Quality of Protein Isolates and Hydrolysates from Baltic Herring (Clupea harengus membras) and Roach (Rutilus rutilus) Produced by pH-Shift Processes and Enzymatic Hydrolysis

Role of lingonberry press cake in producing stable herring protein isolates via pH-shift processing: A dose response study

The effects of cross-processing lingonberry press cake (LPC) (2.5-30 %, dw/dw) with herring co-products on protein yield, oxidative stability and color of pH-shift-produced protein isolates were investigated. Even at 2.5 % LPC, the formation of volatile oxidation-derived aldehydes, including hexanal, (E)-2-hexenal, heptanal, octanal, and 2,4-heptadienal, were prevented during the actual protein isolate production. Adding 10 % LPC successfully prevented formation of all these aldehydes also during eight days ice storage which was explained by the partitioning of phenolics, especially ideain (1.09 mg/g dw) and procyanidin A1 (65.5 mg/g dw), into isolates. Although higher amounts of LPC (20-30 %) further prolonged the oxidation lag phase, it reduced total protein yield, increased the consumption of acid and base, and darkened protein isolates. Therefore, it is recommended to use 10 % LPC when pH-shift-processing sensitive fish raw materials as a route to mitigate lipid oxidation and at the same time promote industrial symbiosis and more circular food production.

Changes in the Main Physicochemical Properties and Electrochemical Fingerprints in the Production of Sea Buckthorn Juice by Pectinase Treatment

Enzymatic hydrolysis using pectinase is critical for producing high-yield and quality sea buckthorn juice. This study determined the optimal temperature, time, and enzyme dosage combinations to guide manufacturers. A temperature of 60 °C, hydrolysis time of 3 h, and 0.3% enzyme dosage gave 64.1% juice yield-25% higher than without enzymes. Furthermore, monitoring physicochemical properties reveals enzyme impacts on composition. Higher dosages increase soluble solids up to 15% and soluble fiber content by 35% through cell wall breakdown. However, excessive amounts over 0.3% decrease yields. Pectin concentration also declines dose-dependently, falling by 91% at 0.4%, improving juice stability but needing modulation to retain viscosity. Electrochemical fingerprinting successfully differentiates process conditions, offering a rapid quality control tool. Its potential for commercial inline use during enzymatic treatment requires exploration. Overall, connecting optimized parameters to measured effects provides actionable insights for manufacturers to boost yields, determine enzyme impacts on nutrition/functionality, and introduce novel process analytical technology. Further investigations of health properties using these conditions could expand sea buckthorn juice functionality.

Development of patty meat analogue using anchovy protein isolate (Stolephorus insularis) as a binding agent

The development of meat analogues focuses on sustainable production and requires attention to their nutritional, physicochemical, and sensory values. Anchovy protein isolate (API) is a novel and potential binding agent in the development of meat analogues. This study aimed to produce API and evaluate the physical, proximate, and sensory qualities of patty meat analogue (PMA) with the addition of API. The preparation method for API uses pH-shifting. The ratios of API added to the meat analogues were 0 % (F0), 4 % (F1), 8 % (F2), and 12 % (F3) per textured vegetable protein (TVP) weight. Furthermore, PMA was analysed for physical, proximate, and sensory properties. API had 87.23 % dry basis (db) protein content. The amino acid composition of API generally complied with the nutritional requirements of adults and children. The addition of API significantly affected the physical properties, proximate composition, and sensory (taste) qualities of PMA (p < 0.05). The protein content of PMA met Indonesian national standards (SNI) and was similar to both McDonald's and ground beef patty based on United States Department of Agriculture (USDA) standards. F3 was found to be the best based on its physical, proximate, and sensory properties.

Enzyme-assisted aqueous extraction of fish oil from Baltic herring (Clupea harengus membras) with special reference to emulsion-formation, extraction efficiency, and composition of crude oil

Enzyme-assisted aqueous extraction (EAAE) is a green, and scalable method to produce oil and protein hydrolysates from fish. This study investigated the role of different parameters on emulsion formation, oil recovery, and the composition of crude oil during EAAE of Baltic herring (Clupea harengus membras). Fatty acid compositions, lipid classes, tocopherols, and oxidation status of the EAAE crude oils were studied. Compared to solvent-extracted oil, EAAE resulted in a lower content of phospholipids accompanied by a 57% decrease in docosahexaenoic acid. Changing fish to water ratio from 1:1 to 2:1 (w/w) with ethanol addition led to the greatest reduction (72%) of emulsion, which resulted in an increase in oil recovery by 11%. The addition of ethanol alone, or reduction of enzyme concentration from 0.4% to 0.1% also reduced emulsion-formation significantly. Overall, emulsion reduction resulted in higher content of triacylglycerols and n - 3 polyunsaturated fatty acids in the crude oil extracted.

Comparison of Commercial Fish Proteins' Chemical and Sensory Properties for Human Consumption

To stop overfishing and meet the protein needs of a growing population, more information is needed on how to use marine by-catches, by-products, and undervalued fish species for human consumption. Turning them into protein powder is a sustainable and marketable way to add value. However, more knowledge of the chemical and sensory properties of commercial fish proteins is needed to identify the challenges in developing fish derivatives. This study aimed to characterize the sensory and chemical properties of commercial fish proteins to compare their suitability for human consumption. Proximate composition, protein, polypeptide and lipid profiles, lipid oxidation, and functional properties were analyzed. The sensory profile was compiled using generic descriptive analysis, and odor-active compounds were identified with gas-chromatography-mass spectrometry-olfactometry (GC-MS/O). Results indicated significant differences in chemical and sensory properties between processing methods but not between fish species. However, the raw material had some influence in the proteins' proximate composition. Bitterness and fishiness were the main perceived off-flavors. All samples, apart from hydrolyzed collagen, had intense flavor and odor. Differences in odor-active compounds supported the sensory evaluation results. The chemical properties revealed that the lipid oxidation, peptide profile, and raw material degradation are likely affecting the sensory properties of commercial fish proteins. Limiting lipid oxidation during processing is crucial for the development of mild-tasting and -smelling products for human consumption.

Lingonberry (Vaccinium vitis-idaea) press-cake as a new processing aid during isolation of protein from herring (Clupea harengus) co-products

High acid-consumption and lipid oxidation are challenges when recovering functional proteins from herring co-products via pH-shift-processing. Here, lingonberry press-cake (LP), which is abundant in organic acids and phenolics, was added to alkali-solubilized herring-co-product-proteins (2.5-30 % LP per dry weight) aiming to aid protein precipitation, save hydrochloric acid (HCl) and provide oxidative stability. The results revealed 5-30 % LP addition reduced HCl-consumption by 13-61 % and 19-79 % when precipitating proteins at pH 5.5 and 6.5, respectively. Higher LP% decreased protein content and lightness of protein isolates but raised the lipid content. Precipitation at pH 6.5 used less acid, reduced total protein yield and raised moisture content and darkness of isolates. Contrary to controls, lipid oxidation-derived volatiles did not develop in protein isolates precipitated with 10 % and 30 % LP, neither during the process itself nor during 21 days on ice. Altogether, LP was identified as a promising all-natural processing-aid to use during herring protein isolation.

Protein Characteristics and Bioactivity of Fish Protein Hydrolysates from Tra Catfish (Pangasius hypophthalmus) Side Stream Isolates

Enzymatic hydrolysis is a novel method to recover highly potent bioactive fish protein hydrolysates (FPHs) from fish processing side-streams. The common way of producing FPHs directly from fish side-streams may be inappropriate due to the excess of lipids and pro-oxidants, especially in lipid-rich streams, as obtained from Tra catfish. This study aimed to optimise the hydrolysis conditions for a commercial enzyme (Alcalase® 2.4 L) (enzyme concentrate, temperature, and time) in FPH production from the fish protein isolate obtained from Tra catfish dark muscle (DM-FPI) using the pH-shift method. The degree of hydrolysis (DH), protein recovery (PR), and antioxidant properties, including DPPH radical scavenging activity (DPPH-RSA) and total reducing power capacity (TRPC), were measured to evaluate the effects of the hydrolysis conditions on the FPHs. Optimal hydrolysis was obtained at an enzyme/substrate protein ratio of 3% (v/w) and a hydrolysis temperature of 50 °C for 3 h. The FPHs obtained from different substrates, including DM-FPI, abdominal cut-off (ACO) FPI, and head and backbone blend (HBB) FPI, had similar DHs under these optimum conditions, ranging from 22.5% to 24.0%. However, the FPH obtained from abdominal cut-off isolate (ACO-FPH) showed the highest PR of 81.5 ± 4.3% and the highest antioxidant properties, with a DPPH-RSA of 86.1 ± 1.6% and a TRPC of 6.4 ± 0.4 equivalent mg vitamin C/g protein. The resulting FPHs present a natural source of antioxidants with great potential for food applications, especially the ACO-FPH. In addition, all FPHs had excellent amino acid profiles, indicating strong potential for their use as supplements. Tra catfish protein-rich side-streams can thus be processed into high-value bioactive FPHs using Alcalase for human consumption.

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.