Iskanje po katalogu digitalne knjižnice

Opis: The objectives of this study were to inactivate the enzymes α-amylase, lipase, protease, and peroxidase in flour with supercritical carbon dioxide (scCO2), and to optimize the enzymatic treatment conditions. Enzyme inactivation is important, due to the undesirability of certain flour enzymes that cause adverse reactions during storage as unpleasant rancidity of flour, and, at the same time, reduce the shelf life of flour. Therefore, crude enzymes and flour were initially exposed to scCO2 to determine the effect on specific enzyme activity under appropriate conditions. The activity of the unwanted enzymes lipase and peroxidase decreased under optimal process conditions of scCO2 exposure, lipase by 30%, and peroxidase by 12%, respectively. It was discovered that the inactivation of enzymes in wheat flour occurred, where, at the same time, this sustainable method allows the regulation of enzyme activity in the baking process. Afterwards, the effect of scCO2 on the physicochemical properties of flour, morphological changes on starch granules, and content of total lipids was studied. In scCO2-treated white wheat flour, the fat content decreased by 46.15 ± 0.5%, the grain structure was not damaged, and the bread as the final product had a lower specific surface volume. Therefore, this could be a promising technology for flour pretreatment, potentially impacting the prolonging of its shelf-life.
Ključne besede: enzymes, enzyme activity, proteins, supercritical fluids, wheat flour
Objavljeno v DKUM: 10.04.2025; Ogledov: 0; Prenosov: 1
Celotno besedilo (2,16 MB)
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Opis: The present work represents a profound investigation of material pretreatment, comparison of different isolation methods (conventional and supercritical), and characterization of phenolic compounds and amino acids from bee pollen. The determination of amino acids was carried out after developing a novel hydrophilic interaction chromatography combined with quadrupole time-of-flight tandem mass spectrometric method (HILIC-QTOF-MS/MS) with limits of detection over the range 1 mg/kg -5 mg/kg and recoveries over the range 87.6% - 97.1%. The optimal conditions for the isolation of amino acids are in the range of temperatures between 25°C to 55°C and at pressures between 300 bar and 350 bar. It can be concluded that the extraction temperature and the pressure affect antioxidant activity. The favored conditions are lower temperatures and higher pressures.
Ključne besede: bee pollen, in vitro antioxidant activity, HILIC-LC-QTOF-MS.MS, amino acids, WM-266-4 cells
Objavljeno v DKUM: 20.03.2025; Ogledov: 0; Prenosov: 2
Celotno besedilo (1,27 MB)

Opis: Nanocellulose is considered a promising and sustainable biomaterial, with excellent properties of biorenewability with improved mechanical properties. As a unique natural biopolymer, it has been applied to many different industries, where efficient and environmentally friendly productions are in demand. For the first time, ferns from the class Polypodiopsida were used for the isolation of cellulose fibers, which was performed using a chemo-mechanical method. As chemical treatment plays a crucial role in the isolation of nanocellulose, it affects the efficiency of the extraction process, as well as the properties of the resulting nanocellulose. Therefore, mechanical fibrillation was performed via grinding, while the chemical process consisted of three different treatments: alkali treatment, bleaching, and acid hydrolysis. In three different experiments, each treatment was separately prolonged to investigate the differing properties of isolated nanocellulose. Structural analysis and morphological analysis were investigated by SEM, EDS, FT-IR, and DLS. The thermal stability of cellulose fibers was investigated by TGA/DSC. The morphology of obtained nanocellulose was confirmed via SEM analysis for all samples, with particles ranging from 20 nm up to 600 nm, while the most consistent sizes were observed for NC3, ranging from 20 to 60 nm. FT-IR spectra showed prominent absorption peaks corresponding to cellulose, as well as the absence of absorption peaks, corresponding to lignin and hemicellulose. The EDS confirmed the elemental purity of nanocellulose, while TGA/DSC indicated higher thermal stability of nanocellulose, compared to untreated fern, which started to degrade earlier than nanocellulose. Such characteristics with unique properties make nanocellulose a versatile biomaterial for the industrial production of cellulosic materials.
Ključne besede: nanocellulose, isolation, Polypodiophyta fern, chemo-mechanical method, biomaterial, biopolymers
Objavljeno v DKUM: 31.01.2025; Ogledov: 0; Prenosov: 2
Celotno besedilo (3,75 MB)

Opis: Cannabinoids are the main active ingredients of Cannabis sativa L., obtained by a suitable extraction method and decarboxylation, in which the acid forms of the cannabinoids are converted into active forms. Supercritical CO2 extraction method and decarboxylation process were optimized for 7 cannabinoids (CBD, CBDA, THC, THCA, CBGA, CBN and CBC). The optimal extraction conditions for all cannabinoids were determined at a temperature of 60 °C and a pressure of 300 bar to 550 bar. At higher temperatures and reaction times, a significant depletion of neutral cannabinoids was observed. The optimal conditions of the decarboxylation process varied depending on the component. For the CBD component, which could be measured in the highest concentrations (560 mg/g), the optimal conditions were 140 °C and 10 min. The study can be an important model for predicting the behavior of cannabinoids under certain parameters.
Ključne besede: supercritical fluids, extraction, cannabinoids, decarboxilation, Cannabis sativa I
Objavljeno v DKUM: 08.01.2025; Ogledov: 0; Prenosov: 7
Celotno besedilo (10,15 MB)

Ključne besede: antioxidant activity, chestnut wood, conventional extraction, extraction, fractionation, polyphenols, tannins, ultrasound extraction
Objavljeno v DKUM: 05.09.2024; Ogledov: 70; Prenosov: 22
Celotno besedilo (1,27 MB)