Effects of Enzymatic Hydrolysis Conditions on the Antioxidant Activity of Red Tilapia (<i>Oreochromis spp</i>.) Viscera Hydrolysates

Protein Hydrolysates from Fishery Processing By-Products: Production, Characteristics, Food Applications, and Challenges

Fish processing by-products such as frames, trimmings, and viscera of commercial fish species are rich in proteins. Thus, they could potentially be an economical source of proteins that may be used to obtain bioactive peptides and functional protein hydrolysates for the food and nutraceutical industries. The structure, composition, and biological activities of peptides and hydrolysates depend on the freshness and the actual composition of the material. Peptides isolated from fishery by-products showed antioxidant activity. Changes in hydrolysis parameters changed the sequence and properties of the peptides and determined their physiological functions. The optimization of the value of such peptides and the production costs must be considered for each particular source of marine by-products and for their specific food applications. This review will discuss the functional properties of fishery by-products prepared using hydrolysis and their potential food applications. It also reviews the structure-activity relationships of the antioxidant activity of peptides as well as challenges to the use of fishery by-products for protein hydrolysate production.

Optimization and scale up of the enzymatic hydrolysis of Californian red worm protein (Eiseniafoetida)

Although the best-known use of the different species of earthworm is the production of organic fertilizer, they can also be considered a rich source of biologically and pharmacologically-active compounds, for use in the treatment of various diseases. In recent decades, with the development of biochemical technologies, research on the pharmaceutical effects of compounds extracted from different species of earthworms has begun. Enzymatic hydrolysis is the most common and widely used technique for producing bioactive hydrolysates, because it uses moderate operating conditions, with a certain specificity for the substrate. In the present study, the objective was to optimize and scale up the enzymatic hydrolysis of Eisenia foetida protein to obtain peptides with biological activity. The substrate characterization was carried out according to AOAC, a response surface design was performed for the optimization of the enzymatic hydrolysis and then the scaling was performed by means of dimensional analysis. The results show that the major component of the paste is protein, 65% of which is albumin, and the absence of pathogenic microorganisms was also found. Regarding optimization, it was found that the optimal hydrolysis conditions are achieved with pH = 8.5; temperature = 45 °C; amount of substrate = 125 g and volume of enzyme = 1245μL. For the scaling, 4 dimensionless pi-numbers were calculated which describe the process with no statistically significant differences between the model and the prototype; it can be concluded that the enzymatic hydrolysate of Eisenia foetida presents high values of antioxidant activity evaluated by different methodologies.

Protein hydrolysates derived from aquaculture and marine byproducts through autolytic hydrolysis

Autolysis technology has shown potential for protein hydrolysates production from marine and aquaculture byproducts. Viscera are a source of cheap proteolytic enzymes for producing protein hydrolysates from the whole fish or processing byproducts of the most valuable commercial species by applying autolysis technology. The use of autolysis allows economical production of protein hydrolysate and provides an opportunity to valorize downstream fish and shellfish processing byproducts at a lower cost. As a result, production and application of marine byproduct autolysates is increasing in the global protein hydrolysates market. Nevertheless, several restrictions occur with autolysis, including lipid and protein oxidation mediated by the heterogeneous composition of byproducts. The generally poor storage and handling of byproducts may increase the formation of undesirable metabolites during autolysis, which can be harmful. The formation of nitrogenous compounds (i.e., biogenic amines), loss of freshness, and process of autolysis in the byproducts could increase the rate of quality and safety loss and lead to more significant concern about the use of autolysates for human food applications. The current review focuses on the autolysis process, which is applied for the hydrolysis of aquaculture and marine discards to obtain peptides as functional or nutritive ingredients. It further addresses the latest findings on the mechanisms and factors contributing the deterioration of byproducts and possible ways to control oxidation and other food quality and safety issues in raw materials and protein hydrolysates.

Electrically Switchable Nanolever Technology for the Screening of Metal-Chelating Peptides in Hydrolysates

Metal-chelating peptides (MCP) are considered as indirect antioxidants due to their capacity to inhibit radical chain reaction and oxidation. Here, we propose a new proof of concept for the screening of MCPs present in protein hydrolysates for valorizing their antioxidant properties by using the emerging time-resolved molecular dynamics technology, switchSENSE. This method unveils possible interactions between MCPs and immobilized nickel ions using fluorescence and electro-switchable DNA chips. The switchSENSE method was first set up on synthetic peptides known for their metal-chelating properties. Then, it was applied to soy and tilapia viscera protein hydrolysates. Their Cu²⁺-chelation capacity was, in addition, determined by UV-visible spectrophotometry as a reference method. The switchSENSE method has displayed a high sensitivity to evidence the presence of MCPs in both hydrolysates. Hence, we demonstrate for the first time that this newly introduced technology is a convenient methodology to screen protein hydrolysates in order to determine the presence of MCPs before launching time-consuming separations.