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The effect of mushroom extract, with or without acidification with glucono-8-lactone, and the overnight incubation of the spores in CaCl 2 , on the heat resistance of B. stearothermophilus ATCC 12980 spores was studied. The temperature range considered was 121 to 140°C for mushroom extract and CaCl 2 and 121 to 145°C for double-distilled water as a reference substrate. The results indicated that mushroom extract without added acid significantly reduces the thermal resistance of the spores in comparison to the double-distilled water. Acidification of the mushroom extract reduces the heat resistance of spores of B. stearothermophilus at 121°C. However, above 130°C lowering of the pH did not significantly reduce the thermal resistance of the spores, and so no generalizations should be made with regard to the effect of the pH when high temperature-short time (HTST) processes are being considered. Overnight incubation in CaCl 2 and subsequent heat treatment lead to increased heat resistance at 121°C compared to that observed in double-distilled water. However, at 130°C and above CaCl 2 did not increase the apparent heat resistance of the spores.

The effect of subculture medium composition (pH, type of acidulant, presence of EDTA) on the germination of spores of Clostridium sporogenes PA 3679, both with and without heat treatment in phosphate buffer (30 s at l25°C), was studied. Additionally, the effect of the heating medium substrate and pH and subculture medium pH and composition on the heat resistance of the spores was evaluated. The results indicate that the pH of the recovery medium and the type of acidulant have significant effects (P ≤ 0.05) on counts of PA 3679. Adding EDTA only increases inhibition of this microorganism when the pH is near neutral. For a given pH level, citric acid provided greater inhibiting power than glucono-δ-lactone, although the percentage of undissociated acid was less for citric acid. No growth was observed at pH 5.7, although in the case of glucono-δ-lactone sporadic colony development was seen in some plates. The pH of the heating medium acidified with glucono-δ-lactone did not affect the heat-resistance paramet...

In the present study, thermally stable silver complexes were produced and incorporated into a poly-( l -lactide) (PLA) matrix by melt-compounding. The effect of the different formulations on the mechanical and color properties was first evaluated. Additionally, the release of silver ions to an aqueous environment was also monitored over time by anodic stripping voltammetry and correlated with the antimicrobial performance against Salmonella enterica. The incorporation of some silver compounds with contents of 1 wt% did not affect the mechanical or optical properties of the films. The films showed a good potential for application in surface treatment and demonstrated a sustainable, antibacterial effectiveness in liquid and solid food environments. These results give new unreported insight into the production of transparent thermally stable and antimicrobial polymers based on the release of ionic silver and about their potential application in antimicrobial food packaging.

The increase of consumer demand for higher quality and longer shelf-life in foods, while reducing the use of non-compostable packaging materials, has encouraged research on biopolymers incorporating natural antimicrobial compounds. Cinnamaldehyde (CNMA) and allyl isothiocyanate (AITC) were incorporated into polycaprolactone (PCL) films by solvent casting. The release study was carried out by means of ATR and transmission FTIR spectroscopy and showed high volatility of the essential oils during the film forming process. While only negligible quantities of AITC were retained in the polymer matrix after film curing, the release of CNMA was prolonged for at least 50 h at room temperature. PCL films incorporating 10 wt.-% and 20 wt.-% CNMA were further investigated using both a macrodilution technique and a vapour diffusion technique. MICs against Salmonella enterica, and Listeria monocytogenes in the liquid phase were determined to be 5.87 and 4.49 mM, for films containing 10 and 20 wt.-% of CNMA with regard to the polymer in solution. The influence of relative humidity (RH) and temperature on the antimicrobial performance of the active films was investigated in the vapour phase. RH was not found to play a key role in the release and antimicrobial performance of the films, while decreasing temperatures resulted in a considerable increase in the antimicrobial effect. In a sealed environment, a concentration of less than 5.34 mg CNMA/L air from PCL with 20 wt.-% CNMA was able to cause complete inhibition of bacterial growth at 4 °C and 10 °C during at least 30 days. These results suggest that the combination of cold storage with biodegradable polyesters incorporating CNMA or other EOs could be an interesting approach in active packaging technologies.

Although silver is being extensively used in food or other applications as the key component to control microbial proliferation, many factors affecting its real potential are still unknown. In the present work, the presence of specific ligands or the contents in organic matter was correlated with silver speciation and its antibacterial performance. Silver was found to be only active in form of free silver ions (FSI). The presence of chloride ions produced an equilibrium of stable silver chloride complexes which were void of antimicrobial efficacy. However, even at relatively high concentrations of chlorides, a small fraction of FSI may still be present, producing a bactericidal effect with concentrations at the nanomolar level under optimum conditions. Low concentrations of thiol groups completely inactivated silver, while methylsulphur groups only affected its efficacy at very high concentrations. Antibacterial performance revealed differences of about 1000-fold between results for environments with high organic matter content and results for aqueous salt buffers. Thiol groups were nonetheless not found directly associated with the decrease in antimicrobial performance in a nutrient rich environment. These results point out the complexity of the antimicrobial systems based on silver and can have relevance in food or other applications of silver as an antimicrobial.

There is a growing trend to develop packaging materials with an active role in guarantying that the quality and safety characteristics of packaged products will remain or improve from preparation throughout shelf-life. In the present study, 0.001-1.0 wt.% silver ions were satisfactorily incorporated into polylactide (PLA) films by a solvent casting technique. Silver migration from the films was measured by voltamperometry and then correlated with its antimicrobial efficacy against Salmonella enterica and feline calicivirus (FCV), a human norovirus surrogate, by using the Japanese industrial standard (JIS Z 2801). The PLA-silver films showed strong antibacterial and antiviral activity in vitro, with increasing effects at higher silver concentrations. Moreover, results show that FCV was less susceptible to silver than Salmonella. When films were applied on food samples, antibacterial and antiviral activity was reduced as compared to in vitro. Antimicrobial activity was very much dependent on the food type and temperature. In lettuce samples incubated at 4 °C during 6 days, 4 log CFU of Salmonella was inactivated for films with 1.0 wt.% and no infectious FCV was reported under the same conditions. On paprika samples, no antiviral effect was seen on FCV infectivity whereas films showed less antibacterial activity on Salmonella.

In the present study, tailor-made ethylene vinyl alcohol copolymer (EVOH) fibers containing different amounts of antimicrobial silver ions and nanoparticles were developed by electrospinning and subsequent thermal annealing. The morphology of the fibers was examined by scanning and transmission electron microscopy and thermal properties were characterized by differential scanning calorimetry. Speciation and controlled release of silver from the fibers was monitored by anodic stripping voltammetry and energy dispersive X-ray spectroscopy. Before aging, 100 % of the silver recovered from the electrospun structures was in ionic form to be instantly released in contact with moisture with varying temperature-dependent kinetics. Thermal annealing of the fibers at 100 °C for 1, 2, and 4 days prompted the gradual transformation of 70, 93–94, and 98–99 % of the total silver into nanoparticles homogeneously distributed along the fibers, which were mostly retained within them, producing a substantial decrease in their release capacity. Speciation and release profiles from the fibers were correlated with their antibacterial performance against Listeria monocytogenes and Salmonella enteric. This study is a step forward in the understanding of silver-based electrospun antimicrobial polymers and puts forth the suitability of EVOH for the development of targeted delivery systems in a number of applications.

The use of silver as an antimicrobial in the food area has raised wide interest in recent years. In the present work, 0.001-10 wt % silver ions was satisfactorily incorporated into an ethylene-vinyl alcohol (EVOH) copolymer matrix by a solvent casting technique. The antibacterial efficacy of the composite was evaluated under laboratory conditions and in contact with some foods. The ionic compound did not affect the crystallinity or the water-induced plasticization of the materials and was homogeneously distributed across the surface and thickness of the films. When immersed in water, sorption-induced release of 50-100% of the silver ions took place in30 min. In the bacterial minimal growth medium M9, the minimal inhibitory concentration (MIC) of the film was in the range of 0.01-0.1 ppm. High protein content food samples displayed low susceptibility to the films (1 log reduction in any case), whereas low protein content food samples exhibited no detectable bacterial counts for films with 1 and 10 wt % silver and about 2 log reduction for films with 0.1 wt % silver. These results represent a step forward in the understanding of silver antimicrobial efficacy and its possible application in the food-packaging industry, most likely as food coatings.

The purpose of this study was to generate ultrathin fibers based on polylactide (PLA) biopolyester with antimicrobial controlled release capacity to treat bacterial infections. To achieve this objective, gentamicin antibiotic was encapsulated into pure PLA fibers, a blend of PLA–collagen and coaxial fibers containing a skin of PLA and a core of collagen using the electrospinning technique. The morphology of the gentamicin-loaded fibers and the antibiotic distribution within the fibers were examined by SEM and TEM. The drug delivery profile of the different electrospun fibers was analyzed using a spectrophotometric method. The performance for treating common possible post-surgical infections was investigated against Staphylococcus epidermis, Pseudomonas aeruginosa and Escherichia coli. The morphology of the electrospun fibers as well as the hydrophilicity of the polymer blends ultimately determined the antibiotic release characteristics. The results indicated that such drug-loaded fibers can serve as advanced delivery platforms with strong and timing controllable antibacterial properties.

Bone tissue interfacial scaffolds, which encourage cell growth, are critical determinants for clinical success after implant surgery. Over the years, a number of resorbable configurations have emerged for bone cell support and growth, but only a few have demonstrated clinical efficacy. Polymer coatings produced by electrospinning are regarded as very promising bone interfaces because of the ultrathin-scaled dimensions of its physical structure. In this study, the morphology, composition, thermal properties, and cell growth viability of a number of polylactide-based systems containing different binary and ternary formulations of this biomaterial with collagen and commercial hydroxyapatite nanoparticles were characterized. The best performance in terms of biocompatibility was obtained for the tricomponent system in which the submicron fibers were further subjected to uniaxial orientation process during formation. The in vitro proliferation of the cells, which harbored on these ultrathin-structured mats, was examined by means of a metabolic activity indicator and ensured by means of scanning electron microscopy, and cell anchorage was checked by fluorescent optical microscopy. Finally, the optimum tricomponent material was successfully sterilized for the first time by gamma radiation without noticeable losses in cell-seeding capacity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

This study reports for the first time about the formulation, morphology, water barrier and the antimicrobial activity of high and low molecular weight chitosonium-acetate based solvent-cast blends with ethylene–vinyl alcohol (EVOH) copolymers. The blends based on the low molecular weight chitosan grade showed enhanced phase morphology, transparency, enhanced water barrier properties, up to 86% water permeability reduction compared to pure chitosonium-acetate films, as well as excellent antimicrobial activity. When the fraction of low molecular weight chitosan exceeded the phase inversion in the blend, phase segregation became noticeable but good interfacial adhesion was still observed. On the other hand, the blends with the high molecular weight chitosan grade were translucent, even when this component was in the dispersed phase, and exhibited clearly separated phase morphology but also presented antimicrobial performance. In both cases, and in accordance with previous works in our laboratory, the release from the blends of protonated glucosamine groups (so-called active species) correlated well with the antimicrobial phenomenology of the developed materials. The study also showed that EVOH copolymers can also be made antimicrobial by a water sorption-induced release mechanism, if acetic acid is incorporated into the polymer formulation before casting from solution. On the overall, antimicrobial chitosan-based blends with EVOH copolymers, when low molecular weight chitosan was used as the dispersed phase in the blend, exhibited optimum performance in terms of optical properties, water resistance, enhanced water barrier and, therefore, excellent application outlook in antimicrobial applications.

Electrospinning of uniform biohybrid fibers with concealed cellulose microfibrils (CMF) is reported as a promising and environmentally sound concept for reinforcement of polymer nonwoven fiber syst ...

This paper describes the formulation, morphology and biocide properties of novel antimicrobial electrospun zein based ultrathin fiber structures. From the results, it was found that the electrospun fibers of zein can turn the material into a new strong antimicrobial ultrathin-structured system due to retention of remnant amounts of trifluoroacetic acid as determined by ATR–FTIR spectroscopy. Unfortunately, this system may be considered to yield very aggressive high acidic media due to release of the strong acid, which causes the antimicrobial behavior. Nevertheless, since biocide properties are more desirable at mild acidic conditions, blending zein with the natural antimicrobial chitosan (up 10 wt.%) was found to be the route of choice to yield water insoluble fiber mats, with efficient biocide properties, attributed in this case not to the acid but to the chitosan component. Differential scanning calorimetry thermograms indicated that despite the fact that both components, as suggested by scanning electron microscopy observation, are not miscible, the presence of the chitosan phase leads to slightly enhanced glass transition temperature for the zein phase. Selective removal of chitosan from the blend indicated that this component is primarily present in beaded regions of the ultrathin fiber mats.

The electrospinning technology opens up enormous possibilities for the implementation of bio-based materials and food hydrocolloids in numerous applications. In this context, chitosan is a sustainable, biocompatible, biodegradable, antimicrobial and non-toxic polysaccharide of great relevance in many fields of application. Because of its abundance in nature and excellent biocompatibility, the cationic polysaccharide chitosan is a very promising polymer for producing functional nanofibers. Although the material has good physicochemical properties, the electrospinning of the polymer is far from easy. In the current study, the effect of an unprecedented number of parameters (including solvent nature, polymer origin, molecular weight and spinning conditions) on morphology is reported. The work also aims to ascertain the antimicrobial properties of the generated biofibers of chitosan and relate them to its chemical structure. Finally, a new route is provided to generate chitosan based nanoporous structures starting from blends of chitosan and polylactic acid.

The biocide properties of chitosan-based materials have been known for many years. However, typical antimicrobial formulations of chitosan, mostly chitosonium salts, are known to be very water sensitive materials which may impair their use in many application fields such as food packaging or food coating applications. This first work reports on the development and characterization of the antimicrobial properties of novel fully renewable blends of chitosan with more water-resistant gliadin proteins isolated from wheat gluten. Chitosan release to the nutrient broth from a wide range of blends was studied making use of the ninhydrin method. The results indicated that both pure chitosan and its blends with gliadins presented significant antimicrobial activity, which increased with increasing the amount of chitosan in the composite formulation as expected. The gliadins-chitosan blends showed good transparency and film-forming properties and better water resistance than pure chitosan. The release tests revealed that dissolution of the biocide glucosamine groups, i.e. the chitosan water soluble fractions, also increased with the amount of chitosan present in the formulation. The release of these groups was for the first time directly correlated with the antimicrobial properties exhibited by the blends. Thus, incorporation of chitosan into an insoluble biopolymer matrix was revealed as a very feasible strategy to generate novel chitosan-based antimicrobial materials with potential advantages, for instance active food packaging applications.

Since the market for minimally processed foods is broadening, packaging is being implemented in strategies that actively contribute to the food preservation and transformation concepts. One opportunity is given by the incorporation of biocatalysts, usually in prefabricated carriers, where they can fully retain their activity. These biocatalysts can be repeatedly reused within the packaging or, under controlled conditions, migrate to the product. The potential use of packages composed of classic polymers with functional surfaces or highly swellable biopolymers is being successfully tested, showing good perspectives for the controlled release when directly used in contact with the product or as part of combined strategies. Moreover, new nanostructured materials (modified clays, LBL assemblies, electrospun fibres) are being implemented as part of more innovative solutions. This review summarizes the most recent developments and upcoming possibilities to incorporate biocatalysts in polymers traditionally used in food packaging applications and in some recently introduced biopolymers.

The purpose of this chapter is to conduct a structured and systematic review of published literature on the current state of knowledge regarding silver-based antimicrobial packaging; in particular, the antibacterial capacity of silver nanoparticles (AgNPs) has been compiled in this chapter. The release kinetics and antimicrobial properties of AgNPs incorporated into biobased polymers such as polylactic acid and polyhydroxyalkanoates have been extensively reviewed. Additionally, enteric viruses are a growing concern in many areas, especially in foods. This chapter reviews the usage of silver to fight enteric viruses.

ATR-FTIR spectroscopy has been used in this study to characterize the molecular mechanisms and kinetic processes that take place when a chitosonium acetate thin coating is put in contact with water solutions, Staphylococcus aureus solutions, microbial nutrient solutions, and with a high water activity TSA hydrogel medium to simulate the effect of direct contact with high moisture foods such as fresh meats, fish, and seafood products or beverages. The results of this work suggest that the biocide carboxylate groups that form when chitosan is cast from acetic acid solutions are being continuously evaporated from the formed film in the form of acetic acid (mechanism I) in the presence of environmental humidity, rendering weak biocide film systems. On the other hand, upon direct contact of the cast chitosonium acetate film with liquid water, water solutions, or the high moisture TSA hydrogel, a positive rapid migration, with a diffusion coefficient faster than 3.7 x 10(-12) m2/s, of protonated glucosamine water soluble molecular fractions (mechanism II) takes place from the film into the liquid phase, yielding strong antimicrobial performance and leaving in the remaining cast film only the non-water soluble chitosan fractions. Finally, this study describes a refined spectroscopic methodology to predict the antimicrobial properties of chitosan and gives insight into the capacity of chitosan as a natural biocide agent.

Strawberries (Fragaria x ananassa Duch.) were treated either with 1% calcium gluconate dips, 1.5% chitosan coatings or with a coating formulation containing 1.5% chitosan + 1% calcium gluconate and stored at 20 °C for up to 4 days. The effectiveness of the treatments was assessed by evaluating their impact on the following parameters: fungal decay incidence, loss of weight, firmness, external color, pH, titratable acidity and soluble solids content. Calcium dips were effective in decreasing surface damage and delaying both fungal decay and loss of firmness compared to untreated fruit. No sign of fungal decay was observed in fruit coated with 1.5% chitosan which also reduced fruit weight loss. Chitosan coatings markedly slowed the ripening of strawberries as shown by their retention of firmness and delayed changes in their external color. To a lesser extent titratable acidity and pH were also affected by coatings. Whilst addition of calcium gluconate to the chitosan coating formulation did not further extend the shelf-life of the fruit, the amount of calcium retained by strawberries was greater than that obtained with calcium dips alone, thus resulting in increased nutritional value of the strawberries.

A mathematical model based on Weibull parameters was built to describe the joint effect of temperature and pH on thermal inactivation of Bacillus cereus spores (strain INRA TZ415). The effect of these factors on Weibull model parameters ( β , 1/ α ) was also studied. Heat inactivation tests were carried out in acidified carrot broth as vegetable substrate, following a full factorial design at four levels for temperature (80, 85, 90 and 95 °C) and pH (6.2, 5.8, 5.2 and 4.7). The Weibull distribution model provided good individual fits for the different combinations of temperature–pH tested, with discrepancy factors, D f , coming close to 25% for most cases. The temperature and pH did not have a significant effect on the shape parameter ( β ), which yielded a mean value of 0.88. The scale parameter ( α ) decreased with pH, and its inverse (1/ α ) followed an Arrhenius-type relationship with temperature. A global model was built, including the dependence of the α parameter on temperature and pH, and the model parameters were estimated by using a one-step nonlinear least-squares regression to improve the precision of the estimates. Results indicated that the global model provides a satisfactory description of the thermal inactivation of B. cereus spores, with R 2 equal to 0.983.

Isothermal and non-isothermal heat resistance studies were carried out on Bacillus pumilus spores. The non-isothermal study revealed a non-linear behavior of the survivor curve, which was revealed as a tail after an isothermal study. Results indicated that the spores obtained by isolating cells from colonies of the tail section were more heat resistant than the original ones (D 104°C = 0.15 and 1.9 min for spores from the original population and from the tail, respectively). Application of the Weibull distribution model to analyze the tail produced good results at the 3 temperatures studied. Nevertheless, when the model was applied to curves having both concave downward and concave upward sections a poor result was obtained, with an accuracy factor greater than 1. Dans cette etude, la resistance de spores de Bacillus Pumilus, isolees de legumes, a des traitements thermiques isothermes ou non isothermes est evaluee. L'etude non isotherme revele un comportement non lineaire de la courbe de survie. Elle explore l'utilisation d'un modele optionnel, le modele de distribution de Weibull qui permet une prediction plus precise du nombre de spores de B. pumilus qui peuvent survivre a un traitement thermique doux.

In the present study, silver ions were incorporated into a poly-(l-lactide) (PLA) matrix by a solvent casting technique using different solvents and glycerol as plasticizer. The effect of the different formulations on the morphology, thermal, mechanical and color properties were first evaluated. Additionally, a thorough study of the silver ions release to an aqueous environment was also monitored over time by anodic stripping voltammetry and correlated with the antimicrobial performance against S. enterica. The incorporation of silver contents of up to 1 wt % did not affect morphology, thermal or mechanical properties of the films. A sustainable, antibacterial effectiveness was found for the films in liquid medium and a breakpoint of 10–20 μg L−1 silver was established under the stated conditions, evincing silver ion releasing technologies may be applied to liquid environments while complying with current legislation. This study provides insight into the structure properties relationship of these antibacterial polylactide materials of significant potential in coating applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41001.

Two enterotoxigenic Bacillus cereus strains, isolated from cooked chilled foods containing vegetables, were characterized in relation to safe food production by studying their heat resistance characteristics. The kinetic parameters of thermal resistance were determined by one-step nonlinear regression and were compared with those calculated by using two linear regressions. Results showed that the new analysis methodology applied in this study can improve the estimation ofD - and z - values. Great differences were found in the thermal resistance of the two strains. TheD90°C were 4·04 and 39 min for the AV TZ415 and AV Z421 strains respectively. Growth studies indicated that the two strains were able to grow at refrigeration temperatures, but the minimum growth temperature for the AV Z421 strain was 10°C, while the less heat-resistant strain, AV TZ415, grew at 5°C.

The effect of different concentrations of sodium chloride (NaCl) in the recovery medium on the apparent thermal resistance of Bacillus stearothermophilus spores (strain ATCC 12980) was studied. Spores were heated at different temperatures (115–125°C) and subcultured in medium with different NaCl concentrations [1, 2, 3 and 3.5% (w/v)]. The results indicate that increasing NaCl levels decreases the apparent heat resistance of the spores, over a temperature range of 115–125°C. No significant difference was found between 3 and 3.5% (w/v) NaCl although both reduced B. stearothermophilus heat resistance considerably. A second-order polynomial equation provided a good description of the spores’ D value, as influenced by the temperature and NaCl concentration. Predictions from the model compared well with published data, and therefore the model is suitable for predicting the effect of NaCl concentration on thermal inactivation of B. stearothermophilus.

The effect of recovering Bacillus stearothermophilus spores under anaerobic conditions on their apparent thermal resistance was studied. Spores were suspended in bidistilled water as a reference medium, heated at 115, 117, 119, 121, 123 and 125°C and recovered under aerobic and anaerobic conditions. D values (decimal reduction time) obtained following recovery under anaerobic conditions were lower than those obtained under aerobic conditions. Reductions of between 31 and 48% were found for all the temperatures studied. When spores were suspended in mushroom extract and recovered under anaerobic conditions the apparent heat resistance was much lower than that obtained under aerobic conditions (D121°C was 4.3 min and 1.7 min, under aerobic and anaerobic conditions, respectively). Heating the spores in mushroom extract and recovering the spores under anaerobic conditions produced an additive effect, decreasing the apparent heat resistance of the B. stearothermophilus spores.

Cylindrical particles of alginate and alginate/starch food puree were developed for use as carriers in a microbiological time temperature integrator (TTI). The mechanical properties of the restructured food particle, stress (σ f ) and strain at failure (e f ), were studied as a function of different composition parameters (alginate and food concentration, pH, type offood added, and addition of starch). Addition of food puree produced gels that were weaker than puree alginate ones, although no differences in mechanical properties were obtained among the three levels of food puree concentration studied in this work. However, the type of food significantly affected these rheological parameters, producing the weakest gel when artichoke puree was added to the alginate. The pH also affected the mechanical properties: the lower the pH, the weaker the particle. When starch was added, the particles developed could be frozen without losing their mechanical resistance and handling. The results indicated that particles containing 2% alginate and 4% starch showed the best mechanical stability.

A mathematical treatment for a heat penetration phenomenon with variable boundary conditions is presented. The system of differential equations for determining the unsteady-state temperature distribution inside a particle was solved by use of spectral methods as a new tool in food process development. A preliminary study was conducted on the use of a mathematical model to predict lethality in a sterilizing process. The model was validated using a calibrated time-temperature integrator (TTI) with immobilized Bacillus stearothermophilus spores, commonly used in TTIs for process validation. A comparison between the experimental data using Bacillus stearothermophilus and the predicted data obtained with the proposed model showed good agreement.

A time temperature integrator (TTI) was developed by immobilizing Bacillus stearothermophilus spores in a cylindrical particle consisting of an alginate-starch-mushroom puree. The particle showed homogeneous spore distribution, and when heated over a temperature range of 121 – 130° C negligible spore leakage was observed after the thermal process. The experimental data on spore survivor levels obtained for each temperature-time combination were compared with theoretical predictions using a mathematical model. The results showed a good correlation between the experimental and theoretical data. All these results provide evidence that this artificial particle could be a very reliable TTI for monitoring the thermal impact on micro-organisms during validating sterilization processes in continuous aseptic systems.

Although the application of silver based antimicrobial systems is a widespread technology, its implementation in areas such as food packaging is still challenging. The present paper describes the fabrication of poly(lactic acid) (PLA) coated with beeswax with controlled release properties for sustained antimicrobial performance. Release of silver ions from the polymers was monitored voltammetrically under various conditions (surface contact, immersion in various liquid media and at different pH values) throughout at least 7days. A higher release was noted with decreasing pH while surface release was much slower than the release when immersed in liquid medium. While uncoated films demonstrated a high burst release which in some instances implied surpassing some current migration restrictions (

Thermal resistance of Bacillus stearothermophilus spores has been established inoculating spores in alginate-mushroom puree mixture (ungelled) and in alginate-mushroom puree mixture set in calcium chloride (gelled). Data are compared with those obtained suspending the spores in distilled water, mushroom extract and in calcium chloride. Results indicated that, in general, D values obtained in gelled mixture were higher than D values obtained in distilled water, mushroom extract or in ungelled mixture, while the D value in the ungelled mixture was similar to that obtained in distilled water. D121 value in gelled mixture was close to that obtained in 2% (w/v) calcium chloride.

This chapter deals with a very trendy topic related to the design of efficient antimicrobials based on natural extracts, which are of particular consideration in food-packaging applications. The reason why natural extracts generate significant interest lies in the fact that they are natural compounds, typically extracted from foods or plants, and are, therefore, perceived as safer antimicrobials. Additionally, viruses are a growing concern in many areas, but since more recently also in foods. This chapter uniquely reviews the usage of natural compounds to fight viruses.

Silver is known to inhibit microorganisms and therefore it is an ideal candidate for its incorporation in a wide variety of materials for food applications. However, there is still a need for understanding how silver prolonged exposure to bacterial contamination affects the bioavailability of the active silver species. In the present study, growth curves of Listeria monocytogenes and Salmonella enterica were performed for 3–5 days in Tryptic Soy Broth (TSB) and M9 minimal medium (M9) in the presence of silver ions and silver solutions previously in contact with the growth media. The cultivability of the bacteria under these conditions was correlated with the viability of the bacterial populations as measured by flow cytometry analysis (FC) using a LIVE/DEAD BacLight kit. It was found that, after a period where viable counts were not detected, bacterial populations recovered and were able to proliferate in most cases. The resuscitation of the cultures was explained by both the existence of a resilient fraction of bacteria in a compromised state and the parallel inactivation of the silver species. This inactivation was found to be highly influenced by time dependant chemical reactions taking place in the environment of exposure, producing differences of at least 3 fold between results for nutrient rich environments and results for limiting environments. This study points out the need for understanding these chemical interactions and bacterial mechanisms of adaptation and may have relevance in the design of silver-based antimicrobial systems for food-related applications.

The thermal resistance of Bacillus stearothermophilus spores was studied in bidistilled water as the reference medium, mushroom extract and acidified mushroom extract. Citric acid and glucono-δ-lactone were used as acidulants. Results indicated that mushroom extract affects the heat resistance of spores; D values were lower than for those in bidistilled water. The pH effect was lower with higher treatment temperatures. Acidification reduced the thermal resistance of spores, the reduction being similar for both types of acidulants, and in general it also had the effect of increasing the z values. It has been confirmed that acidification of the canned mushrooms could actually help to control the thermophilic spoilage. This acidification could also be obtained by the use of glucono-δ-lactone, which has been shown to be as effective as citric acid in reducing the heat resistance of spores.

1.1 Pathogens in Food: Public Health Importance . . . . . . . . . . . . . . . . . . . . . . 2 1.2 Primary Contamination and Its Causes . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2.1 Salmonella spp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2.2 L. monocytogenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2.3 S. aureus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2.4 C. jejuni . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2.5 E. coli O157:H7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.3 Prevention and Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.4 Antimicrobial Agents for Food Preservation. . . . . . . . . . . . . . . . . . . . . . . . 8 1.5 Methods to Determine the Antimicrobial Activity . . . . . . . . . . . . . . . . . . . . 9 1.6 Plastics and Bioplastics in Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.7 Antimicrobials in Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Docosahexaenoic acid (DHA) is a long chain polyunsaturated fatty acid of the omega-3 series (omega-3), which exerts strong positive influences on human health. The target of this study was the stabilization by encapsulation of this bioactive ingredient in zein ultrathin capsules produced by electrospraying. The zein ultrathin DHA encapsulation was observed by ATR-FTIR spectroscopy to be more efficient against degradation under both ambient conditions and in a confined space (so-called headspace experiment). In the latter case, that more closely simulates a sealed food packaging situation, the bioactive DHA was considerably more stable. By fitting the degradation data to a specific auto-decomposition food lipids kinetic model, it was seen that the encapsulated omega-3 fatty acid showed a 2.5-fold reduction in the degradation rate constant and also had much higher degradation induction time. Moreover, the ultrathin zein-DHA capsules resulted to be more stable across relative humidity and temperature. Finally, headspace analysis by gas chromatography coupled with mass spectrometry showed that the presence of 3 main flavor-influencing aldehydes in the headspace was much lower in the zein encapsulated DHA, suggesting that the encapsulated bioactive also releases much less off-flavors. Electrosprayed ultrathin capsules of zein are shown to exhibit potential in the design of novel functional foods or bioactive packaging strategies to enhance the stability of functional ingredients. Practical Application: This article presents a novel methodology for the stabilization by encapsulation of omega 3 nutraceuticals via electrospraying and has potential application in the development of functional foods.

[EN] Collagen, as the major structural protein of the extracellular matrix in animals, is a versatile biomaterial of great interest in various engineering applications. Electrospun nanofibers of collagen are regarded as very promising materials for tissue engineering applications because they can reproduce the morphology of the natural bone but have as a drawback a poor structural consistency in wet conditions. In this paper, a comparative study between the performance of different cross-linking methods such as a milder enzymatic treatment procedure using transglutaminase, the use of N-[3-(dimethylamino)propyl]-N¿-ethylcarbodiimide hydrochloride/ N-hydroxysuccinimide, and genipin, and the use of a physical method based on exposure to ultraviolet light was carried out. The chemical and enzymatic treatments provided, in this order, excellent consistency, morphology, cross-linking degree, and osteoblast viability for the collagen nanofibers. Interestingly, the enzymatically cross-linked collagen mats, which are considered to be a more biological treatment, promoted adequate cell adhesion, making the biomaterial biocompatible and with an adequate degree of porosity for cell seeding and in-growth., The authors acknowledge the EU integrated project NEWBONE, the company Nanobiomatters Ltd. (Paterna, Spain), and the Spanish MEC (Project MAT2006- 10261-C03) for financial support and Impex Química Corp. for supplying TG

The aim of this work was to assess the antimicrobial capacity of chitosan-based films obtained by a dissolution and solvent evaporation (solvent casting) method at various temperatures (i.e., 37, 80, and 120 degrees C) on the growth of Staphylococcus aureus and Salmonella spp. bacteria. The effect of temperature (4, 23, 37 degrees C) and relative humidity (RH; 0, 75%) during storage on the biocide performance was also investigated. Color parameters and ATR-FTIR spectra were analyzed for each sample to investigate the relationship between structural and/or chemical alterations in the films during storage and biocide performance. The results indicated that films formed at 37 and 80 degrees C presented a significant inhibitory effect for both types of bacteria; however, when cast at 120 degrees C, the films ceased to exhibit antimicrobial properties. Curiously, chitosonium acetate films were seen to diminish to a large extent their biocide properties when stored at 23 degrees C and 75% RH for 2 months or alternatively when stored and 37 degrees C and 0% RH over the same period of time. In good agreement with this behavior the FTIR results indicated that under the previous conditions a significant fraction of the biocide carboxylate chemistry remained in the polymer after contact with the bacterial solution due to a strong reduction in cast film solubility. Because biopolymer active species migration from the film to the culture media is needed for the biomaterial to exhibit measurable antimicrobial effect, proper control of temperature and humidity during film formation and storage is necessary to design the optimum performance of chitosan as a biocide.

The objective of this study was to assess the antimicrobial effectiveness of chitosonium acetate films on the growth of Listeria monocytogenes, Salmonella spp. and Staphylococcus aureus. The samples were tested in both laboratory conditions using Tryptone Soy Broth (TSB) and in a real food system using fish soup. The study was carried out at different temperatures (4, 12, and 37 degrees C) in order to discern the influence of such variables. Moreover, a sensory evaluation of the final product was performed as a parameter of consumer acceptance. The results showed a significant reduction of the bacterial growth, which greatly depended on the bacteria type, the temperature of incubation and the food substrate. Although the effectiveness of chitosan films decreased in the fish soup, neither the sensory properties nor the pH of the soup was affected upon their addition. The application of chitosonium acetate as an internal coating of the packaging material could be a very suitable means to assure safety of liquid food products such as fish soup at the range of temperatures studied.

Publisher Summary Retortable plastic pouch has been considered the most significant advance in food packaging since the metal can and has the potential to become a feasible alternative to the metal can and the glass containers. The choice of materials for the manufacture of retortable pouches is very important. The packaging materials must protect the food product against light degradation, moisture changes, microbial invasion, oxygen ingress, and food–package–environment interactions. The plastic material must maintain its structural integrity and be able to withstand retort temperatures as well as normal handling abuse. It must also comply with regulatory requirements. It is known that seal and burst strengths of plastic packages are much lower at thermal processing temperatures. These packaging materials must maintain adequate seal strength to assure protection of package integrity when high temperature processing is applied. Another concern in food quality and safety regarding the use of retortable plastic-based structures is the potential employment of reusable plastic food materials. Polymers containing polar groups, such as polyamides and the most widely implemented material in retortable plastics, the ethylene–vinyl alcohol copolymers, which are the most suitable barrier elements in retortable plastics, suffer from barrier deterioration after retorting. It has been proved that even protected by hydrophobic layers, the oxygen permeability of the copolymers is greatly deteriorated during the sterilization processes. This chapter focuses on the improvement of the performance of retortable plastics.

[EN] The aim of this work was to develop antimicrobial photosensitizer-containing edible films and coatings based on gelatin as the polymer matrix. incorporating sodium magnesium chlorophyllin (E-140) and sodium copper chlorophyllin (E-141). Chlorophyllins were incorporated into the gelatin film-forming solution and the inhibiting effect of the cast films was tested against Staphylococcus aureus and Listeria monocytogenes. The results demonstrated that water soluble sodium magnesium chlorophyllin and water soluble sodium copper chlorophyllin reduced the growth of S. aureus and L monocytogenes by 5 log and 4 log respectively. Subsequently, the activity of self-standing films and coatings containing E-140 was assessed on cooked frankfurters inoculated with S. aureus and L monocytogenes. These tests showed that it was possible to reduce microorganism growth in cooked frankfurters inoculated with S. aureus and L monocytogenes by covering them with sodium magnesium chlorophyllin-gelatin films and coatings., The authors would like to thank I. Galdeano for technical support. They are also grateful for the financial support of the Generalitat Valenciana (Project GV04B-194) and the Spanish Ministry of Education and Science (project AGL2003-07326-C02-01).

This pioneering study reported about the film-forming properties of high-molecular-weight chitosan as followed in situ by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, and has implications in fields such as biomedical, pharmaceutical, packaging, and coating applications. From the results, it was observed that immediately after dissolution in an acetic acid aqueous solution and subsequent casting over the ATR crystal, the formed carboxylate antimicrobial (-NH3+ -OOCH) species are not stable in the film formulation and become reduced over time; further assays confirmed previous research, which suggested that the presence and stability of these groups is strongly dependent, among other factors, on storage conditions. As-received chitosan and chitosan neutralized in NaOH films did not exhibit biocide performance towards Staphylococcus aureus. The antimicrobial tests were also found to strongly relate the presence of a sufficient quantity of these carboxylate groups to the chitosan activity as a biocide agent. Moreover, a novel methodology based on the use of a normalized infrared band centered at 1405 cm(-1) is proposed which can be correlated with the antimicrobial character of the biopolymer.

Unheated and heated (1 min at 121 o C) Bacillus stearothermophilus spores were grown in non-acidified (pH 7) and acidified recovery medium at different pH levels (6.7, 6.5, 6.2 and 5.9) using citric acid or glucono-δ-lactone (GDL) as acidulants. It was observed that the lower the pH, the lower the proportion of micro-organisms which recovered. The level of recovery was not the same for both acidulants, meaning that at the same pH level citric acid showed a greater inhibitory effect that glucono-δ-lactone. Heat treatment sensitized spores to pH effect. A linear relationship of the behaviour of spores with each acidulant is proposed

Rough and smooth variants of Bacillus stearothermophilus strains ATCC 12976 and 12980 were isolated. These variants showed morphologically different colonies. In both strains the rough variants were less heat-resistant than the smooth ones, and their activation occurred in a shorter time; on the other hand, their dipicolinic acid (DPA) content was higher. These results indicate that a relationship between higher DPA content and higher thermal resistance does not exist. Therefore, this evidence supports the hypothesis that DPA is not the determining factor in the degree of spore heat resistance but that it could, instead, have a role in maintaining thermal resistance obtained by other means.

The effect of isothermal and non-isothermal heat activation on germination and thermoresistance of two strains of Bacillus cereus spores was studied. Results indicated that the germination after isothermal activation was lower than after non-isothermal heating. The activation rate affected the z value, which increased with faster heating rates. For each temperature and inactivation rate, the non-isothermal activation at rate of 2 degrees C/min resulted in larger D values (D90 = 4.70 min) than isothermal activation (D90 = 4.04 min). The two mathematical equations used to analyse non-isothermal data produced similar predicted D and z values, nevertheless the Hayakawa equation modified in this work for non-linear regression analysis, requires less computational effort.

Two mathematical models have been studied to establish the relationship between the pH, treatment temperature and thermal destruction constant (k) of Bacillus stearothermophilus and Clostridium sporogenes spores. The study was carried out by heating the spores in mushroom extract acidified with two different acidulants (citric acid and glucono-delta-lactone). Among the models studied, the one that best described the inactivation was a second order polynomial equation, the precision of which depended on the microorganism studied.

Bacillus stearothermophilus spores were heated in a mixture of mushroom puree with alginate, in the temperature range 110–130°C. Both Arrhenius and the traditional Bigelow models were used to describe the dependence of the constant inactivation rate (K) or (D) with the temperature. Results showed that both are very good linear regression models, but a discrepancy between 20 and 45% was found in the constant inactivation rate predicted by both models at high temperatures (125–140°C). Despite this discrepancy, the Arrhenius model was a better predictor of the inactivation rate constants at temperatures of 125 and 130°C for B. stearothermophilus spores heated in an alginate-mushroom mixture.