Effects of freeze-thaw cycles on in-vitro digestive properties of myofibrillar protein in mirror carp (Cyprinus carpio L.), based on protein degradation, oxidation, and structural properties

β-Cyclodextrin/resistant dextrin induced disparate gelling behaviors of high-protein liquid systems

High-protein, high-fiber foods are in the spotlight because of their health properties. Due to aggregation during heat treatment when dietary fiber is added, the amount of soy protein that can be used in the formulation of high-protein, high-fiber foods is limited. The effects of two types of soluble dietary fibers, β-cyclodextrin (β-CD) and resistant dextrin (RD), on the tunable thermal stability of soy proteins (SPs) and preheat-modified soy protein particles (SPPs), as well as the underlying mechanisms, were investigated. Results showed that β-CD (0.5-3.0 %, w/v) weakened the gels and introduced some degree of mobility, while RD (0.5-3.0 %, w/v) increased the gel strength and viscoelastic properties of SP and SPP gels. Dynamic light scattering analysis revealed that β-CD mitigated the increase in particle size of SPs and SPPs during heating, delaying gel formation at high protein concentrations. In contrast, RD promoted protein agglomeration into larger particles, speeding up the gelation process. Structural analysis revealed that β-CD preserved the integrity of protein structure, while RD promoted the unfolding of protein structure, leading to protein cross-links and aggregation formation. In summary, the effect of β-CD and RD on soy protein thermal stability provides valuable insights for developing new health-focused, high-protein, high-fiber products.

The effect of freeze-thaw cycles on the characteristics of Symplectoteuthis oualaniensis of different sizes

The objective of this study was to investigate the changes in the characteristics of different sizes of Symplectoteuthis oualaniensis during the freezing-thaw cycle as a means to provide some advice for its storage. The results showed that as the freeze-thaw cycles increase, the medium sizes (MS) group has better freshness. And there was a significant decrease in water holding capacity (WHC) in all groups after the seventh freeze-thaw cycle compared to the first time (p<0.05). Conversely, the large sizes (LS) group was extremely variable in terms of textural properties, and these variations can all be explained by changes in protein. In addition, the SDS-PAGE results showed that all groups' proteins were degraded, this can be equally reflected by the microstructure, while the MS group was more stable. Therefore, the MS group has the best freeze-thaw stability among the three squid groups and is suitable as the main exploitation resource.

Effects of freeze-thaw cycles on texture and protein digestive properties of scallop adductor muscles: Role of protein oxidative changes

This study investigated the effects of freeze-thaw cycles (F-T cycles) on texture and protein digestive properties of scallop adductor muscles and the underlying mechanisms involved. Results showed that F-T cycles significantly increased free radical intensity of scallop adductor muscles and oxidation level of scallop protein. Simultaneously, the protein oxidative degradation occurred, as evidenced by increased levels of TCA-soluble peptides and water-soluble Hyp, which led to myofiber breakage and decreased textural properties. Nile Red staining showed that F-T cycles-induced oxidation promoted protein aggregation, which in turn reduced protein digestibility. Peptidomics analysis further showed that F-T cycles-induced oxidation altered the enzymatic cleavage sites in scallop protein, resulting in an increased abundance of macromolecular peptides (>2500 Da) and decreased release of bioactive peptides. These results highlight the role of protein oxidation in the deterioration of texture and protein digestibility of scallops during frozen storage, providing a basis for improving quality preservation strategies.

Effects of ohmic heating thawing under an appropriate electric field on the quality and structure of duck breast meat

Ohmic heating thawing (OHT), as a novel thawing technique, possesses distinct advantages and is currently garnering attention from researchers. We have investigated the effects of OHT on the structure and protein quality of duck breast meat. Compared to conventional thawing (CT) methods (water thawing [WT], 20 ± 0.5°C; air thawing [AT], 20 ± 0.5°C), OHT (10, 15, and 20 V/cm) has been shown to enhance thawing efficiency, reducing thawing time by 28%-86% (p < 0.05), lowering thawing loss rates by 2.55% (p < 0.05), and resulting in milder protein oxidation with better preservation of protein secondary structures. Microscopically, OHT resulted in minimal damage to myofibrils in the duck breast meat. In this experiment, the optimal thawing electric field strength for duck breast was 15 V/cm. Moreover, the efficacy of OHT also relies on variations in voltage, with the most suitable thawing voltage determined by the specific characteristics of the material. These findings reveal the potential of OHT for thawing meat products. PRACTICAL APPLICATION: Ohmic heating thawing (OHT) shortens thawing time and enhances thawing efficiency while reducing thawing loss rates. It has a minimal impact on proteins and a minor effect on muscle fiber structure.

Elevating the critical gelling concentration of soy protein by disulfide bond cleavage during preheating treatment

There has been a growing demand for the development of high protein beverages in the food industry. However, during thermal processing, high-protein beverages undergo protein aggregation and gelation. In this study, thermostable soy protein was prepared by disulfide bond cleavage combined with preheating treatment. Thermostable soy protein had a higher denature extent than the control sample, which prevented the formation of larger aggregates upon reheating. Thermostable soy protein possessed lower viscosity (nearly 0 Pa·s) and an excellent fluidity index (around 0.8) after reheating at a concentration of 10 % (w/v), whereas the control sample had gelled. Moreover, rheology and dynamic light scattering collectively demonstrated that a minimum of 2.5 mM sodium metabisulfite (Na2S2O5) was required to prepare thermostable protein solutions. The present study shows an innovative method to produce thermostable soy protein.

Glycation-induced gel and digestive properties for 3D printing and conventional gels of myofibrillar protein from oyster (Crassostrea gigas)

Glycation has great potential to enhance protein gel properties. The purpose was to investigate the glycation of oyster myofibrillar protein (MP) with monosaccharides (glucose [Glu]) and oligosaccharides (dextran 5 [Dex5]) combined with scallop columns for 3D printing and conventional gels to elucidate the differences in gel properties (texture characteristics, water-holding capacity, cooking yield, cooking loss, thermal characteristic, and water distribution) and digestive properties (in vitro digestibility, degree of hydrolysis, and molecular weight distribution) between the two gels. The results demonstrated that Glu-modified oyster MP had the best gel and digestive properties. The digestibility in vitro of MP-Glu modified 3D printing and conventional gels increased by 17.1% and 11.88%, while the degree of hydrolysis increased by 12.19% and 10.62%, respectively. Hydrogen and disulfide bonds were determined to be the main intermolecular forces maintaining the protein gels, and all prepared gels conformed to the transitional foods in the International Dysphagia Diet Standardization Initiative (IDDSI). In vitro digestibility was significantly positively correlated with gel hardness, degree of hydrolysis, L*, ΔE*, WHC and cooking loss. This study could fully utilize the potential advantages of glycation modification and 3D printing technology, aiming to provide theoretical support for the development of shellfish 3D printing products with personalized needs for people with dysphagia.

Effects of sterilization intensity on the flavor profile of canned Antarctic krill (Euphausia superba): Moderate vs. excessive

Selecting the appropriate sterilization intensity is crucial for the canning of Antarctic krill (Euphausia superba). This study investigated the effects of different sterilization intensities on volatile organic compounds (VOCs) of canned krill. Using gas chromatography-ion mobility spectrometry (GC-IMS) and gas chromatography-mass spectrometry (GC-MS), which identified 45 and 36 VOCs, respectively. As the sterilization intensity was increased, the flavor profile became more stabilized; however, excessive sterilization led to the generation of off-flavor compounds. Eight key flavor markers were identified at different sterilization intensities. Cluster analysis could distinguish between samples obtained from low (F = 6, 9) and high (F = 12, 15) sterilization intensities. Odor Activity Value (OAV) analysis revealed that higher sterilization intensities led to the generation of fishy, fatty, and earthy notes. The findings suggest that sterilization at F = 9 can best maintain the desired flavor characteristics. Overall, this work provides valuable insights into the optimization of the canning process of Antarctic krill.

Effect of sous-vide processing duration on flavor and taste variations of oyster (Crassostrea gigas)

Sous-vide (SV), as a mild processing technique, exhibits some potential for keeping the original flavor of oyster. The dynamic changes mechanism of flavor and taste in oyster during SV processing (0-30 min/75 °C) were investigated. SV processing for 10-15 min improved the umami of oysters, likely due to the increase in adenosine monophosphate and glutamate, while processing for 20-30 min resulted in a significant loss of "grassy" flavor. GC-MS and GC-IMS analysis showed that the loss of short-chain aldehydes, such as (E)-2-pentenal, (E)-2-hexenal and (E, E)-2,4-hexadienal may be related to the weakening of the "grassy" flavor, and the formation of 2,3-diethylpyrazine and octanal produced a "cooked" and "fatty" flavor. The analysis of lipidomics indicated that phosphatidylethanolamine, lysophosphatidylcholine and sphingomyelin, synthesized mainly through glycerophospholipid and sphingolipid metabolism, were key precursors for aldehyde formation. This study provides a theoretical basis for controlling the flavor quality of oyster during mild processing.

Effect of Liquid Nitrogen Freezing on Maintaining the Quality of Crayfish During Freeze-Thaw Cycles: Muscle Structure and Myofibrillar Proteins Properties

The quality of frozen crayfish (Procambarus clarkii) is challenged by freeze-thaw (FT) cycles during storage. The effect of freezing methods on the quality of crayfish during FT cycles was investigated by comparing physicochemical properties, microstructure, and myofibrillar protein (MPs) properties. Three methods were used for crayfish freezing, including air convective freezing (AF) at -20 °C and -50 °C, as well as liquid nitrogen freezing (LNF) at -80 °C. The frozen crayfish were thawed at 4 °C after 45 d of frozen storage as 1 FT cycle. After 5 FT cycles, the water holding capacity of LNF crayfish (70.8%) was significantly (p < 0.05) higher than that of -20 °C AF crayfish (60.6%) and -50 °C AF crayfish (63.5%). The drip loss of LNF crayfish (7.83%) was significantly lower than that of AF crayfish. Moreover, LNF maintained the gel strength and the thermal stability of MPs from crayfish with higher gel storage modulus and enthalpy. These results demonstrated that LNF minimized the formation of large ice crystals, preserving the structural integrity of muscle and the properties of MPs, thereby maintaining crayfish quality. This study investigated the effect of LNF in preserving crayfish quality during FT cycles, providing valuable insights for reducing the quality degradation of aquatic products during storage and transportation.

Changes in basic composition and in vitro digestive characteristics of pork induced by frozen storage

Introduction

Frozen pork can reduce the quality of the meat and alter the digestibility and bioavailability of meat proteins in the human body. In this study, we investigated the changes in the basic composition during frozen storage and their effects on the structural properties of digestion products after protein digestion.

Methods

The impacts of frozen storage at different temperatures (-8, -18, -25, and -40°C) and for different times (1, 3, 6, 9, and 12 months) on the basic components and in vitro digestive characteristics of pork were evaluated.

Results

The moisture, crude fat, and protein contents decreased with extended storage and increased temperature, whereas muscle juice loss increased (p < 0.05). During in vitro digestion of samples frozen at -8°C for 12 months, trichloroacetic acid (TCA)-soluble peptides were decreased by 25.46% and 14.37% in the gastric and small intestinal phases, respectively, compared with fresh samples. Confocal laser scanning microscope (CLSM) showed that samples stored at -8°C had the largest particle size after digestion. Disruption of protein structure was confirmed by the decrease in α-helix, β-turn, and fluorescence intensity (all p < 0.05) and the increase in β-sheet, random coil, and maximum fluorescence wavelength of the digestion products of samples frozen at -8°C (all p < 0.05).

Discussion

Therefore, long-term high-temperature frozen storage brought about a significant decline in basic components of muscle and acceleration of loss of protein structural integrity after digestion.

Protective effects and molecular mechanisms of Litopenaeus vannamei treated with l-arginine/l-lysine against myofibrillar proteins oxidation and quality degradation during freeze-thaw cycles

The storage and processing of Litopenaeus vannamei are often challenged by the freeze-thaw (F-T) cycle phenomenon. This study delved into the influence of pretreatment with l-arginine (Arg) and l-lysine (Lys) on the myofibrillar proteins oxidation and quality of shrimp subjected to F-T cycles. Arg and Lys pretreatment notably improved water-holding capacity (WHC), textural integrity as well as the myofibrillar structure of the shrimps. A lesser reduction in the amounts of immobile and bound water was found in the amino acid-treated groups, and the oxidation of lipids and proteins were both decelerated. Molecular simulation results indicated that Arg and Lys could form hydrogen and salt-bridge bonds with myosin, enhancing the stability of Litopenaeus vannamei. The study concludes that Arg and Lys are effective in alleviating the adverse effects of F-T cycles on the quality of Litopenaeus vannamei, and provides a new solution for the quality maintenance during storage and processing.

Analysis of NADES and its water tailoring effects constructed from inulin and L-proline based on structure, physicochemical and antifreeze properties

The structure, physicochemical and anti-freeze properties of natural deep eutectic solvent (NADES) composed of inulin and L-proline (molar ratio of 1:11) were investigated. Proton nuclear magnetic resonance (1H NMR), Fourier infrared spectroscopy (FTIR), and Raman spectroscopy revealed extensive hydrogen bonding in the pure NADES system, and the addition of water weakens the hydrogen bonding interactions between the components. The smaller transverse relaxation time (T2) represents the stronger hydrogen bond strength, and NADES+40 % H2O exhibited a large T2 (71.68 ms). When 10 % water was added, the viscosity decreased from 3620 mPa·s to 1777 mPa·s, but the conductivity increased to approximately twice the original value. Furthermore, adding 10 % water lowered the glass transition temperature (Tg) of NADES by 5.6 °C. NADES+10 % H2O exhibited favorable thermal stability and freezing resistance, as evidenced by the fact that approximately 82.61 % of the ice crystals area <200 μm2 after 30 min of crystallization. The changes in the structure, physicochemical, and anti-freezing properties of water-tailored NADES are expected to enable the design of novel antifreeze agents.

A review on improving the sensitivity and color stability of naturally sourced pH-sensitive indicator films

Naturally sourced pH-sensitive indicator films are of interest for real-time monitoring of food freshness through color changes because of their safety. Therefore, natural pigments for indicator films are required. However, pigment stability is affected by environmental factors, which can in turn affect the sensitivity and color stability of the pH-sensitive indicator film. First, natural pigments (anthocyanin, betalain, curcumin, alizarin, and shikonin) commonly used in pH-sensitive indicator films are presented. Subsequently, the mechanisms behind the change in pigment color under different pH environments and their applications in monitoring food freshness are also described. Third, influence factors, such as the sources, types, and pH sensitivity of pigments, as well as environmental parameters (light, temperature, humidity, and oxygen) of sensitivity and color stability, are analyzed. Finally, methods for improving the pH-sensitive indicator film are explored, encapsulation of natural pigments, incorporation of a hydrophobic film-forming matrix or function material, and protective layer have been shown to enhance the color stability of indicator films, the addition of copigments or mental ions, blending of different natural pigments, and the utilization of electrospinning have been proved to increase the color sensitivity of indicator films. This review could provide theoretical support for the development of naturally sourced pH-sensitive indicator films with high stability and sensitivity and facilitate the development in the field of monitoring food freshness.

Effect of sulfuric acid hydrolysis on the structure and Pickering emulsifying capacity of acorn starch

The acid-hydrolyzed acorn starch samples (HAS-1, HAS-2, HAS-3, and HAS-4) were prepared from natural acorn starch (NAS) at sulfuric acid concentrations of 1, 2, 3, and 4 mol/L for 2 d. The particle characteristics and structures of HAS were investigated, and Pickering high internal phase emulsions (HIPEs) based on HAS were constructed and characterized. The results showed that with an increase in sulfuric acid concentration, the size, yield, amylose content, molecular weight, and amylopectin chain length of HAS gradually decreased. HAS retained an A-type crystal structure, and its relative crystallinity and short-range order degree gradually increased with increasing sulfuric acid concentration. Acid hydrolysis treatment improved the wettability of NAS, and its effect was positively correlated with the sulfuric acid concentration. HAS-3 and HAS-4 could stabilize the Pickering HIPEs with an oil phase volume fraction of 80% at c ≥ 1.5%. The mechanical properties of the HIPEs were positively correlated with c.

The effects of resonance acoustic mixing modulation on the structural and emulsifying properties of pea protein isolate

The effects of resonant acoustic mixing (RAM) with different treatment times (0, 5, 10, 15, 20 and 30 min) on the structural and emulsifying properties of pea protein isolate (PPI) were investigated for the first time. Increasing the RAM treatment time from 0 to 20 min decreased the α-helix/β-sheet ratio and particle size of the PPI samples by 37.84 % and 46.44 %, respectively, accompanied by an increase in solubility from 54.79 % to 71.80 % (P < 0.05). Consequently, the emulsifying activity index of PPI (from 10.45 m2/g to 14.2 m2/g) and the physical stability of RAM-PPI emulsions were effectively enhanced, which was confirmed by the small and uniformly distributed oil droplets in the micrographs of the emulsions. However, excessive RAM treatment (30 min) diminished the effectiveness of the aforementioned improvements. Therefore, obviously enhanced solubility and emulsifying properties of PPI can be attained through proper RAM treatment (15-20 min).

Effect of clove essential oil nanoemulsion on physicochemical and antioxidant properties of chitosan film

This study evaluated the physicochemical and antioxidant properties of clove essential oil (0, 0.2, 0.4, 0.6, 0.8, 1.0 % v/v) nanoemulsion (CEON) loaded chitosan-based films. With the increasing concentrations of the CEON, the thickness, b* and ΔE values of the films increased significantly (P < 0.05), while L* and light transmission dropped noticeably (P < 0.05). The hydrogen bonds formed between the CEON and chitosan could be demonstrated through Fourier-transform infrared spectra, indicating their good compatibility and intermolecular interactions. Furthermore, the added CEON considerably reduced the crystallinity and resulted in a porous structure of the films, as observed through X-ray diffraction plots and scanning electron microscopy images, respectively. This eventually led to a drop in both tensile strength and moisture content of the films. Moreover, the antioxidant properties were significantly enhanced (P < 0.05) with the increase in the amount of clove essential oil (CEO) due to the encapsulation of CEO by the nanoemulsion. Films containing 0.6 % CEO had higher elongation at break, higher water contact angle, lower water solubility, lower water vapor permeability, and lower oxygen permeability than the other films; therefore, such films are promising for application in meat preservation.

Sodium-alginate-based indicator film containing a hydrophobic nanosilica layer for monitoring fish freshness

In this study, hydrophobic sodium alginate/anthocyanin/cellulose nanocrystal indicator films were fabricated by incorporating nanosilica (NS) as a waterproofing layer. The concentrations and formation methods (spraying (S), coating (C), and impregnation (I)) of the NS layer (denoted as NSS, NSC, NSI, respectively) were optimized. The results indicated that the optimum concentration of the NS layer was 5 % at a water contact angle (WCA) 110.5°. Further, Fourier transform infrared spectra showed the presence of SiOSi and SiCH3 groups in the NSS, NSC, and NSI films, and X-ray diffraction spectra indicated that original structures of these films were disordered. Moreover, the surface morphology, mechanical properties, and light transmission were affected by the NS layer, and the optimal layer was found to be NSI. After 10 days of storage at 100 % humidity, the NSI film exhibited low water vapor adsorption (37.22 g) and permeability (0.1484 g/m·s·Pa·10-11) and a high WCA (110.2°). In addition, the NSI film exhibited a visible color shift with an increasing pH of the buffer solution. A monitoring test of fish freshness showed that the NSI film displayed a distinctive color change corresponding to fish spoilage during 14 days of storage. This indicates that NSI has high potential in indicator film applications.