The increasing consumption of fresh-like food products requires the development of mild processing technologies without loss of nutritional value and sensory quality of foods. Non-thermal plasma ...(NTP) is an emerging and promising technology for extending the shelf-life of food products. However, the further development of a novel preservation technology should base on the adequate understandings of the effects on microbial behaviors. Therefore, the aim of this review is to provide an overview of the inactivation mechanisms of NTP technology on microbes. Topics covered are the basic introduction of NTP, the intrinsic and extrinsic factors affecting microbial inactivation effect and the probable mechanisms for microbial inactivation. Many factors, including processing parameters, environmental conditions and microbial properties have been shown to influence the bactericidal effect of NTP. According to previous research, the inhibitory activity of NTP against microbes includes biological and physical scenarios, though the exact mechanisms still remain unknown, requiring more investigations in the future.
•The intrinsic and extrinsic factors affecting bactericidal efficacy of non-thermal plasma were reviewed.•The probable inactivation mechanisms in biological and physical aspects by non-thermal plasma were summarized.•The non-thermal plasma induced microbial physiological alterations were shown.•The safe application of non-thermal plasma in the future for food industry was proposed.
As a nonthermal sterilization technique, ultrasound has attracted great interest in the field of food preservation. In this study, flow cytometry and transmission electron microscopy were employed to ...investigate ultrasound-induced damage to Escherichia coli and Staphylococcus aureus. For flow cytometry studies, single staining with propidium iodide (PI) or carboxyfluorescein diacetate (cFDA) revealed that ultrasound treatment caused cell death by compromising membrane integrity, inactivating intracellular esterases, and inhibiting metabolic performance. The results showed that ultrasound damage was independent of initial bacterial concentrations, while the mechanism of cellular damage differed according to the bacterial species. For the Gram-negative bacterium E. coli, ultrasound worked first on the outer membrane rather than the cytoplasmic membrane. Based on the double-staining results, we inferred that ultrasound treatment might be an all-or-nothing process: cells ruptured and disintegrated by ultrasound cannot be revived, which can be considered an advantage of ultrasound over other nonthermal techniques. Transmission electron microscopy studies revealed that the mechanism of ultrasound-induced damage was multitarget inactivation, involving the cell wall, cytoplasmic membrane, and inner structure. Understanding of the irreversible antibacterial action of ultrasound has great significance for its further utilization in the food industry.
► The effects of ultrasound on the molecular weight, structure and rheological properties of apple pectin were investigated. ► The degradation products had a uniform and narrow distribution of ...molecular weight. ► Degradation kinetics model of apple pectin fitted to 1/Mt−1/M0=kt from 5 to 45°C. ► Ultrasound treatment could not alter the primary structure properties of apple pectin. ► The viscosity of apple pectin decreased after ultrasound treatment.
The effects of ultrasound on the molecular weight of apple pectin were investigated. The structure and rheological properties of the degradation products were also tentatively identified by High Performance Liquid Chromatography–Photodiode Array Detector (HPLC–PAD), Infrared spectroscopy (IR), Nuclear Magnetic Resonance spectroscopy (NMR) and Rheometer. The results indicated that the weight-average molecular weight of apple pectin decreased obviously after ultrasound treatment. The molecular weight of degradation products had a uniform and narrow distribution. Ultrasound intensity and temperature play an important role in the degradation reaction. Degradation kinetics model of apple pectin fitted to 1/Mt−1/M0=kt from 5 to 45°C. The degree of methylation of apple pectin reduced according to IR analysis when ultrasound was applied. Ultrasound treatment could not alter the primary structure of apple pectin according to the results determined by HPLC, IR and NMR. Meanwhile, the viscosity of apple pectin was 103 times as large as that of ultrasound-treated apple pectin. The ultrasound-treated apple pectin showed predominantly viscous responses (G′<G″) over the same frequency range. The results suggested that ultrasound provided a viable alternative method for the modification of pectin.
Microbial decontamination during the thawing process would offer an effective intervention step to ensure food safety. In this study, plasma-activated water (PAW) and slightly acidic electrolyzed ...water (SAEW) are proposed as the thawing media to assure microbiological safety and retain quality attributes of beef. Compared to the conventional air thawing (AT) and water thawing (WT), PAW thawing (PT) and SAEW thawing (ST) were found to efficiently inactivate the total bacteria, fungi and yeast in beef by 0.83 – 1.76 logs. In addition, PT and ST did not pose any detrimental effect on the physicochemical and sensory quality attributes of beef compared with AT, WT and microwave thawing (MT). The oxidation of lipid and proteins and the structure of proteins in beef was better retarded by PT and ST. PAW and SAEW as active thawing media provided thawed beef with higher microbial safety and maintained quality attributes compared with conventional thawing methods.
•PAW and SAEW were used as active beef thawing media.•PAW and SAEW effectively reduced the microbial loads of beef during thawing.•PAW resulted in non-detective levels of pathogens-S. aureus and Salmonella in beef.•PAW and SAEW retarded lipid oxidation of beef during thawing.•PAW and SAEW did not induce detrimental effects due to protein oxidation or changes on muscle micro-structure.
Cyclodextrin metal–organic framework by ultrasound-assisted rapid synthesis for caffeic acid (CA) loading and antibacterial application (U-CD-MOF) was successfully studied and this method shortened ...the preparation time to a few minutes. It was found that the ultrasonic power, reaction time and temperature would affect the morphology and size of the obtained crystal. Under the optimal conditions, U-CD-MOF had a cubic structure with uniform size of 8.60 ± 1.95 μm. U-CD-MOF was used to load the antibacterial natural product CA to form the composite (CA@U-CD-MOF) and the loading rate of CA@U-CD-MOF to CA could reach 19.63 ± 2.53%, which was more than twice that of γ-CD. Various techniques were applied to characterize the synthesized crystal, including Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and N2 adsorption. In addition, antibacterial tests were performed on the obtained crystal. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of CA@U-CD-MOF for Escherichia coli O157: H7 (E. coli O157: H7) were both 25 mg·mL−1, and the MIC for Staphylococcus aureus (S. aureus). was 25 mg·mL−1. The sustained release behavior of CA@U-CD-MOF to CA in ethanol fitted well to Higuchi model and the loading of CA was supported by molecular docking results. In general, U-CD-MOF was successfully achieved by ultrasound-assisted rapid synthesis and the obtained crystal was further evaluated for potential antibacterial application.
•Transcriptome revealed molecular regulatory mechanisms under ultrasonic stress.•Ultrasonic stress affected differential gene expressions in E. coli O157:H7 cells.•Genes encoded TCA cycle and energy ...metabolism were down-regulated.•Genes encoded ABC transporters and signal transduction were down-regulated.•Protein translation processing might be benefited under ultrasonic stress.
In order to uncover the molecular regulatory mechanisms underlying the phenotypes, the overall regulation of genes at the transcription level in Escherichia coli O157:H7 after ultrasonic stimulation were investigated by RNA-sequencing and real-time quantitative polymerase chain reaction. The results revealed that differential expressions of 1217 genes were significant when exposed at 6.67 W/mL power ultrasonic density for 25 min, including 621 up-regulated and 596 down-regulated genes. Gene transcription related to a series of crucial biomolecular processes were influenced by the ultrasonic stimulation, including carbohydrate metabolism, energy metabolism, membrane transport, signal transduction, transcription and translation. The most enriched pathways were further analyzed in each category. Specifically, genes encoded citrate cycle were down-regulated in E. coli O157:H7, indicating the capacity to decompose carbohydrate and produce energy were decreased under ultrasonic stress. Accompanied with energy loss, the membrane function was affected by the ultrasonic stimulation since the majority of genes encoded ATP-binding cassette transporters were down-regulated. Besides, the autoinducer 2-mediated signal transduction was also inhibited. The interesting thing, however, the protein translation processing was benefited under ultrasonic field. This phenomenon might due to the desperate need of stress response proteins when the bacteria were under stress. We believed that the sonomechanical and sonochemical effects generated by acoustic cavitation were responsible for those gene expression changes.
•Established a method for identifying tyrosinase inhibitors from the complex matrix.•The method avoided false positive activity with good selectivity and sensitivity.•The method exhibited excellent ...tolerance to the sample matrix.•The method enabled minimal sample consumption with high analytical efficiency.•Several tyrosinase inhibitors were identified from green tea and cinnamon extracts.
Tyrosinase plays a primary role in melanin biosynthesis and enzymatic browning of freshly cut fruits and vegetables. Herein, an on-line ultraperformance liquid chromatography diode array detector biochemical detection (UPLC-DAD-BCD) method was established to identify trace amount potent tyrosinase inhibitors and antibrowning agents in complex mixtures. The tyrosinase inhibition activities of some representative compounds were evaluated by using the established method and their chromatography-activity relationships were obtained. Then the proposed UPLC-DAD-BCD method was applied to screen tyrosinase inhibitors in edible herbal extracts and identified two tyrosinase inhibitors in green tea and three in cinnamon. The above active ingredients were determined by ultra-high-performance liquid chromatography linear ion trap/orbitrap high resolution mass spectrometry (UHPLC-FTMS). The on-line UPLC-DAD-BCD in combination with UHPLC-FTMS was confirmed to be a powerful technique to screen and elucidate the active ingredients in complex matrixes and could be applied to evaluate the integrated effects of multiple ingredients against corresponding targets.
Although different delivery systems have been developed to overcome the limits of Epigallocatechin‐3‐gallate (EGCG) and quercetin in food application, none have referred to their simultaneous ...encapsulation. In this study, these two polyphenols were successfully co‐loaded into liposomes. Under the optimal conditions (lecithin‐total polyphenols ratio 25:1, lecithin‐cholesterol ratio 6:1, lecithin‐Tween 80 ratio 8:1 and ultrasonic time 2 min), the mean size, polydispersity index (PDI) and zeta potential of liposomes were 111.10 ± 0.52 nm, 0.259 ± 0.006 and –19.83 ± 0.45 mV, with an encapsulation efficiency of 64.05 ± 1.56% and 61.73 ± 2.55% for EGCG and quercetin, respectively. After 30‐day storage, an increase of 4.05% was observed in the mean size with no significant change (P ≥ 0.05) in the PDI and zeta potential. Moreover, 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay revealed a synergistic antioxidant effect of the two compounds in liposomal system. These results demonstrated that co‐encapsulation of EGCG and quercetin enhances their effectiveness.
Practical Application
EGCG and quercetin are natural polyphenols abound in the human diet with diverse biological activities. These two polyphenols were successfully co‐encapsulated into a homogeneous and stable liposomal system. Interestingly, a synergistic antioxidant effect of the two polyphenols was observed due to co‐encapsulation. This indicated that the simultaneous delivery of EGCG and quercetin was an attractive approach to improve their functionality for expanding their application in food, cosmetic and pharmaceutical industries.
The motion planning and control method of automated vehicles, as the key technology of automated vehicles, directly affects the safety, comfort, and other technical indicators of vehicles. The ...planning module is responsible for generating a vehicle driving path. The control module is responsible for driving the vehicle. In this study, we review the main methods and achievements in motion planning and motion control for automated vehicles. The advantages and disadvantages of various planning and control methods are comparatively analyzed. Finally, some predictions and summaries based on the existing research results and trends are proposed. Through this analysis, it is believed that various types of algorithms will be further integrated in the future to complement each other's strengths and weaknesses. The next area of research will be to establish more accurate vehicle models to describe vehicle motion, improve the generalization-solving ability of algorithms, and enhance the planning and control of integrated 'human-vehicle-road' traffic systems.
•Ultrasound assisted enzymatic process was influenced by temperature and ultrasonic intensity.•Ultrasound accelerated starch degradation and the enzymatic process catalyzed by ...glucoamylase.•Combination of ultrasound and glucoamylase resulted in the highest starch degradation extent.
The present work investigates the synergistic impact of glucoamylase and ultrasound on starch hydrolysis. The extent of starch hydrolysis at different reaction parameters (ultrasonic intensity, temperature, reaction time) was analyzed. The hydrolysis extent increased with the reaction time and reached a maximum value under ultrasonic intensity of 7.20W/mL at 10min. Ultrasound did not alter the optimum enzymatic temperature but speeded up the thermal inactivation of glucoamylase. The evaluation of enzymatic kinetics and starch degradation kinetics indicated a promotion of the reaction rate and enzyme-substrate affinity. According to the thermodynamic results, sonoenzymolysis reactions require less energy than enzymolysis reactions. The measurement of molecular weight, solubility, thermal properties, and structures of the substrates revealed that sonoenzymolysis reaction generated greater impacts on starch properties. The molecular weight and radii of gyration decreased by 80.19% and 90.05% respectively while the starch solubility improved by 136.50%.
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