Acid-soluble Peptides Research Articles

Mechanism of texture deterioration of cockle ( Clinocardium californiense ) during chilled storage

The changes in texture properties of cockle (Clinocardium californiense) meat during 4°C storage and mechanism involved were investigated. The texture indicators including hardness, springiness, chewiness, cohesiveness, gumminess, and resilience of the stored samples were decreased gradually along with the extension of storage. Pearson correlation analysis indicated that the texture indicators were positively correlated with mercapto value and water-holding capacity (WHC), but were negatively correlated with trichloroacetic acid-soluble peptide, myofibril fragmentation index, water-soluble hydroxyproline, carbonyl value, disulfide bonds, surface hydrophobicity, average pore diameter, and average porosity. Thus, it can be inferred that the endogenous proteolysis and oxidation of myofibrillar proteins and collagenous proteins result in changes in protein structures, which destroy the microstructure and decrease the WHC of Clinocardium californiense meat, finally leading to the deterioration in texture properties. The present study provides a theoretical basis for establishing methods to control the texture deterioration of bivalves during cold storage. Practical application With the extension of storage time under 4°C, cockle (Clinocardium californiense) meat occurred progressive texture deterioration. The present study indicated that endogenous proteolysis and oxidation brought about the changes in structure of myofibrillar proteins and connective tissue proteins, which destroyed the microstructure and decreased the WHC of Clinocardium californiense meat, eventually leading to the deterioration in texture properties. This study provides a theoretical basis for exploring quick and safe means to maintain the texture quality of bivalves during chilled storage by inhibiting the endogenous proteolysis and oxidation of proteins.

Effects of heat treatments on texture of abalone muscles and its mechanism

The objective of this study was to develop suitable heating conditions and reveal the mechanism of texture changes in abalone muscles. The milder heat treatments (60 °C-10 min and 70 °C-10 min) increased shear force and hardness of abalone muscles. However, with increased heating time or temperature (70 °C-30 min, 80 °C-10 min and 100 °C-10 min), shear force and hardness significantly decreased in abalone muscles. Decreases in the extraction rate and solubility of myofibrillar proteins (MPs), and increase in myofibrillar fragmentation index were observed in cooked abalone muscles, indicating denaturation of MPs induced by heat treatment. Heat treatment also led to protein degradation in abalone muscles as increases in dissolution rate of protein, trichloroacetic acid-soluble peptides content, soluble collagen content, and dissolution rate of hydroxyproline and glycosaminoglycan were observed. In addition, changes in miscrostructure, water content and water holding capatity (WHC) were noted in cooked abalone muscles. Correlation analysis showed that protein denaturation/degradation was responsible for changes in microstructure and WHC, which ultimately affected the textural properties of cooked abalone muscles.

Occurrence and Development of Off-Odor Compounds in Farmed Hybrid Catfish (Clarias macrocephalus × Clarias gariepinus) Muscle during Refrigerated Storage: Chemical and Volatilomic Analysis.

The goal of this study was to examine the changes in chemical parameters, major volatile compounds, and sensory aspects in farm-raised hybrid catfish (i.e., dorsal, lateral line and ventral muscles) during a 15-day period of refrigerated storage. Trichloroacetic acid-soluble peptides, free fatty acid, total volatile base-nitrogen (TVB-N), and non-heme iron levels in all muscles increased as storage time proceeded. The levels of trans-1,10-dimethyl-trans-9-decalol (geosmin) and 2-methylisoborneol (2-MIB) were higher than their thresholds, which was connected to a stronger earthy odor. The concentrations of geosmin and 2-MIB in all muscles increased, although there was a consistent trend of earthy odor throughout storage; this phenomenon could be attributed to the masking effect of other off-odors. During storage, the largest lipid oxidation was found in ventral muscle, as measured by peroxide value and thiobarbituric acid reactive substances. During storage, the formation of the most volatile products increased in the lateral line and ventral muscle, whereas the dorsal muscle had the lowest concentration. As storage time proceeded, the strength of spoiled, fishy, rancid, and overall off-odor intensity of all tested muscles tended to rise. Those alterations were linked to higher levels of TVB-N and trimethylamine, as well as all other volatile lipid oxidation products (e.g., hexanal, propanal, 2,4 heptadienal, 1-octen-3-ol, octanal, nonanal, trans-2-heptenal, and 1-hexanol).

Microorganism and Physiochemical Characteristic of High-salt (Suan Yu), a Traditional Chinese Fermented Fish

ABSTRACT Microorganisms and physiochemical characteristics were determined in traditional high-salt fermented fish products from six different regions. Results indicated that Lactobacillus content was 7.14–7.65 log CFU/g, and yeast content was 6.21–6.54 log CFU/g in the high-salt fermented fish samples. Enterobacterium content was below the detectable limit, and the dominant Lactobacillus species was Lactobacillus plantarum. The pH value was 4.14–4.73, and the protein content reached 19.37–28.38%. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis results showed that myofibrillar proteins in fish were obviously degraded. Trichloroacetic acid-soluble peptide content was 901–1061 mg/tyrosine kg, and the fat and NaCl contents were 0.92–4.79% and 5.59–7.44%, respectively. Free amino acids and free fatty acids were 1332–2380 mg/100 g and 8.95–23.4 mg/fat g, respectively. The content of thiobarbituric acid reactive substances was 1.97–4.26 mg/kg, the total volatile basic nitrogen was 12.7 ~ 38.9 mg/100 g, and the content of biogenic amine was 26.3–34.6 mg/kg.

Effect of slurry ice during storage on myofibrillar protein of Pseudosciaena crocea.

In order to explore the effect of slurry ice on myofibrillar protein of Pseudosciaena crocea, the changes in myofibrillar protein and muscle microstructure during storage were studied with crushed ice as a control. During the storage period, the rate of decrease in myofibrillar protein content, Ca2+‐ATPase activity, and total sulfhydryl groups in the slurry ice group was lower than in the control group (p < .05). There was a significant linear correlation between the hydrophobicity and the storage time (R crushed ice (4℃) = 0.9881, R slurry ice (4℃) = 0.9878, R slurry ice (−1℃) = 0.9674), and trichloroacetic acid (TCA) soluble peptide content was lower than in the control group at the same time. Slurry ice (−1℃) was optimal in maintaining protein content in P. crocea; the arrangement of myofibrils in P. crocea treated by slurry ice was compact and the gaps were small. Slurry ice can delay the denaturation and degradation of fish myofibrillar protein and maintain its quality.

Preparation and in vitro bioactive evaluation of cashew-nut proteins hydrolysate as a potential source of anti-allergy peptides.

This work proposes a novel potential source of antiallergens based on bioactive peptides. Cashew-nut protein hydrolysate with antiallergic activity was prepared from cashew nuts through protease treatment. The change in the antiallergic activity of cashew-nut protein hydrolysate during in vitro simulated digestion was investigated. Cashew-nut protein hydrolysates were prepared through treatment using five different enzymes, namely, Alcalase, Protamex, Neutrase, papain, and bromelin. According to the results of molecular weight distribution, more small molecular weight peptides could be obtained by selecting Alcalase protease than other proteases, and the degree of hydrolysis, trichloroacetic acid-soluble peptide yield and hyaluronidase inhibitory rate of the hydrolysate were 17.0 ± 61.52%, 26.28 ± 0.13% and 62.06% ± 5.07%, which were significantly higher than those of other proteases. Therefore, Alcalase is the most suitable protease for the preparation of cashew-nut hydrolysates. Cashew-nut protein hydrolysates prepared with Alcalase under optimum conditions were fractionated through ultrafiltration. Fractions with low molecular weight exhibited the highest hyaluronidase inhibitory rate (90.57%) among all fractions. The inhibition of hyaluronidase activity during digestion showed that cashew-nut protein hydrolysate III (CPH III) has persistent antiallergic activity. Therefore, CPH III could serve as a potential source of functional peptides with health-promoting effects.

Effect of Homogenization Pressure on Plasmin Activity and Mechanical Stress-Induced Fat Aggregation of Commercially Sterilized Ultra High Temperature Milk during Storage.

Commercially sterilized ultra high temperature (UHT) milk was manufactured at different homogenization pressures (20, 25, and 30 MPa), and changes in fat particle size, mechanical stress-induced fat aggregation, plasmin activity, and lipid oxidation were monitored during ambient storage of the UHT milk for up to 16 wk. The particle sizes of milk fat globules were significantly decreased as homogenization pressure increased from 20 to 30 MPa (p<0.05). The presence of mechanical stress-induced fat aggregates in milk produced at 20 MPa was significantly higher than for UHT milk produced at either 25 or 30 MPa. This difference was maintained all throughout the storage. There were no significant differences in plasmin activity, trichloroacetic acid (12%, w/v) soluble peptides, and the extent of lipid oxidation. Based on these results, an increase of homogenization pressure from 20 (the typical homogenization pressure employed in the Korea dairy industry) to 25–30 MPa significantly decreased mechanical stress-induced fat aggregation without affecting susceptibility to lipid oxidation during storage.

Effect of protein oxidation and degradation on texture deterioration of ready-to-eat shrimps during storage.

The impact of protein oxidation and degradation on texture deterioration of ready-to-eat (RTE) shrimps during storage was investigated. The deterioration in texture during storage was manifested by decreased instrumental hardness, elasticity, chewiness, and recoverability. The occurrence of protein oxidation was revealed by a significant increase in the contents of free radicals and carbonyls. The increases in trichloroacetic acid-soluble peptide (TCA-soluble peptide) content and myofibril fragmentation index (MFI) were also observed, suggesting the degradation of protein. Pearson correlation analysis showed that the decreased instrumental texture parameters were negatively correlated with the increased carbonyl content, TCA-soluble peptide, MFI, porosity, and pore size as well as the decreased water-holding capacity (WHC), thus, it was hypothesized that protein oxidation and degradation were responsible for changes in the microstructure and reduction of WHC, which ultimately resulted in texture deterioration of RTE shrimps.

Effects of proteolysis and oxidation on mechanical properties of sea cucumber (Stichopus japonicus) during thermal processing and storage and their control.

The effects of endogenous proteolysis and oxidation on mechanical properties of sea cucumber (Stichopus japonicus) during thermal processing and storage and their control were investigated. The lactic acid (LA)+tea polyphenols (TP)-treated sea cucumbers showed relatively higher values in texture and rheological indicators than the blank control group after thermal processing. By contrast, the (LA+TP)-treated sea cucumbers also had lower values in water-soluble hydroxyproline, glycosaminoglycans and proteins, trichloroacetic acid-soluble peptide content, and more orderly secondary structure of proteins, indicating that the additives affected the mechanical properties of thermally processed sea cucumbers by preventing the proteolysis of proteins. All texture and rheological indicators of thermally processed sea cucumbers decreased time-dependently during chilled storage. The additives (LA+TP) significantly prevented the progressive deterioration in mechanical properties by retarding the changes in microstructure as well as phase state and distribution of water through preventing protein oxidation.

Thermal Gel Degradation (Modori) in Sturgeon (Acipenseridae) Surimi Gels.

Sturgeon meat has been found to be suitable as surimi raw materials. The present study determined the modori phenomenon in sturgeon surimi gels and identified its relationship with cathepsins. In all heat-treated gels (25 to 90 °C, at 5 °C intervals), the 40 °C-incubated sturgeon surimi gel showed the weakest gel properties and water-holding capacity (P <0.05), a rough protein gel network under SEM, and the highest protein solubility and trichloroacetic acid-soluble peptides content (P <0.05). SDS-PAGE indicated that the myosin heavy chain band of sturgeon surimi gels was almost completely degraded at 40 °C. Moreover, the highest cathepsin L activity was observed in 40 °C-treated sturgeon surimi gels (P <0.05). Our results suggested that the modori phenomenon in sturgeon surimi gels occurred at 40 °C, which was partially attributed to cathepsin L, thereby allowing for the better exploitation and utilization of sturgeon surimi.

Impact of salted duck egg albumen powder on proteolysis and gelling properties of sardine surimi.

The influences of salted duck egg albumen powder (SDEAP) as salt replacer at various levels (0.5-2.5%) on autolysis and gelling properties of sardine surimi were investigated. SDEAP had high salt (33.67%) and protein contents (64.52%) with trypsin inhibitory activity of 5,975 kunits/g solid. SDEAP was white in color with L*-value of 96.72. It had low moisture content (3.98%) and water activity (0.38). Autolysis of sardine surimi was drastically inhibited when SDEAP was incorporated with increasing levels as indicated by the more retained myosin heavy chain and the reduced trichloroacetic acid-soluble peptide content. Breaking force and deformation of surimi gel increased, while expressible moisture content decreased as the levels of SDEAP added were increased (p < .05). Gumminess, hardness, chewiness, springiness, and cohesiveness of surimi gels also increased as SDEAP levels increased (p < .05). Lightness and whiteness were higher in all surimi gels incorporated with SDEAP than the control (p < .05). For microstructure, surimi gels incorporated with SDEAP at all levels used had finer gel network with smaller voids and more connectivity than the control gel. Thus, SDEAP could be used as a salt replacer for sardine surimi gel preparation and it could improve the properties of resulting gel.

Effect of oxidized phenolic-containing plant extracts on gel properties of goatfish surimi

The effect was studied of oxidized phenolic-containing plant extracts from Vietnamese coriander and holy basil at 0.1–0.4% protein content on the gel properties of goatfish (Mulloidichthys martinicus) surimi. The lowest expressible moisture content and the highest breaking force, deformation,gel strength and texture profile (hardness, gumminess, chewiness) were observed in surimi gel with 0.1% oxidized phenolic-containing plant extracts from Vietnamese coriander. The trichloroacetic acid-soluble peptide content decreased as the concentration of extract increased. Analysis of protein subunits using sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that as the concentration of extract increased the intensity of the myosin heavy chain band decreased, whereas that of the polymerized protein band increased. Compared to the control, the microstructure of surimi gel with 0.1% oxidized phenolic-containing plant extracts from Vietnamese coriander was denser, more ordered and had a more uniform protein network. Compared to the control, sensory evaluation resulted in higher liking scores for surimi gel with 0.1% oxidized phenolic-containing plant extracts from Vietnamese coriander with regard to springiness, texture and overall liking. Therefore, the addition of 0.1% oxidized phenolic-containing plant extracts from Vietnamese coriander could improve the gel-forming ability of goatfish surimi without having any adverse effects on the sensory properties.

Changes in protein compositions and textural properties of the muscle of skate fermented at 10°C

ABSTRACT Chemical properties such as pH, ammonia nitrogen, total volatile base nitrogen, trimethylamine nitrogen, protein composition, and free amino acids composition and textural property were investigated for skate muscle subjected to fermentation at 10°C for 14 days. The values of pH, TVBN, TMAN, and ammonia nitrogen content significantly increased in skate muscle. Principal component analysis indicated a high correlation between changes in textural profiles and ammonia flavor and changes in muscle protein composition. In addition, SDS-PAGE of protein fractions showed that myofibrillar tended to aggregate into large polymers during fermentation. On the other hand, changes in trichloroacetic acid-soluble peptides and free amino acid content during fermentation indicated intensive degradation of muscle proteins. The variations in chemical properties and protein composition of skate muscle during fermentation reveal that decomposition and degradation of muscle proteins are important factors that influence the chemical composition and textural property of skate during fermentation at 10°C.

Effect of serine protease inhibitor from squid ovary on gel properties of surimi from Indian mackerel.

Surimi from dark-fleshed fish is prone to degradation of myofibrillar proteins caused by the endogenous proteases, thereby lowering textural property. To tackle the problem, protease inhibitors (egg white, porcine plasma protein, and bovine plasma protein) have been used by the surimi industries. Due to drawbacks of some particular inhibitors (religious constraints, off-white color, off odor, etc.), the novel additives are still in demand. Ovary from squid processing industry, commonly discarded as the waste, can be an alternative natural protease inhibitor, which can improve the gel properties of surimi, especially produced from dark-fleshed fish.

Quality Evaluation Focusing on Tissue Fractal Dimension and Chemical Changes for Frozen Tilapia with Treatment by Tangerine Peel Extract

This work aimed to establish an effective approach to evaluate the quality of frozen fish, focusing on changes in fish tissue structure and chemical composition during storage. Fresh tilapia samples were treated by coating with tangerine peel (TP) extract and then stored at −4, −8 and −18 °C, respectively, for 40 days. The frozen fish tissues were analyzed for structural and chemical changes. Fractal dimension, which quantifies the porous structure formed in the tissue samples, texture properties including hardness and springiness, and moisture content and water activity all decreased during the storage, while the extents of lipid oxidation, measured as peroxide value and thiobarbituric acid concentration, and protein degradation, monitored with total volatile basic nitrogen and trichloroacetic acid soluble peptides, increased. The change rates of these parameters decreased with decreasing the storage temperature and by applying TP extract. A model was developed for predicting fractal dimension, which indicated the quality of preserved tilapia and thus can be used to predict the shelf life under different storage temperatures. The results demonstrated that TP extract could extend the shelf life of frozen tilapia by 35–45% by inhibiting changes in tissue structure, moisture loss, lipid oxidation and protein degradation during frozen storage.

Serine protease inhibitors from squid ovary: extraction and its effect on proteolysis and gel properties of surimi.

Serine protease inhibitors from squid ovary (SOSPI) were extracted using different extraction media and conditions. Optimal condition included 0.45M NaCl for 1h. After heat treatment at 70°C for 10min, the highest specific activity was obtained. Based on Sephadex G-75 gel filtration and activity staining, the major SOSPIs were present as monomer with molecular weight of 9.10 and 10.27kDa. Impact of SOSPI on autolysis of bigeye snapper surimi was studied. Myosin heavy chain was more retained with coincidentally lower trichloroacetic acid-soluble peptide content as the level of SOSPI increased. When SOSPI at various levels (0.5-3%) was added into surimi, the highest breaking force of both kamaboko and modori gels containing 1% SOSPI was obtained. However, SOSPI had no effect on deformation of kamaboko gel but slightly increased the deformation of modori gel. SOSPI increased water holding capacity of both kamaboko and modori gels in a dose dependent manner, as indicated by the lowered expressible moisture content. SOSPI had no effect on the whiteness of both gels. Thus SOSPI can be used as the protein additive in surimi for increasing breaking force.

Effect of electron irradiation on the gel properties of Collichthys lucidus surimi

This study evaluated the effect of electron irradiation on the gel properties of Collichthys lucidus surimi. The results showed that irradiation decreased the trichloroacetic acid-soluble peptide content of the surimi gel. At 5kGy, a more compact and ordered gel network structure was achieved, resulting in a higher gel strength, whiteness, and water-holding capacity than non-irradiated surimi gel. During heat-induced formation of the gel, the α-helix content decreased, whilst the β-sheet and β-turn content increased. Irradiation treatments also decreased the α-helix content and increased β-sheet content, and this transformation is beneficial for the protein denaturation and gel formation. Collectively, the results suggest that electron irradiation, at an optimal dose of 5kGy, could be an effective method for application in the surimi manufacturing industry

Production of bioactive peptide hydrolysates from deer, sheep, pig and cattle red blood cell fractions using plant and fungal protease preparations

Protease preparations from plant (papain and bromelain) and fungal (FP400 and FPII) sources were used to hydrolyze the red blood cell fractions (RBCFs) separated from deer, sheep, pig, and cattle abattoir-sourced blood. After 1, 2, 4 and 24h of hydrolysis, the antioxidant and antibacterial activities of the peptide hydrolysates obtained were investigated. The increase in trichloroacetic acid-soluble peptides over the hydrolysis period was examined using the o-phthaldialdehyde (OPA) assay and the hydrolysis profiles were illustrated using SDS–PAGE. Papain generated RBCF hydrolysates exhibited higher ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) compared to those generated with bromelain, FP400 and FPII. At certain concentrations, 24h hydrolysates of RBCF using FP400 and FPII were able to inhibit the growth of Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The results indicated that the use of proteases from plant or fungal sources can produce animal blood hydrolysates with antioxidant and antimicrobial activities.

Properties of Salted Shrimp Paste (Kapi) fromAcetes vulgarisas Affected by Postmortem Storage Prior to Salting

The impact of postmortem storage time of shrimp (Acetes vulgaris) on the quality of shrimp and the resulting Kapi, or salted shrimp paste, was investigated. When shrimp were stored at room temperature (28–30C) for up to 15 h, total volatile base, trimethylamine contents, thiobarbituric acid reactive substances, Trichloroacetic acid-soluble peptide content and total viable count increased with increasing storage time. Myosin heavy chain and actin underwent degradation throughout the storage. Kapi with purplish red color became darker and had higher antioxidative activity when shrimp used as raw material were stored for a longer time prior to salting. Kapi showed varying volatile compounds, dependent on the storage time of shrimp and more likely contributed to different flavors. However, Kapi showed the lower odor-likeness score when the unfresh shrimp were used. Therefore, storage and handling time of shrimp before salting had the marked influence on the quality of Kapi. Practical Applications Kapi, or salted shrimp paste, is one of the popular condiments in Thai foods. In general, small shrimp (Acetes spp.) which is used as a raw material for making kapi was susceptible to degradation and oxidation. In addition, the delays in the salting of shrimp always occur due to the transportation before off-loading or processing. During postmortem storage of shrimp, significant deterioration and loss of nutritional value take place, leading to the distorted quality of the final product. Different freshness of raw materials could bring about products with different appearance, flavor, taste as well as other sensorial properties.

Trypsin inhibitor from yellowfin tuna (Thunnus albacores) roe: Effects on gel properties of surimi from bigeye snapper (Priacanthus macracanthus)

Effects of partially purified trypsin inhibitor from the roe of yellowfin tuna (Thunnus albacores) (TIYTR) at different levels (0–3.0 g/100 g) on gelling properties of bigeye snapper (Priacanthus macracanthus) surimi were investigated. TIYTR showed inhibitory activity against proteolysis in kamaboko (40/90 °C) and modori (60/90 °C) gels in a concentration-dependent manner. Myosin heavy chain (MHC) was more retained in both gels when the level of TIYTR increased up to 3.0 g/100 g. This was associated with the increased breaking force and deformation as well as lowered protein degradation as evidenced by the decrease in trichloroacetic acid-soluble peptide content (p < 0.05). Whiteness of kamaboko and modori gels slightly decreased with increasing TIYTR levels (p < 0.05). However, water-holding capacity of both gels was improved as TIYTR level increased (p < 0.05). Incorporation of TIYTR, beef plasma protein (BPP) and egg white (EW) at a level of 3.0 g/100 g resulted in the increased breaking force and deformation of surimi gels. Nevertheless, TIYTR and BPP showed the higher gel strengthening effect than EW. Therefore, TIYTR could be used as an alternative cheap proteinase inhibitor to improve gel strength of surimi.