JB. Quality of crude fish oil extracted from herring by-products of varying states of freshness. J Food Sci, (2002), in press
• Aidos I, Masbernat-Martinez S, Luten JB, Boom RM, van der Padt A. Composition and stability of herring oil recovered from sorted by-products as compared to oil from mixed by-products. J Agr Food Chem, (2002), 50: 2818-2824
• Aidos I, Kreb N, Boonman M, Luten JB, Boom RM, van der Padt A. Influence of production process parameters on fish oil quality in a pilot plant. Submitted publication (2002)
• Aidos I, Lourenço S, van der Padt A, Luten JB, Boom RM. Stability of crude herring oil produced from fresh by-products: Influence of temperature during storage. J Food Sci, (2002) in press
• Aidos I, Jacobsen C, Jensen B, Luten JB, van der Padt A, Boom RM. Volatile oxidation products formed in crude herring oil under accelerated oxidative conditions. Submitted publication (2002)

Erling N Christiansen