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Problems with silver carp protein (SCP) include a strong fishy odor, low gel strength of SCP surimi, and susceptibility to gel degradation. The objective of this study was to improve the gel quality of SCP. The effects of the addition of native soy protein isolate (SPI) and SPI subjected to papain-restricted hydrolysis on the gel characteristics and structural features of SCP were studied. The β-sheet structures in SPI increased after papain treatment. SPI treated with papain was crosslinked with SCP using glutamine transaminase (TG) to form a composite gel. Compared with the control, the addition of modified SPI increased the hardness, springiness, chewiness, cohesiveness, and water-holding capacity (WHC) of the protein gel (p < 0.05). In particular, the effects were most significant when the degree of SPI hydrolysis (DH) was 0.5% (i.e., gel sample M-2). The molecular force results demonstrated that hydrogen bonding, disulfide bonding, and hydrophobic association are important molecular forces in gel formation. The addition of the modified SPI increases the number of hydrogen bonds and the disulfide bonds. Scanning electron microscopy (SEM) analysis showed that the papain modifications allowed the formation of a composite gel with a complex, continuous, and uniform gel structure. However, the control of the DH is important as additional enzymatic hydrolysis of SPI decreased TG crosslinking. Overall, modified SPI has the potential to improve SCP gel texture and WHC. [ABSTRACT FROM AUTHOR]

There is a significant potential to increase the sustainability of the fishing and aquaculture industries through the maximization of the processing of byproducts. Enzymatic hydrolysis provides an opportunity to valorize downstream fish industry byproducts for the production of protein hydrolysates (FPH) as a source of bioactive peptides (BAP) with health benefits. Deteriorative oxidative reactions may occur during the enzymatic hydrolysis of byproducts, influencing the safety or bioactivities of the end product. Lipid oxidation, autolysis mediated by endogenous enzymes in viscera, protein degradation, and formation of low-molecular-weight metabolites are the main reactions that are expected to occur during hydrolysis and need to be controlled. These depend on the freshness, proper handling, and the type of byproducts used. Viscera, frames, trimmings, and heads are the byproducts most available for enzymatic hydrolysis. They differ in their composition, and, thus, require standardization of both the hydrolysis procedures and the testing methods for each source. Hydrolysis conditions (e.g., enzyme type and concentration, temperature, and time) also have a significant role in producing FPH with specific structures, stability, and bioactivity. Protein hydrolysates with good safety and quality should have many applications in foods, nutraceuticals, and pharmaceuticals. This review discusses the oxidative reactions during the enzymatic hydrolysis of byproducts from different fish industry sectors and possible ways to reduce oxidation. [ABSTRACT FROM AUTHOR]

The hydrolysates of tuna dark meat with high angiotensin I-converting enzyme (ACE) inhibitory and antioxidant activities were prepared using three enzymes. The effect of concentration (0.5–3.0%, w/w) and hydrolysis time (30–180 min) on yield, degree of hydrolysis (DH), ACE inhibitory activities, and antioxidant capacity was determined. The optimum conditions were the same: 180 min extraction while the concentration of alcalase, neutrase, and flavourzyme were 2.43, 2.62, and 2.62% (w/w), respectively. The hydrolysate resulted in the range of 36.5–50.0% for DH, 5.79–7.71% for yield, 0.29–1.11, 0.28–0.53, and 0.24–0.31 mg/mL IC50 values with 2,2-diphenyi-l-picrylhydrazyl radical (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), and ACE inhibitory activity, respectively, and 0.41–1.35 FeSO4/g for ferric reducing antioxidant power (FRAP). The hydrolysates showed high solubility. Emulsion stability and emulsifying activity index decreased, while foam stability and expansion increased with increasing concentration. Hydrolysates using flavourzyme were fractioned using ultrafiltration membranes. The <1 kDa fraction had significantly higher ACE inhibitory and antioxidant activities. [ABSTRACT FROM AUTHOR]

The structural and functional properties of slowly digestible starch (SDS) modified using pullulanase and prepared from chestnut starch were studied. The modified chestnut starches had 41.9 % SDS, which was higher than native chestnut starches (6.51 %) and cooked chestnut starches (18.6 %). The hydrolysis rate of the modified starches was 74.1 %. Scanning electron microscopy showed that the modified starch granules had a large surface area with signs of cracks and dents, and the cross-sections showed hollow internal structures. X-ray diffraction indicated that the crystallisation of the starch changed from the Cb-type to the V-type, although it retained a few C-type characteristics. Compared with native chestnut starch, the modified starches have a higher gelatinisation temperature using differential scanning calorimetry; and the texture profile analysis hardness, chewiness, cohesiveness, and gumminess of modified starch gels decreased significantly, while adhesiveness increased. When debranched using pullulanase there was a decreased solubility, swelling power, and freeze-thaw stability of the modified starches. These findings suggest that pullulanase modification changed the in vitro digestibility and crystalline structure of the modified starches. [ABSTRACT FROM AUTHOR]

The isolation and purification of polysaccharides extracted from the cones, bark, and needles ofPinus koraiensis(Korean pine) were studied. The amounts of polysaccharides were 42.7%, 53.4%, and 48.4% for cones, bark, and needles, respectively. All these samples contained uronic acid. The total protein and polyphenols were <4.5% for all three samples. With acid hydrolysis, seven polysaccharides were found in different molar ratios in each sample: D-ribose, L-rhamnose, L-arabinose, D-xylose, D-mannose, D-glucose, and D-galactose. The relationships between in vitro antioxidant properties (AOP) of polysaccharides extracted from different parts of the P. koraiensis tree are correlated with physicochemical properties (the amount of neutral sugars, uronic acid, and proteins). Moreover, the pinecone polysaccharides (PKCP) confirmed previously observed beneficial antioxidant capacity with an EC50of OH radical, ABTS radical scavenging, and reducing power of 6.54, 5.06, and 9.15 mg/mL, respectively. PKCP had the best antioxidant activity among the three samples. [ABSTRACT FROM AUTHOR]

The objective of this study was to characterize and compare the acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) from the scales, skins and swim-bladders of grass carp. Both ASC and PSC from the three tissues were mainly characterized as type I collagen, with similar electrophoretic patterns and amino acid profiles. PSC from the three tissues was more susceptible to hydrolysis by V8 protease than ASC. Both ASC and PSC from the three tissues showed similar peptide hydrolysis patterns. The maximum transition temperatures of both ASC and PSC from the internal tissue (swim-bladders) were only slightly higher than those of ASC and PSC from the external tissues (scales and skins). These results suggest that collagens from the three tissues of grass carp had almost similar biochemical properties, and could be used as potential substitutes for mammalian collagens due to their comparatively high thermostability. [ABSTRACT FROM AUTHOR]

Fish skin gelatin was hydrolyzed with papain to produce antioxidant peptides. Response surface methodology (RSM) was applied to optimize the hydrolysis conditions (including enzyme to substrate ratio [E/S], hydrolysis time, and temperature). The highest degree of hydrolysis (DH) (50.1 ± 1.1%) was obtained at an E/S of 2% at 56.8 °C, 2.11 h, and was not significantly different from the predicted values within a 95% confidence interval. The highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) (96.8 ± 0.9%) and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS•+) (9.80 ± 0.11 mM Trolox [6-hydroxy-2,5,7,8-tetramethychroman-2-carboxylic acid]) radical-scavenging activities of fish gelatin hydrolyzates were obtained at an E/S of 3% at 52.1 °C, 2.65 h, and both DPPH and ABTS•+ radical-scavenging activities were not significantly different from the predicted values 97.3% and 9.86 mM Trolox within the 95% confidence interval. Therefore, RSM is an efficient way to optimize fish gelatin hydrolysation and the resultant hydrolyzates show promise as antioxidant peptides. Practical Application: There is a growing interest in the use of fish gelatin as an alternative to mammalian gelatin. One potential use is as a source of widely acceptable functional compounds. In this study, a search for antioxidant peptides from fish gelatin prepared by an enzymatic method has been successfully done. This suggests that this is a practical way to obtain bioactive peptides. [ABSTRACT FROM AUTHOR]

The optimization of antioxidant and anti-tyrosinase activity during jellyfish hydrolysate preparation was studied using a response surface methodology (RSM) with a face-centered composite design. The influence of the hydrolysis duration and the enzyme concentration on the IC50 of the DPPH and ABTS radical scavenging activity, ferric-reducing antioxidant power (FRAP), the degree of hydrolysis (DH), yield, and the IC50 value of tyrosinase inhibitory activity were determined. The optimum conditions for the production of jellyfish hydrolysate using alcalase (JFAH), flavourzyme (JFFH), or papain (JFPH) were achieved at hydrolysis times of 360, 345, or 360 min, respectively, and at an enzyme concentration of 5.0%. JFFH had the highest antioxidant and tyrosinase inhibitory activity. JFAH, JFFH, and JFPH concentrations of 2.5 mg/mL resulted in HaCaT cells (IC80) having a survival rate of 80%. The amino acid profile of JFFH contained about 43% hydrophobic and 57% hydrophilic amino acids, comprising Gly, Cys, Glx, Asx, which were dominant. The isolation of a peptide fraction from JFFH was carried out using ultrafiltration membranes (10, 3, and 1 kDa) and gel filtration chromatography. Fraction-III (1–3 kDa) showed the highest antioxidative and tyrosinase inhibitory activity. [ABSTRACT FROM AUTHOR]

To determine the nanostructure of gelatin from catfish ( Ictalurus punctatus) skin, atomic force microscopy (AFM) was used to study gelatin aggregates. The gelatin was extracted at an optimized acid concentration after alkaline processing. First, the AFM imaging parameters were optimized to obtain high-quality images. Then height mode with a 2-dimensional plane, 3-dimensional topographical images, and error signal mode images, which removed slow variations in surface topography but highlighted the edges of sample features, were used to analyze the structure of particles. The results describe fish gelatin at a nanoscale level for the first time and are compared with AFM images of mammalian gelatins. Both annular pores with diameters averaging 118 nm and spherical aggregates with an average diameter of 267 nm were seen in the AFM images of fish gelatin. From the AFM images, we propose that the structures formed were determined by whether the solution penetrated into the gelatin molecules evenly or not during hydrolysis. A scheme for the formation of annular pores and spherical aggregates is proposed. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to extract and characterise pepsin-solubilised collagens (PSC) from the fins, scales, skins, bones and swim bladders of bighead carp and to provide a simultaneous comparison of five different sources from one species. The PSC were mainly characterised as type I collagen, containing two α-chains, and each maintained their triple helical structure well. The thermostability of PSC from the internal tissues (swim bladders and bones) was slightly higher than that of PSC from the external tissues (fins, scales and skins). The peptide hydrolysis patterns of all PSC digests using the V8 protease were similar. All PSC were soluble at acidic pH (1–6) and lost their solubility at NaCl concentrations above 30g/l. The resulting PSC from the five tissues would all be potentially useful commercially. [Copyright &y& Elsevier]

Abstract: A two-stage in vitro digestion model system (a pepsin treatment for 2h followed by a pancreatin treatment for 2h, both at 37°C) was used to simulate the process of human gastrointestinal (GI) digestion to determine the changes in antioxidant activities of loach peptide previously prepared by papain digestion. Results showed that the final GI digests contained 38.1% free amino acids, with short chain peptides (<500Da) making up the rest of the biomass. Enzymatic breakdown of the GI digests increased their hydroxyl (12% increase), 2,2′-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) (5% increase) radical scavenging activity, the reducing power (77% increase) and the chelating ability of Cu2+ (12% increase), compared to the blank. The results showed that the digestion by gastrointestinal proteases can be used to produce antioxidant peptides, with the advantage that the peptides formed will resist physiological digestion in GI tract. [Copyright &y& Elsevier]

This study aims to fabricate composite gels using nano citrus fiber (Nano-CF) derived from the hydrolysis process of citric acid (CA) with FeCl 3 , with a simultaneous exploration of its potential as an substitute to fats. Investigation of varying FeCl 3 concentrations (0.01 to 0.03 mmol/g of CA) revealed a significant enhancement in the water-holding and oil-retention capacity of the Nano-CF. The meticulous synthesis of the composite gels involved integrating nano citrus fibers with konjac glucomannan (KGM) through high-speed shearing, followed by a comprehensive evaluation of its microstructure and physicochemical attributes. Increasing the Nano-CF concentration within the gels led to a synergistic interaction with KGM, resulting in enhanced viscosity, improved thermal stability, and restricted water molecule mobility within the system. The gels initially displayed reduced firmness, resilience, and adhesive characteristics, followed by subsequent improvement. When the ratio of Nano-CF to KGM was 0.5:1, the composite gels exhibited texture parameters, viscosity, and viscoelastic stability comparable to whipped animal cream formulations. These findings provide a new idea for the application of Nano-CF/KGM composite gels in whipped cream. [Display omitted] • The treatment with FeCl 3 significantly enhanced the water and oil holding capacities of nano citrus fiber (Nano-CF) • The composite gel properties were induced by the molecular interaction such as hydrogen bonding between Nano-CF and KGM • When the ratio of Nano-CF to KGM was 0.5:1, the composite gels exhibited a high similarity in texture and viscoelastic stability with whipped cream [ABSTRACT FROM AUTHOR]

Abstract: The present study characterized and compared the acid-soluble collagens (ASC) from skins and scales of grass carp, silver carp, bighead carp and black carp. All ASC were mainly characterized as type I collagen with the triple helical structures well maintained. ASC from bighead carp and silver carp showed similar peptide hydrolysis patterns using V8 protease, and ASC from grass carp and black carp also showed similar patterns which were different from those of ASC from the former two species. Maximum transition temperature of all ASC ranged from 34.1 to 36.4 °C. Both ASC from one species and mixed ASC from different species could assemble into collagen fibrils. D-periodicities of fibrils assembled from mixed ASC were slightly smaller than those of fibrils assembled from ASC from one species. Therefore, these results suggested that the skins or scales of the four carp species could be processed together to produce collagen. [Copyright &y& Elsevier]

The effect of limited trypsin hydrolysis on the functional properties and structural characteristics of dehulled walnut proteins (DWP) were studied. The degree of hydrolysis (DH) of DWP was set at 1, 3 and 7.1%. Solubility was higher in all hydrolysates than the native protein, 7.1% DH showed the best protein solubility at 74.8% at pH 7. All hydrolysates showed better functional properties than DWP, including emulsifying properties, foaming capacity and stability, but no improvement of water absorption capacity was observed. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) confirmed the reduction in the molecular weight and the presence of protein bands having an MW < 30 kDa. The protein hydrolysates with higher DH showed higher surface hydrophobicity and intrinsic fluorescence intensity. Intrinsic fluorescence indicated that changes occurred in the tertiary conformation of DWP with enzymatic hydrolysis. Emulsions prepared with hydrolysates were more stable with NaCl addition (0–50 mM) and thermal processing (30–50 °C). The above results indicated that limited enzymatic hydrolysis is a promising approach to improving DWP's functional properties and highlighting the potential use of DWP hydrolysates in the food industry. • Dehulled walnuts were taken as material to reduce the influence of polyphenols. • Limited trypsin hydrolysis increased solubility of dehulled walnut proteins. • Functional properties of hydrolysates improved significantly after hydrolysis. • Dehulled walnut proteins with 3% DH showed the best emulsion stability. [ABSTRACT FROM AUTHOR]