With the anticipated increase in human population to more than 9.5 billion by 2050, it is necessary to provide them with protein, and fish is one of the richest sources of protein available. Production of fish, both wild-caught and in aquaculture, has increased in recent years. This increase means there is more fish waste since, for example, about 36 % of tuna after processing is consider as waste or by-products. However, this by-product is rich in protein, and we are investigating ways to repurpose it and give it a second life.
Tuna trimming meal is made after food processing of tuna and is used in aquaculture. This material is a mixture of bones, skin, scales, muscles and anything else remaining. Although this material contains a lot of protein, it is not rich in some essential amino acids and the percentage of ash content is high.
In this project, we will start by performing a detailed molecular characterisation of tuna trimming meal, in terms of protein, peptides, amino acids, essential fatty acids and lipids, total carbohydrate, fat soluble vitamins and ash content. We will then investigate a range of processing techniques with the aim of improving the nutritional content. This will involve physical separation techniques, and fermentation in the presence of carbohydrate using different bacteria including Lactobacillus, which has been used in a similar context previously and demonstrated the capacity to change the profile of amino acids and peptides.In our initial experiments, amino acid analysis showed that 58% of the sample is protein but it only contains 2% methionine, which is very low. Similarly, the material was found to contain 0.88 % carbohydrate, which indicates that supplemental carbohydrate will be required for any fermentation experiments.We have performed a detailed proteomics characterisation of the material using SDS-PAGE to fractionate proteins and high pH reversed phase fractionation techniques to fractionate peptides, prior to nanoflow liquid chromatography – tandem mass spectrometry. The SDS-PAGE results contained 354 reproducibly identified proteins, with peptides covering the mass range from 822 to 1782 Da, including large amounts of collagens, keratins, actin, myoglobin, cytochrome c oxidase, myosin, and ATP synthase.