Effect of jujube pulp on acid- and rennet-induced coagulation properties of milk.

Milk coagulation is an important step in the production of fermented dairy products such as yogurt and cheese. Jujube is gaining popularity and acceptance as a food ingredient. In China, jujube yogurt is popular among consumers. However, there is limited information on the effect of jujube on acid- and rennet-induced coagulation properties of milk. The objective of this study was to evaluate the effects of jujube pulp at different concentrations on acid- and rennet-induced coagulation kinetics of milk and the microstructure of acid- and rennet-induced gels. During acid-induced coagulation, with increasing jujube pulp concentration, the initial pH value decreased; however, the final pH value increased. The initial elasticity index (EI) value increased, and the time point at which the mean square displacement curves lost the linear trend advanced. The sample with 10% jujube pulp had the densest structure and highest EI value. During rennet-induced coagulation, with increasing jujube pulp concentration, the production rate and amount of caseinomacropeptide decreased, and the final EI value increased. Protein aggregates in rennet-induced gels became rough, and the sample with 20% jujube pulp had the highest EI value. This study provides a new perspective and understanding of the application of jujube in fermented dairy products.

The Impact of Different Cooking Methods on the Flavor Profile of Fermented Chinese Spicy Cabbage.

Chinese spicy cabbage (CSC) is a common traditional fermented vegetable mainly made of Chinese cabbage. In addition to eating raw, boiling and stir-frying are the most common cooking methods for CSC. To identify the impacts of boiling or stir-frying on the quality of CSC, the physicochemical properties, flavor compounds, and sensory properties of CSC were analyzed. A total of 47 volatile flavor compounds (VFCs) were detected by gas chromatography-mass spectrometry. Sulfide was determined as the main flavor compound of CSC, mainly contributed by cabbage, garlic, and onion odors. The content of sulfide decreased significantly after cooking. Nonanal, geranyl acetate, and linalool were newly generated after boiling with odor activity value (OAV) > 1, and contributed fatty, sweet, fruity, and floral odors to BL-CSC. 1-Octen-3-one, 1-octen-3-ol, octanal, nonanal, and (E)-2-nonenal were newly generated after stir-frying with OAV > 1, and contributed mushroom, fatty, and green odors to SF-CSC. Diallyl trisulfide, nonanal, (E)-ß-ionone, ß-sesquiphellandrene, and (E)-2-decenal were considered as the potential key aroma compounds (KACs) to distinguish the CSCs after different heat treatment. After cooking, the total titratable acidity of CSC increased and the sensory properties changed significantly. This study provides valuable information and guidance on the sensory and flavor changes of thermal processing fermented vegetables.

Transcriptome co-expression network analysis identifies key genes and regulators of ripening kiwifruit ester biosynthesis.

BACKGROUND: Aroma is an important organoleptic quality for fruit and has a large influence on consumer preference. Kiwifruit esters undergo rapid and substantial changes contributing to the flavor during fruit ripening. Part of enzymes and their coding genes have been indicated potential candidates for flavor-related esters synthesis. However, there still exist obvious gaps in the biosynthetic pathways of esters and the mechanisms regulating ester biosynthesis in kiwifruit remain unknown. RESULTS: Using gas chromatography-mass spectrometry (GC-MS), volatile compounds of kiwifruit were quantified in response to ethylene (ETH, 100 µl/l, 24 h, 20 °C) and 1-methylcyclopropene (1-MCP, 1 µl/l, 24 h, 20 °C). The results indicated that esters showed the most substantial changes enhanced by ethylene and were inhibited by 1-MCP. Correlations between RNA-seq results and concentrations of esters, constructed using Weighted Gene Co-Expression Network Analysis (WGCNA) indicated that three structural genes (fatty acid desaturase, AdFAD1; aldehyde dehydrogenase, AdALDH2; alcohol acyltransferase, AdAT17) had similar expression patterns that paralled the changes in total ester content, and AdFAD1 transcripts exhibited the highest correlation. In order to search for potential regulators for ester biosynthesis, 14 previously reported ethylene-responsive transcription factors (TFs) were included in the correlation analysis with esters and their biosynthetic genes. Using dual-luciferase assay, the in vivo regulatory activities of TFs on ester biosynthetic gene promoters were investigated and the results indicated that AdNAC5 and AdDof4 (DNA binding with one finger) trans-activated and trans-suppressed the AdFAD1 promoter. CONCLUSIONS: The present study advanced the molecular basis of ripening-related ester biosynthesis in kiwifruit by identifying three biosynthetic related genes AdFAD1, AdALDH2 and AdAT17 by transcriptome analysis, and highlighted the function of two TFs by transactivation studies.

Recent progress in the preparation of bioactive peptides using simulated gastrointestinal digestion processes.

Bioactive peptides (BAPs) represent a unique class of peptides known for their extensive physiological functions and their role in enhancing human health. In recent decades, owing to their notable biological attributes such as antioxidant, antihypertensive, antidiabetic, and anti-inflammatory activities, BAPs have received considerable attention. Simulated gastrointestinal digestion (SGD) is a technique designed to mimic physiological conditions by adjusting factors such as digestive enzymes and their concentrations, pH levels, digestion duration, and salt content. Initially established for analyzing the gastrointestinal processing of foods or their constituents, SGD has recently become a preferred method for generating BAPs. The BAPs produced via SGD often exhibit superior biological activity and stability compared with those of BAPs prepared via other methods. This review offers a comprehensive examination of the recent advancements in BAP production from foods via SGD, addressing the challenges of the method and outlining prospective directions for further investigation.

Comprehensive analysis of key aroma compounds enhanced by Tamarix ramosissima Ledeb in mutton roasted by air-frying roast technology by means of SAFE-GC-O-MS and lipidomics.

Little information is known about the increased aroma compounds and possible mechanism in Tamarix ramosissima Ledeb roasted mutton (TRM). A comprehensive analysis of aroma compounds and lipids were firstly performed by lipidomics and sensomics approach. The results indicated that 9 out of 53 aroma compounds were considered as key odorants, including 5-methyl-2,3-diethylpyrazine. The roasted mutton contained highest levels of phosphatidylcholine (PC, 13.95%), triglyceride (TG, 13.50%), and phosphatidylethanolamine (PE, 12.25%). TG 18:0_18:0_18:1 and nine odorants were the potential biomarkers for discriminating differential samples due to variable importance in projection (VIP) > 1 and p < 0.05. PCs and TGs, including PC 21:0_13:1 and TG 16:0_18:1_18:1, might be predominantly responsible for the formation and retention of aroma compounds, respectively. This will clarify the enhanced effect of Tamarix ramosissima Ledeb on the presence of aroma compounds via lipid pathways in roasted mutton.

Formation and retention of aroma compounds in pigeons roasted by circulating non-fried roast technique by means of UHPLC-HRMS and GC-O-MS.

Lipids are key aroma contributors in meat products. However, the role of different lipids in the presence of aroma compounds in roasted pigeons has not been studied. The formation of aroma compounds and lipids during the circulating non-fried roasting of pigeons was investigated. The results presented that 18 aroma compounds, including 5-methy-2,3-diethylpyrazine, were identified as key aroma compounds. A total of 6324 lipids were classed into 47 categories, such as phosphatidylcholine (PC), phosphatidylethanolamine (PE), and triglyceride (TG). Nine lipids, containing PA(P-20:0/22:4(7Z,10Z,13Z,16Z)) and LPC 16:0-SN1, showed promise as potential biomarkers for discriminating differential pigeons using OPLS-DA. PC (13.76%), TG (13.58%), and their products were major lipids, among which TG 16:0 16:0 18:2, LPC 18:2-SN1, and PC 18:1_18:1 played a crucial role in the presence of aroma compounds. Interestingly, the linoleic acid, an important aroma contributor, was predominantly bonded to the sn-2 position of phospholipid and sn-3 position of neutral lipids.

Antifungal mechanism of phenyllactic acid against Mucor investigated through proteomic analysis.

The primary inhibitory targets of phenyllactic acid (PLA, including D-PLA and L-PLA) on Mucor were investigated using Mucor racemosus LD3.0026 isolated from naturally spoiled cherry, as an indicator fungi. The results demonstrated that the minimum inhibitory concentration (MIC) of PLA against Mucor was 12.5 mmol·L-1. Results showed that the growing cells at the tip of the Mucor were not visibly deformed, and there was no damage to the cell wall following PLA treatment; however, PLA damaged the cell membrane and internal structure. The results of isobaric tags for relative and absolute quantification (iTRAQ) indicated that the Mucor mitochondrial respiratory chain may be the target of PLA, potentially inhibiting the energy supply of Mucor. These results indicate that the antifungal mechanism of PLA against mold is independent of its molecular configuration. The growth of Mucor is suppressed by PLA, which destroys the organelle structure in the mycelium and inhibits energy metabolism.

Characterization of morphological and chemical changes using atomic force microscopy and metabolism assays: the relationship between surface wax and skin greasiness in apple fruit.

Introduction: Skin greasiness occurred on stored apples (Malus domestica Borkh.) is generally believed to result from changes in surface wax components. Previous reports have typically correlated wax changes with greasiness scores to reveal the contributing wax components. A notable limitation of this approach is that greasiness scores are highly subjective and influenced by individual perception. Methods: This study aimed to assess skin quality by quantitatively analyzing wax morphology changes in greasy 'Jonagold' apples using Atomic Force Microscopy (AFM) roughness parameters Ra, Rq, Rmax, and Rz, and to correlate these changes with wax composition. Results: AFM results revealed that wax crystals disappeared as skin greasiness increased, accompanied by significant declines in roughness parameters Ra, Rq, Rmax, and Rz, which decreased by 70% to 85%. Chemical analysis showed a significant increase in liquid esters, including linoleate and oleate esters, in the surface waxes, which negatively correlated with the decline in roughness parameters. Key genes related to ester production, such as MdFAD2, MdWSD1, and MdWBC11, exhibited increased expression and were also negatively correlated with decreases in Rq, Ra and Rz. Additionally, 1-Methylcyclopropene (1-MCP) treatment suppressed both the development of greasiness and the associated changes. Discussion: Our findings suggest that the increased liquid esters contribute to alternations in wax morphology in greasy apples, and that MdFAD2, MdWSD1, and MdWBC11, play crucial roles in ester biosynthesis. These results highlight the effectiveness of AFM roughness parameters Ra, Rq, Rmax, and Rz in quantifying wax morphology changes in apples during skin greasiness development.

Unraveling the formation mechanism of aroma compounds in pork during air frying using UHPLC-HRMS and Orbitrap Exploris GC-MS.

Lipids are the key matrix for the presence of odorants in meat products. The formation mechanism of odorants of air-fried (AF) pork at 230 °C was elucidated from the perspectives of lipids and heat transfer using physicochemical analyses and multidimensional statistics. Twenty-nine key aroma compounds were identified, with pyrazines predominantly contributing to the roasty aroma of air-fried roasted pork. Untargeted lipidomics revealed 1184 lipids in pork during roasting, with phosphatidylcholine (PC), phosphatidylethanolamine (PE), and triglyceride (TG) being the major lipids accounting for about 60 % of the total lipids. TG with C18 acyl groups, such as TG 16:1_18:1_18:2 and TG 18:0_18:0_20:3, were particularly significant in forming the aroma of AF pork. The OPLS-DA model identified seven potential biomarkers that differentiate five roasting times, including PC 16:0_18:3 and 2-ethyl-3,5-dimethylpyrazine. Notably, a lower specific heat capacity and water activity accelerated heat transfer, promoting the formation and retention of odorants in AF pork.

Feasibility of Tenebrio molitor larvae protein to partially replace lean meat in the processing of hybrid frankfurters: Perspectives on quality profiles and in vitro digestibility.

The aim of this study was to investigate the effect of replacing different amounts (5 %, 10 %, 15 %, 20 % and 25 %) of lean meat with Tenebrio molitor larvae protein (TMLP) on the quality profiles of hybrid frankfurters. The results showed that there were no obvious differences in moisture, protein or fat content of all the hybrid frankfurters (P > 0.05), only a higher substitution rate (from 10 % to 25 %) resulted in a higher ash content than the control group (P < 0.05). With the increasing replacement rate (5 %, 10 % and 15 %), the cooking loss of the hybrid frankfurters showed the similar effects as the control group (P > 0.05), whereas the higher replacement rates of 20 % and 25 % obviously decreased the emulsion stability of the hybrid frankfurters. Moreover, with lower substitution rate (5 %, 10 % and 15 %) there were no significant differences in cooking loss between the hybrid frankfurters and the control group (P > 0.05), whereas the higher substitution rates (20 % and 25 %) obviously increased the cooking loss of the hybrid frankfurters (P < 0.05). Meanwhile, as the level of substitution increased, the hybrid frankfurters had higher digestibility, poorer texture than the standard frankfurters, as well as the rheological behaviour of hybrid meat batters (P < 0.05). The results showed that a moderate level (15 %) of TMLP was used to replace lean pork could be potentially and successfully be used to produce hybrid frankfurters.

Predictive model for growth of Pseudomonas spp. on fresh duck breast as a function of temperature.

This study was performed to develop a predictive growth model of Pseudomonas spp. to ensure the safety of fresh duck breast. Sterile fresh duck breasts were inoculated with Pseudomonas spp. and stored at 4°C, 10°C, 15°C, 20°C, 25°C, and 30°C to measure the microbial change. The Baranyi primary model was used to simulate the growth changes of Pseudomonas spp. at different temperatures. The square root type model and hyperbolic function as secondary models were used to model the effect of temperature on the maximum specific growth rate and lag phase duration. The results showed that the primary models fitted the growth data well (all R2 > 0.900 and RMSE were close to 0). In validation study of secondary model, R2 were 0.987 and 0.925, RMSE were 0.017 and 1.825, respectively, indicating that the parameters of primary models were accurately predicted by secondary models. The validation experiments at tested temperatures proved that the changes of Pseudomonas spp. could be predicted accurately by the developed models combining primary and secondary models both at constant and variable temperatures. The model could be applied to predict the growth of Pseudomonas spp. in logistics for avoiding microbial spoilage on fresh duck breast.

Comprehensive binding analysis of glycated myosin with furan derivatives via glucose by means of multi-spectroscopy techniques and molecular docking simulation.

Myosin is an ideal binding receptor for aroma compounds and its functional properties are easily affected by glucose. The study comprehensively clarified the effects of glucose glycation-induced structural modifications of myosin on its binding ability with furan derivatives, including 2-methylfuran, 2-furfural, and 2-furfurylthiol. The results demonstrated that the binding levels of furan derivatives were obviously affected by the glycation levels of myosin due to the changes of myosin structure and surface. The increased glycation levels caused the unfolding of myosin structure and accelerated the aggregation, as were exhibited by the data of zeta potential, particle size, microstructure, and secondary structure. The glycated myosin with wrinkled surfaces favored the significant increase of hydrophobic interactions (31.59-69.50 µg), the more exposure of amino acid residues (3459-6048), the formation of free sulfhydryl groups (16.37-20.58 mmol/104g) and hydrogen bonds. These key (non)covalent linkages accounted for the generation of glycated myosin-odorants complex, including 2-furfurylthiol (29.17-47.87 %), thus enhancing the resultant binding ability as evidenced by the free furan derivatives concentrations, fluorescence quenching and molecular docking simulation analysis. The glycated myosin for 8 h bound highest concentrations of furan derivatives. The results will provide comprehensive data on the retention of aroma compounds in meat products.

Understanding the role of lipids in aroma formation of circulating non-fried roasted chicken using UHPLC-HRMS-based lipidomics and heat transfer analysis.

The role of lipids in aroma formation of circulating non-fried roasted (CNR) chicken with different roasting times was studied using ultra-high performance liquid chromatography high-resolution mass spectrometry (UHPLC-HRMS)-based lipidomics and heat transfer analysis. Thirteen odorants were confirmed as important aroma compounds of CNR chicken, including dimethyl trisulfide, 3,5-dimethyl-2-ethylpyrazine, nonanal, and 1-octen-3-ol. A comprehensive lipidomics analysis identified 1254 lipids in roasted chickens, classified into 23 distinct lipid categories that included 281 phosphatidylcholines (PC), 223 phosphatidylethanolamines (PE), and 202 triglycerides (TG). Using OPLS-DA analysis, the lipid PG (18:1_18:1) showed promise as a potential biomarker for distinguishing between chickens subjected to CNR treatments with varying roasting times. The lipids PC, PE, and their derivatives are likely to play a crucial role in the formation of aroma compounds. In addition, TGs that contributed to the retention of key odorants in roasted chicken included TG (16:0_16:0_18:1), TG (16:0_16:0_18:0), and TG (16:0_18:1_18:1). Findings further showed that lower water activity and specific heat capacity promoted the formation and retention of aroma compounds during the CNR process. This study contributed to a better understanding of the formation of aroma compounds through lipid oxidation in roasted chicken.

The effect of thermal times of circulating non-fried roast technique on the formation of (non)volatile compounds in roasted mutton by multi-chromatography techniques and heat transfer analysis.

The circulating non-fried roast (CNR) technology was firstly applied to roast mutton. The formation of (non)volatile compounds in the mutton roasted for 0-15 min was investigated. The samples roasted at varying times were discriminated using GC-O-MS and multivariate data analysis. A total of 40 volatile compounds were observed, in which 17 compounds were considered as key odorants with odor activity values (OAVs) higher than 1, such as dimethyl trisulfide and 2-ethyl-3,5-dimethylpyrazine. Composition and concentrations of volatile compounds were significantly changed during the process. The key nonvolatile compounds that contributed to flavor were 5'-inosine monophosphate (5'-IMP) and glutamic acid based on taste active values (TAVs) greater than 1. The reduced concentrations of most free amino acids and 5'-nucleotides decreased the equivalent umami concentrations (EUC). The higher thermal conductivity, lower thermal diffusivity and water activity were responsible for the formation of volatile compounds with increased roasting times. The CNR technology was an efficient tool to roast meat products.

Effect of Levilactobacillus brevis as a starter on the flavor quality of radish paocai.

The aim of this study was to investigate the effectiveness of Levilactobacillus brevis on the fermentation kinetics and flavor quality of radish paocai. Compared with spontaneous fermentation (SF), the radish paocai of inoculated fermentation (IF) using Levilactobacillus brevis PL6-1 as a starter could rapidly utilize sugar to produce acid, thus accelerating the fermentation process. The texture including hardness, chewiness, and springiness of the IF were all higher than that of the SF, and the IF paocai showed higher L value in color. L. brevis PL6-1 as a starter could increase the final levels of metabolites of mannitol (5.43 mg/g), lactic acid (543.44 mg/100 g) and acetic acid (87.79 mg/100 g). Fifteen volatile organic compounds (VOCs) were identified as key aroma-active compounds in radish paocai and 8 differential VOCs were considered as the potential markers. L. brevis PL6-1 could improve the levels of 1,8-cineole, 1-hexanol, hexanoic acid, 2-methoxy-4-vinylphenol, and eugenol, giving the radish paocai floral, sweet, and sour aroma, and reduce the unpleasant odor of garlic, onion, and pungent, contributed by erucin, diallyl disulfide, and allyl trisulfide. Sensory evaluation results showed that the appearance, taste, texture, and overall acceptability of IF paocai were all better than the SF group. Therefore, L. brevis PL6-1 could be a potential starter to improve the flavor and sensory quality for radish paocai fermentation.

Characterization of key aroma compounds in Chinese smoked duck by SAFE-GC-O-MS and aroma-recombination experiments.

Smoked duck is a popular meat product in China. The aroma profile and key aroma compounds in smoked ducks were elucidated using solvent-assisted flavor evaporation-gas chromatography-olfactometry-mass spectrometry (SAFE-GC-O-MS), odor activity values (OAVs), aroma recombination and omission experiments, and sensory evaluation. The results indicated that the predominant aroma profiles of rice-, tea oil- and sugarcane-smoked ducks all contained strong smoky, roasty, fatty, meaty, and grassy aromas. A total of 31 aroma compounds were identified as important odorants by OAVs, including 8 aldehydes, 6 pyrazines, 5 phenols, and 2 sulfur compounds. The aroma recombination and omission experiments confirmed that 13 odorants were key aroma compounds in smoked ducks. Of these odorants, 2-methoxyphenol, 4-methylphenol, 5-ethyl-2,3-dimethylpyrazine, methional, 2-methyl-3-furanthiol, (E, E)-2,4-decadienal, 1-octen-3-ol, and anethole significantly contributed to the aroma profile of smoked duck flavor (p < 0.01).

Effects of postharvest coating using chitosan combined with natamycin on physicochemical and microbial properties of sweet cherry during cold storage.

Sweet cherry is prone to senesce and decay due to high postharvest respiration rate and fungal infection. The effects of natamycin-chitosan coating on physicochemical and microbial properties of sweet cherries stored at 4 °C were investigated. Scanning electron microscopy results revealed that natamycin was more uniformly distributed on sweet cherry pericarps with the help of chitosan coating. Respiration rate of sweet cherries was suppressed by chitosan coating during the storage and as a result, total soluble solids (13.53 %-13.80 %) and titratable acidity (0.91 %-0.93 %) were remained higher values and weight loss (2.54 %-2.85 %) was decreased in chitosan and natamycin-chitosan groups. Although both natamycin and chitosan were effective in inhibiting yeast and mold, sweet cherries treated with the combination of natamycin and chitosan showed significantly lower yeast and mold count (3.31 log CFU/g) and decay rate (1.67 %) compared with control. Natamycin combined chitosan inhibited the pathogenic fungi of sweet cherries, such as Alternaria, Cladosporium and Penicillium. These results indicated that postharvest natamycin-chitosan coating has great advantages in maintaining fruit quality, inhibiting fungi, and reducing decay rate of sweet cherry.

Metabolome and Transcriptome Analyses of Anthocyanin Accumulation Mechanisms Reveal Metabolite Variations and Key Candidate Genes Involved in the Pigmentation of Prunus tomentosa Thunb. Cherry Fruit.

Prunus tomentosa Thunb. has excellent nutritional, economic, and ornamental values with different fruit color. The red coloration of fruit is determined by anthocyanin pigmentation, which is an attractive trait for consumers. However, the mechanisms underlying fruit color formation in the P. tomentosa cherry are not well understood. In this research, the pigmentation patterns in red-color P. tomentosa (RP) fruit and white-color P. tomentosa (WP) were evaluated. Anthocyanin content in matured RP fruit was significantly abundant compared with WP fruit. Metabolomic profiling revealed that pelargonidin 3-O-glucoside, cyanidin 3-O-rutinoside, and pelargonidin 3-O-rutinoside were the predominant anthocyanin compounds in the RP fruit, while, WP fruit had less anthocyanin compositions and lower level. Then, integrative analyses of transcriptome and metabolome identified 285 significant differentially expressed genes (DEGs) closely related to anthocyanin differentially expressed metabolites (DEMs). Among them, nine genes were involved in anthocyanin biosynthesis, transport and degradation pathway, including four biosynthesis genes (PtPAL1, PtDFR, PtANS, and PtUFGT), two transport genes (PtGST11, PtABC10), and three degradation genes (PtPOD1, PtPOD16, PtPOD73). Transcriptome data and real-time PCR showed that the transcript levels of biosynthesis and transport genes were significantly higher in RP than in WP, especially PtANS, PtUFGT, and PtGST11, suggesting they may play key roles in red-colored fruit formation. Meanwhile, the degradation-related genes PtPOD1/16/73 took on exactly opposite trend, suggesting their potential effects on anthocyanin degradation. These results provide novel insights into color patterns formation mechanisms of cherries fruit, and the candidate key genes identified in anthocyanin biosynthesis, transport and degradation may provide a valuable resource for cherry breeding research in future.

Integrative analyses of metabolome and transcriptome reveals metabolomic variations and candidate genes involved in sweet cherry (Prunus avium L.) fruit quality during development and ripening.

Sweet cherry (Prunus avium L.), one of the most appreciated and most important commercial temperate fruits, has high sensory quality and nutritional value. Investigating its metabolic variations provides valuable information on the formation of fruit quality. In this study, widely targeted LC-MS/MS based metabolomics was used to identify and quantify metabolic changes during 'Black Pearl' sweet cherry development and ripening. A total of 263 significant differentially expressed metabolites (DEMs) were detected during the four fruit-development stages. Significant differences were observed in the composition and content of compounds in the four stages of cherry development, especially sugars, organic acids, and flavonoids. Moreover, transcriptome analysis provided a molecular basis for metabolic variations during fruit development. A total of 6724 significant differentially expressed genes (DEGs) were identified. Further correlation analysis of major DEMs and DEGs showed that 19 key DEGs were involved in sugar metabolism, 23 key DEGs in organic acid metabolism, and 13 key DEGs in flavonoid metabolism. The upregulated genes involved in the flavonoid pathway probably play an important role in regulating the rapid increase of anthocyanin content during fruit development. These comprehensive analysis data provide a better understanding to improve fruit quality traits based on molecular and metabolic levels.

Mode of action of plantaricin MG, a bacteriocin active against Salmonella typhimurium.

Plantaricin MG is a 2,180-Da bacteriocin produced by Lactobacillus plantarum KLDS1.0391, which was isolated from Chinese traditional fermented cream. Plantaricin MG showed a broad inhibitory activity against not only Gram-positive bacteria but also Gram-negative bacteria including Listeria monocytogenes and Salmonella typhimurium. The mode of action of plantaricin MG on S. typhimurium was reported in this article. The addition of plantaricin MG to energized cells of S. typhimurium dissipated both, the transmembrane potential (Δψ) and the pH gradient (ΔpH). Energized membrane, obtained after the addition of glucose, was more susceptible to plantaricin MG action, leading to the release of intracellular K(+)ions, inorganic phosphate, ATP and UV-absorbing materials. These data suggest that the presence of a proton motive force promotes the interaction of plantaricin MG with the cytoplasmic membrane of energized cells, leading to pores formation which allows the efflux of ions, thereby ensuring efficient killing of target bacteria.