Steam Explosion-Assisted Extraction of Protein from Fish Backbones and Effect of Enzymatic Hydrolysis on the Extracts

Valorization of fish processing by-products for protein hydrolysate recovery: Opportunities, challenges and regulatory issues

Protein-rich fish processing by-products, often called rest raw materials (RRM), account for approximately 60% of the total fish biomass. However, a considerable amount of these RRM is utilized for low-value products such as fish meal and silage. A promising and valuable approach for maximizing the utilization of RRM involves the extraction of bioactive fish protein hydrolysate (FPH). This review assesses and compares different hydrolyzation methods to produce FPH. Furthermore, the review highlights the purification strategy, nutritional compositions, and bioactive properties of FPH. Finally, it concludes by outlining the application of FPH in food products together with various safety and regulatory issues related to the commercialization of FPH as a protein ingredient in food. This review paves the way for future applications by highlighting efficient biotechnological methods for valorizing RRM into FPH and addressing safety concerns, enabling the widespread utilization of FPH as a valuable and sustainable source of protein.

Blue food proteins: Novel extraction technologies, properties, bioactivities and applications in foods

With the growing demand for healthy and sustainable food, blue food proteins have emerged as an important way to address resource-intensive production and environmental concerns. This paper systematically reviewed the extraction technologies, properties and bioactivities of blue food proteins and explored their wide range of applications. The novel extraction technologies not only improve the extraction efficiency of the proteins, shorten the production time and have environmental advantages, but also enhance the protein properties and facilitate subsequent applications. The amino acid composition of the blue food proteins is close to the FAO recommended standard and better than most of the livestock proteins, with excellent solubility and water holding capacity. Some of the proteins also have significant bioactivity and show great potential for improving health. Applications include emulsions, protein films, microcapsules, food colorants, dietary supplements, 3D printing materials, and cultured meat. This paper provides theoretical support for further research and application of blue food proteins and promotes their wider application in future food products.

Extraction and improvement of protein functionality using steam explosion pretreatment: advances, challenges, and perspectives

Protein has become an increasingly valuable food component with high global demand. Consequently, unconventional sources, such as industrial and agroindustrial wastes and by-products, emerge as interesting alternatives to meet this demand, considering the UN Sustainable Development Goals and the transition to a circular economy. In this context, this work presents a review of the use of Steam Explosion (SE), a green technique that can be employed as a pretreatment for various waste materials, including bones, hide/leather, feathers, and wool, aimming the extraction of protein compounds, such as low molecular weight biopeptides, gelatin, and keratin, as well as to enhance the protein functionality of grains and meals. The SE technique and the main factors affecting the process's efficiency were detailed. Promising experimental studies are discussed, along with the mechanisms responsible for protein extraction and functionality improvement, as well as the main reported and suggested applications. In general, steam explosion favored yields in subsequent extraction processes, ranging from 27 to 95%, in addition to enhancing solubility and functional protein properties. Nonetheless, it is crucial to maintain the continuity of research on this topic to drive advancements in ensuring the safety of the extracted compounds for use in consumable products and oral ingestion.

Physical properties, phenolic profile and antioxidant capacity of Java tea (Clerodendranthus spicatus) stems as affected by steam explosion treatment

Java tea (Clerodendranthus spicatus) has been favored for its various health benefits and abundance of phenolic substances. Steam explosion (SE) treatment was performed in the pretreatment of Java tea stems and the physical properties, phenolic profile and antioxidant capacity were investigated. Extraction kinetics study showed that the phenolics yields of Java tea stems treated at 2.4 MPa for 10 min reached the maximum in 40 min, which was approximately 3 times the yields of raw stems in 180 min. The antioxidant activities of the extracts of Java tea stems were also significantly increased after SE treatment (P < 0.05). In addition, 19 phenolics were detected in Java tea stems by HPLC/QTOF-MS/MS, and rosmarinic acid was found to be hydrolyzed to danshensu during the SE process. SE could be an efficient pretreatment technology to improve the extraction rates of phenolics and conversions of their high-value hydrolyzed products, which could facilitate further research of Java tea products.

Green Chemistry to Valorize Seafood Side Streams: An Ecofriendly Roadmap toward Sustainability

A major challenge facing sustainable seafood production is the voluminous amounts of nutrient-rich seafood side streams consisting of by-catch, processing discards, and process effluents. There is a lack of a comprehensive model for optimal valorization of the side streams. Upcoming green chemistry-based processing has the potential to recover diverse valuable compounds from seafood side streams in an ecofriendly manner. Microbial and enzymatic bioconversions form major green processes capable of releasing biomolecules from seafood matrices under mild conditions. Novel green solvents, because of their low toxicity and recyclable nature, can extract bioactive compounds. Nonthermal technologies such as ultrasound, supercritical fluid, and membrane filtration can complement green extractions. The extracted proteins, peptides, polyunsaturated fatty acids, chitin, chitosan, and others function as nutraceuticals, food supplements, additives, etc. Green processing can address environmental, economic, and technological challenges of valorization of seafood side streams, thereby supporting sustainable seafood production. Green processing can also encourage bioenergy production. Multiple green processes, integrated in a marine biorefinery, can optimize valorization on a zero-waste trade-off, for a circular blue economy. A green chemistry-based valorization framework has the potential to meet the Sustainable Development Goals (SDGs) of the United Nations.

The Principle of Steam Explosion Technology and Its Application in Food Processing By-Products

Steam explosion technology is an emerging pretreatment method that has shown great promise for food processing due to its ability to efficiently destroy the natural barrier structure of materials. This narrative review summarizes the principle of steam explosion technology, its similarities and differences with traditional screw extrusion technology, and the factors that affect the technology. In addition, we reviewed the applications in food processing by-products in recent years. The results of the current study indicate that moderate steam explosion treatment can improve the quality and extraction rate of the target products. Finally, we provided an outlook on the development of steam explosion technology with a reference for a wider application of this technology in the food processing field.

A review on the processing of functional proteins or peptides derived from fish by-products and their industrial applications

To understand the production and characteristics of protein hydrolysates pertaining to individual fish species, we selected and analyzed the most important commercial fish species according to the market value based on the Statistics on International Exports of Fishery Commodities by Food and Agriculture Organization. Accordingly, salmon, shrimp, cod, tuna, squid, and herring are marine species with high global value. Peptides obtained from their by-products were predominant in hydrophobic amino acids such as alanine, phenylalanine, methionine, proline, valine, tyrosine, tryptophan, leucine, and isoleucine. Bioactive peptides are short with a length of 2-20 amino acids. They remain inactive when they are within their parent proteins. Low molecular weight (0.3-8 kDa) peptides from hydrolyzed protein are easily digestible, readily absorbed by the body and are water-soluble. The hydrophobic nature contributes to their bioactivity, which facilitates their interactions with the membrane lipid bilayers. Incomplete hydrolysis results in low yields of hydrophobic amino acids. The glycosylation type of the resulting peptide fragment determines the different applications of the hydrolysate. The degree of conservation of the glycosidic residues and the size of the peptides are influenced by the method used to generate these hydrolysates. Therefore, it is crucial to explore inexpensive novel methodologies to generate bioactive peptides. According to the current studies, a unified approach (in silico estimation coupled with peptidomics) can be used for the identification of novel peptides with diverse physiological and technological functions. From an industrial perspective, the reusability of immobilized enzymes and membrane separation techniques (e.g., ultrafiltration) on marine by-products can offer low operating costs and higher yield for large-scale production of bioactive peptides. This review summarizes the production processes and essential characteristics of protein hydrolysates from fish by-products and presents the advances in their application.

Protein Hydrolysates from Pleurotus geesteranus Modified by Bacillus amyloliquefaciens γ-Glutamyl Transpeptidase Exhibit a Remarkable Taste-Enhancing Effect

Long-term high salt intake exerts a negative impact on human health. The excessive use of sodium substitutes in the food industry can lead to decreased sensory quality of food. γ-Glutamyl peptides with pronounced taste-enhancing effects can offer an alternative approach to salt reduction. However, the content and yield of γ-glutamyl peptides in natural foods are relatively low. Enzyme-catalyzed synthesis of γ-glutamyl peptides provides a feasible solution. In this study, Pleurotus geesteranus was hydrolyzed by Flavourzyme to generate protein hydrolysates. Subsequently, they were modified by Bacillus amyloliquefaciens γ-glutamyl transpeptidase to generate γ-glutamyl peptides. The reaction conditions were optimized and their taste-enhancing effects were evaluated. Their peptide sequences were identified by parallel reaction monitoring with liquid chromatography-tandem mass spectrometry and analyzed using molecular docking. The optimal conditions for generation of γ-glutamyl peptides were a pH of 10.0, an enzyme condition of 1.2 U/g, and a reaction time of 2 h, which can elicit a strong kokumi taste. Notably, it exhibited a remarkable taste-enhancing effect for umami intensity (76.07%) and saltiness intensity (1.23-fold). Several novel γ-glutamyl peptide sequences were found by liquid chromatography-tandem mass spectrometry, whereas the binding to the calcium-sensing receptor was confirmed by molecular docking analysis. Overall, γ-glutamyl peptides from P. geesteranus could significantly enhance the umami and salt tastes, which can serve as promising taste enhancers.

Valorisation of keratinous wastes: A sustainable approach towards a circular economy

The valorisation of keratinous wastes involves biorefining and recovering the bioresource materials from the keratinous wastes to produce value-added keratin-based bioproducts with a broad application, distribution, and marketability potential. Valorisation of keratinous wastes increases the value of the wastes and enables more sustainable waste management towards a circular bioeconomy. The abundance of keratinous wastes as feedstock from agro-industrial processing, wool processing, and grooming industry benefits biorefinery and extraction of keratins, which could be the optimal solution for developing an ecologically and economically sustainable keratin-based economy. The transition from the current traditional linear models that are deleterious to the environment, which end energy and resources recovery through disposal by incineration and landfilling, to a more sustainable and closed-loop recycling and recovery approach that minimises pollution, disposal challenges, loss of valuable bioresources and potential revenues are required. The paper provides an overview of keratinous wastes and the compositional keratin proteins with the descriptions of the various keratin extraction methods in biorefinery and functional material synthesis, including enzymatic and microbial hydrolysis, chemical hydrolysis (acid/alkaline hydrolysis, dissolution in ionic liquids, oxidative and sulphitolysis) and chemical-free hydrolysis (steam explosion and ultrasonic). The study describes various uses and applications of keratinases and keratin-based composites fabricated through various manufacturing processes such as lyophilisation, compression moulding, solvent casting, hydrogel fabrication, sponge formation, electrospinning, and 3D printing for value-added applications.

Physicochemical, Structural and Antioxidant Properties of Collagens from the Swim Bladder of Four Fish Species

This study aimed to isolate and characterize pepsin-solubilized collagen (PSC) from marine and freshwater fish swim bladders. The physicochemical properties, protein pattern, amino acid composition, structure, thermal denaturation temperature, and antioxidant activity of PSC from four different swim bladder sources were investigated and compared. The results demonstrated that the four types of collagen extracted were all type I collagen. The yield of PSC extracted from grass carp (GCSB-PSC), bighead carp (BCSB-PSC), grouper (GSB-PSC), and monkfish swim bladders (MSB-PSC) were 38.98, 27.97, 18.16, and 10.35%, respectively. Compared to the other three PSCs, BCSB-PSC has the highest thermal denaturation temperature (38.60 °C). Based on FTIR spectroscopy and circular dichroism (CD) analysis, the extracted PSCs retained the triple helix and secondary structure well. Antioxidant studies showed that in the swim bladders of four species the swim bladder PSC could scavenge DPPH and ABTS radicals. Overall, swim bladders from marine and freshwater fish can be utilized as raw materials for collagen extraction, and the extracted collagen has potential commercial applications.

Functional proteins through green refining of seafood side streams

Scarcity of nutritive protein is a major global problem, the severity of which is bound to increase with the rising population. The situation demands finding additional sources of proteins that can be both safe as well as acceptable to the consumer. Food waste, particularly from seafood is a plausible feedstock of proteins in this respect. Fishing operations result in appreciable amounts of bycatch having poor food value. In addition, commercial processing results in 50 to 60% of seafood as discards, which consist of shell, head, fileting frames, bones, viscera, fin, skin, roe, and others. Furthermore, voluminous amounts of protein-rich effluents are released during commercial seafood processing. While meat from the bycatch can be raw material for proteinous edible products, proteins from the process discards and effluents can be recovered through biorefining employing upcoming, environmental-friendly, low-cost green processes. Microbial or enzyme treatments release proteins bound to the seafood matrices. Physico-chemical processes such as ultrasound, pulse electric field, high hydrostatic pressure, green solvent extractions and others are available to recover proteins from the by-products. Cultivation of photosynthetic microalgae in nutrient media consisting of seafood side streams generates algal cell mass, a rich source of functional proteins. A zero-waste marine bio-refinery approach can help almost total recovery of proteins and other ingredients from the seafood side streams. The recovered proteins can have high nutritive value and valuable applications as nutraceuticals and food additives.

Effects of Spray Drying and Freeze Drying on Physicochemical Properties, Antioxidant and ACE Inhibitory Activities of Bighead Carp (Aristichthys nobilis) Skin Hydrolysates

The physicochemical, structural properties, antioxidant, and angiotensin I-converting enzyme (ACE) inhibitory activities of fish skin protein hydrolysate (SPH) that were freeze-dried (SPH-FD) and spray-dried (SPH-SD) were investigated. SPH-SD showed abundant volatile compounds, higher DPPH radical scavenging activity and ferrous iron chelating activity than SPH-FD, while the ABTS radical scavenging activity and ACE inhibitory activity were not influenced by the drying method. Amino acid compositions showed a higher proportion of proline and hydroxyproline residues in SPH-FD. The major molecular weights were both distributed below 1000 Da. SPH-SD had spherical structures, while SPH-FD had glass shard-like structures. The results indicated that the drying method could affect the physicochemical properties of hydrolysates, and SPH-SD showed potential prospects in developing functional fortified foods.

Lactic Acid-Based Natural Deep Eutectic Solvents to Extract Bioactives from Marine By-Products

Natural deep eutectic solvents (NaDES) were used to extract bioactive compounds from marine by-products: codfish bones, mussel meat, and tuna vitreous humor. NaDES were prepared using natural compounds, including lactic acid (Lac), fructose (Fru), and urea (Ur), and were characterized to define their physicochemical properties, including the viscosity, density, surface tension, and refractive index. FTIR and NMR analysis confirmed the presence of intermolecular hydrogen bonding in NaDES. The extracts obtained using these NaDES were characterized to define their composition. Results demonstrated that the extract’s composition differed highly, depending not only on the DES used, but also on the structure and composition of the raw material. Proteins and lipids were mainly present in extracts obtained from mussels, while ash content was highest in the extracts obtained from codfish bones. The biocompatibility of NaDES and the soluble fractions (SF) of the raw materials in NaDES was evaluated, and it was possible to conclude that the soluble ingredients obtained from the raw materials improved the biocompatibility of NaDES.