Mario Ščetar

Shelf life of packaged sliced dry fermented sausage under different temperature.

The aim of this study was to investigate the shelf-life of commercial sliced dry fermented sausage during storage at different temperatures. Different laminate composition was used for vacuum and nitrogen (100% N(2)) packaging. The microbiological, physico-chemical and sensory parameters were analysed during 120 days storage at 4, 22 and 37°C. Packaging materials were analysed for their barrier characteristic (oxygen permeability). Sensory quality limited the shelf-life of sliced dry fermented sausages before the limiting effects of microbial proliferation occurred. Nitrogen atmosphere packaging allowed longer storage (>120 days) than vacuum (95 days) packaged dry fermented sausages at 4°C.

Carvacrol affects interfacial, structural and transfer properties of chitosan coatings applied onto polyethylene.

Different chitosan coating solutions were tested with the aim of investigating their adhesion and wettability onto polyethylene film to improve packaging performance and provide antimicrobial properties. Surface wetting kinetics was monitored by contact angle measurements. Addition of ethanol and carvacrol improved wettability and adhesion of the thin chitosan layer. Structure, water vapour, O2, CO2 and air permeabilities of self supported chitosan films and coated polyethylene were determined. The formation of a thin chitosan layer on polyethylene improved gas barrier properties decreasing the Permeability Coefficient for oxygen and carbon dioxide ( [Formula: see text] , [Formula: see text] ) from 100 to 10,000 times. Presence of carvacrol in the chitosan coating layer increased [Formula: see text] , [Formula: see text] and Pair by a factor of ten. Moreover, it influenced film microstructure. However chitosan was shown to be good gas barrier film in the dry state.

Development of low density polyethylene nanocomposites films for packaging

Requirements for adequate permeability of polymeric materials to gases and vapors, good barrier and mechanical properties of polymers have boosted interest in developing new strategies to improve these properties. Research and development in polymeric materials coupled with appropriate filler, matrix-filler interaction and new formulation strategies to develop composites have potential applications in various types of packaging (agricultural produce, dried food, frozen food etc.). In this study, LDPE composites containing various types of fillers (zeolite TMAZ 7, nanoclay Cloisite 20A and precipitated calcium carbonate, CaCO3) were prepared using extrusion/injection molding. The microstructural and morphological changes as well as mechanical features of samples were characterized by scanning electronic microscopy and by tensile tests. The thermal degradation of LDPE composites was studied using thermogravimetric analysis. Barrier properties (permeability, the diffusion and the solubility constant) in modified LDPE samples were determined. It is found that used minor clay concentration is already very effective for achievement of good morphology. In the presence of nanoparticles, at lower content, the value of oxygen permeability of LDPE decreases. Also, the results have revealed that the samples containing fillers have increased thermal stability in comparison to pure LDPE.

Polyethylene/Polycaprolactone Nanocomposite Films for Food Packaging Modified with Magnetite and Casein: Oxygen Barrier, Mechanical, and Thermal Properties

ABSTRACT Polyethylene (PE) was modified and prepared as double-layer polyethylene/polycaprolactone (PE/PCL) film. Magnetite and casein were added to the PCL-coating film to improve barrier properties and prevent destruction of basic structure of primary polymer PE. Significant improvements were observed with regards to mechanical (tensile strength, elongation at break) and thermal properties, while barrier (O2 permeability) properties were slightly improved. Overall migration values into acetic acid were lower (from 1 to 4.6 mg/dm2) than the upper limit set by the legislation. Specific migration of iron in PE/PCL-Fe samples is also below (µg/L) specific migration limit value set by the legislation (mg/kg). GRAPHICAL ABSTRACT

Preparation and Properties of Low Density Polyethylene Film Modified by Zeolite and Nanoclay

PE-LD samples containing two types of filler in concentrations of 2–10 wt.% (zeolite TMAZ 7 and nanoclay Cloisite 20A). The microstructural and morphological changes as well as mechanical features of samples were characterized by scanning electronic microscopy (SEM) and by tensile tests. The thermal degradation of PE-LD composites were achieved using thermogravimetric analysis (TGA). The permeability, the diffusion and the solubility constants of the gases in modified PE-LD films were calculated and the gas separation (N2/O2; O2/CO2) ability was determined. In the presence of nanoparticles, at lower content, the value of oxygen permeability of PE-LD decreases.

Modification of Physico-Chemical Properties of Acryl- Coated Polypropylene Foils for Food Packaging by Reactive Particles from Oxygen Plasma

This investigation was focused on the influence of long-living neutral reactive oxygen species on the physico-chemical properties of acryl-coated polypropylene foils for food packaging. Reactive species were formed by passing molecular oxygen through a microwave discharge and leaking it to a processing chamber of a volume of 30 L, which was pumped by a rotary pump. The density of neutral O-atoms in the chamber was tuned by adjustment of both the effective pumping speed and the oxygen leak rate. The O-atom density was measured with a catalytic probe and was between 3 × 1018 and 5 × 1019 m−3. Commercial foils of biaxially oriented polypropylene (BOPP) coated with acrylic/ poly(vinylidene chloride) (AcPVDC) were mounted in the chamber and treated at room temperature by O atoms at various conditions, with the fluence between 1 × 1021 and 3 × 1024 m−2. The evolution of the surface wettability versus the fluence was determined by water contact angle (WCA) measurements, the formation of functional groups by X-ray photoelectron spectroscopy (XPS), and the morphology by atomic force microscopy (AFM). The WCA dropped from the initial 75° to approximately 40° after the fluence of a few 1022 m−2 and remained unchanged thereafter, except for fluences above 1024 m−2, where the WCA dropped to approximately 30°. XPS and AFM results allowed for drawing correlations between the wettability, surface composition, and morphology.

Barrier Properties of Plastic Polymers

The barrier property of a plastic polymer is a measure of its ability to permit the transfer of permeants such as gases, water vapor and aromas. Barrier polymers are often multiple layer laminates composed of a water vapor and gas barrier layer, a heat sealable layer and a structural or protective layer. As barriers they separate food from the external environment and limit the movement of permeants such as gases, vapors and aromas. Physical factors such as temperature, humidity, polymer orientation, and cross-linking can affect the barrier properties of a polymer. Knowledge of the barrier properties of plastic polymers is crucial for the design of food packaging that will deliver the desired shelf life.

Influence of Barley Sourdough and Vacuum Cooling on Shelf-Life Quality of Partially Baked Bread

Driven by the bakery industry urge to satisfy consumer demand for fresh, diverse and high quality bakery products, we investigated the influence of barley sourdough and vacuum cooling on shelf life quality of partially baked bread stored in modified atmosphere packaging at ambient conditions. Barley sourdough was fermented with Lactobacillus reuteri (DSM 20016, F275). Partially baked bread with sourdough was microbiologically acceptable during 30 days of storage, while bread without sourdough had detectable mould on the 30th day. Stored bread samples were rebaked after 1, 8, 15, 22 and 30 days to determine moisture content, physical and sensorial properties. Moisture loss (5%) was detected on the 15th day, after which it remained stable until the end of investigated storage period. Nevertheless, textural quality of stored bread continuously declined due to crumb firming. Bread flavour did not change during mould-free storage time. The principal component analysis identified major differences in the flavour of sour and control bread, also in crumb firmness and moisture content of samples. This study indicates the positive role of barley sourdough fermented with L. reuteri in improving crumb texture for at least 15 days, and ensuring mould- and bacteria-free partially baked bread for 30 days. Vacuum cooling combined with sourdough improved bread shape, porosity, and reduced sour taste, crust colouring and crumbliness. Hence, it can successfully extend shelf life quality of partially baked bread in modified atmosphere packaging.