Genomic characterization of the most barotolerant Listeria monocytogenes RO15 strain compared to reference strains used to evaluate food high pressure processing

BackgroundHigh pressure processing (HPP; i.e. 100-600MPa pressure depending on product) is a non-thermal preservation technique adopted by the food industry to decrease significantly foodborne pathogens, including Listeria monocytogenes, from food. However, susceptibility towards pressure differs among diverse strains of L. monocytogenes and it is unclear if this is due to their intrinsic characteristics related to genomic content. Here, we tested the barotolerance of 10 different L. monocytogenes strains, from food and food processing environments and widely used reference strains including clinical isolate, to pressure treatments with 400 and 600MPa. Genome sequencing and genome comparison of the tested L. monocytogenes strains were performed to investigate the relation between genomic profile and pressure tolerance.ResultsNone of the tested strains were tolerant to 600MPa. A reduction of more than 5 log(10) was observed for all strains after 1min 600MPa pressure treatment. L. monocytogenes strain RO15 showed no significant reduction in viable cell counts after 400MPa for 1min and was therefore defined as barotolerant. Genome analysis of so far unsequenced L. monocytogenes strain RO15, 2HF33, MB5, AB199, AB120, C7, and RO4 allowed us to compare the gene content of all strains tested. This revealed that the three most pressure tolerant strains had more than one CRISPR system with self-targeting spacers. Furthermore, several anti-CRISPR genes were detected in these strains. Pan-genome analysis showed that 10 prophage genes were significantly associated with the three most barotolerant strains.ConclusionsL. monocytogenes strain RO15 was the most pressure tolerant among the selected strains. Genome comparison suggests that there might be a relationship between prophages and pressure tolerance in L. monocytogenes.Peer reviewe

Photobacterium profundum under Pressure:A MS-Based Label-Free Quantitative Proteomics Study

Photobacterium profundum SS9 is a Gram-negative bacterium, originally collected from the Sulu Sea. Its genome consists of two chromosomes and a 80 kb plasmid. Although it can grow under a wide range of pressures, P. profundum grows optimally at 28 MPa and 15°C. Its ability to grow at atmospheric pressure allows for both easy genetic manipulation and culture, making it a model organism to study piezophily. Here, we report a shotgun proteomic analysis of P. profundum grown at atmospheric compared to high pressure using label-free quantitation and mass spectrometry analysis. We have identified differentially expressed proteins involved in high pressure adaptation, which have been previously reported using other methods. Proteins involved in key metabolic pathways were also identified as being differentially expressed. Proteins involved in the glycolysis/gluconeogenesis pathway were up-regulated at high pressure. Conversely, several proteins involved in the oxidative phosphorylation pathway were up-regulated at atmospheric pressure. Some of the proteins that were differentially identified are regulated directly in response to the physical impact of pressure. The expression of some proteins involved in nutrient transport or assimilation, are likely to be directly regulated by pressure. In a natural environment, different hydrostatic pressures represent distinct ecosystems with their own particular nutrient limitations and abundances. However, the only variable considered in this study was atmospheric pressure

NATO-SPS Pilot Study on Food Chain Security: Findings and Recommendations

The chapter reports the outcomes of an ongoing NATO-SPS Pilot Study on "Food Chain Security." These include (1) Overview of the food system in participating countries; (2) Prevention, surveillance and detection systems and (3) Response systems. A survey was carried out in order to identify the concerns of the food industries with regard to contamination of the food chain (i.e. what did the industry perceive as the main hazards associated with the food chain?); to evaluate the extent to which food safety management systems had been implemented as a safeguard against contamination incidents and to determine the feasibility and limitations of conducting such a survey within participating countries. A survey tool was prepared and sent to public and private food sector(s) by each group member. A total of 18 different countries participated in the pilot study and nine countries completed the survey. Participants' views were gathered, and the outcomes are discussed in terms of reducing possible risks and threats to the food system. The detailed analysis of the outcomes will be a key to address to the countermeasures that are necessary to be taken to minimize the adverse effect(s) on human health, society, and environment at large. The possible scenarios developed by the experts in the project duration are shared. These are believed to be useful in developing a prototype system and for sharing information related to acts of terrorism to the environment, agriculture, and water systems. The final outputs given here allow some comparison between country partners and identify common weaknesses of the food systems in general. The importance of continuing exchange of experience between participating countries in the area of legal regulations, logistical and institutional aspects of food safety is highly encouraged

Evaluation of the Effect of Different Extraction Techniques on Sour Cherry Pomace Phenolic Content and Antioxidant Activity and Determination of Phenolic Compounds by FTIR and HPLC

Abstract: Sour cherry pomace derived from mashed cherries that maintains the color and beneficial properties of the cherries (Prunus cerasus L.). In this study, microwave-assisted extraction (MAE) (900 W for 30, 60 and 90 s.), high hydrostatic pressure (HHP) (400 and 500 MPa for 1, 5 and 10 min at 20 °C) and ultrasonic-assisted extraction (UAE) (for 5,10 and 15 min with a power of 100%) was used as novel processes. Total phenolic content (TPC), morphological changes, antioxidant activity (AA) and structural changes of cherry pomace were measured by the Folin–Ciocalteu assay, high performance liquid chromatography (HPLC), DPPH-scavenging activity, scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR). According to the results, all novel technologies (MAE-HHP-UAE) increase PC and AA with respect to conventional solvent extraction method (50 °C and 30 min) (CSE). Among novel technologies, MAE (90 s) had highest TPC (275.31 ± 4.26 GAE/100 g FW) and also had highest antioxidant activity (89.9 ± 0.22%). The lowest TPC and AA values were 108.36 ± 3.99 mg gallic acid equivalent (GAE)/100 g fresh weight (FW) and 71.30 ± 1.21% in CSE, respectively. According to FTIR results, there are no significant structural changes in samples when different extraction techniques were applied. Individual phenolics were quantified by using HPLC for different extraction techniques. Graphic Abstract: [Figure not available: see fulltext.]. © 2019, Springer Nature B.V

Mathematical expression of the temperature profile and experimental determination of compression heating of ethylene glycol during high hydrostatic pressure processing

In this study, we aimed to describe the temperature profile in the pressure vessel and the compression heating during high hydrostatic pressure (HHP) processing..

Mathematical expression of the temperature profile and experimental determination of compression heating of ethylene glycol during high hydrostatic pressure processing

In this study, we aimed to describe the temperature profile in the pressure vessel and the compression heating during high hydrostatic pressure (HHP) processing..

Effect of high hydrostatic pressure in physicochemical properties and in vitro digestibility of cornstarch by nuclear magnetic resonance relaxometry

Starch is the major polysaccharide consumed by human being. It is not classified as a dietary fiber as it is digestible by the enzymes present in the saliva and small intestines. However, it is possible to modify starch with thermal and nonthermal techniques. High hydrostatic pressure (HHP) is a cold pasteurization technique that has increased application in food industry with minimum effect on nutritional quality of the food products. It is hypothesized that the use of HHP could be a modification strategy for starch. In this study, effects of different HHP parameters (400 and 500 MPa) at different temperatures (20, 30, and 40°C) for 5, 15, and 30 min on in vitro digestibility and physicochemical properties of cornstarch were studied by Nuclear magnetic resonance (NMR) relaxometry. Results showed that HHP treatment increased slowly digestible starch (SDS) and rapid digestible starch (RDS) significantly with pressure and temperature (p <.05). In addition, it was shown that HHP treatment decreased the solubility and swelling power of the cornstarch and it is proposed that 30 min HHP treatment at 500 MPa and 40°C is the onset for cornstarch gelatinization according to NMR relaxometry results. Practical Applications: High hydrostatic pressure (HHP) is a nonthermal processing technology that is commonly used in the food industry for extending the shelf life of food products by destroying vegetative cells, enzymes, microorganisms effectively, and it can modify the starch so the aim of this study was to investigate the effects of different HHP parameters on in vitro digestibility and physicochemical properties of cornstarch by nuclear magnetic resonance relaxometry. © 2019 Wiley Periodicals, Inc