l-arginine and l-lysine supplementation to NaCl tenderizes porcine meat by promoting myosin extraction and actomyosin dissociation.

This study investigated the individual and combined effects of l-arginine, l-lysine, and NaCl on the ultrastructure of porcine myofibrils to uncover the mechanism underlying meat tenderization. Arg or Lys alone shortened A-bands and damaged M-lines, while NaCl alone destroyed M- and Z-lines. Overall, Arg and Lys cooperated with NaCl to destroy the myofibrillar ultrastructure. Moreover, these two amino acids conjoined with NaCl to increase myosin solubility, actin band intensity, and the protein concentration of the actomyosin supernatant. However, they decreased the turbidity and particle size of both myosin and actomyosin solutions, and the remaining activities of Ca2+- and Mg2+-ATPase. The current results revealed that Arg/Lys combined with NaCl to extract myosin and dissociate actomyosin, thereby aggravating the destruction of the myofibrillar ultrastructure. The present results provide a good explanation for the previous phenomenon that Arg and Lys cooperated with NaCl to improve meat tenderness.

Myofibrillar proteins' intermolecular interaction weakening and degradation: Are they mainly responsible for the tenderization of meat containing l-arginine, l-lysine, or/and NaCl?

This study explored the effects of l-arginine, l-lysine, and NaCl alone and in combination on the tenderness of porcine meat. Arg, Lys, and NaCl alone improved the tenderness, decreased the cooking loss, and increased the myofibrillar fragmentation index (MFI) of porcine meat; Both Arg and Lys cooperated with NaCl to better achieve this effect. Furthermore, Arg/Lys collaborated with NaCl to increase muscle fiber swelling and moisture content of the meat and promoted the extraction of main myofibrillar proteins. FT-IR revealed that Arg, Lys, or NaCl alone or in combination caused changes in protein-water interactions. Western blotting revealed varying degrees of meat protein degradation in all cases, but the results did not well coincide with those of shear force and the MFI. Therefore, the weakening of intermolecular forces between myofibrillar proteins was considered the main reason for meat tenderization under the present study conditions.

Injection of l-arginine or l-lysine before freezing delays the emulsifying and gelling properties deterioration of myofibrillar proteins of frozen porcine Longissimus lumborum muscle.

This study aimed to investigate the effects of injecting l-arginine and l-lysine solution before freezing and after thawing on the emulsifying and gelling properties of myofibrillar proteins (MPs) of frozen porcine longissimus dorsi. The results showed that the pre-freezing injections were more effective in alleviating the decrease in emulsifying properties of MPs compared with the post-thawing injections, as evidenced by higher emulsion creaming index, oil droplet size, interfacial absorptive protein amount, and viscoelasticity. Additionally, the pre-freezing injections could effectively mitigate the damage to the gelling properties of MPs, as evidenced by the formation of a homogeneous and compact gel network with stronger water retention, strength and chemical forces, as well as a higher proportion of non-flowing water, whereas the post-thawing injections could not. These results demonstrated that the injection of l-arginine and l-lysine solution before freezing could delay freezing-induced damage to the emulsifying and gelling properties of MPs, keeping the processing characteristics of frozen porcine.

Effect of different concentrations of gellan gum with/without 0.50% basil essential oil on the physicochemical properties of gellan gum-rice bran oil coating emulsions and their application in egg preservation.

This work investigated the effects of different concentrations (0.10 %, 0.15 % or 0.20 %, w/v) of gellan gum (GG) with/without 0.50 % (v/v) basil essential oil (BEO) on physicochemical properties of gellan gum-rice bran oil (GG-RBO) emulsions. The results showed that GG-RBO emulsions with 0.15 % or 0.20 % GG were more stable than GG-RBO emulsion with 0.10 % GG (as evidenced by higher apparent viscosity and absolute zeta potential, but smaller average particle size and lower turbidity), thus displaying better coating performances (as evidenced by bigger contact angle but lower moisture content). The presence of BEO further improved their stability and coating performances. Coating with GG-BRO or GG-RBO-BEO emulsion with 0.15 % GG significantly delayed the increase in weight loss, and the decrease in haugh unit, yolk index and albumen pH of eggs during 42 days storage; moreover, GG-RBO-BEO emulsion caused lower total aerobic plate count. Therefore, GG-RBO, especially GG-RBO-BEO emulsion has potential in egg preservation.

Effects of manual washing with three alkaline sterilizing agent solutions on egg quality during storage.

This study aimed to investigate the abundance of microorganisms and quality of eggs washed with different washings (tap water, 0.03% calcium hypochlorite solution, 0.25% hydrogen peroxide solution, or 1% sodium percarbonate solution) and unwashed for 28-day storage. The results showed that the washing significantly decreased the abundance of microorganisms in all cases. Washing with one of the three alkaline sterilizing agent solutions significantly inhibited the deterioration of egg quality (evidenced by lower weight loss, air cell depth, albumen pH, yolk pH, and total volatile base nitrogen, but higher Haugh unit and yolk index) during storage, while washing with tap water showed opposite effects. The texture profile analysis and high-resolution scanning electron microscopy observation showed that all washings had slight negative effects on eggshell quality (eggshell breaking strength and microstructure), and washing with the alkaline sterilizing agent solution had no additional effects. The results might be attractive to egg preservation industry.

Individual effects of rosemary extract and green tea polyphenols on the physicochemical properties of soybean oil-myosin emulsion with l-arginine or l-lysine.

This study aimed to investigate the individual effects of rosemary extract and green tea polyphenols on the stability of the soybean oil-myosin emulsions with l-arginine or l-lysine. The results showed that l-arginine or l-lysine increased the physical stability of emulsion in all cases. In the presence of metallic cations, rosemary extract increased the physical stability, while green tea polyphenols decreased the physical stability. l-Arginine or l-lysine retarded the lipid and protein oxidation of emulsion in the absence of metallic cations during storage, but accelerated it in the presence of metallic cations. The two antioxidants delayed l-arginine- or l-lysine-induced lipid and protein oxidation in the presence of metallic cations. The results provide a new method for improving the physical and chemical stability of emulsion sausages in which l-arginine or l-lysine is applied to improve the quality attributes of emulsion sausage.

l-Arginine and l-lysine retard aggregation and polar residue modifications of myofibrillar proteins: Their roles in solubility of myofibrillar proteins in frozen porcine Longissimus lumborum.

This study investigated the ability of l-arginine and l-lysine to inhibit the adverse effects of freezing on the structure and solubility of myofibrillar proteins extract (MPE) in porcine Longissimus lumborum. The results showed that freezing decreased solubility of MPE, band densities of actin and myosin heavy and light chains, fluorescence intensity, and contents of free amino group and total sulfhydryls, but increased content of carbonyl groups and absolute zeta-potential of MPE. l-Arginine and l-lysine effectively alleviated the adverse effects of freezing. l-Arginine and l-lysine significantly increased ß-sheet content, Tmax1 and ΔH1, but decreased α-helix content and disulfide bond content in MPE. Additionally, the SDS-PAGE analysis showed that l-arginine and l-lysine could prevent appearance of bands at about 150 kDa. Overall, this study shows that both l-arginine and l-lysine could not only abate the aggregation and disruption of MPs, but also reduce the oxidation of their polar amino groups, which ultimately contribute to their superior solubility. The results may be interesting in meat industry.

Quality of frozen porcine Longissimus lumborum muscles injected with l-arginine and l-lysine solution.

This study investigated the effects of l-arginine and l-lysine on the water holding capacity, shear force, color, and protein denaturation of frozen porcine Longissimus lumborum. Four batches were prepared, each corresponding to samples of an experimental treatment: without a cryoprotective solution, injecting a 0.3% sodium tripolyphosphate and 0.5% NaCl solution, a 0.5% l-arginine solution, or a 0.5% l-lysine solution. The results showed that both l-arginine and l-lysine decreased thawing loss, cooking loss, shear force, L⁎ values, b⁎ values, and surface hydrophobicity, but they increased pH values, a⁎ values, percentages of peak areas for T21 relaxation times, and Ca2+-ATPase activity. Additionally, both histological and transmission electron microscopy images showed that l-lysine, and especially l-arginine could inhibit the formation of gaps between fiber bundles, alleviate the disruption of intracellular spaces, and maintain the structural integrity of sarcomeres. Overall, the results showed that both l-arginine and l-lysine hindered the structural damage of muscle fibers during freezing and protected myofibrillar proteins from denaturation, ultimately contributing to superior quality attributes.

l-Arginine and l-Lysine Alleviate Myosin from Oxidation: Their Role in Maintaining Myosin's Emulsifying Properties.

This study investigated the alleviative effects of l-arginine and l-lysine on the emulsifying properties and structural changes of myosin under hydroxyl radical (·OH) stress. The results showed that ·OH decreased the emulsifying activity index and emulsifying stability index but increased the creaming index and droplet size of a soybean oil-myosin emulsion (SOME). Confocal laser scanning microscopy demonstrated that ·OH caused larger and more inhomogeneous SOME droplets. l-Arginine and l-lysine effectively alleviated ·OH-induced destructive effects on the emulsifying properties of myosin. In addition, ·OH increased the extent of protein carbonylation and dityrosine formation, surface hydrophobicity, and ß-sheet content, but decreased the tryptophan fluorescence intensity, solubility, total sulfhydryl, and α-helix content of myosin. Although l-lysine increased dityrosine fluorescence intensity, l-arginine and l-lysine effectively alleviated the aforementioned structural changes of myosin. Therefore, l-arginine and l-lysine could mitigate ·OH-induced structural changes of myosin, which enabled myosin to maintain its emulsifying capacity under oxidative stress.

L-arginine and L-lysine degrade troponin-T, and L-arginine dissociates actomyosin: Their roles in improving the tenderness of chicken breast.

This work investigated the effects of L-arginine (Arg) and L-lysine (Lys) on the tenderness of chicken breast and explored the possible mechanisms underlying this effect for the first time. The results showed that both Arg and Lys decreased the shear force and increased the pH value, sarcomere length and myofibrillar fragmentation index as well as degraded the troponin-T by keeping calpain activity in chicken breast. In addition, Arg effectively reduced Ca2+/Mg2+-ATPase activities and promoted actomyosin dissociation. These results indicated that both Arg and Lys could enhance the tenderness of chicken breast, and it could also explain why Arg was more effective than Lys in improving the tenderness of chicken breast. These results will help facilitate the development of industrial-scale methods for improving the tenderness of meat products.

Reduction and coordination properties of l-Lysine/l-arginine/l-cysteine for the improvement of the color of cured sausage.

This study investigated how l-lysine/l-arginine/l-cysteine improved cured sausage color. Visible detection showed that Mb(Fe2+)NO did not form when MetMb(Fe3+) was treated with a combination of l-lysine and NaNO2, l-arginine and NaNO2, or l-cysteine and NaNO2. Visible spectra and electron paramagnetic resonance (EPR) detection together indicated formation of Mb(Fe2+)O2 when MetMb(Fe3+) was treated with l-lysine, l-arginine, or l-cysteine; Mb(Fe2+)NO was formed when MetMb(Fe3+) was treated with a combination of l-lysine and NO, l-arginine and NO, or l-cysteine and NO. Visible, EPR, and fourier transform infrared results suggested formation of a complex of Mb(Fe2+) and l-cysteine by the coordination of sulfydryl and ferrous porphyrin. Therefore, l-lysine, l-arginine, or l-cysteine can promote the formation of Mb(Fe2+)NO by reducing MetMb(Fe3+) to Mb(Fe2+)O2, and l-cysteine promotes formation of a complex of Mb(Fe2+) and l-cysteine via coordination of sulfydryl and ferrous porphyrin, which may improve cured sausage color.

l-Lysine/l-arginine/l-cysteine synergistically improves the color of cured sausage with NaNO2 by hindering myoglobin oxidation and promoting nitrosylmyoglobin formation.

This study aimed to evaluate the effects of l-lysine (Lys)/l-arginine (Arg)/l-cysteine (Cys) on the color of cured sausage and the possible mechanism underlying these effects. The results indicated that the combined addition of Arg/Lys/Cys and NaNO2 effectively increased the a* values and nitroso pigment content but decreased the MetMb(Fe3+) content in cured sausage, compared with the individual addition of Arg/Lys/Cys and NaNO2. The cured sausage treated with combined Arg/Lys/Cys and NaNO2 contained significantly lower residual nitrite than those treated with only NaNO2. UV-vis spectroscopy and electron paramagnetic resonance spectroscopy revealed that pentacoordinate nitrosyl ferrohemochrome was the main pigment component in the cured sausage treated with NaNO2 or combined Arg/Lys/Cys and NaNO2 and higher content in the latter one. The results suggest that Arg/Lys/Cys hindered myoglobin oxidation and promoted pentacoordinate nitrosylmyoglobin formation, which could contribute to the improved color of cured sausage. The results are of interest in the meat industry.

Study of polycyclic aromatic hydrocarbons generated from fatty acids by a model system.

BACKGROUND: The characteristics of carcinogenic polycyclic aromatic hydrocarbons (PAHs) produced from various fatty acids, as important components of fats and oils, at high temperature are still little known. The reason is because the existing data are from experiments conducted in complex food systems. In this study, 12 PAHs produced from nine fatty acids, representing saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs), were investigated in a model system heated at 98, 165 and 240 °C. RESULTS: SFAs can with difficulty be pyrolyzed to generate PAHs at 98 °C, but small amounts of PAHs were determined in MUFAs (44.97 µg kg-1 ) and PUFAs (177.73 µg kg-1 ). When the temperature reached 165 °C, there were totals of 27.59, 142.8 and 449.68 µg kg-1 PAHs assayed in SFAs, MUFAs and PUFAs, respectively. The amounts of PAHs generated from SFAs, MUFAs and PUFAs at 240 °C were higher when compared with those of the 165 °C group (P < 0.05). With an increase of heating temperature, the proportion of PAHs with four to five rings increased. Under the same heating conditions, the concentration of PAHs in fatty acids increased with an increase in the number of double bonds. CONCLUSIONS: More PAHs, especially carcinogenic ones with four to five rings, will be produced in fatty acids heated at higher temperature. The content of PAHs generated from fatty acids increased with an increase in the number of double bonds. This study will increase the understanding of the production characteristics of PAHs from various fatty acids under heating condition. © 2019 Society of Chemical Industry.

L-lysine and L-arginine inhibit the oxidation of lipids and proteins of emulsion sausage by chelating iron ion and scavenging radical.

OBJECTIVE: To evaluate the effects of L-lysine (Lys)/L-arginine (Arg) on lipid and protein oxidation of emulsion sausage during storage and its possible mechanism. METHODS: Four samples were prepared based on the presence or absence of additional sodium isoascorbate, Lys, or Arg: sample A (control), sample B (0.05 g of sodium isoascorbate), sample C (0.4 g of Lys), and sample D (0.4 g of Arg). Peroxide value (POV), thiobarbituric reactive substances (TBARS), protein carbonyls and thiols were measured. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical-scavenging, ferrous ion-chelating ability were also measured. RESULTS: Compared with the control, the sample treated with sodium isoascorbate, Lys or Arg had significantly lower POV during the initial 20 days, TBARS during the initial 15 days. Protein carbonyls were significantly lower compared Sample B, C, and D with A during the later storage (10 to 25 days); basically, protein thiols became lower during storage when the samples were treated with sodium isoascorbate, Lys, or Arg. Both Lys and Arg had weak reducing power but strong ferrous ion-chelating activity and DPPH radical- and hydroxyl radical-scavenging activity. CONCLUSION: Both Lys and Arg effectively inhibited the oxidation of lipids and proteins in emulsion sausage by scavenging free radicals and chelating ferrous ions. The results obtained may be favorable for the prevention of lipid and protein oxidation during processing and storage of meat products.

l-Lysine and l-arginine inhibit myosin aggregation and interact with acidic amino acid residues of myosin: The role in increasing myosin solubility.

The objective of this paper is to investigate the potential affecting mechanisms of l-lysine (Lys)/l-arginine (Arg) on myosin solubility. The results showed that both Lys and Arg increased the solubility of myosin at the examined pH values. Additionally, both Lys and Arg decreased the hydrodynamic size of myosin but increased the hydration capacity (HC), the surface aromatic hydrophobicity of myosin, the surface tension of the myosin solution and the absolute transfer free energy (TFE) of the major amino acids that constitute myosin. The results indicate that the properties of Lys or Arg that result in an inhibition of myosin aggregation and an interaction with hydrophobic amino acid residues may play important roles in increasing the myosin solubility. The results are attractive to the meat industry.

Effects of l-lysine on thermal gelation properties of chicken breast actomyosin.

The effects of l-lysine (l-Lys) on the water holding capacity (WHC) and texture of actomyosin (AM) gel and the possible mechanisms were investigated. l-Lys increased the WHC and hardness of the AM gel. These effects may be related to the even and continuous microstructure of the gel according to the scanning electron microscopy analysis. Furthermore, l-Lys increased the surface hydrophobic residues and the reactive sulfhydryl groups. l-Lys decreased the storage modulus at the first transition temperature but increased it at the second transition temperature and the third transition enthalpy. These results suggested that l-Lys varied the thermal behaviors and the microstructure of the AM gel by increasing the surface hydrophobicity and reactive sulfhydryl groups, ultimately contributing to the increased WHC and hardness. The changes in pH did not fully explain the results from the present study. The results were useful for understanding previous findings and may serve as a reference for the preparation of reduced-sodium and phosphate-free meat products.

Effects of l-arginine on the physicochemical and gel properties of chicken actomyosin.

The objective of this study is to investigate the effects of l-arginine (Arg) on the physicochemical and gel properties of chicken actomyosin. The results showed that Arg increased the content of surface hydrophobicity and reactive sulfhydryl group of chicken actomyosin, but decreased storage modulus (G0). Also, Arg enhanced the first thermal transition temperature (TM1) but decreased the second thermal transition temperature (TM2). The addition of Arg favored to form a dense and uniform gel with the increased water holding capacity (WHC), strength and transverse relaxation time (T2). These results suggested that Arg may result in the formation of a uniform and continuous gel by changing the structural and thermal behavior of actomyosin in turn, ultimately contributing to the elevated WHC and strength. The results may provide new insight into the effects of Arg on the WHC and texture of meat products in the previous literatures.

The role of monoxide hemoglobin in color improvement of chicken sausage.

The role of monoxide hemoglobin (COHb) in improvement of chicken sausage color was investigated. COHb and NaNO2 synergistically increased a* values. Addition of 0.1% COHb decreased the residual nitrite content in the presence of 0.001% NaNO2. Compared with controls, the combined treatment resulted in significantly higher nitroso pigment contents while the single treatment resulted in slightly higher nitroso pigment contents. Visible spectrometry indicated that both nitrosohemochrome (NH) and hematin were the main ingredients of pigments extracted from chicken sausage treated with a combination of 0.006% NaNO2 and 0.6% COHb. Formation of NH and hematin caused an increase in a* values and a decrease in L* values, respectively. COHb showed potential for use in meat product formulations.

Feasibility of combining spectra with texture data of multispectral imaging to predict heme and non-heme iron contents in pork sausages.

To precisely determine heme and non-heme iron contents in meat product, the feasibility of combining spectral with texture features extracted from multispectral imaging data (405-970 nm) was assessed. In our study, spectra and textures of 120 pork sausages (PSs) treated by different temperatures (30-80 °C) were analyzed using different calibration models including partial least squares regression (PLSR) and LIB support vector machine (Lib-SVM) for predicting heme and non-heme iron contents in PSs. Based on a combination of spectral and textural features, optimized PLSR models were obtained with determination coefficient (R(2)) of 0.912 for heme and of 0.901 for non-heme iron prediction, which demonstrated the superiority of combining spectra with texture data. Results of satisfactory determination and visualization of heme and non-heme iron contents indicated that multispectral imaging could serve as a feasible approach for online industrial applications in the future.

A novel method to stabilize meat colour: ligand coordinating with hemin.

Carbon monoxide (CO), L-cysteine and L-histidine were tested to coordinate with hemin chloride (pigment containing haem iron). In the presence of sodium dithionite, both CO and L-cysteine could react with hemin to afford respectively the corresponding complexes: CO-hemin and L-cysteine hemin; while L-histidine could not react with hemin. Both CO-hemin and L-cysteine hemin could decompose and release the corresponding ligand to generate hemin. Both light and temperature had an obvious effect on stabilization of these complexes. By sensory evaluation, both CO-hemin and L-cysteine hemin have bright red colour and show a potential as cured cooked-meat pigments (CCMP) in the manufacture of meat product.