Polyelectrolyte multilayers (PEMs) deposited on porous composite polylactic acid/poly(ε-caprolactone) (PDLA/PEC) substrates were studied. The substrates were previously charged in a corona discharge. Time dependences of the normalized surface potential for positively and negatively charged electrets were investigated. The morphology of the obtained porous substrates was examined by means of scanning electron microscopy (SEM). The chitosan and the casein polyelectrolytes were deposited on the substrates using the layer-by-layer (LbL) technique. The drug loading efficiency and the release kinetics were determined spectrophotometrically.

Polyelectrolyte multilayers (PEMs) deposited on porous composite poly-lactic acid (PDLA)/poly(ε- caprolactone) (PEC) substrates are investigated. The substrates are charged with a corona discharge. The dependence of the normalized surface potentials on the storage time of the charged substrates is studied. Layer-by-layer (LbL) technique enables multilayer deposition on the substrates. A model drug Benzydamine hydrochloride is loaded into the chitosan layers. A study of the drug release kinetics in saline buffer is carried out and the amount released is quantified spectrophotometrically.

Polyelectrolyte multilayers (PEMs) deposited on non-porous and porous blend substrates were studied. Films, prepared from two biodegradable polymers poly (D-lactic acid) (PDLA) and poly(ε-caprolactone) (PCL) and their blends were used as substrates in the present paper. All films were initially charged in a corona discharge (positive or negative corona). After charging, the initial surface potential of the samples V₀ was measured and the normalized surface potential was calculated. The dependencies on time of the normalized surface potential for electrets, possessing either positive or negative charges, were studied. It was found that the steady-state values of the normalized surface potential for the porous substrates were higher than those of the non-porous ones, independently of material type and corona polarity. It was also shown that the values of the normalized surface potential for the PCL electrets were the highest and decreased when the content of PDLA increased. Scanning electron microscopy (SEM) was utilized for the determination of the substrates’ surface morphology. With the largest pore size, PCL substrates allowed for a greater capture of charges on their surface and facilitated the retention of said charges for prolonged periods of time. Differential scanning calorimetry (DSC) measurements were performed to determine the degree of crystallinity, which was very high for PCL substrates, when compared to the other investigated substrates. The wettability of the investigated substrates was measured using the static water contact angle method. The obtained results demonstrated that the created blends were more hydrophilic than the pure films. The two chosen polyelectrolytes were layered onto the surface of the substrates with the use of the layer-by-layer (LbL) technique and benzydamine hydrochloride was loaded in the multilayers as a model drug. Its loading efficiency and release profile were carried out spectrophotometrically. It was determined that for non-porous substrates, independently of the corona polarity, the best fitting model was Korsmeyer-Peppas, while for the porous substrates the best fitting model was Weibull.

Polyelectrolyte multilayers films containing Benzydamine hydrochloride (Benz) loaded casein nanoparticles were developed aiming to increase the structure drug loading efficiency and to prolong the drug release. The multilayers were built on biodegradable polyester substrates, which were previously charged in a corona discharge. Medium viscosity sodium alginate (SA) was used as a partner in the multilayer formulation. The SA and the casein nanoparticles were deposited on the substrate using the layer-by-layer (LbL) deposition technique. The drug loading efficiency and the release kinetics in artificial saliva were determined spectrophotometrically.

Deep frying is one of the most commonly used methods of food preparation. An essential factor in the frying process is the choice of a suitable oil – it plays a role in the heat transfer and as a product impregnation medium. Repeated use at high temperature leads to a number of reactions of oxidation, polymerization, and thermal destruction, which lead to changes in oils’ physical, chemical, nutritional, and sensory properties. Since the changes result from different processes, they cannot be evaluated by a single method. The processes differ in their extent for the different oil types. Therefore, the aim of the present study is to investigate the quality changes in three vegetable oils, namely refined sunflower oil, high oleic acid sunflower oil (HOSO), and rapeseed oil using different physical and physico-chemical methods. General chemical parameters, such as acid value and fatty acid composition were measured by standard methods, namely titrimetry and gas chromatography. The oxidation stability and oxidation degree along with the dynamics of the oxidation processes during frying were assessed by Rancimat method along with UV spectroscopy and electric impedance spectroscopy. The thermal behaviour of the oils and more precisely the amount of polar compounds formed during frying and their effect on the recrystallization phenomena are examined by differential scanning calorimetry.

Extending the shelf life of food products is of great importance to the food industry. Polylactic acid (PLA) is known as a promising biopolymer that can be used for food packaging due to its high mechanical and permeability properties. However, its low elasticity and high rigidity at room temperature, as well as poor moisture and gas barrier properties limit its applicability. On the other hand, this biopolymer has a significant potential for optimizing physical properties through material modifications, including in combination with natural additives as different polyphenols. Polyphenols are a class of naturally occurring compounds found in plants, exhibit a wide range of beneficial properties, including antioxidant, anti-inflammatory, and antimicrobial activities. Curcumin, is prominent polyphenol with potent antioxidant properties [1]. Blending PLA with polyphenols offers the opportunity to improve the properties of PLA by utilizing the beneficial properties of the polyphenol [2]. The present paper aims to develop new PLA - based composite films with incorporated polyphenol curcumin with different concentration (0 %, 10 %, 15 %, 20 % against PLA) and to examine their electret properties. PLA composite films are prepared using a solution casting method. Curcumin with different concentration is added to the PLA solution. The film-forming solution is cast on levelled glass petri dishes and dried at a temperature of 35 °C until complete chloroform evaporation. All created composite films are cut into 30x30 mm samples and charged in a negative corona in normal atmospheric conditions. The charging of the samples in a corona discharge is carried out by means of a conventional corona triode system consisting of a corona electrode (needle), a grounded plate electrode and a grid placed between them [3]. The electrets surface potential of the charged samples is measured by the vibrating electrode method with compensation and the estimated error is less than 5%. Time and temperature dependences of the normalized surface potential for all investigated electrets are studied. The results obtained show a significant change in the electret behavior of the composite films after the inclusion of curcumin with different concentration into the PLA film. The possible surface potential decay mechanisms responsible for the electret's behavior are discussed. It is established that the surface potential decay depends on the corona polarity and the concentration of the curcumin. The conductivity of all of the investigated films is also determined and the collected results demonstrate that the increase of the curcumin concentration within the PLA films causes a respective increase in conductivity. The wettability of the investigated films is measured using the static water contact angle method. The surface free energy is also calculated and discussed.