Glass bottles having a metal closure are preferred for oxygen sensitive beverages e.g. beer. Using thinner closure which comprise polyvinyl chloride-free component is more sustainable. However, protecting the sealing performance as a result of metal closure thickness reduction is challenging. Here we show the relation between the leakage in beer bottles and surface roughness of three different thermoplastic elastomer seals. Compression relaxation and creep-recovery behavior of seals have been analyzed by using a dynamic mechanical analyzer. The results showed that metal downsizing was possible with Liner A (low density polyethylene (LDPE)/styrene-ethylene-butylene-styrene) and B (LDPE/ styrene-butadiene-styrene), but not with Liner C (high-density polyethylene/butyl rubber). Optimizing smaller surface topography parameters such as the surface roughness depth R_z, kurtosis S_ku, average void volume V_vv, arithmetic mean peak curvature S_pc, the density of surface peaks S_pd and higher peak material volume V_mp, peak material portion S_mr resulted in a better sealing performance. Liner C was found to show an increased leakage risk, since there was a high level of stress relaxation leading to a reduced sealing force. The sealing liner material with low relaxation, low elastic modulus and high creep recovery compliance was found to ensure better sealing when thinner metal closures are used.

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Seal area represents the most problematic part in food packaging for controlling the moisture and gas ingress and preserving product quality. Understanding the mechanism of heat sealing, which is a widely used method in flexible packaging, is critical for maintaining product quality throughout the storage and preventing food waste. Likewise, understanding the factors causing the leak formation in the seal interface helps to avoid failures and increase integrity for all seal types produced by heat sealing methods. This review looks at heat sealing and its mechanisms in flexible food packaging materials and particularly focuses on the reasons behind the encountered seal integrity problems that have a detrimental effect on food quality and shelf life. Heat sealing mechanisms, form fill seal systems and seal types were analyzed. Then, factors affecting the leak formation have been grouped as process parameters, material properties, contaminants, and further processes, which is uncharted territory in open literature. Finally, the details of these groups and their interrelationships were examined and discussed. Revealed key factors as shown in this study are expected to guide future research for understanding leak formation mechanisms in flexible food packaging.

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Thermoresponsive films are favorable for the packaging of fresh fruits and vegetable products as their gas permeabilities increase to a greater extent than commercial films when temperature abuse occurs during refrigerated storage. Thermoresponsive polyurethane (PU) films were synthesized from polyethylene glycol (PEG) with three different molecular weights (400, 1000, and 1500 g mol⁻¹), castor oil (CO) with two different proportions (30 and 50 %, CO/PEG ratio) and a constant level of 1,4-butanediol (BDO). The effects of these compositional factors on the thermal, mechanical, physical, structural, and gas barrier properties of the films were investigated. Melting temperatures (T_m) of the PU films varied from 25 to 29 °C and decreased with CO content. Glass transition temperatures (T_g) of the films were all below −32 °C and decreased by increased CO content. PU films with 1500 g mol⁻¹ PEG and 30 % CO/PEG ratio had better shape memory (R_r) and shape fixity (R_f) properties than others. O₂ permeabilities of the PU films were in the range of 1.99–7.25 barrer while their CO₂ permeabilities were between 10.3 and 18.3 barrer. The temperature sensitivity of the gas permeabilities of the PU films was higher than that of a commercial LDPE film, which makes them more appropriate for fresh produce packaging. Nevertheless, PU films were mechanically weaker and they had higher water vapor permeability compared to the LDPE film. These properties of the PU films need further improvements for potential packaging applications.

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Metal closures with a polymer-based sealing for beer bottles have been known since the late nineteen-sixties. However, to what extent which parameter of the polymer sealing gasket plays a role in closure performance to keep the beer quality to a highest level possible is not fully understood. For this purpose three thermoplastic elastomer (TPE) liners were investigated by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectrometry, dynamical mechanical analysis (DMA), scanning electron microscopy (SEM) and surface roughness in order to understand the effect of relative humidity (RH) and carbon dioxide (CO2) on their physical and chemical properties as well as their macromolecular structures. The TPEs’ viscoelasticity in the frequency domain under different isothermal conditions was evaluated. RH and CO2 were effective for changes in thermomechanical and surface properties. Liner C was found to have lower seal performance attributed to its relatively higher crystallinity, stiffness, weaker bond structure and rougher surface. Vibrations can lead to seal leakage in Liner B due to its higher damping behavior during production and transportation. Liner A outperforms others due to stabile behavior within the operational temperature range.@en

A series of drug-loaded pectin hydrogels were prepared by mixing method in two ion types, Ca⁺² or Zn⁺², for wound dressing applications and their drug release performances were investigated at pH 6.4 in four different calcium ion concentrations of external solution. Pectin hydrogels were synthesized in three different concentrations of initial pectin solution and theophylline was used as a model drug. Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy were used for hydrogel characterization. Additionally, fluid handling capacity, swelling behavior, dehydration rate, dispersion characteristic, dressing pH determination, water vapor permeability, oxygen permeability, surface contact angle, flexibility, mass per unit area, and thickness were determined for selected hydrogels. One of the most valuable contributions of our study is that the concentration of initial pectin solution and calcium ion concentration of external solution are very important parameters to obtain an effective drug release. After evaluating all data, we have shown that flexible and transparent pectin-based wound dressings can be synthesized as a controlled drug release system. Zinc-containing hydrogel was antibacterial against Staphylococcus aureus and Escherichia coli but not suitable for cell migration. On the other hand, calcium-based hydrogel was nontoxic on the fibroblast cells and it had no negative effect on cell migration.

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A thermoplastic polyurethane (PU) polymer was synthesized, casted into films, and specific and overall migration (OM) tests were applied. A new method with gas chromatography–flame ionization detector was proposed to measure specific migration (SM) of 1,4-butanediol from the PU film. OM values in the four established simulants were under the legal limits. Determination of 1,4-butanediol migrating from PU film to the three established simulants showed maximum SM result as 1.5 mg/kg which was far below the legal limits. Therefore, the PU film has a good potential as a safe food contact material. Moreover, the analytical method used for determination of SM of 1,4-butanediol resulted in good analytical characteristics and detection limits at ppm level.

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Thermoplastic polyurethane (PU) polymers with different chemical compositions were synthesized and casted to films, and their water vapor barrier properties at different range of relative humidity (RH) were characterized. The water vapor permeability (WVP) of packaging films is one of their most important properties to identify their suitability for use as packaging materials and is rather a complicated phenomena if the polymer has polar nature. The WVPs of PU films are determined both by permeation measurements which are a steady-state method and water vapor sorption measurements which are a non-steady-state method. Effective permeability (P_eff), solubility (S_eff), and diffusion (D_eff) coefficients of PU films were determined at 23 °C within the RH range of 0–97%. It was found that P_eff, S_eff, and D_eff increased with increasing RH gradient due to water vapor and polymer interactions. Microscopic images showed that 1,4-butanediol (BDO) helped to improve porous structure. Castor oil (CO) caused a decrease in the intensity of active absorption sites, namely, the C=O···H-N hydrogen bonds between chains. Results of two methods were yielded in the same magnitude of order. In most cases, the non-steady-state (sorption) method yields higher WVP values than steady state. At 0➔85% RH, the difference was up to 8-fold. Conditioning and equilibrating of films at 50% RH helped to reach sorption data approximate to permeation data. It was suitable to use sorption measurements to estimate the WVP which is a considerable simplification for polar polymers, e.g., developed PU film.

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The conjugation reaction of electrospun fibers of a mixture of whey protein isolate (WPI) and dextran using different molecular weights (40, 70, and 100 kDa) and mixing ratios was studied. This study includes the electrospinnability of a mixture of WPI and dextran, and the conjugation reaction between them via the initial stage of the Maillard reaction. The WPI-dextran fibers were characterized using optical and transmission electron microscopy. The covalent attachment of dextran to WPI was confirmed using sodium-dodecyl-sulfate-polyacrylamide gel-electrophoresis with protein and glycoprotein staining. Both 70 and 100 kDa of dextran and WPI at mixing ratios of 2:1 and 3:1 in phosphate buffer (30 mM, pH 6.5) were electrospun using needleless electrospinning. The solution concentration of the mixture was 50 wt% (33.3/37.5 wt% for dextran/16.5/12.5 wt% for WPI). The optimal conjugation conditions chosen from the experiments were a mixture of dextran (70 kDa)-WPI at 3:1 (75% relative humidity, 60 °C, 48 h).

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Thermoplastic shape memory polyurethane (SMPU) polymers were synthesized, cast to films, and their gas barrier properties were characterized. In addition, performance of an optical method was assessed by measuring oxygen permeability (PO2) of the films. PO2 of the SMPU film was at least two times higher than that of low density polyethylene (LDPE and increased at higher relative humidity. Permselectivity (PCO2/PO2) of the SMPU film was 15, which is approximately three times higher than for LDPE. The film absorbed circa 18% water vapor at 98% relative humidity. The optical method agreed very well (maximum 20% deviation) with a standard carrier gas method in PO2 measurement. Overall our results show that SMPU is an attractive polymer for fresh produce packaging.@en

There is an increasing concern on the environmental issues related to petroleum-based plastics as packaging materials. Therefore, the interest for biodegradable packaging materials from renewable sources (biopolymers) has been increased steadily, particularly for the utilization in short-term packaging and throwaway applications. However, biopolymers have usually low barrier and mechanical characteristics with poor processability resulting in limitations for their scalable production and industrial use. To overcome these limitations, bio-nanocomposites with enhanced packaging characteristics such as mechanical strength, barrier properties against gases and water, and optical clarity have been developed. Moreover, bioactive ingredients can be added to give the targeted functional properties to the subsequent packaging materials. This chapter reviews distinctive sorts of new biobased nanocomposite materials, for example, biodegradable and edible nanocomposite films, and their commercial applications as packaging materials, and relevant regulations.

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Currently, there is a growing interest for encapsulation of bioactive ingredients using calcium alginate microspheres or beads. Diffusion of the Ca in the alginate droplets provokes an ionic gelation and their conversion to hydrogel beads. The main objective of this study is to investigate the influence of physical properties of alginate and CaCl₂ solutions on alginate droplet formation and penetration into gelling bath, in size and shape of Ca-alginate beads. The droplet formation and penetration in the calcium bath was investigated using a high-speed video recording. Viscosity of alginate solution was modified by changing the alginate concentration (from 10 to 30 g/L) and the viscosity of the bath was modified by using different water/glycerol mixes (0–90% of glycerol) to prepare the CaCl₂ solution. Surface tension of CaCl₂ solution is reduced by adding different concentrations of surfactants (Tween 20) in a range of 0.01–1 g/L. Droplets detach from the tip with a tear shape. In all conditions tested, the droplets reach a spherical shape in less than 15 ms after detachment and less than 25 mm from the tip. Spherical beads are obtained when the kinetic energy is high enough to break the surface resistance of the calcium bath and droplet viscosity high enough to avoid deformations. Penetration depth of alginate droplets were mainly affected by viscosity and surface tension of CaCl₂ solution. When viscosity and surface tension of CaCl₂ solution increases, sphericity decrease and shape deformations are observed. The surfactant addition enhanced penetration and prevented shape deformations of Ca-alginate beads.

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The demand for minimally processed fresh fruits and vegetable products by consumers has been increasing around the world. Minimally processed fruits and vegetables are convenient fresh products with high nutritional quality. They are prone to microbiological and biochemical degradations, and thus, technologies to prevent these degradations without adversely affecting the fresh quality are desired. Conventional thermal preservation treatments are not suitable for these products. Several emerging nonthermal technologies have great potential alone or in combination for preserving minimally processed fresh produce products. This chapter provides a brief overview of the nonthermal technologies such as ozone, electrolyzed water, gamma irradiation, ultraviolet light (UVC), pulsed light, ultrasound, cold plasma, dense-phase CO₂ processing, high-pressure processing, pulsed electric field, and edible coatings. Their applications alone or in combination on minimally processed fresh produce products including fresh cuts and freshly squeezed juices are discussed.

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The aim of this work was to investigate the effect of film formulations in an effort to obtain a fresh produce packaging film with increased temperature sensitivity for gas permeability. Series of shape-memory polyurethane (SMPU) were synthesized using poly(ethylene glycol) (PEG), 1,6-hexamethylene diisocyanate, 1,4-butanediol and castor oil (CO) and casted into films. The changes in thermal, viscoelastic, shape-memory properties and oxygen permeability of the films were studied. The polyurethane films with 1500 g mol−1 PEG showed a phase transition temperature (switching temperature) between 20 and 27°C. The SMPU consisting of 50/50 CO/PEG had a log E′ value of 8.32 Pa and showed good elasticity as low density polyethylene. SMPU prepared from 1500 g mol−1 PEG with 50/50 CO/PEG and 40/60 butanediol/(PEG + CO) ratios showed excellent shape-memory properties with shape recovery ratio >85% and shape fixity ratio >90%. This film had higher oxygen permeability and showed up to 67% increase in Q10 value for oxygen permeability compared with commercial packaging films like low density polyethylene. This film can be used to develop smart packaging with increased thermally responsive gas permeability to similar levels observed in respiration rates of fresh produce.@en

In this study, the influences of roasting and the amount of hazelnut flour on the formation and stabilization of emulsions containing different amounts of oil were investigated. After hazelnuts were roasted in an oven at 140 °C for 40 min, the oil content was removed. The emulsions with defatted hazelnut flour containing corn oil at 3%, 10% and 50% were prepared. Roasting process significantly decreased the interfacial tension values of samples down to 1.9 mN/m due to protein denaturation. There was no significant difference between the particle sizes of oil droplets in emulsions with roasted and raw hazelnut flour at the same concentration. However, diffusion coefficients of oil droplets increased for emulsions containing roasted defatted flour samples. The zeta (ζ) potential values of all emulsions increased when roasted hazelnut flour was used, indicating the stabilization of suspensions and the solution resistance against aggregation. Storage modulus (G′), loss modulus (G″) and complex viscosity (η^*) of emulsions were measured. G′ value was found to be greater than the G″ value, which fits into weak gel model. The roasting process resulted with lower transition temperatures but with increased transition enthalpies of the flour samples based on differential scanning (DSC) measurements. Lower transition temperatures may be attributed to the partial gelatinization of starch in the flour and partial denaturation of proteins. These results may help to tailor the properties of defatted hazelnut flour when it is used in food products containing emulsions such as sauces, dressings and creams for stabilizing purposes.

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The effect of roasting on functional properties of defatted hazelnut flours was evaluated by using response surface methodology (RSM). Color, water absorption capacity, emulsion and foaming properties were the main responses that determine the degree of roasting. After roasting of hazelnuts, the oil absorption and water absorption capacity, foam and emulsion stability of the flour were increased, whereas bulk density, foaming capacity and emulsion activity of flours decreased. The roasting temperature was found to be the main factor affecting color development, emulsion properties and foaming capacity. The maximum responses for color, emulsion and foaming properties were obtained at 140 ° C and 40 min from the regression equations. RSM is a useful tool which can be applied to adjust the desired functional properties of flours. The results indicated that roasted defatted hazelnut flours may have a good potential to be used as value-added food ingredients, similar to other protein sources with various functional properties for food applications due to their nutritional value and improved functionality.@en