Introduction: The circular bioeconomy concept revolves around biological production cycles that reintroduce products or waste from one production system to another, aiming to maximize resource utilization while minimising environmental impact. The purpose of this study was to evaluate and compare the element flow when integrating black soldier fly larvae (BSF) production with Nile tilapia production using varying experimental fish feed.
Methods: Tilapia (42.5 ± 11.2 g) were reared in recirculating aquaculture systems (RAS) at 25.5°C for 10 weeks and fed equal daily rations of four experimental diets containing fishmeal (FM), poultry blood meal (PBM), black soldier fly meal (BSF) and poultry by-product meal (PM) as the single main protein source, respectively. Faeces was collected daily from settling columns installed in the RAS and subsequently fed to BSF larvae.
Results and discussion: The fish exhibited the highest biomass gain when fed with FM (1,001 g) or PM (901 g). The growth was lowest for those fed with PBM (406 g). The fish fed with PBM also produced the highest amount of faeces (234 g). When the fish faeces were utilized as a substrate for rearing black soldier fly (BSF) larvae and although the biomass gain did not differ significantly, the feed conversion ratio (FCR) varied among larvae fed with different fish faeces, ranging from 8.36 to 25.04. Furthermore, the concentration of analysed elements (Al, B, Ca, Co, Cu, Fe, K, Mg, Mn, Mo, Na, P, S, and Zn) varied based on the type of fish faeces provided. Results illustrate that a modulation of BSFL elemental composition is possible through manipulating the feed provided to the fish and emphasize the importance of fish feed composition for fish performance as well as the compositional quality of the larvae reared on the resulting fish faeces. Hence, if BSF larvae production is to be harnessed for the recycling of aquaculture sludge, ingredient choice and subsequent elemental composition of fish feeds are pivotal to larvae composition.
Introduction: Fish rest raw material generated from the fish processing industry may be a useful resource for recovery of added value compounds. The application of non-thermal novel technologies can improve the extraction. High-pressure processing (HPP) has long been used for the preservation and extension of the shelf life of seafood. It also constitutes a promising technology for the increased recovery of valuable compounds, such as lipids and proteins. The objective of this study was to assess the yield and the chemical composition of the fractions obtained after enzymatic hydrolysis on a mixture of Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) rest raw material pretreated by high-pressure (HP).
Methods: Six different pretreatments were applied prior to enzymatic hydrolysis; 600 MPa x 8 min, 600 MPa x 4 min, 400 MPa x 8 min, 400 MPa x 4 min, 200 MPa x 8 min, 200 MPa x 4 min.
Results and discusssion: These applied pretreatments did not yield higher oil extraction compared to the control. However, the fish protein hydrolysates (FPH) contained higher amount of protein when compared to the FPH obtained from the control.
This study’s main aim was to utilize green extraction protocols to recover collagen from by-products originating from European plaice. Moreover, the objective was to evaluate pre-treatments, the composition of the up-cycled product as well as to identify the most promising by-product fraction. Microwave (MAE) and ultrasound-assisted extractions (UAE) were performed on untreated, pre-treated (salt-washed or enzymatic hydrolysis) fractions of backbones, skins, and heads. Both MAE and UAE were performed for 15 and 35 min. After pre-treatment and extraction, the quality and yield of products were evaluated. Protein and collagen concentration, as well as amino acid profiles, were measured. Skins deliver significantly higher yields of collagen and protein than heads and backbones (p < 0.05). Enzymatic hydrolysis resulted in the highest collagen yields for skins (77%), while salt-washing gave the highest results for backbones (43%) and heads (41%) regardless of extraction method and time. Total and free amino acid profiles differed between the three fractions, with backbones and heads showing overall more similarity in composition compared to skins. The study showed that MAE and UAE technologies are suitable for generating collagen from marine by-products. Additional research is recommended to optimize pre-treatment and extraction for skin, as most promising collagen supplier.
The post-mortem rigid of farmed rainbow trout (Oncorhynchus mykiss) affects the texture of the meat and might even be risky for microorganisms, undermining the popularity of frozen filets among consumers. This study investigated the importance of different conditions (0°C, 4°C, and 25°C for 0–4 days) and physicochemical characteristics of rainbow trout filet storage on fish’s characteristics, freshness, quality, and shelf-life. Results showed that the fish easily underwent rigor mortis and resolution of rigor mortis when stored at 25°C. However, rigor mortis was more likely to occur under storage at 0°C than at 4°C [with 100 kV/m high voltage electrostatic fields (HVEF)] due to low-temperature stimulation, but resolution of rigor mortis began to appear after 24 h of storage at either temperature. The protein solubility and gel strength of fish stored at 25°C continued to decrease due to thermal denaturation, and those of fish stored at 4°C and 0°C also showed a decrease owing to rigor mortis and then an increase when rigor mortis disappeared. The K values increased rapidly at 25°C and reached 61% at 14 h. Under storage at 4°C and 0°C, the K values only slightly increased before resolution of rigor mortis. However, the K-values did not exceed 40% for 4 days post-resolution of rigor mortis. Differential Scanning Calorimetry analysis and tissue sectioning showed that protein denaturation and separation between muscle fibers persisted during storage at various temperatures, most notably at 25°C. It is important to note that storing at 0°C for 96 h did not result in any significant changes in the molecular protein composition. Moreover, the muscle tissue remained in excellent condition compared to storage at 25°C and 4°C. Additionally, there was no significant difference in the total viable count (TVC) and psychrophilic bacteria between storage at 0°C and 4°C, considered safe for food consumption. These promising findings are conveyed in a circular economy based on the food industry, particularly adequate raw materials, stable prices, measures to reduce food loss and waste, and contributing to developing efficient, diverse, and sustainable food processing systems.
Changes in protein structure are closely related to gel strength. Dense phase carbon dioxide (DPCD) treatment is an excellent non-thermal food processing method that can be used to induce gel formation in surimi. The sensory, water holding capacity and gel strength of DPCD induced gels are superior to heat-induced gels. Fourier-transform infrared spectroscopy was used to investigate the role of DPCD in the quality of golden pompano surimi gels and changes in protein structure. The intermolecular forces of surimi gels were analyzed in terms of ionic and hydrogen bonds, disulfide covalent and non-disulfide covalent bonds, as well as hydrophobic interactions. Correlation analysis was used to investigate the relationship between the changes in advanced protein structure and gel strength during DPCD-induced gel formation in golden pompano surimi. The results showed that the α-helix and random coil levels of surimi gel were significantly decreased (p < 0.05), while the β-sheet and β-turn content was significantly increased (p < 0.05). The number of ionic and hydrogen bonds in gel proteins decreased significantly (p < 0.05), while the hydrophobic interactions, and disulfide and non-disulfide covalent bonds increased significantly (p < 0.05) after DPCD treatment. Correlation analysis showed that β-sheets, β-turns, hydrophobic interactions, and disulfide and non-disulfide covalent bonds were strongly positively correlated with gel strength, whereas α-helices, random coils, and ionic and hydrogen bonds were strongly negatively correlated with gel strength. Therefore, the α-helix and random coil structures of surimi gels were transformed into β-sheet and β-turn structures after DPCD treatment. Hydrophobic interactions, and disulfide and non-disulfide covalent bonds were the main intermolecular forces during the DPCD-induced gel formation of surimi. Ionic and hydrogen bonds were not the main intermolecular forces. The results provide fundamental data for elucidating the mechanism of DPCD-induced protein gel formation.
Rainbow trout (Oncorhynchus mykiss) are currently consumed as live fish, primarily for catering or consumers, as an alternative to salmon in sashimi or dishes. However, Covid-19 has hampered store and restaurant operations. Therefore, developing suitable processing conditions to extend its shelf life, such as online distribution specifications while enhancing the filets’ commercial value, would raise its production value. In this study, we investigated the fish filets salted in a 5% salt solution for 2 days and then smoked at 65°C for 4 h under different storage conditions. As result, the higher rate of salt penetration and water loss in the resolved rigor mortis group was associated with tenderization of the meat compared to the rigor mortis group. Thermal-shrinkage and thermal-induced tissue destruction of the smoked fish filets during processing which affects the appearance, flavor, chewiness and overall acceptability. Nevertheless, according to the results of a consumer-type evaluation, the product characteristics of the fish filets from the resolution of rigor mortis group were consistent with those of the rigor mortis group, except for a weaker aroma. Thus, these results explain the relationship between frozen stored fish and the quality of processed products. The economic concept of regulating and distributing scheduling production between raw materials and finished products in the food industry conveys promising findings that will contribute to developing sustainable food processing systems.