Search

The mechanism of action of plantaricin against Escherichia coli and its potential application in dairy products remain unclear. In this study, the antibacterial activity and mechanism of action of plantaricin LP21-2 against the E. coli strain ATCC25922 were investigated. The results showed that crude plantaricin LP21-2 inhibited the growth of E. coli _22 as well as inhibited and degraded the biofilm formation in E. coli _22. The mechanism of action of plantaricin LP21-2 against E. coli _22 cells involves the reduction of cell viability and metabolic activity, triggering the leakage of intracellular substances (e.g., DNA, proteins, and ATP) and inducing oxidative stress damage and morphological deformation. Moreover, plantaricin LP21-2 exhibited no hemolytic activity and negligible toxicity in mammalian Caco-2 cells, indicating good biosafety. When yak milk was used as a food model, E. coli _22 viable counts (6.19 ± 0.03 log CFU/ml) were effectively reduced by 0.23, 0.6 and 1.94 log CFU/ml, with the use of crude plantaricin LP21-2 at 1/2, 1 × , and 2 × MIC, respectively, after 12 days of storage at 4 °C. Notably, the addition of crude plantaricin LP21-2 also maintained the nutrient composition, antioxidant parameters, and sensory properties of yak milk. Overall, these findings provide novel insights into plantaricin LP21-2 against E. coli and highlight its promising application in dairy foods. • Plantaricin LP21-2 exhibits excellent antibacterial and antibiofilm activity against E. coli. • Plantaricin LP2l-2 exerts antimicrobial activity against E. coli by multiple mechanisms. • Crude plantaricin LP21-2 can as a promising biopreservative for application in dairy products. [ABSTRACT FROM AUTHOR]

We prepared double layer membranes containing eugenol (0.2, 0.3, and 0.4 g/100 g) using electrospinning technology and investigated their effects on the postharvest quality of cucumbers. The poly (lactic acid) (PLA) membrane was attached to the collector, and the nanofibers were prepared using an electrospinning device and deposited on the surface of the PLA membrane to form double layer membrane. The results informed that the shelf life of cucumbers packaged with double layer membranes increased from 15 days to 21 days at 4 °C. The double layer membrane containing 0.3 g/100 g eugenol had greater effects on delaying the spoilage process and prolonging the shelf life of cucumber fruits than other membrane. Compared with unpackaged samples, packaged samples had higher hardness values, Peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) enzyme activities, and protein and proline content; and they had lower weight loss, skin color differences values, stickiness values, microbial growth, and malondialdehyde (MDA) and total soluble sugar content. Our results suggest that double layer membranes may be used to extend the shelf life of cucumbers at 4 °C. [Display omitted] • Electrospinning was used to develop active packaging to prolong the shelf-life of cucumbers. • Nanocomposite films have beneficial effects on the postharvest storage of cucumbers. • The shelf-life of cucumbers packaged with nanocomposite films has been extended by 6 days. [ABSTRACT FROM AUTHOR]

The aim of this work was to develop a novel degradable bioactive film with poly (lactic acid), gelatin and eugenol, and electrospinning technology was used to develop an active internal layer for the active films to encapsulate eugenol. An annealing treatment was used to improve the adhesion of the active layer onto the poly (lactic acid) film. The results showed that eugenol could be efficiently encapsulated in nanofibers (92.72 g/100 g). The internal active layer containing it showed a uniform fiber morphology observed by scanning electron microscope. The diameter of nanofibers was enlarged and the hydrophobicity was enhanced, the antioxidant activity and antibacterial activity were improved as the addition of eugenol compared with pure gelatin nanofibers. In particular, nanofibers containing 4 μL/mL eugenol (G3) showed the highest antioxidant activity (32.99 mg DPPH/g dry weight), radical scavenging activity (43.80%), and significant microbial growth inhibition with CFU of about 3 log units (E. coli) and 2.5 log units (S. aureus) lower than the control. In conclusion, our results suggested that active layer could be an effective method to encapsulate eugenol, and the poly (lactic acid)/gelatin nanofibers bilayer film was a novel biodegradable packaging material with excellent antioxidant activity and antibacterial activity. • Electrospinning was used to develop active internal layer for composite film. • Eugenol was encapsulated in nanofibers and enhanced its hydrophobicity. • The composite film is a novel biodegradable material for active packaging. [ABSTRACT FROM AUTHOR]

Organophosphorus pesticides (OPPs) are a group of common residual pollutants in food that cause serious harm to human health. In the present study, the ability of 10 lactic acid bacteria (LAB) to degrade OPPs (dimethoate, parathion methyl, trichlorfon and chlorpyrifos) was explored for their potential application to degrade OPPs in fermented food. The results showed that some LAB can survive in the presence of OPPs and degrade them significantly in a short time. Among these, Lactiplantibacillus plantarum subsp. plantarum CICC20261 (L. plantarum 20261) showed the highest degradation ability. The degradation behavior of OPPs by L. plantarum 20261 followed pseudo-zero-order kinetic model (k = 1.0939–1.5915). Phosphatase produced by the strain played the key role in the degradation of OPPs because its activity was positively related to the degradation of OPPs (r = 0.975–0.995). Phosphatase could degrade OPPs rapidly in vitro , further confirmed that L. plantarum 20261 degraded rather than adsorped the OPPs. In addition, the excellent antioxidant ability of LAB and the tolerance of simulated gastric and intestinal juices showed their potential protective effects against oxidative damage induced by pesticides in vivo. • Lactic acid bacteria were screened for degrading organophosphorus pesticides (OPPs). • The phosphatase activity was positively related to the degradation rate of OPPs. • The crude phosphatase could rapidly degrade OPPs in vitro. • First study on reducing oxidative stress caused by pesticides by lactic acid bacteria. [ABSTRACT FROM AUTHOR]

Fusarium solani (CICC 2603) is one of the main postharvest spoilage strains of many fruits and vegetables. This research was to investigate the synergistic antifungal mechanism of thymol and salicylic acid (S TSA) on F. solani. Morphological observation showed that the cell structure and morphology changed seriously after S TSA treatment. Determination of F. solani stained cells with propidium iodide (PI) indicated that S TSA damaged the integrity of cell membrane, and the contribution of salicylic acid was greater than that of thymol. Meanwhile, the increase in the absorbance of 260 nm and 280 nm demonstrated that S TSA caused the leakage of cell contents severely, and the contribution of thymol was greater than that of salicylic acid. In addition, the decrease of ergosterol biosynthesis showed that S TSA interfered with membrane function of F. solani. Mitochondrial membrane potential (MMP) and enzymes activities of tricarboxylic acid (TCA) cycle experiments demonstrated that the mitochondrial function was seriously injured in F. solani. These results showed that S TSA inhibited the activity of F. solani more effectively than thymol or salicylic acid alone, by disrupting integrity and function of the cell membrane, causing leakage of the cell contents, meanwhile inhibiting function of the mitochondria, ultimately resulting in cell death. • The combination of thymol and salicylic acid (S TSA) had synergistic inhibition effect on F. solani. • S TSA treatment induced the disruption of cell membrane integrity and permeability. • S TSA treatment severely damage the morphology and function of mitochondria. • Thymol and salicylic acid played different role in synergistic antifungal effect. [ABSTRACT FROM AUTHOR]

Traditional packaging has reached its limits in ensuring food quality and prolonging shelf life. In this study, we developed antifungal sachets containing essential oils (EOs) in microcapsules (ASEOs-CM) and evaluated their application potential in bread preservation. The results showed that the release of EOs from ASEOs-CM at 25 °C followed first-order kinetics. In addition, EOs-containing ASEOs-CM had strong inhibitory effects on microorganisms in vitro and effectively inhibited the growth of molds and yeasts on sliced bread. In the experimental group, the contents of eugenol and citral EOs on bread increased during storage. Breads in three different packages (LDPE, PP and HDPE) had a total shelf life of 13, 13, and 15 d, respectively, while control breads had a shelf life of 5 d. Sachets did not affect the sensory properties of bread. Therefore, the use of ASEOs-CM was an effective, safe, and sustainable preservation method for breads. • The sachets of compound essential oil containing microcapsules were developed. • The sachets has good antifungal activity. • The sachets has no effect on the sensory characteristics of bread. • The sachets can be used to extend the shelf life of baked products. [ABSTRACT FROM AUTHOR]

The synergistic effects of different essential oils can not only reduce their dosage and cost, but also improve their biological activity. The aim of this study was to evaluate the synergistic antifungal effect of eugenol and citral (S EC) on Penicillium roqueforti. Determination of reactive oxygen species (ROS) and malondialdehyde content indicated that S EC could induce membrane lipid peroxidation, and the contribution of citral was greater than that of eugenol. In addition, downregulation of the gene encoding an NADPH oxidase subunit indicated that the ROS burst induced by S EC was mediated by NADPH oxidase. Scanning electron microscope (SEM) and transmission electron microscope (TEM), propidium iodide treatment, DNA gel electrophoresis and cell leakage experiments showed that S EC destroyed the integrity of the cell membrane and internal structures, and degraded the cell contents, and the contribution of eugenol was greater than that of citral. These results showed that S EC inhibited the activity of P. roqueforti more effectively than eugenol or citral alone, by inducing membrane lipid peroxidation and promoting the ability of eugenol to destroy the cell membrane. The combined agents eventually caused leakage of the cell contents, and ultimately cell death. •The combination of eugenol and citral (S EC) had synergistic inhibition effect against P. roqueforti. •S EC treatment could significantly induce lipid peroxidation. •S EC treatment resulted in damaged the morphology of cells. •S EC treatment resulted in loss of plasma membrane integrity. [ABSTRACT FROM AUTHOR]

To control the spoilage of bread products and reduce the costs associated with preventing their spoilage, the synergistic antifungal effects of natural agents against the main bread spoilage fungi Penicillium roqueforti and Aspergillus niger were studied. After screening 66 groups antifungals using the checkerboard method, only one combination, i.e., that of eugenol and citral (S EC), showed synergistic effects against both the fungi. Their average minimal inhibitory concentrations (MICs) decreased significantly when they were present as a combination, i.e., by 3.40-fold, compared to the case when each agent was used separately. S EC inhibited the spore germination of both the fungi by more than 95% at 2 × MIC. At the same time, their mycelial growth was almost completely inhibited. The morphology of the mycelia was further observed by SEM. Serious wrinkles and deformations were found on the surface of the mycelia at 2 × MIC. Finally, the shelf life tests showed that treatment with S EC significantly prolonged the molding time of bread. These results showed that S EC may serve as a spoilage control measure and reduce the costs associated with preventing bread spoilage. • The combination of citral and eugenol (S EC) had a synergistic effect on both mold. • S EC effectively inhibited spore germination and mycelial growth. • S EC could significantly prolong the shelf life of bread. [ABSTRACT FROM AUTHOR]

To prevent the spoilage of vegetables in food processing, hexanal, a quorum-sensing (QS) inhibitor, was first used to inhibit the formation of Erwinia carotovora and Pseudomonas fluorescens biofilms. Their growth curves were not markedly inhibited by hexanal below the minimum inhibitory concentration (MIC), but the biofilm formation could be inhibited. Motility, exopolysaccharide production, and biofilm formation of E. carotovora and P. fluorescens were significantly inhibited by hexanal at sub-MICs (P < 0.05). There was a positive dose-dependent relationship (r = 0.8167–0.9998) between the inhibition ratio and concentrations of hexanal during the critical biofilm-formation stage (1–3 d), as well as a negative relationship (r = −0.8168 to −0.9998) between the inhibition ratio and culture time. The biomass, as well as average and maximum of biofilm thicknesses, decreased significantly (P < 0.05) relative to those of the control group. Luminescence, which represents the AI-2 molecule, decreased significantly with the increase in hexanal concentration (P < 0.05), indicating that inhibition of motility, exopolysaccharide production, and biofilm formation of E. carotovora and P. fluorescens was related to the decrease in the autoinducer AI-2. Therefore, hexanal could be developed as a new QS inhibitor for preventing decay of vegetables in the food industry. • Biofilm formation was inhibited with good dose-dependent under MIC. • Inhibition occurred significantly in the earlier stage of biofilm formation. • Hexanal inhibited biofilm formation due to the reduction of AI-2. [ABSTRACT FROM AUTHOR]

Abstract In order to explore the safety of bisphenol A (BPA) degradation in food packaging, the degradation effect of six common probiotics to BPA was first explored in this paper. The result showed that the degradation rate of BPA by Lactobacillus reuteri was the highest among the six common probiotics, which was 69.83%. In addition, no toxic substances were found in the degradation products of Lactobacillus reuteri by GC-MS analysis. Based on this, the enzyme microsphere sustain-released preparation (EMSP) of Lactobacillus reuteri was prepared and characterized. Then the effects of different treatment conditions on the degradation rate of BPA were investigated. Finally, it was applied to orange juice, black tea and mung bean cold tea. The contents of BPA in canned beverage (black tea beverage, orange juice beverage and mung bean cold tea) added with EMSP decreased by 92.74%, 92.33% and 92.33%, respectively, after storage of 1 d. After 27 d, the contents of BPA in these three kinds of canned beverages reached 0. It can be seen that Lactobacillus reuteri has a significant degradation effect on BPA and has great potential and commercial value. Highlights • Lactobacillus reuteri has a significant effect on the degradation of bisphenol A. • No toxic or harmful substances were found in the degradation products of Lactobacillus reuteri. • EMSP has a good slow-release effect and can significantly reduce the content of bisphenol A in canned beverages. [ABSTRACT FROM AUTHOR]

Abstract This study was to develop the quorum sensing (QS) inhibitors from Traditional Chinese Medicinal Plants (TCMs). The water extracts of twenty-nine plants were screened for quorum sensing inhibitory (QSI) activity using two biomonitor strains, Chromobacterium violaceum CV026 (CV026), Agrobacterium tumefaciens A136 (A136). Two of the plants, Galla chinensis and Coptis chinensis , showed a good QS inhibition capacity far below their MIC values, and no effect on their growths. The inhibition zones were 5.16 mm and 12.50 mm for CV026 respectively, and the production of violacein were decreased by 34.5% and 50.44% at 100 μg/mL respectively. QS-mediated β-galactosidase activity in A136 was inhibited strongly of 33.20% at 100 μg/mL by Galla chinensis while Coptis chinensis showed no inhibition. The QS-regulated virulence factors, including swarming motility and biofilm on Pseudomonas aeruginosa PAO1 were inhibited significantly at 10, 50 and 100 μg/mL respectively (P < 0.05). The higher the sub-MIC concentration, the greater the inhibitory effect on the production of violacein, β-galactosidase activity, swarming motility or biofilm formation, showing a good dose-dependent manner (r = 0.9286–0.9999). These findings may be helpful to provide a new aspect regarding the treatment of bacterial infections under a lower concentration of the TCMs. Highlights • Two Traditional Chinese Medicinal Plants showed QSI activities under MIC. • They inhibited violacein production of CV026, motility and biofilm of PAO1. • Galla chinensis inhibited β-galactosidase activity of A136, Coptis chinensis not. • Their QSI activities showed dose-dependent manner under MIC. [ABSTRACT FROM AUTHOR]

Essential oil components have antifungal preservative effects, but are only effective individually at relatively high concentrations that can degrade the sensory quality of foods. Therefore, the synergistic antifungal mechanism of eugenol and citral (S EC) against Aspergillus niger was investigated in this paper. The preservative coupon containing the S EC was prepared and its application in bread preservation was evaluated. The S EC disrupted many aspects of A. niger structure and metabolism, especially mitochondrial morphology and membrane potential, and the tricarboxylic acid cycle (TCA). The effects of S EC were strong enough to apparently induce cellular apoptosis, whereas those of eugenol and citral were not. The application experiment shows that the preservative coupon can significantly prolong the shelf life of bread. Compared with the control group, the shelf life of bread was extended by 6 days at 28 °C. At the same time, this method will not affect the sensory properties of bread products. [Display omitted] • The eugenol and citral (S EC) had synergistic inhibition effect against A. niger. • The S EC can change the mitochondrial morphology and inhibit energy metabolism. • The S EC could inhibit the expression of SDH, IDH and FH related genes. • The preservative coupon can extend the shelf life of bread to the 11th day. [ABSTRACT FROM AUTHOR]

The application of microwaves on sunflower kernels, as a new flavour generation technique, to produce sunflower oil was investigated. Using solvent-assisted flavour evaporation (SAFE), HS-SPME and GC-O-MS, 75 odourants were identified in sunflower oils, where 44 were newly found. With the increasing microwave time, aroma-active terpenes decreased from 74 to 33 mg/kg, aroma-active heterocyclics increased from 0 to 196 mg/kg, and aroma-active carbonyls increased from 2 to 28 mg/kg in sunflower oils (p < 0.05). Meanwhile, the perceived intensities of roasted and smoky aromas enhanced, while the intensities of raw sunflower seed and woody aromas decreased in sunflower oils (p < 0.05). Microwaves did not cause surface rupture but increased the interior porosity of sunflower kernel. The tocopherol loss in sunflower oils was less than 7.2% and the oil yield increased from 19.45% to 35.10% after microwaves. The temperature rise by microwaves was responsible for the gradually decreased protein solubility and increased HCAs (7.3–820.6 ng/g) and PAHs (7.78–109.76 ng/g) in oils. Microwave technology, when being applied at appropriate power and duration, is promising for producing sunflower oil, however, process temperature needs to be controlled to balance between sufficient flavour formation and denaturation of protein as the by-product. • Microwaving sunflower kernel affected flavor, nutrition and safety of sunflower oil. • Microwaves increased oil yield by increasing porosity inside the sunflower kernels. • Microwaves gave sunflower oil a similar sensory profile to traditional roasting. • 75 (44 new) odorants were identified in sunflower oil by SAFE, HS-SPME & GC-O-MS. • Tocopherol retention in sunflower oil was 93% after microwave pretreatment. [ABSTRACT FROM AUTHOR]

In industry, Polygalacturonase (PG) is typically used for enzymatic hydrolysis of fruit juice to increase the yield. In the present study, it was found that two pesticides, namely trichlorfon and carbosulfan, which are frequently applied to fruit trees, inhibited the activity of PG and reduced the yield of apple juice. The presence of trichlorfon and carbosulfan reduced the yield by 3.58% and 4.12% during enzymatic hydrolysis of apple juice, respectively. Undoubtedly, this might lead to enormous losses in the juice industry. Analysis of the catalytic mechanism of PG on pectin revealed that the N-acetyl-D-(+)-glucosamine (NAG-404) and tyrosine (TYR-197) residues in the active site played key roles in the process. Nonetheless, it was also determined that various moieties in the pesticides interacted with these amino acids, which led to a decrease in the catalytic activity of the enzyme. Evaluation of the flavor components in enzymatically hydrolyzed apple juice demonstrated that the two pesticide residues could reduce the content of esters, alcohols, and acids by 6.75%, 4.64%, and 3.20%, respectively. Thus, pesticide residues would not only lead to a decrease in the juice yield and change in flavor but would also exhibit potential inhibitory effects on fruit ripening. • The effect of pesticides on apple juice yield was analyzed. • The effect of pesticides on PG activity was evaluated. • The interaction between PG and pesticides was studied. • The effect of pesticides on flavor in apple juice was analyzed. [ABSTRACT FROM AUTHOR]

During preservation of nuts, nut oils are easily oxidized; hence, peroxide value (PV) is an important evaluation index. In this study, a novel method for the determination of the PV of nuts based on partial-least-square regression (PLSR) and Forest random PLSR (RF-PLSR) model was established. Meanwhile, the Raman spectrum was processed by 24 spectral pretreatment methods to transform the whole Raman band, and the best band was selected by RF method. Among the whole bands, 36 wavenumbers were selected to establish the PLSR model. The R-square of the correction set (R2c) and prediction set (R2p) of the optimal Standard normal variate transformation + first Derivative-PLSR model and RF-PLSR were 0.9552, 0.8672, 0.8048, and 0.7927, while the root-mean-square error of calibration (RMSEC) and prediction (RMSEP) were 0.067, 0.1100, 0.1514, and 0.1547, respectively. These results showed that Raman spectroscopy combined with chemometrics could be used to establish a rapid, nondestructive, and precise method for the determination of oil oxidation index. • Dynamic monitoring of nut oil oxidation was done through Raman technology. • Comparison was done on the stability and precision of different models established by different pretreatments. • PLSR modeling was performed by the Random Forest algorithm to quantify oil peroxide values. [ABSTRACT FROM AUTHOR]

Bacteriocins are known to inhibit various foodborne bacteria and their biofilms; however, few bacteriocins with activity against food-derived Staphylococcus aureus have been reported. Here, a novel bacteriocin (XJS01) from the Lactobacillus salivarius strain CGMCC2070 was obtained, purified, and extensively characterized. Molecular mass and amino acid composition of XJS01 were 666.31 Da and F–S-G-L-A-G-D, respectively. XJS01 inhibited the S. aureus strain 2612:1606BL1486 (S. aureus _26), which was originally isolated from chicken meat. Also, XJS01 showed good resistance to heat treatment, and was only susceptible to pepsin treatment. The minimum inhibitory concentration of XJS01 against S. aureus_ 26 was 9.85 μg/mL, which is lower than previously reported levels for most described bacteriocins. Furthermore, exposure to XJS01 also decreased viability and significantly inhibited (p < 0.05) planktonic S. aureus _26 cells. Biofilm formation of S. aureus _26 was also significantly inhibited (p < 0.05). The results of electron microscopy showed that XJS01 impaired membrane permeability in S. aureus_ 26, caused leakage of cytoplasmic content, and led to cell deformation. In summary, this study identifies the bacteriocin XJS01 as a potentially candidate for the control of S. aureus in foods in either planktonic or biofilm states. • A novel bacteriocin designated as XJS01 was purified and characterized. • Molecular mass and amino acid composition of the bacteriocin were revealed. • The bacteriocin reduce viability and promote death of planktonic S. aureus cells. • The biofilm formation is inhibited after bacteriocin treatment. • The bacteriocin cause permeability and deformation of S. aureus cells. [ABSTRACT FROM AUTHOR]