Analysis of volatile compounds and nutritional properties of enzymatic hydrolysate of protein from cod bone

Effects of different slaughtering methods on the energy metabolism, apoptosis process and quality of grouper (Epinephelus fuscoguttatus) during cold storage at 4 °C

BACKGROUND

The aquatic processing industry is increasingly aware of the need to ensure that slaughtering is carried out under high welfare standards, so there is a need to explore the impact of slaughter methods on fish fillets. This study aimed to investigate the effects of different slaughtering methods (M1, lethality by hammering; M2, gas mixture causing death; M3, lethality by clove oil anesthesia + ice slurry; M4, lethality by ice slurry; M5, lethality by gradient cooling) on the energy metabolism, apoptosis and flesh mass in grouper (Epinephelus fuscoguttatus).

RESULTS

Therefore, 120 fish (24 per treatment) were slaughtered by the five methods. The results showed that the succinate dehydrogenase (SDH) enzyme activity of M5 sample was higher. The serum glucose level of M2 samples and DAPI staining fluorescence of M2 samples were the highest, indicating that the stress response of M2 was strong. In addition, the texture, pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA) and K value results showed M5 samples had better flesh quality.

CONCLUSION

Gradient cooling lethality had the least effect on oxidative damage and apoptosis in grouper during cold storage as the gradient cooling lethality had the least effect on antioxidant enzyme activities. © 2024 Society of Chemical Industry.

Characterization and application of Bacillus velezensis D6 co-producing α-amylase and protease

BACKGROUND

Research on the co-production of multiple enzymes by Bacillus velezensis as a novel species is still a topic that needs to be studied. This study aimed to investigate the fermentation characteristics of B. velezensis D6 co-producing α-amylase and protease and to explore their enzymatic properties and applications in fermentation.

RESULTS

The maximum co-production of α-amylase and protease reached 13.13 ± 0.72 and 2106.63 ± 64.42 U mL-1, respectively, under the optimal fermented conditions (nutrients: 20.0 g L-1 urea, 20.0 g L-1 glucose, 0.7 g L-1 MnCl2; incubation conditions: initial pH 7.0, temperature 41 °C, 8% inoculation size and 30% working volume). Moreover, the genetic co-expression of α-amylase and protease increased from 0 to 24 h and then decreased after 36 h at the transcriptional level, which coincided with the growth trend of B. velezensis D6. The optimal reaction temperature of α-amylase was 55-60 °C, while that of protease was 35-40 °C. The activities of α-amylase and protease were retained by over 80% after thermal treatment (90 °C, 1 h), which indicated that two enzymes co-produced by B. velezensis D6 demonstrated excellent thermal stability. Moreover, the two enzymes were stable over a wide pH range (pH 4.0-8.0 for α-amylase; pH 4.0-9.0 for protease). Finally, the degrees of hydrolysis of corn, rice, sorghum and soybeans by α-amylase from B. velezensis D6 reached 44.95 ± 2.95%, 57.16 ± 2.75%, 52.53 ± 4.01% and 20.53 ± 2.42%, respectively, suggesting an excellent hydrolysis effect on starchy raw materials. The hydrolysis degrees of mackerel heads and soybeans by protease were 43.93 ± 2.19% and 26.38 ± 1.72%, respectively, which suggested that the protease from B. velezensis D6 preferentially hydrolyzed animal-based protein.

CONCLUSION

This is a systematic study on the co-production of α-amylase and protease by B. velezensis D6, which is crucial in widening the understanding of this species co-producing multi-enzymes and in exploring its potential application. © 2024 Society of Chemical Industry.

Enhancement of the flavor and functional characteristics of cod protein isolate using an enzyme-microbe system

Cod protein isolate (CPI), a by-product of the cod processing industry, represents a novel source of high value-added products. However, off-flavors in cod protein such as bitterness and fishy odor reduce its acceptability to consumers. Here, CPI was first debittered using aminopeptidase from Streptomyces canus (ScAPase) and then deodorized through probiotic fermentation. This is the first reported demonstration of complete removal of the bitterness of CPI using ScAPase. Subsequently, Syn3 and Syn4, as aromatic CPI (ACPI), were prepared from debittered CPI (DCPI) via fermentation with Lactobacillus acidophilus and Bifidobacterium longum, respectively. These products, DCPI and ACPI, were characterized by the absence of bitterness and fishy odor, along with a strong aromatic scent and high overall acceptability. Additionally, these products exhibited improved physicochemical properties, including enhanced oil-holding capacity, emulsifying activity, and resistance to digestion, compared to untreated CPI. However, significant differences were observed in their radical scavenging activities. The highest scavenging activity was detected in Syn3 against DPPH˙ (63.5%) and ˙OH (79.2%), in DCPI against O2- (32.0%), and in post-digestion Syn4 against ABTS˙+ (95.2%). Furthermore, after digestion treatment, these products significantly promoted the proliferation of probiotics. Notably post-digestion Syn4 showed the most substantial proliferation effect on Lactobacillus reuteri, Lactobacillus rhamnosus, and Bifidobacterium breve compared to other post-digestion samples. These results indicate that the treated CPI has the potential for applications in health food products.

Co-Immobilization of Alcalase/Dispase for Production of Selenium-Enriched Peptide from Cardamine violifolia

Enzymatically derived selenium-enriched peptides from Cardamine violifolia (CV) can serve as valuable selenium supplements. However, the industrial application of free enzyme is impeded by its limited stability and reusability. Herein, this study explores the application of co-immobilized enzymes (Alcalase and Dispase) on amino resin for hydrolyzing CV proteins to produce selenium-enriched peptides. The successful enzyme immobilization was confirmed through scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and Fourier-transform infrared spectroscopy (FTIR). Co-immobilized enzyme at a mass ratio of 5:1 (Alcalase/Dispase) exhibited the smallest pore size (7.065 nm) and highest activity (41 U/mg), resulting in a high degree of hydrolysis of CV protein (27.2%), which was obviously higher than the case of using free enzymes (20.7%) or immobilized Alcalase (25.8%). In addition, after a month of storage, the co-immobilized enzyme still retained a viability level of 41.93%, showing fairly good stability. Encouragingly, the selenium-enriched peptides from co-immobilized enzyme hydrolysis exhibited uniform distribution of selenium forms, complete amino acid fractions and homogeneous distribution of molecular weight, confirming the practicality of using co-immobilized enzymes for CV protein hydrolysis.

Effect of enzymolysis combined with Maillard reaction treatment on functional and structural properties of gluten protein

In this work, the modified gluten was prepared by enzymolysis combined with Maillard reaction (MEG), and its functional and structural properties were investigated. The result showed that the maximum foamability of MEG was 19.58 m2/g, the foam stability was increased by 1.8 times compared with gluten, and the solubility and degree of graft were increased to 44.4 % and 28.1 % at 100 °C, whereas the content of sulfhydryl group decreased to 0.81 μmol/g. The scavenging ability on ABTS+radical and DPPH radical of MEG was positively correlated with reaction temperature, and the maximum values were 86.57 % and 71.71 % at 140 °C, respectively. Furthermore, the fluorescence quenching effect of tryptophan and tyrosine residues was enhanced, while the fluorescence intensity decreased with the temperature increase. Scanning electron microscopy revealed that the surface of enzymatically hydrolyzed-gluten became smooth and the cross section became straightened, while MEG turned smaller and irregular approaching a circular structure. FT-IR spectroscopy showed that enzymatic hydrolysis promoted the occurrence of more carbonyl ammonia reactions and the formation of precursors of advanced glycosylation end products. These results provide a feasible method for improving the structure and functional properties of gluten protein.

Antioxidant Activities of Aqueous Extracts and Protein Hydrolysates from Marine Worm Hechong (Tylorrhynchus heterochaeta)

Hechong (Tylorrhynchus heterochaeta) is an edible marine worm widely distributed in the estuary area. The objective of this study is to determine the antioxidant activities of extracts and protein hydrolysates from Hechong. Results showed that the aqueous extracts of steamed Hechong had the highest antioxidant values using the methods of DPPH, ABTS, and FRAP testing (76.29 μmol TE/g, 181.04 μmol TE/g, and 10.40 mmol Fe²⁺/100 g, respectively). Furthermore, protein hydrolysates of Hechong were observed significant antioxidant activities when compared to crude Hechong. The purification was carried out by DEAE-52 cellulose and Sephadex G-100 column chromatography. The microspatial structure of glycoprotein showed fibrous shapes and cracks with uniform distribution. The study has concluded that the extract and protein hydrolysates of Hechong have significant antioxidant activities, which is merited to be further investigated in the food and pharmaceutical fields.

Valorization of poultry slaughterhouse waste for fertilizer purposes as an alternative for thermal utilization methods

Slaughterhouse waste and dead animals are mainly disposed of by incineration, which generates greenhouse gases and NO_x. These wastes are a source of nutrients that can be recovered by circular economy techniques if material recycling is given a priority over energy recovery. To valorize high-protein animal waste (containing bones, meat, feather) for fertilizer purposes, the waste was processed by acid solubilization and neutralized with potassium hydroxide solution, which yielded a liquid fertilizer with plant growth biostimulating properties (due to the amino acids presence). The composition analysis showed that new fertilizers met all quality requirements set by the law, contain ~0.5% m/m amino acids and are microbiologically pure. The fertilizer was enriched with microelements to the level of 0.2% m/m and tested for biological effectiveness in germination tests and field studies. Compared with the commercial formulation, the fertilizer increased stem length and chlorophyll content (by 8.2% and 27.0%, respectively), wheat crop yield and grain micronutrients density (Cu by 31.2%, Mn by 10.5%, Zn by 33.9%) and improved the wheat flour baking properties. The described solution propose a safe way to utilize hazardous waste via technological mobile installation, enabling no transportation of waste, which is an important aspect of sanitary-epidemiological risk minimization.

Effect of Gum Tragacanth-Sodium Alginate Active Coatings Incorporated With Epigallocatechin Gallate and Lysozyme on the Quality of Large Yellow Croaker at Superchilling Condition

This research was done to investigate the synergistic interactions of the gum tragacanth (GT)–sodium alginate (SA) active coatings, incorporated with epigallocatechin gallate and lysozyme, on the quality of large yellow croaker (Larimichthys crocea) during superchilling storage at −3°C. Results showed that the GT-SA active coatings, containing epigallocatechin gallate [EGCG (E), 0.32% w/v], and lysozyme [LYS (L), 0.32% w/v] have reduced the total viable count, psychrophilic bacteria, and Pseudomonas spp. by about 1.55 log CFU/g, 0.49 log CFU/g, and 1.64 log CFU/g compared to the control at day 35. The GT-SA active coatings containing EGCG and LYS were effective in lowering the formations of off-odor compounds such as total volatile basic nitrogen (TVB-N), malondialdehyde (MDA), and off-favor amino acid (histidine). The solid phase microextraction gas chromatography-mass spectrometer (SPME-GC/MS) was applied to characterize and to quantify the volatile compounds of large yellow croaker samples during superchilling storage, while the relative content of the fishy flavor compounds (including 1-octen-3-ol and acetoin) was significantly reduced in the active coatings treated samples. Furthermore, the GT-SA active coatings containing EGCG and LYS treatments was found to be more effective in retarding the migration of water based on magnetic resonance imaging (MRI) results and in maintaining the organoleptic quality of large yellow croaker in superchilling storage at −3°C according to the sensory evaluation results. The results showed that the GT-SA active coating containing EGCG and LYS was effective to be used as a fish preservative to improve the quality and to prolong the shelf life of large yellow croaker in a superchilling storage for at least 7 days.

Influence of Multifrequency Ultrasound-Assisted Freezing on the Flavour Attributes and Myofibrillar Protein Characteristics of Cultured Large Yellow Croaker (Larimichthys crocea)

The influence of multifrequency ultrasound-assisted freezing (UAF) as compared with single- and dual-UAF on the flavour, microstructure, and myofibrillar proteins (MPs) of cultured large yellow croaker was investigated to improve food quality in a sustainable way and address the major global challenges concerning food and nutrition security in the (near) future. Multifrequency UAF-treated samples had lower total volatile basic nitrogen values during freezing than single- and dual-UAF-treated samples. Thirty-six volatile compounds were identified by solid-phase microextraction (SPME) coupled to gas chromatography–mass spectrometry (GC-MS) during freezing, and the multifrequency UAF-treated samples showed significant decreases in the relative contents of fishy flavoured compounds, including 1-penten-3-ol and 1-octen-3-ol. In addition, multifrequency UAF treatment better maintained a well-organised protein secondary structure by maintaining higher α-helical and β-sheet contents and stabilising the tertiary structure. Scanning electron microscopy images indicated that the ice crystals developed by the multifrequency UAF were fine and uniformly distributed, resulting in less damage to the frozen large yellow croaker samples. Therefore, multifrequency UAF improved the flavour attributes and MP characteristics of the large yellow croaker samples. Overall, multifrequency UAF can serve as an efficient way for improving food quality and nutritional profile in a sustainable way.

Inhibitory effects of Atlantic cod (Gadus morhua) peptides on RANKL-induced osteoclastogenesis in vitro and osteoporosis in ovariectomized mice

Atlantic cod (Gadus morhua) is one of the most important fishes in the world with high nutritional value and economic value. However, the impact and underlying mechanism of the G....

Phytochemicals and Amino Acids Profiles of Selected sub-Saharan African Medicinal Plants' Parts Used for Cardiovascular Diseases' Treatment

For years, the focus on the lipid-atherosclerosis relationship has limited the consideration of the possible contribution of other key dietary components, such as amino acids (AAs), to cardiovascular disease (CVD) development. Notwithstanding, the potential of plant-based diets, some AAs and phytochemicals to reduce CVDs' risk has been reported. Therefore, in this study, the phytochemical and AA profiles of different medicinal plants' (MPs) parts used for CVDs' treatment in sub-Saharan Africa were investigated. Fourier-transform infrared analysis confirmed the presence of hydroxyl, amino and other bioactive compounds' functional groups in the samples. In most of them, glutamic and aspartic acids were the most abundant AAs, while lysine was the most limiting. P. biglobosa leaf, had the richest total branched-chain AAs (BCAAs) level, followed by A. cepa bulb. However, A. cepa bulb had the highest total AAs content and an encouraging nutraceutical use for adults based on its amino acid score. Principal component analysis revealed no sharp distinction between the AAs composition of MPs that have found food applications and those only used medicinally. Overall, the presence of medicinally important phytochemicals and AAs levels in the selected MPs' parts support their use for CVDs treatment as they might not add to the AAs (e.g., the BCAAs) burden in the human body.

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

The development of an efficient pretreatment, prior to enzymatic hydrolysis, is a good strategy for the sustainable use of refractory fish byproducts. This study compared hydrothermal pretreatments at 159 °C for 2 min, followed by water extraction (steam explosion-assisted extraction, SE) and 121 °C for 70 min (hot-pressure extraction, HPE), for the recovery of proteins from fish backbones. The effect of enzymatic hydrolysis on the properties of the obtained fish bone protein (FBP) was also evaluated. The results demonstrated that FBP had high contents of protein (81.09-84.88 g/100 g) and hydroxyproline (70-82 residues/1000 residues). After hydrolysis with Flavourzyme, for 3 h, the FBP hydrolysates that were pretreated with SE (SFBP-H) exhibited a better degree of hydrolysis (DH) and nitrogen recovery (NR), and a higher level of umami taste free amino acids (151.50 mg/100 mL), compared with the HPE-treated samples. The obtained SFBP-H mainly distributed below 3000 Da and had strong scavenging effects on 1,1-diphenyl-2-picrylhydrazy (DPPH) (IC₅₀ = 4.24 mg/mL) and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) (IC₅₀ = 1.93 mg/mL) radicals. Steam explosion-assisted extraction is a promising route for recovering proteins from native fish bone materials, and improving the flavor and antioxidant activity of the hydrolysates.

Separation, identification and molecular binding mechanism of dipeptidyl peptidase IV inhibitory peptides derived from walnut (Juglans regia L.) protein

Walnut protein was hydrolyzed with different proteases to evaluate the hydrolytic efficiency and dipeptidyl peptidase IV (DPP-IV) inhibitory activity in vitro. All of walnut protein hydrolysates (WPHs) exhibited DPP-IV inhibitory activity and Alcalase-derived hydrolysate (WPH-Alc) with better DPP-IV inhibitory activity of 33.90% (at 0.50 mg/mL) was subsequently separated by ultrafiltration and cation exchange chromatography on a SP Sephadex C-25 column. The results showed that fractions with lower molecular weight and higher basic amino acid residues possessed stronger DPP-IV inhibitory activity. Comparably, the obtained fraction B with the yield of 19.80% had the highest DPP-IV inhibitory activity of 76.19% at 0.25 mg/mL. Moreover, nine novel DPP-IV inhibitory peptides were identified using MALDI-TOF/TOF-MS. Molecular docking revealed the peptides could interact with DPP-IV through hydrogen bonds, salt bridges, hydrophobic interactions, π-cation bonds and π-π bonds. The walnut DPP-IV inhibitory peptides showed better stability with heating treatment, pH treatment, or in vitro gastrointestinal digestion.

Structural and physicochemical characteristics of lyophilized Chinese sturgeon protein hydrolysates prepared by using two different enzymes

The structural and physicochemical characteristics of protein hydrolysates prepared from Chinese sturgeon through the enzymatic hydrolysis process were evaluated. Two different enzymes including papain and alcalase 2.4L were used in the hydrolysis process. The papain enzyme significantly increased the degree of hydrolysis (20.62%) and decreased the ζ-potential (12.4 ± 1.31 mV) as compared to the alcalase enzyme, which represented 15.55% and 15.53 ± 0.77 mV, respectively. Alcalase 2.4L hydrolysate exhibited smaller particle size (822.047 ± 61.26 nm) than papain hydrolysate (1425.39 ± 44.82 nm). Hydrolysis by papain and alcalase 2.4L enzymes decreased the molecular weights (MW ≤ 1,000 Da) to 98.27% and 86.84%, respectively. The surface hydrophobicity and turbidity of the hydrolysates significantly affected by enzyme type and protein concentrations. By using the X-ray diffraction analysis, the papain hydrolysate showed a higher relative crystallinity degree (30.33%) than alcalase 2.4L hydrolysate (29.40%), whereas the Fourier transform infrared spectroscopy showed more clearly peaks for the amide bands of alcalase hydrolysate. The thermal properties also affected by enzymatic hydrolysis conditions, since the melting temperatures were 159.17 and 149.58 °C, whereas the rate of mass loss was 67.04% and 62.8%, for papain and alcalase hydrolysates, respectively. PRACTICAL APPLICATION: The enzymatic hydrolysis process of proteins is employed to obtain the nutritionally and functionality important peptides that result during the preparation of fish protein hydrolysate. The objective of this study was to investigate the structural and physicochemical characteristics of protein hydrolysate prepared from Chinese sturgeon. This study showed that these characteristics were affected by enzymatic hydrolysis conditions especially enzyme type. The finding of this study may be useful in terms of providing new information on the properties of the protein hydrolysate and the structural changes resulting from controlled enzymatic hydrolysis conditions. Overall, these conditions could potentially alter the secondary structure of the protein hydrolysates or peptides and enhance their functional properties.

Optimization of Oyster (Crassostrea talienwhanensis) Protein Hydrolysates Using Response Surface Methodology

Oyster (Crassostrea talienwhanensis) protein was hydrolyzed by trypsin to produce peptides with different response values, and response surface methodology (RSM) was applied to optimize the hydrolysis conditions. The highest degree of hydrolysis (DH) of the oyster peptide (OP) was obtained at an enzyme concentration of 1593.2 U/g, a pH of 8.2, a hydrolysis temperature of 40.1 °C, a hydrolysis time of 6.0 h, and a water/material ratio of 8.2. The greatest hydroxyl-radical-scavenging activity of OP was obtained at an enzyme concentration of 1546.3 U/g, a pH of 9.0, a hydrolysis temperature of 50.2 °C, a hydrolysis time of 5.1 h, and a water/material ratio of 5.6. The largest branched-chain amino acid (BCAA) content of OP was obtained at an enzyme concentration of 1323.8 U/g, a pH of 8.3, a hydrolysis temperature of 41.7 °C, a hydrolysis time of 6.7 h, and a water/material ratio of 4.8. The three experimental values were significantly in agreement with the predicted values within the 95% confidence interval. Furthermore, ultrafiltration and chromatographic methods were used to purify the OP, and 13 peptides that were rich in Lys, Arg, His, and Thr were identified by LC-MS/MS. The results of this study offer different optimum hydrolysis conditions to produce target peptides from oyster protein by using RSM, and this study provide a theoretical basis for the high-value utilization of oyster protein.

Effects and mechanism of ultrasound pretreatment of protein on the Maillard reaction of protein-hydrolysate from grass carp (Ctenopharyngodon idella)

The effects of two types (energy-divergent/gathered) of ultrasound pretreatment of protein on the Maillard reaction of protein-hydrolysate from grass carp (Ctenopharyngodon idella) were studied. The test and analysis of Fourier transform infrared spectroscopy, surface hydrophobicity and atomic force microscopy of protein, peptide concentration, molecular weight distribution and free amino acid content of protein-hydrolysate were performed to reveal the mechanism. Also, the sensory characteristics of Maillard reaction products were evaluated. Results showed that Maillard reaction products presented higher absorbance value at 294 and 420 nm after pretreated by two types of ultrasound compared to that of control. The grafting degree value of products pretreated by energy-divergent ultrasound increased by 13.87%. Both of these two types of ultrasound pretreatment showed higher (p < 0.05) value of grafting degree compared to that of positive control (thermal denaturation). The random coil content and surface hydrophobicity of protein improved significantly (p < 0.05), and the depth distribution of protein molecules narrowed down after pretreated by ultrasound, especially energy-divergent type ultrasound. The change of protein structure increased small molecular peptide/amino acid content in protein-hydrolysate, so that it promoted the Maillard reaction process of protein-hydrolysate and glucose. The mouthfulness and overall acceptance of Maillard reaction products increased after pretreated by two types of ultrasound. Results indicated that ultrasound, especially energy-divergent type ultrasound pretreatment of protein was an effective method to promote Maillard reaction evolution of protein-hydrolysate from grass carp protein and improved the flavor of Maillard reaction products.

Preparation of sheep bone collagen peptide-calcium chelate using enzymolysis-fermentation methodology and its structural characterization and stability analysis

In this study, enzymatic hydrolysis and Lactobacillus fermentation were used in combination to prepare collagen peptide with high free calcium content, followed by the addition of anhydrous ethanol to obtain peptide-calcium chelate. The optimal conditions for the fermentation of enzymatic hydrolysate (glucose 3%, inoculum size 6%, 24.5 h, 37 °C and pH 6.5) were determined by response surface methodology (RSM), under which a free calcium content of 2212.58 mg/100 g was obtained. The calcium-chelating capacity was 42.57 ± 0.09%. The results of ultraviolet absorption spectrum, Fourier transform infrared (FT-IR) spectra, differential scanning calorimeter (DSC), X-ray diffraction and amino acid analysis indicated that calcium could be chelated through carboxyl oxygen and amino nitrogen atoms of collagen peptides, forming peptide-calcium chelate. The chelate is stable at 30-80 °C of temperatures and during in simulated gastrointestinal digestion, which could promote calcium absorption in human. The test intended to provide a basis for developing a novel calcium supplement and promoting utilization of sheep bone.

Preservative Effects of Gelatin Active Coating Containing Eugenol and Higher CO2 Concentration Modified Atmosphere Packaging on Chinese Sea bass (Lateolabrax maculatus) during Superchilling (-0.9 °C) Storage

The purpose of this research was to explore the fresh keeping effect of modified atmosphere packaging (MAP) with different gas ratios combined with gelatin active coatings containing eugenol on Chinese sea bass stored at −0.9 °C for 36 days. The results showed that MAP3 (60% CO₂/10% O₂/30% N₂), together with gelatin active coatings containing eugenol, could prevent water loss, which maintained high field NMR, MRI, and organoleptic evaluation results. This hurdle technology could also effectively delay the bacterial reproduction, protein degradation, and alkaline accumulation, so it showed the lowest K value, total volatile basic nitrogen, free amino acids, total viable count, Pseudomonas spp., and H₂S-producing bacteria, which better maintain the quality of sea bass.

Biological and conventional food processing modifications on food proteins: Structure, functionality, and bioactivity

Food proteins are important nutrients for human health and thus make significant contributions to the unique functions of different foods. The modification of proteins through physical and biological processing could improve the functional and nutritional properties of food products; these changes can be attributed to modifications in particle size, solubility, emulsion stability, secondary structure, as well as the bioactivities of the proteins. Physical processing treatments might promote physical phenomena, such as combined friction, collision, shear forces, turbulence, and cavitation of particles, and lead to changes in the particle sizes of proteins. The objective of this review is to illustrate the effect of physical and biological processing on the structure, and physical and chemical properties of food-derived proteins and provide insights into the mechanism underlying structural changes. Many studies have suggested that physical and biological processes, such as ultrasound treatment, high pressure homogenization, ball mill treatment, and enzymatic hydrolysis could affect the structure, physical properties, and chemical properties of food-derived proteins. Some important applications of food-derived proteins are also discussed based on the relationships between their physical, chemical, and functional properties. Perspectives from fundamental or practical research are also brought in to provide a complete picture of the currently available relevant data.

Fish Scale Valorization by Hydrothermal Pretreatment Followed by Enzymatic Hydrolysis for Gelatin Hydrolysate Production

Protein hydrolysates from fish by-products have good process suitability and bioavailability in the food industry. The objective of this work was to develop a method for protein recovery from fish scales and evaluate the hydrolysis of the scale protein. The effect of the hydrothermal process on protein recovery, degree of hydrolysis (DH) and structural properties of the hydrolysates was investigated. Results showed that hydrothermal treatment could enhance protein recovery of tilapia scales without demineralization and dramatically improve the DH of the hydrolysates. The hydrothermal treated scales showed a better protein recovery (84.81%) and DH (12.88%) and released peptides more efficiently than that of the conventional treated samples. The obtained gelatin hydrolysates mainly distributed in the range of 200–2000 Da with an angiotensin I-converting enzyme (ACE) IC₅₀ value of 0.73 mg/mL. The ACE inhibitory activity of gelatin hydrolysates was stable under high temperature, pH and gastrointestinal proteases. Hydrothermal treatment followed by enzymatic hydrolysis offers a potential solution for preparation of gelatin hydrolysates for food ingredients from fish processing by-products.

Preservative Effects of Gelatin Active Coating Enriched with Eugenol Emulsion on Chinese Seabass (Lateolabrax maculatus) during Superchilling (−0.9 °C) Storage

This research was to evaluate the effects of gelatin (G) active coating containing eugenol/β-cyclodextrin (βCD) emulsions combined with superchilling (−0.9 °C) on physicochemical, microbiological, and organoleptic properties of Chinese seabass samples during 30 days of storage. Results showed that seabass samples dipped in G-βCD coatings containing 0.15% or 0.3% eugenol combined with superchilling could significantly lower the total volatile basic nitrogen, K value, total viable count, H2S-producing bacteria, Pseudomonas spp. and Psychrophilic counts, and free fatty acids. Further, G-βCD coatings containing eugenol with superchilling (−0.9 °C) were more effective in retarding the water migration by low field NMR and MRI results, maintaining quality of seabass during storage according to organoleptic evaluation results.

The dual functions of flavor and antioxidant potential of porcine bone marrow extract (PBME)

To improve and confirm the dual functions of flavor and antioxidant potential of porcine bone marrow extract (PBME). Response surface methodology and Box-Behnken design was employed to optimize the conditions for enzymatic hydrolysis of PBME. The optimal hydrolysis conditions were: hydrolysis time, 3h; temperature, 55 °C; substrate concentration, 375g/L; and amount of enzyme, 0.4%. L₁₆(3⁵) orthogonal experimental was utilized to obtain the optimal Maillard reaction conditions for PBME and enzymatic hydrolysate of PBME (EH-PBME). The optimal conditions for PBME were: components, 4% glucose, 2% xylose, 1.5% Tyr, 1.5% Ala, and 4% VB₁; reaction time, 40 min; and reaction temperature, 115 °C. The optimal conditions for EH-PBME were: components, 2% glucose, 2% xylose, 3% Ala, and 5% VB₁; reaction time, 40 min; temperature, 110 °C. The antioxidant activities for PBME, EH-PBME, Maillard reaction products of PBME (MPRs A) and Maillard reaction products of EH-PBME (MPRs B) were 50%, 86%, 84% and 41% respectively. The content of taste-active substances and volatile compounds were also determined. Finally, PLSR was employed to evaluate the correlation between flavor compounds and sensory data.

Protein hydrolysates of porcine hemoglobin and blood: Peptide characteristics in relation to taste attributes and formation of volatile compounds

The objective of this study was to investigate the impact of endo- and exo-peptidase treatment on certain structural characteristics of peptides and volatile compounds of porcine hemoglobin and whole blood hydrolysates. Porcine hemoglobin and whole blood were hydrolyzed by endo- and exo-peptidases. The presence of exopeptidases reduced the bitterness and altered the volatile profiles of protein hydrolysates. Exopeptidase treatment can release terminal amino acids from peptides, which in turn may contribute to formation of volatile compounds by Maillard reactions. In contrast, endopeptidases conferred a slightly bitter taste and different volatile profiles. For hemoglobin hydrolysates, principal component analysis revealed that proteases were categorized into three groups based on endo- or exo-peptidase activity. Whole blood is a more complex raw material, yet the proteases were still categorized in a similar fashion. This work contributes to understanding structural characteristics responsible for taste and volatile profiles of protein hydrolysates.