High hydrostatic pressure effects on mold flora,citrinin mycotoxin,hydroxytyrosol, oleuropein phenolics and antioxidant activity of black table olives

High hydrostatic pressure (HHP) as a non-thermal technology is an effective tool for microbiologically safe and shelf-stable fruits. Mycotoxin citrinin (CIT) is a toxic secondary metabolite, especially produced from filamentous fungus Penicillium citrinum and is also produced by other species of Penicillium, Aspergillus, and Monascus that are able to develop on olive after harvest, during brine and storage of olives. Nutritional benefits of olive fruit are mainly related to phenolics such as hydroxytyrosol, oleuropein and antioxidative effects. With HHP application of olives, total mold was reduced to 90% at 25 °C whereas it was 100% at 4 °C based on Rose-Bengal Chloramphenicol Agar (RBCA). Total Aerobic-Mesofilic Bacteria load was reduced to 35–76% at 35 ± 2 °C based on the Plate Count Agar (PCA). Citrinin load was reduced to 64–100% at 35 ± 2 °C. 2.5; 10; 25; and 100 ppb of spiked citrinin in sample were degraded as %56; %37; %9; and %1.3, respectively. 2.5 ppb and less citrinin contamination in table olive were degraded more (56%). Total phenolics were increased to 2.1–2.5-fold after HHP (as mgGA/100 g). Hydroxytyrosol in olives increased on average 0.8–2.0-fold whereas oleuropein decreased on average 1–1.2-fold after HHP (as mg/kg dwt). Antioxidant activity values varied from 17.238 to 29.344 mmol Fe²⁺/100 g for control samples whereas 18.579–32.998 mmol Fe²⁺/100 g for HHP-treated samples. HHP could be used in the olive industry as non-thermal preservation.     

A combined treatment of UV-assisted TiO2 photocatalysis and high hydrostatic pressure to inactivate internalized murine norovirus

Human norovirus (HuNoV) is a major cause of foodborne illness associated with shellfish consumption. A solidified agar matrix (SAM) was experimentally prepared using agar solution for inactivation of murine norovirus (MNV-1) as a surrogate for HuNoV in a simulation model approach. MNV-1 was injected inside the SAM for virus internalization, and the effects of single and combined UV-assisted TiO₂ photocatalysis (UVTP) and high hydrostatic pressure (HHP) treatments were determined. The internalized MNV-1 were reduced by 2.9-log₁₀ and 3.5-log₁₀, respectively, after single treatments of UVTP (4.5 mW/cm², 10 min) and HHP (500 MPa, 5 min, ambient temperature). However, the internalized MNV-1 was reduced by 5.5-log₁₀ (below the detection limit) when UVTP was followed by HHP, indicating a synergistic inactivation effect. Analysis of viral morphology, proteins, and genomic RNA allowed elucidation of mechanisms involved in the synergistic antiviral activity of combined treatments, which appeared to disrupt the MNV-1 structure and damage both the capsid protein and genomic RNA.Industrial relevanceHHP treatment of raw oysters has proved commercially successful, but there is a less evidence available regarding the potential of HHP for inactivation of localized viruses present inside foods. A sequential combination of UV-assisted TiO₂ photocatalysis (UVTP) and high hydrostatic pressure (HHP) achieved significantly higher inactivation of localized virus compared to individual treatments due to a synergistic mechanism. An experimentally prepared model food system was found useful to simulate foods with morphological variations and unpredictable viral internalization patterns. This UVTP-HHP combined treatment for inactivation of localized MNV-1 can be useful for disinfection of raw oysters and other similar foods.     

Preparation and characterization of whey protein isolate films reinforced with porous silica coated titania nanoparticles

Whey protein isolate (WPI) films embedded with TiO₂@@SiO₂ (porous silica (SiO₂) coated titania (TiO₂)) nanoparticles for improved mechanical properties were prepared by solution casting. A WPI solution of 1.5 wt% TiO₂@@SiO₂ nanoparticles was subjected to sonication at amplitudes of 0, 16, 80 and 160 μm prior to casting in order to improve the film forming properties of protein and to obtain a uniform distribution of nanoparticles in the WPI films. The physical and mechanical properties of the films were determined by dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and tensile testing. Water vapor permeability (WVP) measurements revealed that the water vapor transmission rates are slightly influenced by sonication conditions and nanoparticle loading. The DMA results showed that, at high sonication levels, addition of nanoparticles prevented protein agglomeration. The thermal stability of the materials revealed the presence of 3–4 degradation stages in oxidizing the protein films. The addition of nanoparticles strengthens the WPI film, as evidenced by tensile stress analysis. Sonication improved nanoparticle distribution in film matrix; such films can potentially become effective packaging materials to enhance food quality and safety.     

Sodium lactate loaded chitosan-polyvinyl alcohol/montmorillonite composite film towards active food packaging

A sodium lactate loaded chitosan-polyvinyl alcohol/montmorillonite (NaL-CS/PVA/MMT) barrier film with antibacterial activity was developed by coating method and the effectiveness and diffusion behavior were investigated. An intercalated structure was achieved for CS/PVA/MMT film and the interfacial interactions among CS, PVA and MMT were intermolecular hydrogen bonds. An appropriate increase of MMT contents (15 wt% and below) could achieve a remarkable enhancement in tensile strength and Young's modulus, meanwhile, the water vapor, oxygen and carbon dioxide barrier properties of the films were also significantly improved. The NaL-CS/PVA/MMT film exhibited good antibacterial activity against E. coli and well controlled release of NaL. Moreover, the diffusions of NaL from films were dependent on the pH value of aqueous solution and ionic strength, and the initial diffusions (M_t/M_∞ < 2/3) could be well described by Fickian equation. The NaL-CS/PVA/MMT film may have potential as a good barrier film with antibacterial activity towards food packaging.     

Moisture sorption isotherms of high pressure treated fruit peels used as dietary fiber sources

High hydrostatic pressure (HHP) treatments can improve the potential of orange, mango, and prickly pear peels as food formulation fiber sources. Akaike Information Criteria differences identified Peleg and GAB as the best model alternatives to describe experimental moisture isotherms. HHP (600 MPa/10 min/22 and 55 °C) effects on moisture isotherms expressed as relative water sorption content change with respect to controls (RWSC_aw) showed that in the 0.1–0.93 a_w range, HHP improved the adsorption water retention of orange peels. The same was true for the desorption water retention for all HHP-treated fruit peels except for prickly pear HHP-treated at 22 °C and > 0.35 a_w. The area under the hysteresis curve (A_H) in the 0.15–0.51 a_w range showed that HHP increased hysteresis for all fruit peels tested. All this illustrates the HHP potential to modify the hygroscopic properties of fruit peels at lower temperature and in less processing time than conventional processes.Industrial relevanceOrange, mango, and prickly pear peels are potential food fiber formulation sources with differentiated hygroscopic and functional properties. In this study, 600 MPa treatments at 22 and 55 °C for 10 min modified the adsorption and desorption moisture retention capacity of all fruit peels tested in this study. HHP technology can improve the potential of fruit peels as dietary fiber sources with the advantage of shorter processing times and lower temperatures than conventional technologies used to treat food fibers.     

Combined effect of ozonated water and chitosan on the shelf-life of Pacific oyster (Crassostrea gigas)

Effects of ozonated water and chitosan treatment on the shelf-life extension of Pacific oysters (Crassostrea gigas) stored at 5 ± 1 °C were studied. Results indicated that ozonated water treatment reduced the total microbial load of fresh oysters by about 10-fold (from 3.2 × 10³ CFU/g to 1.8 × 10² CFU/g) before storage and the microbial flora was different with that of raw samples. The wide-spectrum antibacterial property of chitosan against bacteria isolated from oysters was confirmed, and chitosan concentration of 5.0 g/l was eventually determined for application in oyster preservation. Based on microbiological analysis, biochemical indices determination and sensory evaluation, shelf-lives of 8–9 days for control, 10–12 days for ozonated water treated samples, 14–15 days for chitosan treated samples and 20–21 days for samples with combined treatment were observed, indicating that ozonated water and chitosan have a great potential for oyster preservation.Industrial relevanceAs seafood, Pacific oysters have a short shelf-life. Improvements in the shelf-life of oysters can have an important economic impact by reducing losses and by allowing the products to reach distant and new markets.In this work, Shelf-life of oysters with combined treatment of ozonated water and chitosan doubled, which has great practical meaning, and the process could be fully adopted by the food industry.We also did some research about the changes in microbial flora after ozonated water treatment. This work could help in preservation of oysters when ozone or ozonated water concerned.We discovered Wide-spectrum antibacterial property of chitosan against the strains isolated from raw oysters. The potential for using chitosan as a natural preservative in oysters was approved.     

Effects of high hydrostatic pressure on physicochemical properties,enzymes activity,and antioxidant capacities of anthocyanins extracts of wild Lonicera caerulea berry

Wild Lonicera caerulea berries were subjected to five different high hydrostatic pressure (HHP) treatments (which resemble the conditions of active component extraction and commercial sterilization). The content of anthocyanins and total phenolics increased by 6.84% and 14.35% (p < 0.05), respectively after treatment at 200 MPa for 5 and 10 min. As HHP increased, a higher loss of active component was observed. The total phenolic contents did not differ significantly between the control and the 400 MPa/20 min treated group (p > 0.05); HHP processing demonstrated better sterilization effect but severely destroyed enzymes. Polyphenol oxidase (PPO) and peroxidase (POD) activity were activated at lower HHP, such as 200 MPa, and decreased at 400–600 MPa. Superoxide dismutase (SOD) maintained good stability under HHP processing. The antioxidant capacities of anthocyanins extracts of wild L. caerulea berry were evaluated by 3 different methods (DPPH assay, oxygen radical absorbance capacity assay, and cellular antioxidant activity assay).Industrial RelevanceFactors such as color, luster, and nutrition often affect consumer choice in food. However, the color and nutrition of foods tend to be destroyed during processing and storage. The demand for healthier and more nutritious food while retaining the color and flavor after processing highlights the need to develop novel and gentler technologies for fruit processing. Recently, high hydrostatic pressure (HHP) technologies have been used in different branches of the food industry. In the present study, the content of active component in blue honeysuckle fruit pulps such as anthocyanins and polyphenols showed tendency to increase and then decrease with increasing pressure at room temperature. Five different HHP treatment groups (resembling the conditions of active component extraction conditions and commercial sterilization) were compared to the control (fresh fruit) and heat-treated group to determine the effects of HHP processing on L. caerulea berry pulps. The aim of this study was to investigate the changes in active component particularly the content and composition of anthocyanins under different high-pressure treatment at room temperature; the color and physicochemical indexes were also analyzed at the same conditions. Low HHP for a long period of time (400 MPa/20 min) demonstrated better results than that with high HHP for a short time (600 MPa/10 min), as indicated by the higher contents of anthocyanins and phenols and stronger antioxidant capacities. Therefore, Low HHP conditions can be used as an auxiliary means of active component extraction. The conditions of HHP processing at low HHP for a long period of time (400 MPa/20 min) can be altered to retain active components during food processing.     

Kinetic desorption models for the release of nanosilver from an experimental nanosilver coating on polystyrene food packaging

To predict the kinetic desorption of silver from an experimental nanosilver coated polystyrene food packaging material into food simulants (0, 1, 2 and 3% acetic acid (HAc) in distilled water (dH₂O)) at 4 temperatures (10, 20, 40 and 70 °C), 5 sorption models were examined for their performance. A pseudo-second order kinetic sorption model was found to provide the best prediction of an unseen desorption validation dataset with R² = 0.90 and RMSE = 3.21. Poor predictions were witnessed for desorption at 70 °C, potentially due to re-adsorption of the silver back onto the polystyrene substrate, as shown in the kinetic migration experiments. Similarly, the temperature dependence of the desorption rate constant was satisfactorily described using the Arrhenius equation with the exception of the 70 °C scenario. The use of sorption models identified scenarios that may limit human exposure to nanosilver migrating from this experimental nanocoating, i.e. low temperature applications.Industrial relevanceThe use of antimicrobial packaging has the potential to reduce food spoilage and risk from pathogenic microorganisms while reducing food waste by extending the shelf life of food products. Coating of antimicrobial silver nanoparticles (AgNPs) to polymer surfaces is a highly advantageous technology as microbial contamination predominantly occurs on the surface of fresh and processed food products. However, uncertainty related to the potential release of nanoparticles from food packaging materials, subsequent potential human exposure and toxicology is a barrier to the uptake of these novel materials. In the European Union, where the safety assessment of these materials is stringent, mathematical models used to predict the worst case migration of nanoparticles from food packaging materials have supported the acceptance of some nanomaterials for use in food packaging. The performance of a number of desorption models was evaluated to predict the release of AgNPs from AgNP coated polystyrene. The model identified factors that influenced migration and possible industrial applications for the developed material to minimise human exposure. The study highlights the potential benefits of using predictive models to assess migration of NPs from polymers into food simulants instead of time consuming and expensive migration studies.     

Monitoring nisin desorption from a multi-layer polyethylene-based film coated with nisin loaded HPMC film and diffusion in agarose gel by an immunoassay (ELISA) method and a numerical modeling

Polyethylene-based films coated with nisin loaded HPMC films were put in contact with food simulants, i.e. agarose gels with 5 or 30% (w/w) fat. Nisin desorption from the multi-layer films and diffusion in agarose gels were monitored by ELISA (Enzyme Linked ImmunoSorbent Assay). The data obtained after 2 or 6 days of contact between antimicrobial films and agarose gels were employed to determine nisin mass transfer by numerical modeling following Fick's second law. The values were in the range from 0.87 × 10^? 3 m s^? 1 to 4.30 × 10^? 3 m s^? 1 and 6.5 × 10^? 11 m² s^? 1 to 3.3 × 10^? 10 m² s^? 1, for nisin apparent desorption and diffusion coefficients, respectively. The diffusion process was governed by interactions between food matrix simulant and nisin. Moreover, it was observed that the polymer in the coating did not modify plastic film initial mechanical resistance and water vapor permeability.Industrial relevanceThis paper concerns active packaging, considered as a new approach to preserve food shelf life. Active packaging is a real gain for plastic and Food industrials. The paper deals with coating as a manner to activate packaging. The impact of coating on film properties is investigated.Also, predictive models are proposed to determine antimicrobial agent desorption and diffusion during some storage conditions.     

Preparation of water-soluble chitosan from shrimp shell and its antibacterial activity

Crude chitosan was prepared from shrimp shell by HCl, NaOH and ethanol solution successively. Hydrogen peroxide was used to degrade the crude chitosan into water-soluble chitosan. A mathematical model between degradation conditions (H₂O₂ level, time and temperature) and the recovery of water-soluble chitosan was constructed using response surface methodology. Each factor showed a significant effect on the recovery. The model was confirmed to have a good fitness by analysis of variance. The optimal conditions to obtain the highest recovery of water-soluble chitosan were 5.5% of H₂O₂ level, 3.5 h of time and 42.8 °C of temperature. The predicted recovery was 93.5%. Through testing the number of colony, both crude and water-soluble chitosan showed good inhibition activities against B. subtilis. By determination of inhibition zone diameter, water-soluble chitosan showed significantly (P < 0.05) higher inhibition capabilities against E. coli, B. subtilis and S. aureus than crude chitosan.Industrial relevanceChitin is the second abundant polymer next to cellulose over the world. Its deacetylated product, chitosan, is an important ingredient in medicine and food. However, the low solubility in water limits the application of chitosan. In this work, the chitosan was degraded by H₂O₂ to produce water-soluble chitosan. Response surface methodology was taken to construct a model between degradation conditions and the recovery of water-soluble chitosan. By determination of the antibacterial activity, water-soluble chitosan showed better antibacterial activity than crude chitosan without degradation treatment. The results indicated the high potential of water-soluble chitosan as an antibacterial agent. This work was helpful for applying this product in industry.     

High hydrostatic pressure effect in extraction of 5-methyltetrahydrofolate (5-MTHF) from egg yolk and granule fractions

High hydrostatic pressure (HHP) and centrifugation were combined to produce a 5-methyltetrahydrofolate (5-MTHF)-enriched extract from egg yolk. This study focused on the effect of HHP treatment (200–600 MPa; 5, 10 min) in extraction of 5-MTHF from egg yolk and granule. Specifically, HHP-treatment at 400 MPa for 5 min significantly (p < 0.05) impacted protein extraction and was the optimum condition for 5-MTHF extraction, with recoveries of 230 ± 2.7 μg/100 g and 1264.6 ± 61.4 μg/100 g from yolk and granule, respectively. The applications of HHP combined with centrifugal separation resulted in recovery of free 5-MTHF from granule which was 5.5 times higher compare to yolk. The optimal parameters of HHP at 400 MPa for 5 min improve 93% the recovery of 5-MTHF from non-soluble granule and convert it to a soluble state. Electrophoresis of fractions revealed that high-pressure treatment of yolk and granule at 200–600 MPa resulted in considerable solubilization of low-density lipoproteins (LDL) and high-density lipoproteins (HDL)-phosvitin, which may be due to disruption of hydrophobic interactions. High pressure can be used to further fractionate yolk and granule in the development of new biotechnological applications.Industrial relevance: HHP combined with centrifuge separation was used an efficient and eco-friendly process for improving the recovery of water soluble vitamin 5-MTHF extracted from egg yolk granule. HHP treatment at 400 MPa for 5 min was the optimum condition where a higher concentration of 5-MTHF separated from granule. This study shows promising results in relation to applications of HHP in improving extraction and recovery of bioactive components from egg yolk and the future applications of granules as an ingredient in the food industry.     

Characteristics and in vitro anti-inflammatory activities of protein extracts from pre-germinated black soybean [Glycine max (L.)] treated with high hydrostatic pressure

We investigated the influence of high hydrostatic pressure (HHP) and pre-germination on black soybean protein and peptide characteristics. Black soybean was germinated (2 or 4 d) and subjected to HHP (0.1–150 MPa; 24 h), followed by preparation of extracts and testing for anti-inflammatory activity. The highest soluble protein content (815.85 mg/g) was in soybeans subjected to HHP (100 MPa) after germination (4 d). Germination and HHP caused the degradation of high molecular weight proteins; we detected the highest content of < 3 and < 10 kDa peptides (60.46 and 88.47 mg) and free amino acids (65.70 mg) in extracts from pre-germinated soybeans that received HHP (150 MPa). Pre-germinated (4 d) soybean extracts treated with HHP (150 MPa) significantly inhibited LPS-induced expression of inflammatory markers, nitric oxide (25.01%), TNF-α (76.78%), IL-1β (58.99%), and IL-6 (84.48%) by RAW 264.7 macrophages. These results suggest that peptides derived from black soybeans subjected to HHP and pre-germination may mediate anti-inflammatory activity.     

Okara treated with high hydrostatic pressure assisted by Ultraflo® L: Effect on solubility of dietary fibre

Okara is an abundant and inexpensive by-product from soybean, rich in total dietary fibre (> 55% dry weight), but poor in soluble dietary fibre (SDF, < 5% dw). A combined method of high hydrostatic pressure (HHP) aided by the food grade enzyme Ultraflo® L was used for SDF maximization. At atmospheric pressure, incubation time was not a key factor, and a ratio of 1:40 (enzyme:Okara, v/w) was able to saturate the enzyme within 120–150 min. When HHP plus Ultraflo® L were applied, a synergy between both treatments was observed. Thus, at 600 MPa, 0.025% Ultraflo® L and 30 min treatment, soluble carbohydrate added up to 15.64 ± 0.32%, consisting of two peaks (9.14 ± 0.18 and 0.57 ± 0.01 kDa), determined by HPLC-ELSD. The combination of HHP plus Ultraflo® L on Okara improved the solubility of the dietary fibre, making it more suitable to be used in functional foods.Industrial relevanceThere is an increasing interest in finding new prebiotics from food industrial waste. Okara has been simultaneously treated with Ultraflo® L and HHP, taking into account the industrial costs of the procedure, and adjusting the quantity of enzyme and time of treatment to the minimum, by a Response Surface Methodology and an enzymatic activity assay. Besides, an HPLC-ELSD direct analysis (High Performance Liquid Chromatography with Evaporative Light Scattering Detector) was employed to monitor soluble fibre, as an easy and fast analytical method.     

Isolation and characterisation of a novel antibacterial peptide from bovine αS1-casein

Bovine casein was hydrolysed with a range of proteolytic enzymes including pepsin, trypsin, α-chymotrypsin and β-chymotrypsin, and assessed for antibacterial activity. The pepsin digest of bovine casein, which showed antibacterial activity, was fractionated using reverse phase high performance liquid chromatography and the antibacterial peptides isolated were characterised using electrospray ionisation mass spectrometry. Two antibacterial peptides were identified, a novel peptide (Cp1) which corresponded to residues 99–109 of bovine α_S1-casein and a previously reported peptide (Cp2) which corresponded to residues 183–207 of bovine α_S2-casein. The minimum inhibitory concentration (MIC) of Cp1 and Cp2 were determined against a range of bacterial cultures. Cp1 exhibited an MIC of 125 μg mL⁻¹ against all Gram-positive bacteria tested, and MIC ranging between 125 and >1000 μg mL⁻¹ against the Gram-negative bacteria tested. Cp2 was generally far more potent against the Gram-positive bacteria, exhibiting an MIC of 21 μg mL⁻¹, compared to MICs ranging from 332 to >664 μg mL⁻¹ against most of the Gram-negative bacteria tested.     

Use of microwave processing to reduce the initial contamination by Alicyclobacillus acidoterrestris in a cream of asparagus and effect of the treatment on the lipid fraction

The effects of a short-time microwave (MW) treatments on the survival of Alicyclobacillus acidoterrestris spores (10⁵ spores/g) inoculated in a cream of asparagus, along with the oxidation of the fat component (olive oil), were investigated.The samples were MW-treated at 60–100% of power (2450 MHz) for 3–7 min; power and processing time changed according to a Central Composite Design at two variables/five levels. The combinations resulting in a 2-fold reduction in the number of alicyclobacilli spores (100% of power–5 min; 80%–6 min; 80%–7 min) were stored at different temperatures and times (25 °C/27 days, 37 °C/18 days and 50 °C/9 days), to determine the decay of the qualitative characteristics of the lipid fraction. Peroxide value, K₂₃₂, K₂₇₀ and Rancimat test (induction time) were chosen as indexes of primary and secondary oxidation. MW-effect on the spores depended upon both the power and the treatment time; moreover the interaction [power] × [time] was the most significant variable. As regards the effect of MW on the lipid fraction, the results suggested that MW affected slightly induction time, peroxide values and spectrophotometric determinations, especially at low powers.Industrial relevanceSince the middle of 1990s, MW-processing has been regarded as a convenient approach for the stabilization of vegetable preserves. In Southern Italy, olive oil is an essential ingredient for this kind of food; however, it is well known that a strong thermal processing as well as not-correct storage could affect it significantly and increase the art of oxidation.This research provides some useful information on the effects of MW for a new product, an asparagus cream, focusing on the influence of this approach on olive oil oxidation, thus suggesting that MW could be a convenient preservation technique.     

Packaging-specific influence of chitosan on color stability and lipid oxidation in refrigerated ground beef

We examined the influence of chitosan on lipid oxidation and color stability of ground beef stored in different modified atmosphere packaging (MAP) systems. Ground beef patties with chitosan (1%) or without chitosan (control) were packaged either in high-oxygen MAP (HIOX; 80% O₂ + 20% CO₂), carbon monoxide MAP (CO; 0.4% CO + 19.6% CO₂ + 80% N₂), vacuum (VP), or aerobic packaging (PVC) and stored at 1 °C. Chitosan increased (P < 0.05) redness of patties stored in PVC and CO, whereas it had no effect (P > 0.05) in HIOX. Chitosan patties demonstrated lower (P < 0.05) lipid oxidation than controls in all packaging. Control patties in PVC and HIOX exhibited greater (P < 0.05) lipid oxidation than those in VP and CO, whereas chitosan patties in different packaging systems were not different (P > 0.05) from each other. Our findings suggested that antioxidant effects of chitosan on ground beef are packaging-specific.     

Chemical changes of thermoxidized virgin olive oil determined by excitation–emission fluorescence spectroscopy (EEFS)

The fluorophores present in virgin olive oil evolve during any thermoxidation process and thereby fluorescence spectroscopy can be used as a straightforward approach to study the oxidative degree of oils. Samples of heated virgin olive oils collected from a fryer every two hours up to 94 h were analyzed to study their excitation–emission matrix (EEM) and the evolution of the fluorescent composition during the thermoxidation process. The potential usefulness of EEM to study thermoxidized virgin olive oils has been explored. For this purpose, parallel factor analysis (PARAFAC) was used to interpret the results. The emission profile obtained from three-factor PARAFAC model calculated for 47 samples of thermoxidized oil in the range of λ_ex = 250–298 nm and λ_em = 300–700 nm allows the decomposition of the fluorescence landscape in specific information about phenols, pigments and oxidation products respectively. The chemical interpretation from the PARAFAC model was checked with chemical analysis of phenols, tocopherols and chlorophyll pigments.     

The effects of high hydrostatic pressure at subzero temperature on the quality of ready-to-eat cured beef carpaccio

We compared the application of high hydrostatic pressure (HHP) on unfrozen carpaccio (HHP at 20 °C) and on previously-frozen carpaccio (HHP at − 30 °C). HHP at 20 °C changed the color. The pressure increase from 400 to 650 MPa and the time increment from 1 to 5 min at 400 MPa increased L* and b*. a* decreased only with 650 MPa for 5 min at 20 °C. The prior freezing of the carpaccio and the HHP at − 30 °C minimized the effect of the HHP on the color and did not change the shear force, but increased expressible moisture as compared to the untreated carpaccio. HHP at 20 °C was more effective in reducing the counts of microorganisms (aerobic total count at 30 °C, Enterobacteriaceae, psychrotrophs viable at 6.5 °C and lactic acid bacteria) than HHP at − 30 º C. With HHP at 20 °C, we observed a significant effect of pressure and time on the reduction of the counts.     

Reducing SO2 in fresh pork burgers by adding chitosan

The use of 0.02 or 0.05% chitosan is proposed to reduce from 450 to 150 mg kg^− 1 the SO₂ required to preserve pork burgers aerobically packed and stored at 2 °C for up to 21 days under retail display conditions. The effects of chitosan and/or sulfite addition and the storage time were determined in fresh (color deterioration, lipid oxidation, pH, total viable counts, Escherichia coli and coliforms, Salmonella, appearance and odor) and cooked (appearance, odor, flavor and texture) burgers. The addition of either 0.02 or 0.05% chitosan was not detected by sensory analysis, and extended the shelf life of low-SO₂ burgers from 7 to 14 days. Chitosan enhanced the preservative effects of sulfite at a low dose, acting on the main causes of meat deterioration (bacterial spoilage, color stability and lipid oxidation), and provided good sensory properties to fresh and cooked pork burgers.     

Effects of drying methods and conditions on antimicrobial activity of edible chitosan films enriched with galangal extract

The aim of this work was to study the effects of drying methods and conditions (i.e., ambient drying, hot air drying at 40 °C, vacuum drying and low-pressure superheated steam drying within the temperature range of 70–90 °C at an absolute pressure of 10 kPa) as well as the concentration of galangal extract on the antimicrobial activity of edible chitosan films against Staphylococcus aureus. Galangal extract was added to the film forming solution as a natural antimicrobial agent in the concentration range of 0.3–0.9 g/100 g. Fourier transform infrared (FTIR) spectra and swelling of the films were also evaluated to investigate interaction between chitosan and the galangal extract. The antimicrobial activity of the films was evaluated by the disc diffusion and viable cell count method, while the morphology of bacteria treated with the antimicrobial films was observed via transmission electron microscopy (TEM). The antimicrobial activity, swelling and functional group interaction of the antimicrobial films were found to be affected by the drying methods and conditions as well as the concentration of the galangal extract. The electron microscopic observations revealed that cell wall and cell membrane of S. aureus treated by the antimicrobial films were significantly damaged.