Degree Of Hydrolysis Research Articles

Impact of heat treatment and high moisture extrusion on the in vitro protein digestibility of sunflower and pea protein ingredients

This study aimed to evaluate the protein quality of sunflower and pea protein and how processing (fermentation, mild heating, and high moisture extrusion) would affect their digestibility. The protein quality was assessed by the amino acid profile (calculated scores) and in vitro protein digestibility via the degree of protein hydrolysis (DH) using the INFOGEST digestion model. The amino acid profile indicated that sunflower protein was deficient only in lysine (0.62) and leucine (0.86), while pea protein lacked tryptophan (0.83) and sulfur-containing amino acids (0.96). The blend of these materials (1:1) provided a complete amino acid profile reaching a score above 1 for all the essential ones. Fermentation and blending did not have a significant impact of the protein digestibility of the raw materials. The DH of sunflower protein concentrate increased from 33.6 to 46.9% (p < 0.05) after mild heat treatment (15% solids, 90 °C, 15 min) and up to 52.8% (p < 0.05) after high-moisture extrusion. Differently, the digestibility of pea protein or the blends was not affected by any of the heat treatments. The extruded sunflower protein had a similar DH than the beef reference (47.5%) and mixing beef with plant-based ingredients did not affect the DH. These results highlight the potential of sunflower as good protein source, especially when blended with pea protein or extruded into meat analogs.

Lactiplantibacillus plantarum for the Preparation of Fermented Low-Bitter Enzymatic Skim Milk with Antioxidant Ability

A high degree of hydrolysis can reduce the allergenicity of milk, while lactic acid bacteria (LAB) fermentation can further enhance the antioxidant ability of enzymatic milk. LAB with a strong antioxidant ability was screened, and the effects of LAB on the bitterness, taste and flavor of enzymatic skim milk (ESM) with a high degree of hydrolysis were investigated in this paper, in addition to the response surface methodology optimized the conditions of the LAB fermentation of ESM. The results indicate that the skim milk hydrolyzed by Protamex has a higher degree of hydrolysis and lower bitterness. The scavenging rate of 2,2-Diphenyl-1-picrylhydrazyl (DPPH) free radical, the inhibition rate of hydroxyl radical (·OH) and the superoxide dismutase (SOD) activity of Lactiplantibacillus plantarum 16 and Lactococcus lactis subsp. lactis m16 are significantly higher than those of other strains (p &lt; 0.05), while the improvement effect of L. plantarum 16 on the bitterness and flavor of ESM is better than that of L. lactis subsp. lactis m16. The fermented ESM has a strong antioxidant ability and low bitterness when the inoculum quantity of L. plantarum 16 is 5%, fermentation at 37 °C for 18 h and the pH of the ESM is 6.5, for which the DPPH free radical scavenging rate is 61.32%, the ·OH inhibition rate is 83.35%, the SOD activity rate is 14.58 and the sensory evaluation is 4.25. The contents of amino acids related to bitterness and antioxidants were reduced and increased, respectively. The ESM fermented by L. plantarum 16 has a good flavor, antioxidant ability and low bitterness.

Electrospinning and Rheological Characterization of Polyethylene Terephthalate and Polyvinyl Alcohol with Different Degrees of Hydrolysis Incorporating Molecularly Imprinted Polymers

This study investigates the electrospinning and rheological properties of polyethylene terephthalate (PET) and polyvinyl alcohol (PVA) with varying degrees of hydrolysis (DH) for molecularly imprinted polymer (MIP) incorporation. The morphology and properties of the electrospun nanofibers were evaluated, revealing that PVA nanofibers exhibited smoother and more uniform structures compared to PET fibers. The rheological behavior of the polymer solutions was also characterized, showing that PVA 99 DH solution exhibited shear-thinning behavior due to the unique structural properties of the polymer chains. The introduction of MIP and NIP additives had no significant impact on the rheological properties, except for PVA 99 MIP and NIP solutions, which showed deviations from Newtonian behavior. The electrospun MIP nanofibers showed a conductivity of 1054 µS/cm for PVA (87–90% DH) and a viscosity of 165.5 mPa·s, leading to optimal fiber formation, while displaying a good adsorption capacity of 0.36 mg for PVA-MIP to effectively target pharmaceuticals such as emtricitabine and tenofovir disoproxil, showing their potential for advanced water treatment applications. The results suggest that the electrospinning process and rheological properties of the polymer solutions are influenced by the molecular structure and interactions within the polymer matrix, which can be exploited to tailor the properties of MIPs for specific applications.

Pilot Study on a Liquid Mineral Foliar Fertilizer Mixed with Herbicides for Maize Protection and Nutrition

The purpose of this study was to develop a complex composition of a foliar liquid mineral fertilizer containing NPK macroelements and microelements including Fe, Mg, B, S, Zn, Cu, Mo, Ni, V, and Cr. This complex fertilizer aims to support the optimal development and maturation of maize crops, thereby enhancing both the quality and quantity of production. In our study, an original recipe was established for a complex composition of foliar liquid mineral fertilizer, and a technological process was developed in order to obtain the recipe at the laboratory level. The designed fertilizer was a complex mixture of fertilizers with herbicides with multiple purposes, which can be used in different pedo-climatic areas and which present, at the same time, low toxicity and minimal ecological impact. A wide-spectrum mixture DICOPUR TOP containing 2,4-D acid and Dicamba was chosen as a systemic herbicide which is absorbed by plants both in the root system and also on the leaves. For conditioning the complex mixture of fertilizers with herbicides, different types of polyvinyl alcohol with different degrees of hydrolysis were used. The liquid fertilizer mixture with DICOPUR TOP was applied over two years (2021 and 2022) to the Felix maize hybrid, demonstrating significant positive effects on grain yield while effectively controlling both dicotyledonous and monocotyledonous weeds.

Oral Intake of Collagen and Collagen Hydrolysate From Takifugu bimaculatus Attenuates Ultraviolet‐Induced Skin Photoaging in Mice

ABSTRACTWith the rapid emergence of pufferfish aquaculture and processing industries, fish skin is underutilized as a byproduct of processing, leading to resource waste. In this study, Takifugu bimaculatus skin collagen (TBSC) was extracted by acetic acid solubilization and its physicochemical properties were analyzed. The effects of TBSC and the TBSC hydrolysate (TBSCH) on ultraviolet (UV) irradiation‐induced photoaging were investigated using a mouse model. The purity of TBSC was 90.02%. Electrophoresis and Fourier infrared spectroscopy characterization of TBSC showed that the type of collagen in TBSC was typical standard type I. The degree of hydrolysis was selected to optimize the hydrolysis conditions for TBSC. The papain enzyme dosage, temperature, pH, and hydrolysis duration of 51,000 U/g, 48.03°C, 5.35, and 4 h have been demonstrated to be the optimum hydrolysis conditions for TBSCH. Oral administration of either TBSC or TBSCH ameliorated UV‐induced skin erythema and hyperkeratosis. TBSC and TBSCH treatment increased collagen content and had an inhibitory effect on matrix metalloproteinase (MMP)‐2 and MMP‐3 expression, whereas MMP‐9 expression was significantly reversed only in the TBSCH‐treated groups. The expression of the c‐Jun protein was much lower in these groups, suggesting that TBSCH had a greater alleviating effect on collagen degradation and extracellular matrix breakdown. Therefore, it is proposed that TBSCH has the potential to be used as a nutricosmetic agent with protective attributes against UV‐induced skin damage and concurrent collagen depletion.

Antinutritional factors and protein digestibility of broad bean flours hydrolysed during soaking using vacuum enzyme impregnation

The hydrolysis of legume proteins improves their nutritional and functional properties. Usually done by mixing flour with an enzyme solution, the process can be simplified using vacuum enzyme impregnation during soaking. This study used vacuum impregnation with papain or bromelain to obtain hydrolysed broad bean flours. It examined the impact of vacuum impregnation and enzyme incorporation on hydration kinetics and the impact of hydrolysis and dehulling on antinutritional factors and protein digestibility. Vacuum impregnation accelerated hydration and enzyme incorporation did not alter the hydration rate. Maximum hydrolysis degrees were 9.1 % with papain and 8.8 % with bromelain after 4 h of soaking. Hydrolysis increased phytic acid, total phenolics, and tannins content while decreasing trypsin inhibitors. Dehulling increased phytic acid and trypsin inhibitors, reduced tannins, and enhanced protein digestibility. Vacuum enzyme impregnation during soaking was effective for hydration and protein hydrolysis, modifying the nutritional properties of broad bean flours.

Enzymatic hydrolysis of white-cheek shark skin gelatin: Optimization, structural transformations, functional characteristics, and antioxidant potential

This study investigates the enzymatic hydrolysis of white-cheek shark (Carcharhinus dussumieri) skin gelatin using Alcalase to produce antioxidant peptides. Response surface methodology was employed to optimize enzyme-substrate ratio (E/S) and hydrolysis time. The optimal conditions, with an E/S of 4.8% for 133 min, achieved the highest degree of hydrolysis (DH) of 23.4%, as well as maximum DPPH radical scavenging activity (56.8%) and FRAP value (0.24 mg AAE/g). Subsequent evaluations of hydrolyzed (WCSG-H) and non-hydrolyzed gelatin (WCSG) revealed significant differences in their properties (p<0.05). Specifically, gel electrophoresis showed molecular weight fractions of 72–165 kDa for WCSG and <8 kDa for WCSG-H, while amino acid profiling indicated high levels of glycine, proline, and alanine in both samples. ATR-FTIR spectroscopy demonstrated that enzymatic hydrolysis led to a more disordered secondary structure in WCSG. Furthermore, WCSG exhibited superior emulsion activity, foaming capacity, and foam stability, though differences in emulsion stability were not statistically significant (p>0.05). In contrast, WCSG-H showed significantly higher solubility (97.7%) and antioxidant capacity (56.8% DPPH radical scavenging activity and FRAP of 0.24 mg AAE/g) compared to WCSG (85.22%, 52.82%, and 0.08 mg AAE/g, respectively). Therefore, these findings suggest that both WCSG and WCSG-H are promising natural antioxidants for functional food applications.

Double-crosslinked hydrogels and hydrogel beads formed by garlic protein hydrolysates for bioactive encapsulation and gastrointestinal delivery.

Garlic protein is one of the main components of garlic. It has several beneficial characteristics. This study aimed to characterize a double crosslinked hydrogel formed with alginate, calcium ions (Ca2+), and garlic protein hydrolysates (GPH), and to develop hydrogel beads for targeted delivery of bioactive constituents to the gastrointestinal tract. The results indicated that the degree of GPH hydrolysis was approximately 3% following trypsin treatment. The inner structure of the double crosslinked hydrogel showed a honeycomb pattern, with solid-like gel rheology and improved texture properties at a 4% (w/v) GPH concentration. The GPH-based hydrogel beads demonstrated pH sensitivity, swelling in near-neutral and alkaline environments, and the encapsulated paclitaxel (PTX) exhibited an amorphous phase with preferential release in intestinal conditions. The GPH group also achieved greater drug encapsulation efficiency than a soy protein hydrolysate (SPH) group, and proteomic analysis suggested that lower molecular weight and peptide charge favored the formation of peptide-integrated double crosslinking hydrogels. This work indicated that GPH was helpful and could inspire the development of drug delivery systems involving GPH with the required mechanical strength and target-release properties. © 2024 Society of Chemical Industry.

Block copolymer nanoparticles doping polyacrylonitrile membranes for efficient adsorption of water-soluble dyes from water

Polyacrylonitrile (PAN) membranes doped with cross-linked fluorinated block copolymer nanoparticles of poly[(poly(ethylene glycol) methacrylate)-b-poly(2,2,2-trifluoroethyl acrylate)-b-polystyrene] [P(PEGMA)-b-PTFEMA-b-PS] with high flux and high adsorption of water-soluble dyes were prepared by phase transition method. The preparation of the PAN membranes includes (1) preparation of P(PEGMA)-b-PTFEMA-b-PS nanoparticles containing the –OH terminal by polymerization induced self-assembly (PISA); (2) preparation of hydrolyzed PAN containing the –COOH moieties with about 1% hydrolysis degree to increase the adsorption of water-soluble dyes; (3) grafting hydrolyzed PAN onto the P(PEGMA)-b-PTFEMA-b-PS nanoparticles through esterification between the –OH terminal and –COOH; (4) formation of modified PAN membranes through phase transition method in the presence of the HPAN-grafting block copolymer nanoparticles. The flux and equilibrium absorption of the modified PAN membranes are 8 times higher and 143% higher than those of the unmodified PAN membranes, respectively. It suggests that modifying PAN membranes by doping with cross-linked fluorinated block copolymer nanoparticles may be a promising method to prepare high performance membranes.

Enzymatization of Nila Fish (Oreochromis Niloticus) Protein Hydolysate by Combination of Bromelin and Pepsin Enzymes

Nile Tilapia (Oreochromis niloticus) is a freshwater fish with better nutritional content compared to other freshwater fish, making it suitable for use as a source for protein hydrolysate production. Protein hydrolysate is the result of the breakdown of protein into short-chain compounds through hydrolysis. This research aims to hydrolyze the minced Nile tilapia meat using a combination of bromelain and pepsin enzymes at a concentration of 5% and pH 7 conditions for 5-6 hours. The hydrolysis results using the combination of bromelain and pepsin enzymes (B100: P0) have a yield value of 12.68%, ash content of 2.94%, protein of 57.25%, water 2.65%, and fat 10.25% with a degree of hydrolysis of 61.46%. The hydrolysate has antibacterial properties against Staphylococcus aureus and Escherichia coli bacteria with inhibition zones of approximately 8.3 mm and 8.5 mm, respectively, at a concentration of 1 (mg/µL), contains 15 types of amino acids with the highest composition being lysine 5.12% and the highest non-essential amino acid being aspartic acid 5.75%.

Effect of cheese coagulants on American-style natural cheese proteolysis and functional characteristics of process cheese made therefrom

Recombinant bovine chymosin (RBC) is an enzyme routinely used in cheese manufacture. Recombinant camel chymosin (RCC) is a milk coagulant with higher clotting activity and less proteolytic activity for natural cheese manufacture. This study aimed to determine the effect of RCC and RBC on the proteolysis of natural cheese and the functionality of processed cheese (PC). Six American-style natural cheeses were manufactured utilizing two different chymosin treatments and used to produce PC at 1 month of ripening. The natural cheese made using RCC had a significantly (P < 0.05) lower level of primary proteolysis and a lower degree of hydrolysis of αS1-CN and β-CN. The RCC treatment's hot viscosity, hardness, and loss tangent were significantly (P < 0.05) higher than the RBC in the PC. These results demonstrate that RCC results in a reduced level of primary proteolysis in a natural cheese, and when utilized in PC, it increases firmness and decreases meltability.

Enhanced Oligopeptide and Free Tryptophan Release from Chickpea and Lentil Proteins: A Comparative Study of Enzymatic Modification with Bromelain, Ficin, and Papain.

Plant-based foods offer a sustainable alternative to meet the growing protein demand. Legumes are the most promising of these, as they contain relatively high concentrations of protein, low digestible starch, and dietary fiber, as well as them possibly featuring low levels of fat. Enzymatically modified legume proteins provide us with tempting perspectives in terms of enhancing foods' biological values. However, their bioavailability and digestibility are generally less sufficient than that of proteins of animal origin, which may be improved by well-tailored enzyme modification. In this study, the efficacy of three plant-based proteases (bromelain, ficin, and papain) were evaluated at two distinct concentrations (2.5% and 10%) and three hydrolysis durations (1, 2, and 12 h) when transforming chickpea and lentil proteins. The degree of hydrolysis (DH), peptide profiles, and free amino acid content were analyzed to determine the efficiency of each enzyme. Results showed significant variations in DH, which was influenced by enzyme type, concentration, and hydrolysis duration. Papain exhibited the highest DH, particularly at a 10% concentration, reaching 27.8% efficiency in chickpea and 34.8% in lentils after 12 h. Bromelain and ficin were proven to be less effective, with ficin showing the least hydrolytic activity. SDS-PAGE analysis revealed substantial protein degradation, especially subsequent to papain treatment, pointing out that most proteins were cleaved into smaller peptides. SEC-HPLC indicated a predominant release of peptides within the 200-1000 Da range, suggesting enhanced bioavailability. Papain and bromelain treatments resulted in a significant release of oligopeptides and dipeptides. UHPLC analysis highlighted a marked post-hydrolysis increase in total free amino acids, with arginine, leucine, and lysine being the most abundant ones. Notably, tryptophan, being undetectable in untreated samples, was released in measurable amounts post-hydrolysis. These findings demonstrate papain's superior performance in protein hydrolysis and its potential in producing bioactive peptides, highlighting its applicability in food processing and the development of both nutraceuticals and functional foods.

Differences in protein hydrolysis on quality of fermented milk: The changes in structure and processing characteristics

The functions and sensory properties of fermented dairy products are influenced by numerous factors, including the type of milk, the strain's degree of protein hydrolysis, and the additives of fermented milk. Currently, a large number of studies have demonstrated that the proteolytic ability of probiotics significantly affects the gel properties of fermented milk. However, few studies have examined the effects of probiotics with varying proteolytic abilities on the functions and sensory properties of fermented dairy products from the protein conformation perspective. Therefore, this study screened Lactobacillus helveticus KLDS1.8701 with a high protein hydrolysis rate and Lactobacillus helveticus KLDS1.0633 with a low hydrolysis rate to investigate the effects of varying degrees of protein hydrolysis on the gel properties, sensory properties and protein conformation of fermented milk. The results showed that the fermented milk containing Lactobacillus helveticus KLDS1.0633 with a low protein hydrolysis degree had high WHC, hardness and viscosity, a dense and uniform structure, abundant pores, and good texture and sensory properties. In addition, compared with fermented milk with high protein hydrolysis, low protein hydrolysis also increased the content of disulfide bonds, low surface hydrophobicity, and more hydrophilic structures such as a-helix. This study explains the impact of differences in protein hydrolysis degree among strains on fermented milk from a new perspective of protein secondary and tertiary conformations, which provides new insights for selecting suitable strains to produce fermented milk with better taste and nutrition.

Enhancing zein functionality through sequential limited Alcalase hydrolysis and transglutaminase treatment: Structural changes and functional properties

This study investigated the effects of sequential enzymatic hydrolysis using Alcalase, followed by transglutaminase conjugation on the secondary and tertiary structures, hydrophobicity, free amine content, protein-protein interactions, and functional properties of zein. Fourier-transform infrared spectroscopy showed that the most significant secondary structural changes, characterized by a decrease in α-helix content and an increase in β-turns, occurred at a higher degree of hydrolysis. At a 2 % degree of hydrolysis, it revealed notable emulsifying activity (65.96 m2/g), while at 5 % hydrolysis, it achieved the highest solubility (75.06 %). Additionally, the zein hydrolysate with a 7 % hydrolysis degree, treated with transglutaminase, demonstrated improved H0 values (2992.33), enhanced foam capacity (65.95 %), and increased solubilized protein content in a dithiothreitol extractant (31.35 %). Meanwhile, native zein treated with transglutaminase showed the highest water holding capacity (4.47 g/g). Overall, the combined enzymatic approach modified zein structure and properties, suggesting potential for improving functionality in plant-based food applications.

Enzymatic hydrolysis of buffalo casein enhances DPP-4 inhibition: structural modifications and bioactive peptide identification

Dipeptidyl peptidase-4 (DPP-4), the enzyme responsible for the rapid degradation of incretin hormones, plays a pivotal role in blood glucose regulation, and its inhibition serves as an effective strategy for maintaining glucose homeostasis. The aim of this study was to investigate the effect of enzymatic hydrolysis on the structure of buffalo casein and its DPP-4 inhibitory activity. Results demonstrated that Flavorzyme effectively hydrolyzed buffalo casein, as evidenced by scanning electron microscopy and electrophoretic analysis, with the degree of hydrolysis reaching its maximum value (20.05 ± 0.14%) after 3 h. The results of circular dichroism spectra, as well as endogenous and exogenous fluorescence spectra, indicated significant alterations in the secondary and tertiary structures of buffalo casein following enzymatic hydrolysis. Additionally, the DPP-4 inhibitory effect of buffalo casein was found to increase with longer hydrolysis times. The hydrolysate obtained after 3 h of hydrolysis demonstrated the highest level of inhibition, with a half-maximal inhibitory concentration (IC50) value of 1.04 mg/mL. The DPP-4 inhibitory peptide YPFPGPIPN, with an IC50 value of 0.88 mg/mL, was identified in the 1-3 kDa fraction of the 3-h hydrolysate. This peptide interacted with the active site of DPP-4 via hydrogen bonds, hydrophobic interactions, salt bridges, and π-cation interactions. This study offers a novel scientific foundation for the development of functional antidiabetic foods derived from buffalo casein.

Development of protein hydrolysate as a cost-effective and robust biodispersant: Investigating its performance in dispersing of carbon black pigment in water-based paints

Carbon black pigments hold significant importance as the primary representatives of black pigments in the industry today. The dispersibility of carbon black pigment (CB) in water is limited by the nonpolar and weakly hydrophilic characteristics of the pigment's surface. Therefore, there is a critical need to devise an economical and eco-friendly approach for creating a well-dispersed and stable suspension of carbon black in an aqueous medium. The primary focus of this study was to investigate the dispersion capabilities of protein hydrolysate (HP) derived from sheep wool on CB particles in a water-based pigment concentrate. The hydrolysis degree of protein source was determined by high-performance liquid chromatography and gel permeation chromatography. The dispersion performance was investigated by zeta potential, transmission electron microscopy, Fourier transform infrared spectroscopy, grindometer, spectrophotometer-colorimeter, viscometer, and cryptometer measurements. The HP solution containing amino acids, peptides, and polypeptides with low molecular weight can cover the surface of the CB particles, creating enough electrical repulsion and steric resistance. As a result, this phenomenon can inhibit the collision and interaction among the pigment particles caused by Brownian motion, making it less prone to aggregation. The protein hydrolysate demonstrated a higher capability in producing the stable CB dispersions compared to a commercial reference dispersant, highlighting the effectiveness of amino acids, peptides, and polypeptides as powerful CB dispersing agents.

Regulation on Aggregation Behavior and In Vitro Digestibility of Phytic Acid-Whey Protein Isolate Complexes: Effects of Heating, pH and Phytic Acid Levels.

The impact of heat treatment, pH and phytic acid (PA) concentration on the aggregation behavior and digestibility of whey protein isolate (WPI) was investigated. The experimental results indicated that below the isoelectric point of WPI, heat treatment and elevated PA levels significantly increased turbidity and particle size, leading to the aggregation of WPI molecules. No new chemical bonds were formed and the thermodynamic parameters ΔH < 0, ΔS > 0 and ΔG < 0 suggested that the interaction between PA and WPI was primarily a spontaneous electrostatic interaction driven by enthalpy. After the small intestine stage, increasing phytic acid levels resulted in a significant decrease in hydrolysis degree from 16.2 ± 1.5% (PA0) to 10.9 ± 1.4% (0.5% PA). Conversely, above isoelectric point of WPI, there was no significant correlation between the presence of PA and the aggregation behavior or digestion characteristics of WPI. These results were attributed to steric hindrance caused by PA-WPI condensates, which prevented protease binding to hydrolysis sites on WPI. In summary, the effect of PA on protein aggregation behavior and digestive characteristics was not simply dependent on its presence but largely on the aggregation degree of PA-WPI induced by heat treatment, pH and PA concentration. The findings obtained here suggested that phytic acid may be utilized as an agent to modulate the digestion characteristics of proteins according to production requirements. Additionally, the agglomerates formed by heating phytic acid and protein below the isoelectric point could also be utilized for nutrient delivery.

Enhancement of surimi gel quality using textured proteins from different plant sources: Product characteristics and in vitro digestion paradigm

Soy proteins isolate have been widely applied in the actual production of fish balls, but they still have limitations in improving the quality of fish balls. In this study, the effects of textured soy proteins (TSP), textured wheat proteins (TWP), and textured peanut proteins (TPP) as substitutes for soy proteins isolate on the structure, quality characteristics and digestive properties in vitro of fish balls were investigated. It was demonstrated that 25% TSP maximally promoted the formation of dense microstructure and an increase in the relative content of β-sheet in the fish balls. The improved structural stability further enhanced the gel properties of the fish balls. Notably textured proteins significantly reduced the bitterness of fish balls, and 50% TPP also significantly increased the salty, sweet and fresh flavors. Meanwhile, TSP (25%, 50%) and TPP (50%) increased the degree of hydrolysis of the fish balls. Overall, 25% TSP had more potential to improve the quality of surimi gels. These findings will support the development of theories and methods for textured proteins to regulate fish ball quality.

Multi-frequency power ultrasound (MFPU) pretreatment of crayfish (Procambarus clarkii): Effect on the enzymatic hydrolysis process and subsequent Maillard reaction

Crayfish, as a new consumer trend, has become one of the most popular freshwater aquatic foods in China, and its processed product output has been increasing year by year. In this study, the effect of multi-frequency power ultrasound (MFPU) pretreatment in various working modes including mono-, dual- and tri-frequency on the enzymatic hydrolysis and Maillard reaction of crayfish was investigated. Additionally, the underlying mechanism was also explored. Results showed that the degree of hydrolysis (DH) of crayfish was 23.89 %, while it increased to 40.78 % after MFPU pretreatment at 20/40 kHz dual-frequency, indicating that MFPU pretreatment significantly (p < 0.05) enhanced the enzymatic hydrolysis of crayfish. The crayfish protein after MFPU pretreatment exhibited a decrease in α-helix and increase in β-fold content, and the occurrence in the unfolding of the protein structure and alteration of tertiary structure. According to scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses, the MFPU pretreatment resulted in the fragmentation of crayfish protein. During the analyses of subsequent Maillard reaction, the composition and quantity of volatiles detected by the electronic nose and GC–MS indicated that MFPU pretreatment enhanced flavor of the Maillard reaction products. In conclusion, MFPU pretreatment is a promising technology for improving the degree of hydrolysis of crayfish protein and enhancing the flavor of Maillard reaction products.

Effect of protease hydrolysis on the structure of acidic heating-induced soy protein amyloid fibrils

The effectiveness of using amyloid fibrillation to improve the functional qualities of soy protein had drawn growing attention. However, the relationship between protein subunits and the structural polymorphism of soy protein-derived amyloid fibrils (SAFs) was not yet completely understood. In this study, soy protein subunits were hydrolyzed to different degrees according to the different action sites of different proteases (Pepsin, Papain and Alcalase). The impact of subunits on the amyloid fibrillation of soy protein was investigated through various techniques including atomic force microscopy, thioflavin T fluorescence, 1-anililo-naphthalene-8-sulfonate, and Fourier transform infrared spectrometer. The findings showed that the α and α’ subunits were associated with the formation of fibril branch chains. The degree of hydrolysis of β subunits was found to be proportional to the number of fibrils. The presence of the 11S component was identified as a necessary condition for the formation of long-rigid fibrils. Furthermore, enzymatic hydrolysis unfolded the protein structure, exposing hydrophobic groups, loosening the protein structure, and altering the proportion of parallel and antiparallel β-sheet structures. This promoted the formation of amyloid fibrils and accelerated the development of stable SAFs gel. This study advances the knowledge of the function of subunits in amyloid fibrillation.