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Manipulation of chitosan binding on the polyethylene terephthalate (PET) surface and study of coatings on poultry meat shelf life-time
Tina Tkavc, 2014, doktorska disertacija

Opis: The aim of this study was to activate inert PET surfaces in order to introduce the surfaces’ carboxyl groups and to obtain its hydrophilic character, which was important for the chitosan bonding to it. Films where chitosan was attached to the PET could be used as active packaging material for food like fresh poultry meat. For PET activation two advanced and environmentally friendly techniques were used: 1) O2 plasma activation; and 2) CO2 plasma activation. Differently treated PET foils deposited on Au quartz crystals (model studies - adsorption and desorption) and real films were characterized. Later on, real films were studied in the terms of carboxylic/amino group content, hydrophobic/hydrophilic character, surface composition and adsorption/desorption of chitosan onto/from the surface. Results clearly showed that the use of both surfaces’ activation processes increased the ability of PET foils to adsorb chitosan, but CO2 plasma gave a higher concentration of carboxyl groups on the PET surface and consequently, due to the chemical bonding the chitosan layers were more stable. Even though CO2 plasma pre-treated PET foils gave better results during the experimental work, we could not avoid layer by layer adhesion of chitosan which resulted in non-bound molecules. Pre-treated foils and with chitosan functionalized foils were tested preliminarily with ASTME E1 (2002) microbiological tests. Functionalized CO2 plasma pre-treated foils gave the broadest spectra of antimicrobial activity, and therefore they were chosen for further microbiological analyses, where chitosan`s influence on inoculated poultry models towards selected standard strains, typical for poultry meat, was being tested. By determining the MIC (minimal inhibitory concentration) for selected microorganisms we have proven, that chitosan possesses antimicrobial properties at low concentrations. During the transfer of the experiment to a larger scale (food models, which are a very complex environment), it has been shown that on PET bonded chitosan did not have the inhibitory effect to that extent, with the exception of Staphylococcus aureus, as was expected. Similar results were expressed using both these methods: Colony count technique and real-time PCR. In the end, the organoleptic properties of the chicken models exposed to foils have shown that chitosan changes the color and taste of meat immediately after exposure, but samples were staying edible longer. Therefore, functionalized PET, which has an inhibitory influence towards variety of microorganisms, may be applied as an active packaging system for poultry meat after some optimization of the coating procedure in binding chitosan onto the PET surfaces.
Ključne besede: PET/chitosan/antimicrobial packaging/adsorption-desorption kinetics/microbiological tests
Objavljeno: 22.10.2014; Ogledov: 800; Prenosov: 59
.pdf Polno besedilo (3,65 MB)

Regulation of metabolic changes in shredded cabbage by modified atmosphere packaging
Andrej Plestenjak, Tomaž Požrl, Janez Hribar, Tatjana Unuk, Rajko Vidrih, 2008, izvirni znanstveni članek

Opis: The influence of different storage conditions on the storability of packaged shredded cabbage has been studied. The cabbage cultivar Fieldrocket was cut and packaged in glass jars and in polyethylene (PE) or polypropylene (PP) film. Several initial atmospheres were established within the packaged cut cabbage: 100 % N2, 5 % O2/95 % N2, 10 % O2/90 % N2, normal atmosphere (NA), 70 % O2/30 % N2 and 100 % O2. Samples were stored at two different temperatures of 0 and 10 °C for 7 days. Variation in CO2 and O2 concentrations was higher at 10 °C compared to 0 °C and the highest at the atmosphere consisting of 70 % O2/30 % N2. A decrease of O2 below 3–5 % and an increase of CO2 above 2–5 % in the packed product resulted in the appearance of anaerobic metabolism. An initial atmosphere consisting of 100 % O2, and a storage temperature of 0 °C resulted in delayed anaerobic metabolism compared to other atmospheric conditions and storage temperature of 10 °C. Rinsing of fresh cut cabbage also resulted in lower accumulation of acetaldehyde and ethanol. A higher variation in CO2 and O2 concentrations, and consequent accumulation of anaerobic metabolites had a negative influence on the sensorial properties of the cut cabbage. The higher permeability of PE film compared to PP and glass enabled faster exchange of CO2 and O2, which resulted in lower accumulation of anaerobic metabolites. However, a higher O2 concentration had a negative influence on the colour of fresh-cut cabbage. The best results were achieved by packing the fresh-cut cabbage in PE film with an initial atmosphere of 100 % O2 and stored at 0 °C.
Ključne besede: cabbage, modified atmosphere, packaging, polyethylene, polypropylene, respiration, anaerobic metabolism
Objavljeno: 24.07.2017; Ogledov: 64; Prenosov: 0
.pdf Polno besedilo (156,50 KB)

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