Degradation of Waste Tetra Pak Packaging with Hydrothermal Treatment in Sub-/Supercritical Water.

Tetra pak packaging is one of the most frequently used types of packaging in the food industry. The recycling of the tetra pak packaging waste presents a difficult task because of its multi-layered, multi-component structure. In this study, the degradation of tetra pak packaging in subcritical (SubCW) and supercritical (SCW) water was investigated. The experiments were carried out in one (SCW) or two stages (SubCW and SCW), whereby the influence of the reaction temperature and time on the yield and composition of the products obtained was investigated. The maximum oil phase yield achieved in a one-stage and a two-stage degradation process was 60.7% and 65.5%, respectively. The oil and gas phases were composed of different types of hydrocarbons. Higher temperature and longer time led to higher amounts of saturated aliphatic hydrocarbons in both the oil and gas phases. The aqueous phase contained sugars (glucose, fructose) and sugar derivatives (levulinic acid, glyceraldehyde, furfurals). Based on these results, the degradation pathway of waste tetra pak packaging in SubCW and SCW was proposed. The results of the study show that the degradation of waste tetra pak packaging with SubCW and SCW is a promising recycling process.

Efficient and Green Isolation of Keratin from Poultry Feathers by Subcritical Water.

The isolation of keratin from poultry feathers using subcritical water was studied in a batch reactor at temperatures (120-250 °C) and reaction times (5-75 min). The hydrolyzed product was characterized by FTIR and elemental analysis, while the molecular weight of the isolated product was determined by SDS-PAGE electrophoresis. To determine whether disulfide bond cleavage was followed by depolymerization of protein molecules to amino acids, the concentration of 27 amino acids in the hydrolysate was analyzed by GC/MS. The optimal operating parameters for obtaining a high molecular weight protein hydrolysate from poultry feathers were 180 °C and 60 min. The molecular weight of the protein hydrolysate obtained under optimal conditions ranged from 4.5 to 12 kDa, and the content of amino acids in the dried product was low (2.53% w/w). Elemental and FTIR analyses of unprocessed feathers and dried hydrolysate obtained under optimal conditions showed no significant differences in protein content and structure. Obtained hydrolysate is a colloidal solution with a tendency for particle agglomeration. Finally, a positive influence on skin fibroblast viability was observed for the hydrolysate obtained under optimal processing conditions for concentrations below 6.25 mg/mL, which makes the product interesting for various biomedical applications.

Chemical Recycling of Polyolefins Waste Materials Using Supercritical Water.

In the following work, the hydrothermal degradation of polypropylene waste (PP) using supercritical water (SCW) has been studied. The procedure was carried out in a high-pressure, high-temperature batch reactor at 425 °C and 450 °C from 15 to 240 min. The results show a high yield of the oil (up to 95%) and gas (up to 20%) phases. The gained oil phase was composed of alkanes, alkenes, cycloalkanes, aromatic hydrocarbons, and alcohols. Alkanes and alcohols predominated at 425 °C and shorter reaction times, while the content of aromatic hydrocarbons sharply increased at higher temperatures and times. The higher heating values (HHVs) of oil phases were in the range of liquid fuel (diesel, gasoline, crude and fuel oil), and they were between 48 and 42 MJ/kg. The gas phase contained light hydrocarbons (C1-C6), where propane was the most represented component. The results for PP degradation obtained in the present work were compared to the results of SCW degradation of colored PE waste, and the potential degradation mechanism of polyolefins waste in SCW is proposed. The results allowed to conclude that SCW processing technology represents a promising and eco-friendly tool for the liquefaction of polyolefin (PE and PP) waste into oil with a high conversion rate.

Isolation of Keratin from Waste Wool Using Hydrothermal Processes.

The subcritical water (SubCW) extractions of waste wool to produce keratin were performed at temperatures of 150 °C to 250 °C and at different reaction times between 5 min to 75 min. The resulting proteins in the obtained products were confirmed with Fourier-transform infrared spectroscopy (FTIR). The molecular weight of the protein extracts was determined by using two different methods: with a polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate (SDS-PAGE) and by using a gel permeation chromatography. The results show, that by using SubCW, keratin can be isolated from waste wool in very high yields, much higher than by other chemical methods. Maximal yield was achieved at 180 °C and 60 min and it was 90.3%. The molecular weight distributions of extracted proteins, which were generated from waste wool were between 14 kDa and 4 kDa, what is comparable to the results obtained by other chemical methods.

The new rapid and accurate analytical HPLC-ECD method for the determination of rosmarinic acid in meat products.

A new rapid method has been developed for the determination of low levels of rosmarinic acid extracted from rosemary (Rosmarinus officinalis L.) and has been used as an antioxidant in meat and meat products after cold storage at 4°C. The method is a high performance liquid chromatography using a coulometric electrochemical detector. It provides a significant improvement on the limit of detection, which was 0.33 ppb, while the limit of quantification was 1 ppb of rosmarinic acid. The advantage of the method also lies in the simpler and faster sample preparation, which can quantify a very low concentration of rosmarinic acid (60 ppb), and is more than 40 ppb below the limits of previously existing methods. A coulometric method is well suited for determining low analyte concentrations and is one of the most sensitive analytical approaches available today, in addition to being time efficient and cost effective. PRACTICAL APPLICATION: A new method for determining low concentrations (60 ppb) of rosmarinic acid in meat and meat products is presented. The method is user-friendly, as it does not require complex sample preparation. It is a selective, precise, and accurate method that makes it useful for routine applications in the meat and other food industries.

Sub- and Supercritical Extraction of Slovenian Hops (Humulus lupulus L.) Aurora Variety Using Different Solvents.

This work investigates the efficiency of supercritical fluid extraction of hops with a variety of solvents including carbon dioxide (CO2), propane, sulfur hexafluoride (SF6), and dimethyl ether (DME) at various densities (low-density and high-density). Operating parameters were 50 bar, 100 bar and 150 bar and 20 °C, 40 °C, 60 °C and 80 °C for all solvents, respectively. The influence of process parameters on the total yield of extraction and content of bitter acids in the extracts has been investigated. The mathematical model based on Fick's second law well described the experimental extraction results. Furthermore, HPLC analysis has been used to determine α- and ß-acids in extracts. The yield of bitter compounds in hop extracts was largely influenced by the type of solvent, the temperature and pressure applied during extraction. The results show that CO2 and propane were roughly equivalent to DME in solvating power, while SF6 was a poor solvent at the same conditions. The highest yield as well as the highest concentration of bitter acids in extracts were obtained by using DME, where the optimal operating conditions were 40 °C and 100 bar for the extraction of α-acids (max. concentration 9.6%), 60 °C and 50 bar for the extraction of ß-acids (4.5%) and 60 °C and 150 bar for the maximum extraction yield (25.6%).

Subcritical Water Extraction of Chestnut Bark and Optimization of Process Parameters.

The aim of the work was the optimization of the subcritical water extraction process of chestnut bark using Box-Behnken response surface methodology. The influence of process parameters, such as temperature, extraction time and solvent-solid ratio, on extraction yield, yield of the main compounds, total phenol content, total tannin content and antioxidant activity has been investigated. The identified compounds were ellagic and gallic acids, ellagitannins (vescalagin, castalagin, 1-o-galloyl castalagin, vescalin and castalin), sugars (maltose, glucose, fructose and arabinose) and sugar derivatives (5-HMF, furfural and levulinic acid). Finally, the optimal process conditions for obtaining the bark extract highly rich in ellagic acid and with satisfactory levels of total phenols and total tannins have been determined.

A review: a comparison of different adsorbents for removal of Cr (VI), Cd (II) and Ni (II).

A review of the studies dealing with the removal of chromium, cadmium, and nickel ions with different adsorbents published in the literature between 2014 and 2018 is given in tabular form, along with the adsorption conditions, adsorption isotherm, and kinetic models applied by the authors to model the experimental data and adsorption capacities. The review focuses on the efficiency of ion removal.

Enzyme Immobilization Onto Biochar Produced by the Hydrothermal Carbonization of Biomass.

For improving enzyme utilization in biotechnological processes, process costs have to be reduced, enzyme stability during industrial processes should be enhanced, and the recycle and reuse step should be favorable. The immobilization of enzymes is an important step for enhancing enzyme catalytic properties and operational stability. In order to reduce the costs of immobilization and consequently the cost of processes, a cheaper carrier (e.g. materials reclaimed as by-products) should be used. To achieve this, cellulase from Trichoderma sp. was immobilized on biochar obtained by low temperature hydrothermal carbonization (LTHTC) in two ways: by adsorption and by covalent binding via a crosslinking agent. The effect of immobilization time, enzyme concentration, type and concentration of the crosslinking agent and the types of carrier - biochar (LTHTC of waste from olive oil production (LTHTC of OL waste) or LTHTC of cellulose) on the immobilization efficiency and the residual activity of biocatalyst was studied. Higher immobilization efficiency and residual enzyme activity was achieved when the enzyme was covalently bound to biochar obtained by LTHTC of cellulose.

Separation of Active Compounds from Food by-Product (Cocoa Shell) Using Subcritical Water Extraction.

Large amounts of residues are produced in the food industries. The waste shells from cocoa processing are usually burnt for fuel or used as a mulch in gardens to add nutrients to soil and to suppress weeds. The objectives of this work were: (a) to separate valuable compounds from cocoa shell by applying sustainable green separation process­subcritical water extraction (SWE); (b) identification and quantification of active compounds, sugars and sugar degradation products in obtained extracts using HPLC; (c) characterization of the antioxidant activity of extracts; (d) optimization of separation process using response surface methodology (RSM). Depending on applied extraction conditions, different concentration of theobromine, caffeine, theophylline, epicatechin, catechin, chlorogenic acid and gallic acid were determined in the extracts obtained by subcritical water. Furthermore, mannose, glucose, xylose, arabinose, rhamnose and fucose were detected as well as their important degradation products such as 5-hydroxymethylfurfural (5-HMF), furfural, levulinic acid, lactic acid and formic acid.

Hydrothermal Degradation of Rutin: Identification of Degradation Products and Kinetics Study.

The model glycoside compound quercetin-3-O-rutinoside (rutin) was subjected to subcritical water within the temperature range of 120-220 °C, and the hydrothermal degradation products were analyzed. Two kinetic models describing the degradation of this compound in two different atmospheres (N2 and CO2), used for pressure establishment in the reactor, have been developed and compared. Reaction was considered a successive one with three irreversible steps. We confirmed that rutin degradation to quercetin follows first-order kinetics. At higher temperatures quercetin is further degraded in two degradation steps. Formations of 3,4-dihydroxybenzoic acid and catechol were described with the zero-order kinetic models. Reaction rate constants for hydrolysis of glycoside to aglycone in a CO2 atmosphere are higher compared to those in a N2 atmosphere, whereas at higher temperatures reaction rate constants for further two successive reactions of aglycone degradation are slightly lower in the presence of CO2. The difference in reaction activation energies is practically negligible for both gases. Furthermore, degradation products of sugar moieties, that is, 5-hydroxymethylfurfural and 5-methylfurfural, were also detected and analyzed.

Polyphenols: Extraction Methods, Antioxidative Action, Bioavailability and Anticarcinogenic Effects.

Being secondary plant metabolites, polyphenols represent a large and diverse group of substances abundantly present in a majority of fruits, herbs and vegetables. The current contribution is focused on their bioavailability, antioxidative and anticarcinogenic properties. An overview of extraction methods is also given, with supercritical fluid extraction highlighted as a promising eco-friendly alternative providing exceptional separation and protection from degradation of unstable polyphenols. The protective role of polyphenols against reactive oxygen and nitrogen species, UV light, plant pathogens, parasites and predators results in several beneficial biological activities giving rise to prophylaxis or possibly even to a cure for several prevailing human diseases, especially various cancer types. Omnipresence, specificity of the response and the absence of or low toxicity are crucial advantages of polyphenols as anticancer agents. The main problem represents their low bioavailability and rapid metabolism. One of the promising solutions lies in nanoformulation of polyphenols that prevents their degradation and thus enables significantly higher concentrations to reach the target cells. Another, more practiced, solution is the use of mixtures of various polyphenols that bring synergistic effects, resulting in lowering of the required therapeutic dose and in multitargeted action. The combination of polyphenols with existing drugs and therapies also shows promising results and significantly reduces their toxicity.

Particle Formation and Product Formulation Using Supercritical Fluids.

Traditional methods for solids processing involve either high temperatures, necessary for melting or viscosity reduction, or hazardous organic solvents. Owing to the negative impact of the solvents on the environment, especially on living organisms, intensive research has focused on new, sustainable methods for the processing of these substances. Applying supercritical fluids for particle formation may produce powders and composites with special characteristics. Several processes for formation and design of solid particles using dense gases have been studied intensively. The unique thermodynamic and fluid-dynamic properties of supercritical fluids can be used also for impregnation of solid particles or for the formation of solid powderous emulsions and particle coating, e.g., for formation of solids with unique properties for use in different applications. We give an overview of the application of sub- and supercritical fluids as green processing media for particle formation processes and present recent advances and trends in development.

Simultaneous extraction of oil- and water-soluble phase from sunflower seeds with subcritical water.

In this study, the subcritical water extraction is proposed as an alternative and greener processing method for simultaneous removal of oil- and water-soluble phase from sunflower seeds. Extraction kinetics were studied at different temperatures and material/solvent ratios in a batch extractor. Degree of hydrothermal degradation of oils was observed by analysing amount of formed free fatty acids and their antioxidant capacities. Results were compared to oils obtained by conventional methods. Water soluble extracts were analysed for total proteins, carbohydrates and phenolics and some single products of hydrothermal degradation. Highest amount of oil was obtained at 130 °C at a material/solvent ratio of 1/20 g/mL after 30 min of extraction. For all obtained oils minimal degree of hydrothermal degradation could be identified. High antioxidant capacities of oil samples could be observed. Water soluble extracts were degraded at temperatures ≥100 °C, producing various products of hydrothermal degradation.

Supercritical fluid chromatography and scale up study.

The influence of process parameters on supercritical fluid chromatography (SFC) was investigated together with scaling-up to the preparative scale. Within this scope, separation of model compounds (caffeine and theophylline), dependencies on pressures, temperatures, types and concentrations of the modifiers, and types of stationary phases, were examined separately. Experiments were performed on analytical scale and on pilot preparative scale SFC apparatus. Bare silica and silica 2-ethylpyridine were used as stationary phases, with CO(2)/methanol or CO(2)/ethanol at elevated pressures and temperatures as mobile phase. Observations obtained on the analytical scale were used for scaling-up to preparative scale. The aim of this study is evaluating the influences of process parameters when separating model compounds using SFC, and s practical demonstration of the scaling-up method of SFC along with the operation of a pilot preparative to production scale SFC apparatus, which is one of the bigger similar apparatuses worldwide.

Hydrothermal reactions of agricultural and food processing wastes in sub- and supercritical water: a review of fundamentals, mechanisms, and state of research.

Hydrothermal (HT) reactions of agricultural and food-processing waste have been proposed as an alternative to conventional waste treatment technologies due to allowing several improvements in terms of process performance and energy and economical advantages, especially due to their great ability to process high moisture content biomass waste without prior dewatering. Complex structures of wastes and unique properties of water at higher temperatures and pressures enable a variety of physical-chemical reactions and a wide spectra of products. This paper's aim is to give extensive information about the fundamentals and mechanisms of HT reactions and provide state of the research of agri-food waste HT conversion.

Influence of process parameters on the extraction of flavanones from mandarin peel.

Flavanones are an important group of flavonoids that are characteristic for citrus. In the present work isolation of flavanones from mandarin peel was performed by conventional extraction using water, ethanol, acetone and aqueous solutions of acetone and ethanol. The extracts were analysed on the content and composition of flavanones. Furthermore the DPPH radical scavenging activity of extracts was determined. Finally, the influence of extraction parameters (particle size, extraction temperature, extraction time, material to solvent ratio, number of extraction stages and type of solvent) on the yield and the efficiency of extraction were determined by Plackett-Burman experimental design. The results showed that 70% aqueous solution of acetone was the most efficient solvent for isolation of flavanones from mandarin peel. The main flavanones present in the obtained extracts were hesperidin (HES) and narirutin (NRT). The number of extraction stages influenced the yield of extraction, type of solvent influenced the hesperidin extraction efficiency and particle size of material influenced the narirutin extraction efficiency.

Rosemary extracts improve flow-mediated dilatation of the brachial artery and plasma PAI-1 activity in healthy young volunteers.

Polyphenol antioxidants decrease the risk of atherosclerosis. The study aimed to evaluate prospectively in healthy young participants the effect of oral rosemary extracts (RE), consisting of diphenols, upon endothelial dysfunction (ED), preceding structural atherosclerosis. Nineteen healthy young volunteers were studied prospectively, who received oral RE (77.7 mg) for 21 days, consisting of active substances carnosol (0.97 mg), carnosic (8.60 mg) and rosmarinic acid (10.30 mg). Before and after RE treatment, the study evaluated fasting serum levels of plasminogen-activator-inhibitor-1 (PAI-1), vascular cell adhesion molecule 1 (VCAM-1), inter-cellular adhesion molecule 1 (ICAM-1), superoxide dismutase (SOD), glutathione peroxidase (GPX), fibrinogen, high-sensitivity capsular reactive protein (hs-CRP), tumor-necrosis factor α (TNF-α), the lipid profile and ED, characterized as flow-mediated dilatation (FMD) in the brachial artery of < 4.5%, estimated by ultrasound measurements. After 21 days, any side effects were registered, the mean FMD increased nonsignificantly (6.51 ± 5.96% vs 7.78 ± 4.56%, p = 0.546) and ED decreased significantly (66.6% vs 16.6%, p = 0.040). Among the serum markers, only the mean PAI-1 level decreased significantly (4.25 ± 1.46 U/mL vs 3.0 ± 0.61 U/mL, p = 0.012) after 21-day RE supplementation. It is concluded that oral RE supplementation has the potential to improve serum PAI-1 activity and ED in young and healthy individuals.

Extraction of Lutein Diesters from Tagetes Erecta using Supercritical CO2 and Liquid Propane.

The efficiency of high pressure extraction of lutein diesters from marigold (Tagetes erecta) flower petals has been investigated. The solvents used for extraction were supercritical carbon dioxide and liquid propane. Operating parameters were 300 bar and 40, 60 and 80 °C for CO2 and 100, 150, 200 bar and 40 and 60 °C for propane, respectively. The influence of process parameters on the total yield of extraction and content of lutein diesters in the extracts was investigated. The results show, that solvent power of propane for lutein diesters is approximately 3.5 times higher than of CO2. The calculation procedure based on the Fick's second law was applied to determine the diffusivities of lutein diesters during extraction from marigold flower petals for both extraction stages: a constant rate stage followed by a stage of decreasing rate. The mathematical model based on the Fick's second law well described the experimental extraction results.

Potential of phenolic antioxidants.

In vitro studies have shown a link between the consumption of food rich in (poly)phenols, especially flavonoids, and reduced risk of coronary heart diseases. Several flavonoids have been reported to prevent low density lipoprotein cholesterol oxidation in vitro. The aim of our work was to determine antioxidant and radical scavenging activity of flavonoids myricetin, quercetin, rutin, luteolin, apigenin, kaempferol, catechin, epicatechin and epigallocatechin gallate and to study the influence of chemical structure and flavonoid interactions on the ability to inhibit oxidation and scavenge free radicals. Two in vitro methods, i.e. oxidation of b-carotene in an emulsion system and DPPH (1,1-Diphenyl-2-picrylhydrazyl) radical scavenging assay, were applied. In addition, a review of in vivo studies that investigate the effectiveness of food flavonoids in reducing oxidative damage in human body was done and their results were analyzed and compared to in vitro results obtained in our laboratory. Although all tested flavonoids except apigenin showed strong antioxidant and antiradical properties in vitro, these findings can not be completely confirmed from the reviewed in vivo human studies since those results are sometimes contradictory and inconsistent.