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

Ascorbic acid-loaded fish gelatin nanoparticles/fish skin collagen fiber antioxidant film for extending the shelf life of chilled mirror carp (Cyprinus carpio L.) fillets

This study focused on the impact of ascorbic acid-loaded fish gelatin nanoparticles/fish skin collagen fiber (Col-AA-FGNP) antioxidant films for preserving chilled mirror carp. Both the control and samples wrapped with films exhibited quality deterioration with increased storage time, resulting in spoilage of control samples by the eighth day. The samples treated with the Col-AA-FGNP exhibited significant improvements at 10 days compared to the control. Specifically, the thiobarbituric acid reactive substances, carbonyl content, pH, total volatile base nitrogen, total viable count, and Psychrophilic bacteria count were reduced by 31.7%, 23.9%, 2.2%, 28.1%, 28.6%, and 22.4%, respectively. These findings suggested that the Col-AA-FGNP effectively reduced lipid and protein oxidation, microbial growth, and decline of freshness, thereby extending the shelf life by at least 2 days. In addition, the hardness, springiness, chewiness, resilience, lightness, and whiteness values of the samples wrapped in the Col-AA-FGNP film increased, while the redness, yellowness values and centrifugal loss decreased compared to that of the control, indicating improvements in color, texture, and moisture retention. These beneficial effects were attributed to the controlled release of ascorbic acid by the nanoparticles, which played a key role in scavenging free radicals to prevent quality deterioration. Additionally, the antioxidant film acted as a barrier against oxygen and microorganisms while reducing moisture migration, thereby further extending the shelf life of the fish fillets. This study offers valuable insights into utilization of fishery by-products and application of antioxidant films in meat preservation.

Effect of lysine-assisted ultrasonic and vacuum tumbling treatment on the quality of chicken breast meat in canned foods

Curing is a technological process that improves the tenderness, water retention, and overall quality of canned food. This study aimed to evaluate the effects of different exogenous additives, specifically sodium tripolyphosphate and lysine, on the quality of chicken breast meat in canned assorted vegetables and diced chicken using different curing methods: static curing, ultrasonic curing, vacuum tumbling curing, and ultrasonic combined with vacuum tumbling curing. The texture, moisture mobility and distribution, microstructure, and sensory acceptability of the chicken meat were evaluated. The results showed that lysine demonstrates better water retention than sodium tripolyphosphate, combining ultrasonic and vacuum tumbling treatments with 0.2% Lys (SL-UVT) significantly enhanced the texture characteristics and reduced the cooking loss of chicken breast meat. Additionally, SL-UVT treatment improved the texture, appearance, flavor, and overall acceptability scores. Nuclear magnetic resonance (NMR) analysis showed that SL-UVT treatment affected water distribution and flowability, increasing the retention of less mobile water in chicken breasts. In addition, the gap between myogenic fibers increased after SL-UVT treatment, trapping more water. In conclusion, SL-UVT treatment significantly improved the tenderness and water-holding capacity of the chicken breast from both macroscopic and microscopic perspectives. This study provided a theoretical foundation for refining and optimizing canned meat processing techniques.

Effects of Eucommia ulmoides Leaf Extract on the Technological Quality, Protein Oxidation, and Lipid Oxidation of Cooked Pork Sausage During Refrigerated Storage

The present research work was based on evaluating the effects of Eucommia ulmoides leaf extract (EULE) on the technological quality and protein oxidation of cooked pork sausage during refrigerated storage. Sausages were manufactured with different levels of EULE (0, 0.15, and 0.3 g/kg) and stored at 4 °C for 3, 20, and 40 d, respectively. Quality attributes including cooking loss, texture, and color were evaluated, and the total carbonyl and total sulfhydryl as well as the specific markers α-aminoadipic acid semialdehyde (AAS) and lysinonorleucine (LNL) were analyzed for protein oxidation. The results revealed that the inclusion of EULE exhibited effectiveness in reducing the formation of protein carbonyls, particularly AAS and LNL, while inhibiting the loss of total sulfhydryl. Nevertheless, EULE increased the cooking loss, hardness, and chewiness of the sausages compared to the control group. These findings demonstrated that EULE could be considered a potential natural antioxidant for use in sausage production.

Enhancement of Antioxidant Activity, Stability, and Structure of Heme-Peptides by L-Lysine

Porcine blood is rich in protein and has always been the focus of research. Heme-peptides prepared from porcine hemoglobin are susceptible to oxidative degeneration during preparation and storage, thus affecting their function and stability. This study evaluated the enhancement effects of L-lysine (Lys) on recovery rate, antioxidant activity, stability, and structure. The results indicated that adding 1% Lys during enzymatic hydrolysis significantly increased the recovery rate of ferrous heme and peptide content by 93.88% and 15.30% (p < 0.05), respectively, and maximally enhanced antioxidant activity by 37.85% (p < 0.05). The contents of iron, ferrous ion, and ferrous heme in the heme-peptides were significantly increased by 97.52%, 121. 97%, and 74.45% (p < 0.05), respectively. Additionally, Lys improved the resistance to pH, temperature, metal ions, pepsin, and trypsin. Meanwhile, the effects of Lys resulted in heme-peptides with a smaller particle size, higher zeta potentials, and a smoother micromorphology. Fourier-transform infrared spectroscopy and fluorescence spectroscopy analysis showed that Lys enhanced the conformational stability of the heme-peptides. Molecular docking further suggested that hydrogen bonding was the main driver of the connections between Lys and the heme-peptides. This study provides theoretical guidance for the efficient utilization of heme-peptides in the food industry.

Unraveling the potential of zinc protoporphyrin-forming lactic acid bacteria for replacing nitrite and their role in quality characteristics of Harbin dry sausage

This study evaluated the effects of zinc protoporphyrin-producing lactic acid bacteria specifically Weissella viridescens JX11, Weissella viridescens MDJ8, and Lactobacillus pentosus Q on nitrite substitution and the quality characteristics of Harbin dry sausage. The redness (a*) values in the bacteria-inoculated groups were significantly higher than those in the control group (P < 0.05) during fermentation. Bacteria-inoculated sausages exhibited a higher proportion of oxymyoglobin and a lower proportion of metmyoglobin (P < 0.05). Ferrochelatase activity in the inoculated groups was significantly higher than in the control at days 3 and 6 (P < 0.05). Additionally, the fluorescence intensity of zinc protoporphyrin and its precursor, protoporphyrin IX, in the bacteria-inoculated groups significantly increased during fermentation (P < 0.05), and W. viridescen JX11 exhibited the highest fluorescence intensity and UV-Vis absorption peak (P < 0.05). These results suggest that zinc protoporphyrin-producing lactic acid bacteria could potentially replace nitrite in fermented dry sausages.

L-lysine enhances pork color through antioxidant activity and myoglobin conformational changes

This study aimed to investigate the effect of L-lysine (Lys) on the color of pork and reveal the possible mechanism. The results showed that the L* and a* values increased from 53.69 to 56.32, 56.39, and 56.47, and from 12.93 to 13.21, 13.24, and 13.52 with the addition of 0.1 %, 0.15 % and 0.2 % Lys, respectively. Meanwhile, the oxymyoglobin (Fe2+) levels increased from 21.14 % to 22.63 %, 23.83 %, and 23.53 %, while the metmyoglobin (Fe3+) levels decreased from 44.69 % to 40.28 %, 41.21 %, and 41.63 % with the addition of 0.1 %, 0.15 % and 0.2 % Lys, respectively. Additionally, the addition of Lys increased total sulfhydryl and active sulfhydryl contents, and decreased the levels of reactive oxygen species (ROS) (P<0.05). The particle size and the absolute value of the ζ-potential increased with the addition of Lys, reaching maximum values of 534.39 nm and -13.73 mV, respectively. The molecular dynamics results suggested that Lys can bind to myoglobin (Mb) through hydrophobic interactions and hydrogen bonds, forming a stable Lys-Mb complex, acting as a protective shield to prevent the entry of ROS and other oxidizing agents. Finally, the addition of 0.15 % Lys resulted in the highest surface hydrophobicity, which was 5.79 μg. The multispectral results indicated that Lys primarily induces changes in the secondary and tertiary structures of Mb through interactions with tyrosine residues. These changes stabilized the free-moving rings within the amino acid residues of Mb, thereby improving the structural stability of Mb and ultimately enhancing the color stability of pork. In summary, Lys improved meat color stability through a dual mechanism of antioxidation and interaction with Mb to alter its conformational stability.

Application of lysine as a potential alternative to sodium salt in frankfurters: With emphasis on quality profile promotion and saltiness compensation

This study aimed to investigate the effect of lysine (Lys) on quality profile promotion and saltiness compensation in reduced‑sodium salt frankfurters. The results showed that the cooking loss of reduced‑sodium salt frankfurters decreased from 5.63 to 3.45% when the Lys level increased from 0.1 to 0.7%, as well as enhanced water contents and saltiness in a Lys dose-dependent manner. Moreover, the corresponding peak area percentage (A21) of reduced‑sodium salt frankfurters remarkably increased from 79.63% to 81.48% with the increased level of Lys. However, a higher level of Lys (≥ 0.5%) obviously reduced the textural properties of reduced‑sodium salt frankfurters, which was clearly verified by looser and rougher microstructures. Furthermore, hydrogen bonds were found to be the dominant molecular force in Lys-added reduced‑sodium salt frankfurters. Meanwhile, 0.3% Lys was found to exhibit the optimal sodium salt-replacing effect due to the highest degree of quality profile promotion and saltiness compensation. Additionally, directional triangle sensory evaluation further confirmed that the reduced‑sodium salt frankfurters treated with 0.3% Lys was perceived to be similar to control frankfurters, resulting a 50% salt-reduction effect. Thus, our results suggested that Lys could be applied as an efficient sodium salt alternative in reduced‑sodium salt frankfurters.

Investigating the Effects of Pink-Generating Ligands on Enhancing Color Stability and Pigment Properties in Pork Sausage Model Systems Cured with Sodium Nitrite or White Kimchi Powder

In this study, we investigated the effects of different nitrite sources (sodium nitrite or white kimchi powder) and pink-generating ligands (cysteine, histidine, or nicotinamide) on the development and stability of cured meat color in pork sausage model systems over 30 d of refrigerated storage. The samples were prepared in a 2 × 3 factorial design with two nitrite sources and three ligands, and their physicochemical properties were evaluated on days 0, 15, and 30. Although white kimchi powder induced cured color development similar to that of synthetic sodium nitrite, it resulted in higher cooking loss and lower residual nitrite content in cured pork sausages (p < 0.05). The addition of cysteine resulted in significantly higher CIE a* values, cured meat pigment, and curing efficiency than histidine and nicotinamide (p < 0.05), while yielding lower pH values, residual nitrite content, and total pigment content (p < 0.05). The storage duration significantly reduced the residual nitrite and total pigment contents of the products. These findings suggest that white kimchi powder can serve as a natural alternative to sodium nitrite in pork sausage models and that the incorporation of cysteine has a favorable impact on the development and enhancement of cured meat color.

Effects of basic amino acids on heterocyclic amines and quality characteristics of fried beef patties at low NaCl level

The impact of basic amino acids (Lysine, Arginine, Histidine) on the formation of total heterocyclic amines (HAs) was investigated in fried beef patties at 1% NaCl level. Different levels of basic amino acids (0.1%, 0.5%, 1%) significantly inhibited the formation of the total and individual HAs at 1% NaCl, and the inhibitory effect was more effective than 3% NaCl (6.19 ng/g, 26.93% inhibition) (P < 0.05). Lys at 1% reduced total HAs the most (2.46 ng/g, 70.88% inhibition), followed by 1% His (2.79 ng/g, 67.03% inhibition) and 1% Arg (3.43 ng/g, 59.51% inhibition). Compared to the 3% NaCl, the quality characteristics (moisture content, frying loss, texture profile, and color) of the fried beef patties were significantly improved when basic amino acids were added at 1% NaCl (P < 0.05). The lipid oxidation of fried beef patties was significantly inhibited by 1% Arg and 1% Lys at 1% NaCl level (P < 0.05). The results indicated that basic amino acids could inhibit the formation of total HAs while maintaining the quality of meat products at low NaCl condition.

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.

Exploring the impact of irradiation on the sensory quality of pork based on a metabolomics approach

The effects of irradiation on pork quality characteristics were investigated by combining sensory experiments, pork color, TBARS, volatile components, and differential metabolites. Pork irradiated at a dose of 1 kGy received the highest sensory scores, whereas pork irradiated at doses of 3 and 5 kGy obtained lower sensory scores, particularly with regard to odor. Irradiation makes pork more ruddy and promotes fat oxidation, leading to increased a* and TBARS values. The main volatile substances in irradiated pork were hydrocarbons, aldehydes, and alcohols, and hexanal, heptanal, and valeric acid were considered as important substances responsible for the generation of radiation-induced off-flavors. 65 differential metabolites were identified. l-pyroglutamic acid, l-glutamate, l-proline, fumarate acids, betaine, and l-anserine were considered as the main substances contributing to the differences in pork quality. In addition, metabolic pathways such as arginine biosynthesis, alanine, aspartate and glutamate metabolism were found to be considerably affected by irradiation.

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.

Replacement of nitrates and nitrites in meat-derived foods through the utilization of coagulase-negative staphylococci: A review

Nitrates and nitrites, which are synthetic additives, are traditionally used as curing agents in meat-based products. These synthetic additives are employed in the preparation of fermented meat foods to improve quality characteristics and microbiological safety, develop distinct flavours and red-colour stability, and counteract lipid oxidation. Nitrites also display significant bacteriostatic and bactericidal action against spoilage microorganisms and foodborne pathogens (such as Clostridium botulinum and Listeria monocytogenes). However, meat curing is currently under scrutiny because of its links to cardiovascular diseases and colorectal cancer. Based on the current literature, this review provides recent scientific evidence on the potential utilisation of coagulase-negative staphylococci (CNS) as nitrate and nitrite substitutes in meat-based foods. Indeed, CNS are reported to reproduce the characteristic red pigmentation and maintain the typical high-quality traits of cured-meats, thanks to their arginine degradation pathway, thus providing the nitrite-related desirable attributes in cured meat. The alternative strategy, still based on the NOS pathway, consisting of supplementing meat with arginine to release nitric oxide (NO) and obtain a meat characterised by the desired pinkish-red colour, is also reviewed. Exploiting NOS-positive CNS strains seems particularly challenging because of CNS technological adaptation and the oxygen dependency of the NOS reaction; however, this exploitation could represent a turning point in replacing nitrates and nitrites in meat foods.

From amino acid analysis to improved gel properties: The role of dl-valine in Landaise goose myofibrillar protein

The impact of exogenous limiting amino acids on protein gel formation was investigated to enhance the gelation properties of Landaise goose myofibrillar protein (MP). Amino acid composition and gel properties were analyzed, and homologous protein modeling and molecular docking techniques were used to simulate binding sites. Valine was identified as the first limiting amino acid. The addition of 0.075 % dl-valine proved optimal to enhance the gel strength (59.5 g) and water retention (76.76 %) of MP gels. Hydrophobic interactions and disulfide bonds were found to be the main forces maintaining conformational stability of the MP-dl-valine gels. The propyl group of dl-valine can form hydrophobic interactions with protein, contributing to stable complexes. DL valine could also strengthen chemical bonds and secondary structure, convert free water to immobile water, and improve the microstructure of the gel. Therefore, valine can be utilized as a nutritional and gel enhancer in Landaise goose meat products.

Reducing Effects of Whey Protein Hydrolysate on Coloration of Cured Sausages

Curing produces a characteristic pink color during meat processing through the production of nitrosyl myoglobin (NOMb), which requires nitric oxide (NO). Nitrites and nitrates in coloring agents are crucial NO sources; however, a reducing agent is necessary to facilitate their chemical conversion to NO. This study aimed to investigate the effect of the reducing properties of whey protein hydrolysate (WPH) on the reddening of cured meat products. Cured and cooked sausage models were treated with WPH, which enhanced the reddening of the meat color and increased the a* value in the models compared with that of the controls. Additionally, ethanol-extracted WPH induced Fe3⁺ reduction, lowered oxidation-reduction potential, and decreased nitrite (NO2-) levels. Moreover, ethanol-extracted WPH promoted the formation of NOMb in myoglobin solution. This effect was also observed when ethanol-extracted WPH treated with maleimide was used, implying that certain peptides rather than the thiol group of WPH are involved in promoting NOMb formation. Furthermore, the peptides that decreased NO2- levels were isolated from ethanol-extracted WPH, identified, and synthesized. These synthesized peptides, particularly the FFVAPFPEVFGK peptide, showed NO2--reducing activity. Hence, WPH may promote the coloration of cured meat products through the reducing potential of the peptides contained within.

Zinc protoporphyrin IX generation by Leuconostoc strains isolated from bulged pasteurized vacuum sliced hams

The colour of meat typically fades as it decays. However, it has been observed that certain vacuum-packaged spoiled hams can maintain a pink colour even when the packaging is bulged. A large amount of Zinc protoporphyrin IX (ZnPP) was found in these hams, compared to fresh red hams or spoiled and grey hams. Combined with high-throughput sequencing and cultural isolation, the potential cultures of Leuconostoc mesenteroides S-13 (LM), Leuconostoc citreum OCLC11 (LC), and Leuconostoc mesenteroides subsp. IMAU:80679 (LS) were selected based on their ability to produce ZnPP. Subsequently, these cultures were introduced into a fermented sausage model to assess their effect on colour conversion. The analysis of absorption and fluorescent spectra showed that Nitrite sausages contained nitrosyl heme pigment, while bacteria-inoculated sausages were predominantly composed of ZnPP. In addition, the a* value of the LS sausage was close to the Nitrite group at the end of fermentation, significantly higher than control, indicating the effect of bacterial metabolism on the redness. Meanwhile, the Ferrochelatase (FECH) activity of LM, LC and LS groups were 140 ± 13, 113 ± 16 and 201 ± 20 U/g sausage, respectively, providing a potential method on compensating for nitrite/nitrate substitution based on the presence of ZnPP in meat products.

Impact of L-arginine on the quality of heat-treated Antarctic krill: Influence of pH and the guanidinium group

Antarctic krill suffers from severe water loss after heating, and its quality deteriorates, so it is in urgent need of a green and healthy improver. In this paper, the effects of L-arginine (L-Arg) soaking on the modification of the quality of heat-treated Antarctic krill and the structure of myofibrillar proteins (MPs) in Antarctic krill were investigated. The results showed that L-Arg had an ameliorating effect on heat-treated krill in a concentration-dependent relationship. The water-holding capacity of L-Arg-soaked krill was 1.41 times higher than that of sodium tripolyphosphate (STPP) at an equivalent concentration (80 mM). At 120 mM L-Arg soaked, L* and hardness of krill decreased to 58.31 and 334.81 g, while resilience and moisture content increased to 0.47 and 85.29 % after heating, respectively. The scanning electron microscopy (SEM) results revealed that the tissue state of the pH-corrected groups was better than the control, but not as well as that of the pH-uncorrected groups. pH and the guanidinium group in L-Arg both played roles in promoting the transition of MPs from disordered to ordered secondary structures. This transition reduced the exposure of hydrophobic and sulfhydryl groups in MPs, inhibited the protein aggregation and increased the solubility of MPs to 71.61 %, which ultimately improved the quality of heat-treated krill. It is worth noting that the pH effect had a primary influence on the observed effects, while the guanidinium group made a secondary contribution. These results could broaden the potential application of L-Arg as an improver of the quality of heat-treated krill.

Additive Effects of L-Arginine with Potassium Carbonate on the Quality Profile Promotion of Phosphate-Free Frankfurters

The present study investigated the additive effects of L-Arginine (L-Arg) with potassium carbonate (PC) on the quality characteristics of phosphate-free frankfurters. The results showed that L-Arg combined with PC could act as a viable phosphate replacer by decreasing cooking loss and improving the textural properties of phosphate-free frankfurters (p < 0.05), mainly because of its pH-raising ability. Moreover, L-Arg could assist PC in effectively retarding lipid oxidation in phosphate-free frankfurters during storage (p < 0.05). Furthermore, 0.1% L-Arg combined with 0.15% PC was found to exhibit the best optimal phosphate-replacing effect. This combination could also overcome quality defects and promote the sensory attributes of phosphate-free frankfurters to the maximum extent. Therefore, our results suggest that L-Arg combined with PC can be considered a feasible alternative for the processing of phosphate-free frankfurters with an improved quality profile and superior health benefits.

Bacterial nitric oxide synthase in colorizing meat products: Current development and future directions

Nitrite has been widely used in meat products for its abilities including color formation, antimicrobial properties, flavor formation and preventing lipid oxidation. However, the possible generation of N-nitrosamines through reaction of nitrite with secondary amines arises many concerns in the usage of nitrite. For a long time, nitrite substitution is unsettled issue in the meat industry. Many attempts have been tried, however, the alternative solutions are often ephemeral and palliative. In recent years, bacterial nitric oxide synthase (bNOS) has received attention for its critical roles, especially in reddening meat products. This comprehensive background study summarizes the application of bNOS in colorizing meat products, its functions in bacteria, and methods of regulating the bNOS pathway. Based on this information, some strategies for promoting the nitric oxide yield for effectively substituting nitrite are presented, such as changing the environmental conditions for bacterial survival and adding substrate. Thus, bNOS is a promising nitrite substitute for color formation, and further research on its other roles in meat needs to be carried out to obtain the complete picture.

ε-Polylysine-mediated enhancement of the structural stability and gelling properties of myofibrillar protein under oxidative stress

The effects of ε-polylysine (ε-PL) at different concentrations (0.005 %, 0.010 %, 0.020 %, and 0.030 %) on the structure and gelling behavior of pork myofibrillar protein (MP) under oxidative stress were explored. The incorporation of ε-PL significantly restrained oxidation-induced sulfhydryl and solubility losses (up to 9.72 % and 41.9 %, respectively) as well as protein crosslinking and aggregation. Compared with the oxidized control, ε-PL at low concentrations (0.005 % - 0.020 %) promoted further unfolding and destabilization of MP, while 0.030 % ε-PL led to refolding of MP and enhanced its thermal stability. The ε-PL-induced physicochemical changes favored the formation of a finer and more homogeneous three-dimensional network structure, therefore obviously enhancing the strength and water-holding capacity (WHC) of thermally induced oxidized MP gels, with the ε-PL at 0.020 % showed the greatest enhancement. This work revealed for the first time that ε-PL can significantly ameliorate the oxidation stability and gel-forming ability of meat proteins.

Improving the texture properties and protein thermal stability of Antarctic krill (Euphausia superba) by L-lysine marination

BACKGROUND

The quality deterioration of Antarctic krill (Euphausia superba) after thermal processing limits its industrial application. This study sought to improve the texture characteristics of Antarctic krill after heat treatment through pre-soaking using l-lysine (Lys) solution and sodium tripolyphosphate (STPP). Moreover, the effects of Lys on heat-treated Antarctic krill were explored.

RESULTS

Lys significantly reduced the cooking loss and improved the texture characteristics of Antarctic krill during heat treatment. The low-field nuclear magnetic resonance results showed that Lys reduced the water loss of Antarctic krill during heat treatment. Additionally, the surface hydrophobicity, Fourier transform infrared spectroscopy, and endogenous fluorescence spectroscopy results showed that Lys could inhibit the structural damage of Antarctic krill protein under the thermal denaturation condition and enhance the thermal stability of the protein. The scanning electron microscopy results showed that Lys could protect the structural integrity of Antarctic krill muscle fibers during heat treatment.

CONCLUSION

The cooking loss in the Lys added groups was better than the sodium tripolyphosphate added group, and 2.0% Lys solution could minimize the cooking loss of Antarctic krill. The secondary and tertiary structures of the Antarctic krill protein were actively protected by Lys during heat treatment. Overall, the study will provide insights into the application of Lys in the food industry as a natural additive and an alternative to phosphate. © 2021 Society of Chemical Industry.

Changes in nitrosohemachrome lead to the discoloration of spiced beef during storage

The discoloration of spiced beef during storage is a severe problem that limits the shelf life of products. This study explored the associations between discoloration and pH, water, lipid oxidation, and protein oxidation. Electron paramagnetic resonance and UV-Vis spectroscopy illustrated that the pigment of spiced beef was a pentacoordinate mononitrosylheme compound and its conjugated structure changed during storage. The low-field NMR and magnetic resonance imaging results showed that the mobility of water increased, and the water content decreased with the extension of storage time. Multivariate analysis showed that color attributes were negatively correlated with oxidation. The oxidation of nitrosohemachrome was the primary reason for the lightness (L*) and redness (a*) decline in spiced beef. In addition, water loss exerted a promotion function in the oxidation process. This study provides valuable information on maintaining the quality of spiced beef during storage.

Evaluation of coloration, nitrite residue and antioxidant capacity of theaflavins, tea polyphenols in cured sausage

This study evaluated the effects of theaflavins (TFs), tea polyphenols (TP) and vitamin C (VC) on the nitrite residue amount, color, antioxidant capacity and N-nitrosamines inhibition in cured sausage. The addition of TFs, TP and VC combined with NaNO₂ respectively could significantly increase the a* value, nitroso pigment content and DPPH free radical scavenging rate, and effectively reduced the content of residual nitrite, metmyoglobin (MetMb) and total N-nitrosamines in cured sausages than treated only with NaNO₂ (P < 0.05), of which TFs group was the most significant (P < 0.05). It was indicated that the addition of TFs, TP could better inhibit the oxidation of cured sausages. UV-vis spectroscopy also showed pentacoordinate nitrosyl ferrohemochrome was the main pigment component in the samples. The results demonstrated that TFs and TP could contribute to the desired color and safety of sausage.

The effect of nitric oxide synthase and arginine on the color of cooked meat

In previous studies, it has been suggested that the NO-synthase enzyme may be responsible for color formation in fermented sausages. Thus, this is the first study in which the aim was to analyze the effects of direct NO-synthase and arginine application to meat on its color after heating. Myoglobin forms as well as the presence of NO-myoglobin were investigated. The color of the meat and myoglobin forms present in the samples were mainly affected by pH differences, caused by a HEPES buffer or arginine. None of the variants demonstrated a bright pink color as in the case of the heated nitrite-cured sample. Based on analysis of the absorption spectra, it can be concluded that there is some evidence of nitroso-complex formation. Therefore, it is probable that optimizing the pH/time/temperature conditions for NO-synthase activity would allow to obtain a desirable color effect. NO-synthase could be used as an alternative curing ingredient.

Structural characterization and stability analysis of phosphorylated nitrosohemoglobin

Phosphorylation modification by sodium tripolyphosphate (STP) on nitrosohemoglobin (NO-Hb) and its effect on the protein structure and stability were studied. Phosphate groups were found to bridge to NO-Hb via C-O-P bonds through serine and tyrosine residues. Hydrothermal treatment with STP maintained the α-helix stability of NO-Hb, and this change in secondary structure improved the proteins stability. Compared to NO-Hb, phosphorylated NO-Hb (P-NO-Hb) was more stable with respect to light (outdoor light, indoor light, and dark conditions), oxidant (hydrogen peroxide), high temperature, and non-neutral pH. The absorbance of P-NO-Hb was nearly twice those of Hb and NO-Hb (P < 0.05), and the absorbance of P-NO-Hb decreased more slowly over time than those of Hb and NO-Hb. The results confirm that the presence of phosphate groups can increase the stability of Hb through structural changes.

The use of mutton in sausage production

The work analyzes the quality of sausage with mutton. The proportion of individual commodities was as follows 40% sheep thigh, 40% pork shoulder, and belly 20%. The protein content in pork shoulder was 20.11 g.100g-1 in sheep thigh 23.65 g.100g-1 and sausage 19.89 g.100g-1. Of the monitored amino acids, the highest content was in lysine, in the sausage was 1.9 g.100g-1 and of the raw materials in the belly 2.1 g.100g-1. We also found a higher proportion of leucine 1.7 g.100g-1 in both sausage and sheep thighs. The arginine content in the sausage was also high 1.39 g.100g-1. We found a high content of palmitic acid in the pork shoulder of 24.38 g.100g-1 FAME. The content of palmitic acid in sheep meat was 24.32 g.100g-1 FAME and in sausage 24.16 g.100g-1 FAME. The content of stearic acid in the pork shoulder was 10.89g.100g-1 FAME, in the sheep thigh 10.64g.100g-1 FAME, in the belly 11.07 g.100g-1 FAME, and the sausage 10.92 g.100g-1 FAME. The MDA content in sheep meat was 0.185 mg.kg-1, in pork shoulder 0.141 mg.kg-1, in pork belly 0.22 mg.kg-1 and in sausage on the day of production 0.45 mg.kg-1. On the 30th day, the MDA content was in the sausage 0.78 mg.kg-1. The high MDA content of the sausage was probably most influenced by the technological process, as all raw materials, because there was a lower MDA content.

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 β-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.

Potential Use of Hyssopus officinalis and Borago officinalis as Curing Ingredients in Pork Meat Formulations

Simple Summary

Health risks associated with nitrites as curing agents have led consumers to search for products without those additives. Herbs have been used in medicine for many years and are usually positively perceived by consumers. Good-quality products with medicinal plants may be an alternative for those who try to avoid additives other than salt and spices. Hyssopus officinalis and Borago officinalis were tested for their potential to be used as colour forming and antioxidant agents. Both herbs were used in pork meat formulations along with nitrate reducing bacteria. A colour formation similar to a control product containing nitrite was noted in all the samples. Borage had a stronger antioxidant effect. Those additives can be used as an alternative to nitrite cured pork products.

Abstract

The replacement of nitrites in pork meat products has been a studied issue for many years. Due to potential health threats associated with these additives, consumers tend to search for alternative meat curing methods. In this study, Hyssopus officinalis and Borago officinalis were tested for their potential to be used as colour-forming and antioxidant agents. Dry plant samples from various sources were tested for fat, protein, ash, polyphenol and nitrate content. There were significant differences between the herbs depending on source. Two control samples (containing curing salt and sodium chloride with nitrate reducing bacteria) and samples with herbs (hyssop, hyssop with nitrate reducing bacteria, borage, borage with nitrate reducing bacteria)—0.5% of the meat mass—were prepared and stored for 15 days. In the samples with herbs and bacterial cultures, a red colour was developed, the TBARS values were low and DPPH activity was strong. All the samples with herbs had lower residual nitrite levels compared to the samples with curing salt. Borage had a stronger influence on colour and antioxidant stability of the meat samples compared to hyssop. However, both herbs can be used as colour-forming and antioxidant agents along with nitrate-reducing bacteria.

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-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.

Interrelationship between myoglobin oxidation and lipid oxidation during the processing of Cantonese sausage with d-sodium erythorbate

BACKGROUND

Pork is used as raw material to produce Cantonese sausage, and 0.5 or 1 g kg^-1 of d-sodium erythorbate is added to the pork meat. In this study the myoglobin oxidation rate, relative metmyoglobin content, heme iron content, redness, pH, free radical content and thiobarbituric acid reactive substance (TBARS) value were measured at different processing times and different content of d-sodium erythorbate.

RESULTS

It was found that d-sodium erythorbate significantly reduced the free radical content and myoglobin and lipid oxidation rates and increased heme iron levels. When d-sodium erythorbate was added to the sausage, the absorption peak of myoglobin porphyrin shifted left, migrating from 414 to 405 nm. At 72 h, with an increase in the d-sodium erythorbate content, a significant negative correlation was identified between heme iron and the degree of redness (P < 0.01).

CONCLUSION

During sausage processing, there are strong correlations among TBARS values, free radical content, metmyoglobin levels, heme iron levels, a* and pH at the same d-sodium erythorbate level. At the same processing time, adding d-sodium erythorbate can slow the rate of myoglobin and lipid oxidation and prevent the discoloration of sausage. © 2019 Society of Chemical Industry.

Theoretical basis of nitrosomyoglobin formation in a dry sausage model by coagulase-negative staphylococci: Behavior and expression of nitric oxide synthase

Three coagulase-negative staphylococci (CNS) species were investigated for gene expression of nitric oxide synthase (NOS) and the ability of nitrosomyoglobin (NO-Mb) formation in a dry sausage model without nitrite addition. The expression of nos gene was systematically proven from DNA to RNA to protein, and nitric oxide (NO) generation was also directly detected. In the dry sausage model system, the redness (a*-values) of samples inoculated with the three CNS species were higher than those inoculated with Pediococcus pentosaceus and the control (P < 0.05). The results from UV-vis and electron spin resonance spectroscopies revealed that pentacoordinate NO-Mb was formed in the sausages with either CNS or nitrite added. The sausage inoculated with Staphylococcus vitulinus had the highest NO-Mb content among the CNS-treated sausages. Dimer interface residues and phosphorylation sites of NOS in . itulinus differ from the other two CNS species as revealed by amino acid sequences, which may be responsible for the different catalytic activities.

Chemical and technological properties of bologna-type sausages with added black quinoa wet-milling coproducts as binder replacer

The objective of this study was to evaluate different strategies for adding 3% black quinoa (either as whole seeds or as a fiber-rich fraction of quinoa from its wet-milling process) to bologna-type sausage. This addition was evaluated in terms of its influence on nutritional composition and technological properties (emulsion stability, pH, water activity, color changes, textural properties, residual nitrite level and lipid oxidation). Both strategies resulted in commercially feasible sausages with increased nutritive properties (dietary fiber) and with some modifications in their technological properties. Compared with control sausages, they showed better emulsion stability, lower water activity and lipid oxidation values (interesting properties for sausages shelf-life). Color changes were more evident when the fiber-rich fraction was added. The residual nitrite level increased with the addition of quinoa so that it would be necessary to incorporate less nitrites, or it might even be unnecessary, contributing to the production of more natural products.

Sucrose enhances colour formation in dry sausages by up-regulating gene expression of nitric oxide synthase in Staphylococcus vitulinus

The effects of glucose and sucrose on the gene expression of nitric oxide synthase (NOS) in Staphylococcus vitulinus and colour formation in dry sausages were investigated. The results showed that sucrose addition promoted nitric oxide (NO) production in media when compared with glucose. In addition, sucrose could up-regulate nos (encoding NOS) and katA (encoding catalase KatA) gene expression by enhancing oxidative stress levels. In the sausages inoculated with S. vitulinus, a*-values (indicating redness) of the sausages with added sucrose were higher than those of samples with added glucose (P < 0.05) but did not differ from those in the nitrite treatment group (P > 0.05). The UV-vis spectra results showed that nitrosylmyoglobin (NO-Mb) was formed in the sausages with either S. vitulinus or nitrite added. In the S. vitulinus-inoculated sausages, sucrose addition led to a higher NO-Mb content than that after glucose addition, which was attributed to up-regulation of the nos gene. This study provides a potential method to enhance NO yield in S. vitulinus and colour formation in dry sausages without nitrite addition.