A simple and efficient alginate hydrogel combined with surface-enhanced Raman spectroscopy for quantitative analysis of sodium nitrite in meat products.

Sodium nitrite is a commonly used preservative and color protectant in the food industry. Conventional analytical methods are highly susceptible to food matrix interference, time-consuming and costly. In this study, the ion cross-linking method was employed to prepare alginate hydrogel substrates, and phenosafranin was chosen as a single-molecule probe to analyze sodium nitrite. Our investigation centered on elucidating the effects of alginate and cross-linking ion concentrations on Raman signal characteristics. The optimal Raman response was observed in the precursor solution with 1% sodium alginate and 0.1 mol L-1 cross-linking ions. The relative standard deviations (RSDs) of the feature peaks from the three substrate batches ranged from 1.22% to 16.30%, attesting the robustness and consistency of the substrates. The signal reduction of the substrates after a four-week storage period remained below 10%, indicating that the substrates had good reproducibility and stability. The limits of detection (LODs) for sodium nitrite in extracts from cured meat, luncheon meat, and sliced ham were determined to range from 3.75 mg kg-1 to 8.11 mg kg-1, with low interference from the food matrix. The support vector machine algorithm was utilized to train and predict the data, which proved to be more accurate (98.6%-99.8% recovery) than the traditional linear regression model (81.9%-112.7% recovery) in predicting the spiked samples. The application of hydrogel-based surface-enhanced Raman spectroscopy (SERS) substrates for nitrite detection in food, combined with machine learning for regression prediction in data processing, collectively augmented the potential of SERS technology in the field of food analysis.

Characterization of a novel aromatic ring-hydroxylating oxygenase, NarA2B2, from thermophilic Hydrogenibacillus sp. strain N12.

Polycyclic aromatic hydrocarbons (PAHs) are harmful to human health due to their carcinogenic, teratogenic, and mutagenic effects. A thermophilic Hydrogenibacillus sp. strain N12 capable of degrading a variety of PAHs and derivatives was previously isolated. In this study, an aromatic ring-hydroxylating oxygenase, NarA2B2, was identified from strain N12, with substrate specificity including naphthalene, phenanthrene, dibenzothiophene, fluorene, acenaphthene, carbazole, biphenyl, and pyrene. NarA2B2 was proposed to add one or two atoms of molecular oxygen to the substrate and catalyze biphenyl at C-2, 2 or C-3, 4 positions with different characteristics than before. The key catalytic amino acids, H222, H227, and D379, were identified as playing a pivotal role in the formation of the 2-his-1-carboxylate facial triad. Furthermore, we conducted molecular docking and molecular dynamics simulations, notably, D219 enhanced the stability of the iron center by forming two stable hydrogen bonds with H222, while the mutation of F216, T223, and H302 modulated the catalytic activity by altering the pocket's size and shape. Compared to the wild-type (WT) enzyme, the degradation ratios of acenaphthene by F216A, T223A, and H302A had an improvement of 23.08%, 26.87%, and 29.52%, the degradation ratios of naphthalene by T223A and H302A had an improvement of 51.30% and 65.17%, while the degradation ratio of biphenyl by V236A had an improvement of 77.94%. The purified NarA2B2 was oxygen-sensitive when it was incubated with L-ascorbic acid in an anaerobic environment, and its catalytic activity was restored in vitro. These results contribute to a better understanding of the molecular mechanism responsible for PAHs' degradation in thermophilic microorganisms.IMPORTANCE(i) A novel aromatic ring-hydroxylating oxygenase named NarA2B2, capable of degrading multiple polycyclic aromatic hydrocarbons and derivatives, was identified from the thermophilic microorganism Hydrogenibacillus sp. N12. (ii) The degradation characteristics of NarA2B2 were characterized by adding one or two atoms of molecular oxygen to the substrate. Unlike the previous study, NarA2B2 catalyzed biphenyl at C-2, 2 or C-3, 4 positions. (iii) Catalytic sites of NarA2B2 were conserved, and key amino acids F216, D219, H222, T223, H227, V236, F243, Y300, H302, W316, F369, and D379 played pivotal roles in catalysis, as confirmed by protein structure prediction, molecular docking, molecular dynamics simulations, and point mutation.

Modified paper-based substrates fabricated via electrostatic attraction of gold nanospheres for non-destructive detection of pesticides based on surface-enhanced Raman spectroscopy.

BACKGROUND: Flexible surface-enhanced Raman spectroscopy (SERS) substrates such as paper-based substrates show great potential for rapid detection of residual chemicals on food surfaces. However, controlling the density and distribution of metallic nanoparticles adsorbed on the paper is still challenging. RESULTS: The amount of gold (Au) nanospheres (51 ± 4 nm) attached on the filter paper modified with 3-aminopropyltriethoxysilane (APTES) was tunable, increasing as the level of APTES (2.5-15.0 g kg-1 ) applied for paper modification increased. Moreover, the Au nanospheres were relative evenly distributed on the filter paper modified with 2.5-10.0 g kg-1 of APTES, which resulted in excellent intra- and inter-reproducibility of SERS signals for pesticides including thiram, diquat dibromide, and paraquat dichloride (relative standard deviation = 2.2-10.1%). The modified paper-based substrate could be used to detect as low as 0.05-0.2 mg L-1 of pesticides in standard solutions, and as low as 5-20 ng cm-2 of residual pesticides on apple skins with minimum sample pretreatment. CONCLUSION: This paper-based substrate with tunable feature for the density and distribution of nanoparticles is applicable for rapid SERS detection of residual pesticides in fruits and vegetables. © 2023 Society of Chemical Industry.

A novel Diaphorobacter sp. strain isolated from saponification wastewater shows highly efficient phenanthrene degradation.

Polycyclic aromatic hydrocarbons (PAHs), such as phenanthrene, are a type of organic pollutants that exist widely in the environment. Of the currently known degradation methods, bioremediation is a desirable and feasible option. A novel Diaphorobacter sp. Strain MNS-0 was isolated from saponification wastewater and showed the ability to degrade phenanthrene, fluorene, acenaphthene, anthracene, benzo[a]anthracene, or chrysene using phenanthrene as the sole carbon source. Gas chromatography mass spectroscopy analysis of catabolic intermediates indicates that phenanthrene degradation occurs through the phthalic acid pathway in strain MNS-0. Genome sequencing shows that strain MNS-0 has two plasmids and one chromosome containing a presumptive phenanthrene degradation gene cluster. Strain MNS-0 was able to completely degrade 100 mg/L phenanthrene within 40 h and tolerate up to 10 g/L NaCl at pH 9.0, while maintaining phenanthrene degradation activity. We thus propose that strain MNS-0 is an effective degrader for bioremediation of PAHs pollution, even in relatively harsh alkali environments such as saponification wastewater.

Detection of thiram on fruit surfaces and in juices with minimum sample pretreatment via a bendable and reusable substrate for surface-enhanced Raman scattering.

BACKGROUND: Surface-enhanced Raman scattering (SERS) substrates based on metallic nanoparticles locked in some flexible materials have great potential for rapid detection of pesticide residues in foods, but these substrates are generally not reusable. RESULTS: A bendable and reusable sponge based on polydimethylsiloxane (PDMS) and Au nanospheres was synthesized and employed as SERS substrate to analyze thiram on the surfaces of apples and grapes (20-1000 ng cm-2 ) and in their juices (0.5-5.0 mg L-1 ) with minimum sample pretreatments. The lowest detectible concentrations for thiram in fruit juices and on fruit skins were 0.5 mg L-1 and 20 ng cm-2 , respectively. The Au-PDMS substrate had acceptable intra-reproducibility for SERS analysis of thiram in fruit juices and on fruit skins, resulting in 3.6-16.9% relative standard deviation (RSD) for the SERS signal of the primary peak of thiram. Moreover, the Au-PDMS substrate exhibited distinguished reusability and stability, which could provide a reproducible SERS signal of thiram in apple juice even after the substrate being reused ten times (RSDs for the three major characteristic peaks of thiram were 2.7-10.5% during the ten reused cycles). CONCLUSION: This flexible and reusable Au-PDMS SERS substrate for thiram detection could be readily extended to the analysis of other trace chemicals in a broad range of foods, providing a new possibility for SERS application. © 2022 Society of Chemical Industry.

Trace analysis of organic compounds in foods with surface-enhanced Raman spectroscopy: Methodology, progress, and challenges.

Surface-enhanced Raman spectroscopy (SERS) provides a potential solution for rapid analysis of trace compounds such as residual pesticides, naturally occurred toxicants, banned or restricted drugs, and food additives in complex food matrices. In this review, the basic principles of SERS and general approaches to successfully apply SERS in food analysis are covered from an applications perspective. The key steps including substrate selection and evaluation, sample preparation and simplification, spectral collection, and data analysis during the development of SERS methods for food analysis are summarized, together with the discussion of typical underlying technical barriers or major challenges of these methods and their applications. Future directions in successfully applying SERS technology as a routine analytical approach to solve real-world food problems are analyzed. This comprehensive review summarizes the recent progress on theory, application, and scope of SERS for food analysis, providing a basic understanding of the technology; more importantly, key methodology, potential pitfalls, and possible solutions during the development of rapid SERS methods based on authors' years of SERS experience are shared with researchers in the field.

Cotton fiber elongation requires the transcription factor GhMYB212 to regulate sucrose transportation into expanding fibers.

Cotton is white gold across the globe and composed of fiber cells derived from the outer integument of cotton ovules. Fiber elongation uses sucrose as a direct carbon source. The molecular mechanism transcriptionally controlling sucrose transport from ovules into the elongating fibers remains elusive. In this study the involvement of GhMYB212 in the regulation of sucrose transportion into expanding fibers was investigated. GhMYB212 RNAi plants (GhMYB212i) accumulated less sucrose and glucose in developing fibers, and had shorter fibers and a lower lint index. RNA-seq and protein-DNA binding assays revealed that GhMYB212 was closely linked to the pathways of sucrose and starch transportation and metabolism, directly controling the expression of a sucrose transporter gene GhSWEET12. GhSWEET12 RNAi plants (GhSWEET12i) possessed similar fiber phenotypes to those of GhMYB212i. Exogenous sucrose supplementation in ovule cultures did not rescue the shorter fiber phenotype of GhMYB212i and GhSWEET12i. This finding supported the idea that the attenuated rate of sucrose transport from the outer seed coat into the fibers is responsible for the retardation of fiber elongation. Current investigations support the idea that GhMYB212 functions as the main regulator of fiber elongation by controlling the expression of GhSWEET12, and therefore it is important to study cell expansion and sugar transportation during seed development.

MiR-137 inhibits cell proliferation in acute lymphoblastic leukemia by targeting JARID1B.

AIM: This study aimed to investigate the possible functions of interaction between JARID1B and miR-137 in ALL. METHODS: The levels of H3K4me3 and H3K4me2 and the expression of JARID1B and miR-137 were analyzed in six ALL cell lines and 30 ALL patients. The effects of miR-137 and JARID1B on cell proliferation and apoptosis were investigated by silencing or promoting the respective genes. The interaction between miR-137 and JARID1B was confirmed by double-luciferase report assay. RESULTS: The histone H3K4 expressions and miR-137 expression were lower in 30 ALL patients and in six ALL cell lines, while the expression of JARID1B was elevated. A negative correlation was observed between JARID1B and miR-137. Over-expression of miR-137 led to decreasing cell proliferation and increasing apoptosis in MOLT-4 and BALL-1 cells. MiR-137 inhibitor up-regulated JARID1B in these two cell lines, while promoted proliferation in BALL-1 cells only. Dual-luciferase report assay suggested that JARID1B was a direct target of miR-137 in ALL cell lines. CONCLUSIONS: The expression of miR-137 was declined in ALL, and JARID1B was directly repressed by miR-137. Aberrant JARID1B expression could result in abnormal histone methylation, which might be one cause of ALL.

Novel and rapid osteoporosis model established in zebrafish using high iron stress.

Osteoporosis is a global public health concern and, it can result from numerous pathogenic mechanisms, many of which are closely related with age, nutritional disorders, endocrine imbalance, or adverse drug side effects presented by glucocorticoids, heparin, and anti-epileptics. Given its wide range etiologies, it is crucial to establish an animal model of osteoporosis for use in screening potential drugs quickly and effectively. Previous research has reported that an accumulation of elevated iron in the body is an independent risk factor for osteoporosis. As such, we sought to use both zebrafish larvae and adults to model an osteoporosis phenotype using high iron stress (FAC, ferric ammonium citrate). Skeletal staining results suggested that iron-overload caused a significant decrease in bone calcification as well as severe developmental cartilage defects. In addition, osteoblast and cartilage-specific mRNA expression levels were downregulated after exposure to a high-iron environment. Most importantly, we demonstrated in both larval and adult fish that high iron-induced osteogenic defects were significantly rescued using alendronate (AL), a drug known to be effective against to human osteoporosis. Even more, the repair effect of AL was achieved by facilitating osteoblast differentiation and targeting Bmp signaling. Taken together, our findings propose an rapid and effective osteoporosis model, which could be used widely for future osteoporosis drug screening.

Rapid and sensitive surface-enhanced Raman spectroscopy (SERS) method combined with gold nanoparticles for determination of paraquat in apple juice.

BACKGROUND: Paraquat, a highly efficient herbicide, is widely used in agricultural practices throughout the world. However, paraquat residues in food pose a threat to human health. In order to develop a rapid and sensitive method, surface-enhanced Raman spectroscopy (SERS) coupled with gold nanoparticles was applied to analysis of paraquat in apple juice. RESULTS: Natural organic compounds (sugars and organic acids) in apple juice interfered with SERS measurement. Sample preparation was needed. Paraquat could be detected at concentrations as low as 0.02 and 0.1 µg mL- 1 with the weak cation-exchange solid-phase extraction (WCX-SPE) method and dilution method for sample preparation, respectively. For quantitative analysis, the R2 cv of the partial least-squares regression model with the dilution method (0.939) was not as good as with the WCX-SPE method (0.984), but the dilution method is much less costly, simpler and time saving. Satisfactory recovery values were obtained ranging from 94.73% to 114.81%, with the exception of 56.55% for the lowest concentration. CONCLUSION: This work showed that SERS combined with gold nanoparticles could determine paraquat in apple juice. As a simple, rapid and ultrasensitive method, it has great practical potential for detection of other contaminants in a variety of foods. © 2018 Society of Chemical Industry.

Specific Inhibition of ß-Catenin in Jeko-1 Mantle Cell Lymphoma Cell Line Decreases Proliferation and Induces Apoptosis.

BACKGROUND: The canonical Wnt signaling pathway has been considered as a potent oncogenic signaling in the initiation and progression of hematological malignancies. As a key regulator of the Wnt signaling pathway, the role of ß-catenin in mantle cell lymphoma (MCL) pathogenesis and progression was investigated in this study. MATERIAL AND METHODS: A total of 30 MCL samples were collected from patients and were examined for the expression of ß-catenin and p-GSK3ß using immunohistochemical (IHC) staining. Further in vitro studies employed MTT and Western blot assays detecting proliferation and apoptosis-related proteins in MCL cell line Jeko-1, which were transfected with ß-catenin shRNA or specific inhibitor XAV939. RESULTS: Expression of ß-catenin and phosphorylated glycogen synthase kinase-3 beta (p-GSK3ß) in MCL was significantly higher than those in controlled samples. In vitro studies indicated that ß-catenin knockdown significantly inhibited cell proliferation and induced apoptosis in Jeko-1 cells. Furthermore, XAV939 induced apoptosis and growth arrest in Jeko-1 cells. Both inhibitory agents increased Bax and caspase 3 proteins, and decreased Bcl-2, c-Myc, and Cyclin D1 proteins. CONCLUSIONS: The specific inhibition of ß-catenin induces apoptosis and growth arrest, making it a potential therapeutic target against MCL.

[Application of surface-enhanced Raman spectroscopy to the determination of trace chemical hazards in food products].

In the present review, we summarized the research progress in applying SERS for the determination of illegal food additives, residual pesticides, banned or restricted antibiotics and other drugs. The nanosubstrates used in these studies included, but were not limited to, gold and silver nanosphere colloids, solid surface gold coated nanosubstrates, bimetallic nanosubstrates and spherical magnetic-core gold-shell nanoparticles, and etc. Standard solutions of a targeted chemical were normally tested first before analysis of relevant food in which the targeted chemical was commonly detected, and the tested food products included dairy products, condiments (such as chili powder and spices), fish, fruits and vegetables. The intensity of surface-enhanced Raman scattering signal is affected by various factors, which makes it difficult to obtain reproducible spectra. In addition, interferences of non-targeted food components on the target molecules during SERS analyses further makes it difficult to apply SERS as a routine analytic technique, despite its high specificity and sensitivity. Nevertheless, SERS is a new tool with great potential for analysis of trace amounts of chemical hazards in various food products and other complex systems.

Meta-omics assisted microbial gene and strain resources mining in contaminant environment.

Human activities have led to the release of various environmental pollutants, triggering ecological challenges. In situ, microbial communities in these contaminated environments are usually assumed to possess the potential capacity of pollutant degradation. However, the majority of genes and microorganisms in these environments remain uncharacterized and uncultured. The advent of meta-omics provided culture-independent solutions for exploring the functional genes and microorganisms within complex microbial communities. In this review, we highlight the applications and methodologies of meta-omics in uncovering of genes and microbes from contaminated environments. These findings may assist in future bioremediation research.

Detailed glycan structural characterization by electronic excitation dissociation.

The structural complexity and diversity of glycans parallel their multilateral functions in living systems. To better understand the vital roles glycans play in biological processes, it is imperative to develop analytical tools that can provide detailed glycan structural information. This was conventionally achieved by multistage tandem mass spectrometry (MS(n)) analysis using collision-induced dissociation (CID) as the fragmentation method. However, the MS(n) approach lacks the sensitivity and throughput needed to analyze complex glycan mixtures from biological sources, often available in limited quantities. We define herein the critical parameters for a recently developed fragmentation technique, electronic excitation dissociation (EED), which can yield rich structurally informative fragment ions during liquid chromatographic (LC)-MS/MS analysis of glycans. We further demonstrate that permethylation, reducing end labeling and judicious selection of the metal charge carrier, can greatly facilitate spectral interpretation. With its high sensitivity, throughput, and compatibility with online chromatographic separation techniques, EED appears to hold great promise for large-scale glycomics studies.

[Effect of downregulation the expression of HDAC1 on cells differentiation of HL-60 cells].

This study is to investigate the effect of downregulation histone deacetylases 1 (HDAC1) gene by the technology of RNA interference on the differentiation of HL-60 cells line. The optimal segment targeting HDAC1 gene was designed and transfected into HL-60 cells by Lipofectamine 2000. The HDAC1 mRNA and protein level were detected by RT-PCR and Western blotting. The morphologic change of HL-60 cells was detected by an optical microscope with Wright-Giemsa. Cell differentiation was tested by NBT reduction assay. Expression of CD13, CD33 and CD14 was measured by flow cytometry. The results indicated that HDAC1 mRNA and protein were markedly suppressed by the siRNA targeting HDAC1 in a concentration-dependent manner. HDAC1 siRNA promoted cell differentiation. HL-60 cells became more mature in morphology after transfected to HDAC1 siRNA at a concentration of 30-60 nmol x L(-1) for 24 h. NBT reduction ability of HDAC1 siRNA with 30 nmol x L(-1) was 0.31 +/- 0.09, compared with negative control (0.20 +/- 0.02) (t = -3.1, P < 0.01), and with 60 nmol x L(-1) was 0.25 +/- 0.02 in comparison with negative control (0.21 +/- 0.04) (t = -2.12, P < 0.05). But it has no change in HDAC1 siRNA > or = 120 nmol x L(-1). After transfection with 60 nmol x L(-1) HDAC1 siRNA to HL-60 cells, the expression of CD13 was (96.50 +/- 0.70)% in compared to siRNA-NC (3.39 +/- 0.68) % (t = 164.9, P < 0.000 5), CD33 was (66.73 +/- 0.50) % in compared to siRNA-NC (96.80 +/- 1.70) % (t = 43.4, P < 0.000 5). CD14 was (0.53 +/- 0.00) % by comparison with siRNA-NC (0.49 +/- 0.02) % (t = -0.97, P > 0.1). HDAC1 siRNA promoted cell differentiation in indicated concentration. HDAC1 might be one of the targets of gene therapy for leukemia.

Experimental and Numerical Study of Concrete Fracture Behavior with Multiple Cracks Based on the Meso-Model.

In this paper, a series of experimental and numerical studies were carried out to investigate the effect of multiple cracks on concrete fracture behavior. Seven groups of double-crack concrete three-point bending (TPB) experiments with different crack lengths and different crack distances were carried out. The experimental results showed that the bearing capacity of double-crack specimens was slightly larger than the standard specimen with one central crack. Additionally, with an increase in the second crack length or with a crack distance reduction, the concrete's bearing capacity increased correspondingly. Based on the experiments, a numerical meso-model was developed based on applying cohesive elements. The aggregate, mortar, interface transition zone (ITZ), and potential fracture surfaces were explicitly considered in the model. In particular, cohesive elements were used to characterize the mechanical behavior of the ITZ and potential fracture surfaces. A modified constitutive concrete model was developed by considering the potential fracture surfaces' damage relation and friction effect. The accuracy of the developed meso-model was validated through a comparison between simulation and experiments. Based on meso-models, the influence of multiple cracks on the concrete bearing capacity was investigated by analyzing the energy evolution. The analysis results showed that the bearing capacity has a linear relation with the proportion of mode II energy consumption during the fracture process, which explains why specimens with multiple cracks have a slightly larger bearing capacity than the standard specimens. In summary, this study has found that in three-point bending fracture tests primarily characterized by mode I fractures, the presence of multiple cracks near the main crack slightly enhances the load-bearing capacity of the specimens. This is attributed to a slight increase in internal energy dissipation associated with the presence of these multiple cracks.

A highly sensitive surface-enhanced Raman scattering sensor with MIL-100(Fe)/Au composites for detection of malachite green in fish pond water.

Concerns about food safety have been arisen due to the improper use of chemicals in aquaculture. Malachite green (MG) has attracted attention because of its illegal usage and its potential negative impacts on the environment and public health. Surface-enhanced Raman scattering (SERS) platforms coupled with different SERS substrates have been employed for rapid analysis of MG residues in food. However, the most commonly used SERS substrates were non-reusable and showed limited detection sensitivity. In this study, a novel SERS substrate with a good recyclability and a high sensitivity was prepared by electrostatically assembling together a metal-organic framework material called materials of institute lavoisie-100(Fe) (MIL-100(Fe)) and Au NPs. The lowest detectable concentration of MG was 10-13 M based on the optimal substrate. The SERS sensor was applied for the detection of the trace MG in fish pond water, which was accomplished with the correlation coefficients R2 = 0.991-0.996 in a concentration range of 10-6-10-13 M. Moreover, MIL-100(Fe)/Au was recycled at least five times, realizing a "detection to degradation", showing great potential for food contamination monitoring due to its distinguished performance.

Rapid detection of thiabendazole residues in apple juice by surface-enhanced Raman scattering coupled with silver coated gold nanoparticles.

In recent years, the excessive use of pesticides has posed significant hazards to the ecological environment and human health in the pursuit of high crop yields. In this work, we developed a simple, sensitive, and eco-friendly approach for rapid detection of thiabendazole in apple juice using surface-enhanced Raman scattering (SERS) coupled with silver-coated gold nanoparticles (Au@Ag NPs). The developed Au@Ag NPs exhibited excellent sensitivity, allowing for the detection of thiabendazole in standard solutions at a minimum concentration of 50 ng/mL. Furthermore, two sample preparation methods were compared for detecting thiabendazole in apple juice. As the direct detection method for SERS analysis failed to detect thiabendazole at levels below the maximum residue limit based on the Chinese standard (3000 ng/mL), the effects of main matrix components in apple juice on the detection of thiabendazole were further investigated. The results revealed that both sugars and organic acids in apple juice interfered with the SERS measurement to varying degrees. Consequently, we optimized the QuEChERS method for sample preparation and achieved a higher sensitivity with a minimum detectable concentration of 250 ng/mL, a limit of detection of 0.06 mg/L and the recoveries of spiked samples were ranged from 80.2 % to 108.6 %. This study demonstrated the feasibility of proposed SERS method for pesticide residue analysis, addressing the need for food safety monitoring.

Application and Effect of Pediococcus pentosaceus and Lactiplantibacillus plantarum as Starter Cultures on Bacterial Communities and Volatile Flavor Compounds of Zhayu, a Chinese Traditional Fermented Fish Product.

Zhayu is a type of traditional fermented fish product in China that is made through the fermentation of salted fish with a mixture of cereals and spices. Inoculation fermentation was performed using Pediococcus pentosaceus P1, Lactiplantibacillus plantarum L1, and a mixture of two strains, which were isolated from cured fish in Hunan Province. Compared with the natural fermentation, inoculation with lactic acid bacteria (LAB) accelerated the degradation of myosin and actin in Zhayu, increased the trichloroacetic acid (TCA)-soluble peptide content by about 1.3-fold, reduced the colony counts of Enterobacteriaceae and Staphylococcus aureus by about 40%, and inhibited their lipid oxidation. In the texture profile analysis performed, higher levels of hardness and chewiness were observed in the inoculation groups. In this study, the bacterial community and volatile flavor compounds were detected through 16S high-throughput sequencing and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). Inoculation with L. plantarum L1 reduced around 75% abundance of Klebsiella compared with the natural fermentation group, which was positively correlated with 2,3-Butanediol, resulting in a less pungent alcohol odor in Zhayu products. The abundances of 2-pentylfuran and 2-butyl-3-methylpyrazine were increased over threefold in the L1 group, which may give Zhayu its unique flavor and aroma.

Formation of advanced glycation end-products in minced pork during frozen-then-chilled storage and subsequent heating.

The influences of frozen-then-chilled storage of minced pork on the formation of advanced glycation end-products (AGEs) including Nε-carboxymethyllysine and Nε-carboxyethyllysine, and their corresponding α-dicarbonyl precursors (α-DPs; glyoxal and methylglyoxal) during storage and subsequent heating were investigated in comparison with chilled storage. During cold storage, the levels of AGEs, trichloroacetic acid-soluble peptides, and Schiff bases in minced pork continuously increased while α-DPs decreased. The 30 min heating (100 °C) resulted in 64-560% increase of AGEs in pork, corresponding with an increase of Schiff bases and decreases of α-DPs. Compared to the chilled storage, the frozen-then-chilled storage led to no significant difference (P > 0.05) on the levels of AGEs and α-DPs in raw or heat-treated pork, implying that the formation and thawing of ice crystals in pork during the frozen-then-chilled storage had minor to no effects on the formation of AGEs and their α-DPs.