The intake of omega-3 polyunsaturated fatty acids (PUFA) of the average consumer is generally low and products like fish oils high in omega-3 PUFA have become a popular dietary supplement. There is a need for more sources of omega-3 PUFA to cover the increasing demand. This study investigated whether livers from different lean fish species could be a potential new source of oils rich in omega-3 PUFA. The seasonal variation in lipid content, fatty acid composition, peroxide value and free fatty acid content of livers from cod, hake, ling, coalfish and monkfish was determined and the effect of storage conditions on the fishing vessel (ice vs frozen) was studied. Generally, the lipid content and composition of the livers from the five fish species varied similarly during the two years of sampling period with significantly lower values in spring (March, April) and higher values in fall (November, October). Storage conditions were found to have no significant effect on the quality and oil composition. Monkfish livers were less suitable for production of omega-3 oil due to their lower lipid and EPA content and higher FFA levels. Coalfish had higher fluctuations in oil composition during sampling period, which potentially makes a standardised quality difficult to obtain. Cod, hake and ling were the most suitable species for fish liver oil production.

Metal-catalyzed lipid oxidation is a major factor in food waste, as it reduces shelf life. Addressing this issue, our study investigates the potential of hydrolysates derived from potato protein, a by-product of potato starch production, as metal chelating antioxidants. Through sequential enzymatic hydrolysis using Alcalase or Trypsin combined with Flavourzyme, we produced various hydrolysates, which were then fractionated via ultrafiltration. Using a combination of peptidomics and bioinformatics, we predicted the presence of metal-chelating and free radical scavenging peptides across all hydrolysate fractions, with a trend indicating a higher content of antioxidant peptides in lower molecular weight fractions. To validate these predictions, we utilized Surface Plasmon Resonance (SPR) and a 9-day emulsion storage experiment. While SPR demonstrated potential in identifying antioxidant activity, it faced challenges in differentiating between hydrolysate fractions due to significant standard errors. In the storage experiment, all hydrolysates showed lipid oxidation inhibition, though not as effectively as EDTA. Remarkably, one fraction (AF13) was not significantly different (p < 0.05) from EDTA in suppressing hexanal formation. These results highlight SPR and peptidomics/bioinformatics as promising yet limited methods for antioxidant screening. Importantly, this study reveals the potential of potato protein hydrolysates as antioxidants in food products, warranting further research.

Protein hydrolysates show great promise as bioactive food and feed ingredient and for valorization of side-streams from e.g. the fish processing industry. This study characterizes bulk emulsifying, foaming, and in vitro antioxidative properties of hydrolysates derived from cod frame by application of Alcalase and Neutrase, individually and sequentially as well as the influence of heat-treatment prior to hydrolysis. We present a novel approach that utilizes proteomics data for calculation of weighted mean peptide properties (length, molecular weight, and charge) and peptide-level abundance estimation. Using subsequent bioinformatic prediction of biofunctional properties to describe observed bulk properties, we are able to provide an in-depth hydrolysate characterization not previously seen. All hydrolysates displayed comparable or higher emulsifying activity and stability than sodium caseinate. Heat-treatment significantly increased stability but showed a negative effect on the activity and degree of hydrolysis. Combining peptide abundance with predicted emulsifying activity, we were able to identify several peptides that are likely linked to the observed differences in bulk emulsifying properties. In general, decreased hydrolysis resulted in significantly higher chelating activity, while the opposite was observed for radical scavenging activity. The study highlights the prospects of applying proteomics and bioinformatics for hydrolysate characterization and in food protein science.

P. palmata is a viable source of nutrients with bioactive properties. The present study determined the potential role of post-extraction ultrasonication on some compositional features and antioxidant properties of resulting extracts after sequential enzymatic/alkaline treatment. No significant difference was detected in terms of protein content and recovery as well as amino acid composition of the extracts. The nitrogen-to-protein conversion factor of 5 was found to be too high for the seaweed and its enzymatic/alkaline extracts. The extracts sonicated by bath for 10 minutes and not sonicated showed the highest and lowest total phenolic contents (p&lt;0.05), respectively. The highest radical scavenging and lowest metal chelating activities were observed for the non-sonicated sample, as evidenced by IC50 values. The extract sonicated by bath for 10 minutes showed the most favorable in vitro antioxidant properties since its radical scavenging was not significantly different from that of not sonicated sample (p&gt;0.05), whereas its metal chelating activity was significantly higher (p&lt;0.05). To conclude, post-extraction ultrasonication by an ultrasonic bath for 10 minutes is recommended to increase phenolic content and improve antioxidant properties of enzymatic-alkaline extracts from P. palmata.

The present study adopted a diverse approach to obtain antioxidant peptides from red seaweed, starting with an aqueous extraction of the entire seaweed followed by enzymatic hydrolysis of the solid residues from the first step. Additionally, the impact of three different pH levels (i.e. 3, 6, and 9) during the aqueous extraction phase was examined for their influence on the outcomes. The findings revealed that the solid fraction resulting from the sequential extraction process contained significantly higher levels of proteins and amino acids compared to other fractions (p < 0.05). Furthermore, the solid fractions (IC50 ranging from 2.29 to 8.15) proved to be significantly more effective free radical scavengers than the liquid fractions (IC50 either ranging from 9.03 to 10.41 or not obtained at the highest concentration tested) at both stages of extraction (p < 0.05). Among the solid fractions, those produced under alkaline conditions did not exhibit as potent radical scavenging abilities as those produced under acidic or nearly neutral conditions. The most effective metal ion chelating activity was found in the solid fractions derived from the subsequent enzymatic stage, particularly at pH 3 (IC50 = 0.63 ± 0.04) and pH 6 (IC50 = 0.89 ± 0.07), which were significantly more potent than those from the initial extraction stage (p < 0.05). Given that no significant difference was noted in the total phenolic content of these solid fractions compared to their corresponding liquid fractions (3.79 ± 0.05 vs. 3.48 ± 0.02 at pH 3 and 2.43 ± 0.22 vs. 2.51 ± 0.00 at pH 6) (p > 0.05), the demonstrated properties might be attributed to the potential roles of bioactive amino acids such as histidine, glutamic acid, aspartic acid, tyrosine, and methionine, whether present as free amino acids or integrated within the structure of proteins and peptides.

Malta produces approximately 15,000 tons of bluefin tuna every year, by-products are estimated to count for 55% of the harvest. Maltese tuna farmers established a company that processes these by-products into fish meal and oil that are sold to the pet food industry. In this study the logistic of tuna farming and management in Malta was analysed and the environmental impact of the activity was estimated. The biomass quality and the preservation state of tuna head and liver was assessed. The head had the highest ash content (1.68±0.02%) while the liver had the highest protein content (16.18±0.02%) and the highest crude fat, (34.87±0.76%). The highest concentration of oil was found in the head’s skin (50.07±0.84%). The predominant saturated fatty acids (SFAs) were c14:0, c16:0 and c18:0. Monounsaturated FAs (MUFAs) were the major fatty acids present in all samples, with the highest values in the tuna head. The oxidation levels found in the by-products upon arrival at the processing plant doesn’t compromise their quality. No histamine formation was predicted. Some oxidation was observed in the oil after extraction. The Life Cycle Assessment estimated that the environmental score of the activity is 105pts per ton of fishmeal and 25kg of oil produced (2.82 tCO2 eq). It is concluded that the processing of tuna by-products in Malta is a sustainable alternative to traditional disposal methods and their quality is high enough to be used as a source of proteins and lipids in farmed-animals feed.