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

Colour formation by bacterial nitric oxide synthase in fermented sausages inoculated with and without Mammaliicoccus vitulinus

In the present study, a Bacillus subtilis expression system was used to overexpress the gene of nitric oxide synthase (NOS), and the NOS was subsequently purified and added to fermented sausages to assess its colouration ability. The results indicated that NOS activity in the nos-recombinant strain was approximately 58-fold higher than that in the wild-type strain (P < 0.05). In a meat model system supplemented with metmyoglobin, the addition of NOS alone exhibited a significant effect on colour formation (P < 0.05), whereas inoculation with Mammaliicoccus vitulinus enhanced the red colour (P < 0.05). The results of the ultraviolet-visible (UV-vis) spectral analysis showed that more nitrosyl myoglobin (NO-Mb) was formed in the model system. In fermented sausages, the addition of NOS together with the inoculation of M. vitulinus led to a significant increase in the concentration of NO-Mb and the redness value (P < 0.05). The present study offers a potential solution for enhancing the colour formation in fermented sausages using an enzymatic method.

Enzymatic colouring for meat without nitrite: Exploration of bacterial nitric oxide synthase fused with YkuN-YumC

This study developed an innovative strategy for colouring meat products without nitrite addition, using nitric oxide synthase (NOS) fused with flavodoxin YkuN and flavodoxin reductase YumC derived from Bacillus subtilis. The results showed that the plasmids containing nos linked with ykuN and yumC genes by rigid linkers were constructed and chemically transformed into B. subtilis 168, and the enzyme fused with YkuN and YumC (NOS-YkuN-YumC) was successfully expressed and then purified. The activity of the fusion enzyme was approximately 12 times greater than that of NOS. In a model system, NOS-YkuN-YumC significantly increased the a*-value (redness) compared to those of the control and the sample treated with NOS (P < 0.05). UV-Vis spectral analysis indicated that metmyoglobin was converted to nitrosylmyoglobin (NO-Mb). In minced meat, the addition of NOS-YkuN-YumC significantly promoted the formation of NO-Mb and enhanced the a*-value (P < 0.05). The colour of the minced meat did not differ significantly between the NOS-YkuN-YumC group and the nitrite group (P > 0.05). This study provides a promising solution for enhancing colour formation in meat products without nitrite.

Decoding the aroma landscape of fermented golden pompano: The interplay of ester compounds and symbiotic microbiota as revealed by metagenomics and two-dimensional flavoromics

Fermented pompano (Trachinotus ovatus) is a traditionally popular fermented seafood throughout Asia. Its distinctive flavor profile is primarily attributed to the microbial metabolic conversion of nutrients, which produces specific volatile compounds. Two-dimensional flavoromics of mature pompano revealed that various volatile flavor compounds accumulate throughout fermentation, with fruity (predominantly esters) and oleogustus (primarily ketones) being key flavor markers. S-curve analysis further demonstrated synergistic and additive interactions between these compounds, which enhance flavor release. Metagenomics and Kyoto Encyclopedia of Genes and Genome analysis revealed that amino acid metabolism was the pivotal pathway for ethyl ester synthesis, with Staphylococcus equorum being positively correlated with esters such as ethyl isobutyrate and ethyl enanthate. This study elucidated the interrelationship between flavor compounds and the microbial community in fermented pompano, which is expected to provide insights into flavor modulation and guide the selection of strains that produce key esters in fermented seafood products.

Enhancement of colour formation of fermented sausages by overexpression of nitric oxide synthase in Staphylococcus vitulinus under hydrogen peroxide stress

This study used hydrogen peroxide (H2O2) treatment to overexpress the gene of nitric oxide synthase (nos) in Staphylococcus vitulinus, which was then inoculated into fermented sausages to observe its effect on colour development. The results showed that a low concentration of H2O2 (50 mM) could up-regulate the expression of nos by increasing the oxidative stress level of S. vitulinus. At 2 h after treatment, the expression of nos in S. vitulinus was the highest (P < 0.05), and the relative enzyme activity was increased to about 1.5 times that of the untreated. The growth of S. vitulinus was not substantially affected by 50-mM H2O2 treatment (P > 0.05). When H2O2-treated S. vitulinus was inoculated into fermented sausages, the content of nitrosomyoglobin was increased, and the a*-value (indicating redness) was not significantly different from that in the group treated with nitrite (P > 0.05). This study provides a potential method to enhance the ability of S. vitulinus for colourising fermented sausage by inducing the overexpression of nos.

Study on simulation effect of physical and chemical characteristics of sausage by sausage model system

Introduction

The incorporation of Staphylococcus xylosus in sausage production is hypothesized to affect various physicochemical properties and flavor profiles of sausages. This study aimed to evaluate the simulation of these features in a sausage model and establish its applicability for in vitro studies.

Methods

Both a control and an experimental model, inclusive of Staphylococcus xylosus, were assessed for changes in physicochemical indexes (pH and water activity, Aw) and the concentration of flavoring components (esters and aldehydes). Thiobarbituric acid reactive substances (TBARS) values were also measured to evaluate lipid oxidation.

Results

The introduction of Staphylococcus xylosus resulted in no significant changes in pH and Aw between the sausage and the model. However, there was a considerable increase in the content of volatile flavor compounds, specifically esters and aldehydes, in the experimental groups compared to the control. Additionally, the TBARS values in experimental groups were significantly lower than those in the control group at the end of the testing period.

Discussion

The findings indicate that Staphylococcus xylosus plays a critical role in enhancing the flavor profile of sausages through the increased synthesis of volatile compounds and inhibiting fat oxidation. The sausage model effectively simulated the physicochemical and flavor index responses, demonstrating its potential utility for further in vitro research on sausage fermentation and preservation techniques.

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.

A Comprehensive Review of Cured Meat Products in the Irish Market: Opportunities for Reformulation and Processing

Cured meat products constitute one of the meat categories commonly consumed in Ireland and has been part of the Irish cuisine and diet for many years. Ham, gammon, and bacon are some of the products that involve curing as part of the traditional processing methods. Common among these products are high levels of salt and the addition of nitrites. These products undergo processing treatments to create variety, preserve shelf-life, and develop their unique quality and safety characteristics. However, consumers are becoming more conscious of the level of processing involved in these products, and the effects of some components and ingredients might be perceived as unhealthy. Meat product developers have been exploring ways to reduce the amount of ingredients such as salt, saturated fat, and chemical preservatives (e.g., nitrites), which are linked to health concerns. This is a challenging task as these ingredients play an important techno-functional role in the products' quality, safety, and identity. While innovative processing techniques are being introduced and progress has been made in reformulation and packaging technologies, much is still unknown, especially regarding the applicability of many of the proposed interventions to a wide range of meat products and their sustainability at the industrial scale.

The Contribution of Microorganisms to the Quality and Flavor Formation of Chinese Traditional Fermented Meat and Fish Products

Guizhou sour meat and sour fish, Chaoshan fish sauce, Sichuan sausage and bacon, Cantonese sausage, Jinhua ham, and Xinjiang air-dried beef are eight representatives of Chinese traditional fermented meat and fish products (FMFPs), which are favored by Chinese consumers due to their high nutritional value and quality. The quality of the spontaneously fermented Chinese traditional FMFP is closely correlated with microorganisms. Moreover, the dominant microorganisms are significantly different due to regional differences. The effects of microorganisms on the texture, color, flavor, nutrition, functional properties, and safety of Chinese traditional FMFPs have not been not fully described. Additionally, metabolic pathways for flavor formation of Chinese traditional FMFPs have not well been summarized. This article describes the seven characteristic Chinese traditional FMFPs and correlated dominant microorganisms in different regions of China. The effects of microorganisms on the texture, color, and flavor of Chinese traditional FMFPs are discussed. Furthermore, the metabolic pathways of microbial regulation of flavor formation in Chinese traditional FMFPs are proposed. This work provides a theoretical basis for improvement of Chinese traditional FMFPs by inoculating functional microorganisms isolated from Chinese traditional fermented foods.

The mechanism of Leuconostoc mesenteroides subsp. IMAU:80679 in improving meat color: Myoglobin oxidation inhibition and myoglobin derivatives formation based on multi enzyme-like activities

The Leuconostoc mesenteroides subsp. IMAU:80679 (LM) was chosen for its superior capability in enhancing redness, and was incubated in a broth system containing metmyoglobin (MetMb) to investigate its mechanisms for color improvement. The a* value of LM group reached its highest level of 52.75 ± 1.04 at 24 h, significantly higher than control of 19.75 ± 0.6 (p < 0.05). The addition of LM could inhibit myoglobin oxidation to some extent. Meanwhile, higher content of nitrosylmyoglobin (NOMb) and Zn-protoporphyrin (Znpp) were observed in LM samples during the whole incubation period. Furthermore, enzymatic activity and encoded genes related to MetMb reduction and pigment formation were determined to explain its possible mechanism on color enhancement. Finally, by extracting crude enzymes and adding them to meat batters, the redness of crude enzyme group was comparable to that achieved with 20 ppm nitrite, providing a potential method on compensating for nitrite/nitrate substitution in meat products.

Effects of sorbitol-mediated curing on the physicochemical properties and bacterial community composition of loin ham during fermentation and ripening stages

In this study, the impacts of loin ham with sorbitol-mediated curing on its physicochemical properties and bacterial community composition during fermentation and ripening were investigated. The salt content, pH, and water activity (a_w) were lower in the sorbitol group than in the control group throughout the fermentation and ripening stages (P < 0.05). In addition, the L* values were higher in the sorbitol group (P < 0.05). Additionally, microbial diversity diminished in all groups as the fermentation and ripening process proceeded, with Lactobacillus turning into the dominant genus in the control group and Staphylococcus and Lactobacillus becoming dominant in the sorbitol group. Pearson's correlation analysis confirmed that the physicochemical properties have been significantly correlated with the bacterial community. In conclusion, sorbitol-mediated curing not only facilitates salt reduction while prolonging the storage period of loin ham, but also improves the distribution of bacterial community in loin ham and enhances its quality.

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.

Nitrite-Free Implications on Consumer Acceptance and the Behavior of Pathogens in Cured Pork Loins

Cured pork loins are valued products due to their particular sensory characteristics. These products are usually prepared with nitrite to guarantee adequate color and pathogen control. The use of nitrite in meat products has been criticized due to its potential contribution to carcinogenic N-nitroso-compound formation. The present work aimed to evaluate the effect of eliminating nitrite from the manufacturing of cured loins made with wine- and water-based marinades on the color evaluation of consumers and on the behavior of Clostridium sporogenes, Listeria monocytogenes, and Salmonella. The use of nitrite in processing cured loins resulted in a color considered adequate by more than 50% of the consumers. When nitrite was not used, the color was described mainly as weak. The hedonic evaluation of cured loins did not reflect the color evaluation. The samples with a weak and an adequate color had similar hedonic evaluations. The present work did not allow us to infer the potential interest in injecting S. xylosus into meat to prepare cured loins. The use of nitrite did not affect the survival of Cl. sporogenes, L. monocytogenes, or Salmonella. The reduction in the aw was the primary determinant influencing pathogen survival. The production of nitrite-free cured loins seems possible once the control of pathogens can be achieved. However, the product will have a weaker color. Consumers appreciate sensory aspects other than color, which, combined with the positive impact of the “additive-free” claim, can support the possibility of producing cured loins without nitrite.

Isolation of Antibacterial, Nitrosylmyoglobin Forming Lactic Acid Bacteria and Their Potential Use in Meat Processing

The use of nitrite as a colorant and preservative in meat processing is associated with health risks. This study aimed to isolate nitrite-substituting lactic acid bacteria for use as natural biological colorants and preservatives. Among the 106 strains isolated from fermented foods, two strains with excellent ability to convert myoglobin and metmyoglobin (Met-Mb) to red nitrosylmyoglobin (Mb-NO) were selected. The superior ability to form Mb-NO was confirmed through UV-visible spectrophotometry, Fourier transform infrared spectrometry, electron spin resonance analysis, nitric oxide synthase activity assay, and Met-Mb reductase activity assay. The potent antibacterial activity was confirmed through biofilm and cytomembrane breakage of the indicator bacteria. Though performing 16S rDNA sequencing, they were identified as two different strains of Lactobacillus plantarum. Based on their favorable characteristics, their applications in the meat industry were further evaluated. This study identified a novel dual-function natural biological colorant and preservative to substitute nitrite in meat products. The application of the two strains would decrease the hazardous of nitrite to health.

Nitrosylmyoglobin formation in meat by Lactobacillus fermentum AS1.1880 is due to its nitric oxide synthase activity

The objective of this study was to clarify whether formation of nitrosylmyoglobin (MbFe^IINO) by Lactobacillus fermentum AS1.1880 in meat is due to nitric oxide synthase (NOS) activity. Confocal laser scanning microscopy exhibited strong green fluorescence in the L. fermentum sample treated with a nitric oxide (NO)-specific probe, directly indicating that NO was produced. Furthermore, determination of NOS activity based on the presence of NO metabolites indicated the existence of NOS in L.fermentum. A NOS inhibitor, N^G-nitro-L-arginine methyl ester, significantly inhibited the activity of NOS in L.fermentum (P < 0.05). Futhermore, NOS protein was detected in L.fermentum by Western blot analysis. L-arginine addition largely increased the NOS activity of L.fermentum (P < 0.05). In meat batters, the redness of a sample inoculated with L.fermentum was higher than that of the control and colour was significantly improved with the addition of L-arginine (P < 0.05), indicating that more MbFe^IINO was formed.