Extraction of antioxidants from several berries pressing wastes using conventional and supercritical solvents

Alternative Methods of Bioactive Compounds and Oils Extraction from Berry Fruit By-Products—A Review

Berry fruit by-products are a source of polyphenol compounds and highly nutritious oils and can be reused to fulfill the requirements of the circular economy model. One of the methods of obtaining polyphenol-rich extracts or oils is extraction. Applying conventional solvent extraction techniques may be insufficient to reach high polyphenol or lipid fraction yields and selectivity of specific compounds. Alternative extraction methods, mainly ultrasound-assisted extraction, pulsed electric field-assisted extraction, microwave-assisted extraction and supercritical fluid extraction, are ways to improve the efficiency of the isolation of bioactive compounds or oils from berry fruit by-products. Additionally, non-conventional techniques are considered as green extraction methods, as they consume less energy, solvent volume and time. The aim of this review is to summarize the studies on alternative extraction methods and their relationship to the composition of extracts or oils obtained from berry waste products.

Neuroprotective potentials of selected natural edible oils using enzyme inhibitory, kinetic and simulation approaches

BACKGROUND

Edible oils have proven health benefits in the prevention and treatment of various disorders since the establishment of human era. This study was aimed to appraise neuropharmacological studies on the commonly used edible oils including Cinnamomum verum (CV), Zingiber officinale (ZO) and Cuminum cyminum (CC).

METHODS

The oils were analyzed via GC-MS for identifications of bioactive compounds. Anti-radicals capacity of the oils were evaluated via 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radicals scavenging assays. The samples were also tested against two important acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) which are among the important drug targets in Alzheimer's disease. Lineweaver-Burk plots were constructed for enzyme inhibition studies which correspond to velocity of enzymes (Vmax) against the reciprocal of substrate concentration (Km) in the presence of test samples and control drugs following Michaelis-Menten kinetics. Docking studies on AChE target were also carried out using Molecular Operating Environment (MOE 2016.0802) software.

RESULTS

(Gas chromatography-mass spectrometry GC-MS) analysis revealed the presence of thirty-four compounds in Cinnamon oil (Cv.Eo), fourteen in ginger oil (Zo.Eo) and fifty-six in cumin oil (Cc.Eo). In the antioxidant assays, Cv.Eo, Zo.Eo and Cc.Eo exhibited IC50 values of 85, 121, 280 μg/ml sequentially against DPPH radicals. Whereas, in ABTS assay, Cv.Eo, Zo.Eo and Cc.Eo showed considerable anti-radicals potentials with IC50 values of 93, 77 and 271 μg/ml respectively. Furthermore, Cv.Eo was highly active against AChE enzyme with IC50 of 21 μg/ml. Zo.Eo and Cc.Eo exhibited considerable inhibitory activities against AChE with IC50 values of 88 and 198 μg/ml respectively. In BChE assay, Cv.Eo, Zo.Eo and Cc.Eo exhibited IC50 values of 106, 101 and 37 μg/ml respectively. Our results revealed that these oils possess considerable antioxidant and cholinesterase inhibitory potentials. As functional foods these oils can be effective remedy for the prevention and management of neurological disorders including AD. Synergistic effect of all the identified compounds was determined via binding energy values computed through docking simulations. Binding orientations showed that all the compounds interact with amino acid residues present in the peripheral anionic site (PAS) and catalytic anionic site (CAS) amino acid residues, oxyanion hole and acyl pocket via π-π stacking interactions and hydrogen bond interactions.

THE CURRENT STATE AND TRENDS OF PROCESSING SECONDARY RAW MATERIALS OF WINEMAKING IN UKRAINE

The current state of processing secondary raw materials of winemaking in Ukraine has been analysed. It has been shown that these materials are a rich source of bioactive compounds. This allows using them to manufacture a wide range of products (oenological tannin, food oenocolourant, polyphenolic extracts, tartaric acid, beverages, grape oil, vitamin D, protein, animal feed, food powder, fertilisers, abrasive materials, etc.) with high consumer value for various industries: food, pharmaceutical, perfume and cosmetics, chemical, compound feed, etc. In the light of modern views, phenolic compounds contained in large quantities in grape stems and pomace have been shown to be indispensable factors in nutrition and treatment. It has been noted that in today’s Ukraine, there are no specialised enterprises for complex processing of secondary raw materials of winemaking. In particular, unprocessed grape stalks and pomace are in most cases uncontrollably carried away to farmlands. This leads to acid erosion of the soil and to polluting the environment by micromycete metabolites, which but exacerbates one of mankind’s global problems, the environmental one. It has been concluded that traditional domestic technologies of processing secondary raw materials of winemaking are technologically, economically, and environmentally ineffective. There is no comparative analysis of innovative domestic and foreign technologies and equipment for processing secondary raw materials of winemaking. Modern innovations to obtain bioactive additives and other products cannot be introduced, since there is no necessary home-manufactured equipment, and imported machines are too expensive. Besides, there is but weak interaction among wineries, research institutions, business structures, and administrative authority. Cluster ideology has been suggested as a basis to organise comprehensive processing of secondary raw materials of winemaking in Ukraine. This will unite the interests of wineries (producers of secondary raw materials), processing enterprises (manufacturers of products from secondary raw materials), research institutions, and potential consumers of innovative products

Extraction of Antioxidant Compounds from Blueberry Fruit Waste and Evaluation of Their In Vitro Biological Activity in Human Keratinocytes (HaCaT)

The purpose of this study was to investigate the biological properties of an extract obtained from the waste of blueberry fruit. The study covered the optimization of extraction of antioxidants from blueberry pomace and the determination of antioxidant properties of the extract using HaCaT as the model organism. Research showed that the yield of antioxidants extraction from blueberry waste was dependent on the applied extraction conditions. Based on the mathematical models, the optimal conditions of extraction process in which the maximum quantity of antioxidant compounds is achieved from the waste mass unit, i.e., the relation of the waste mass to the volume of ethanol equal to 1:17.36, and process time equal to 1000 s. The obtained extract was characterized by high antioxidant activity, which was shaped by high content of polyphenols, mainly anthocyanins. Moreover, the extract showed a high ability to protect HaCaT cells from the occurrence of oxidative stress induced by H2O2. Cells treated with the extract and H2O2 generated a lower amount of ROS than cells treated with H2O2 only. The obtained results will be base of further studies on applying the extract in production of diet supplements and functional foods with increased antioxidant activity. Moreover, the main research material is blueberry pomace which is a troublesome waste material for juice producers. Consequently, according to a sustainable development idea, the study results will provide an opportunity to increase interest in the problem of rational use of the waste material to a certain extent.

Supercritical CO2 Extraction of Phytocompounds from Olive Pomace Subjected to Different Drying Methods

Olive pomace is a semisolid by-product of olive oil production and represents a valuable source of functional phytocompounds. The valorization of agro-food chain by-products represents a key factor in reducing production costs, providing benefits related to their reuse. On this ground, we herein investigate extraction methods with supercritical carbon dioxide (SC-CO₂) of functional phytocompounds from olive pomace samples subjected to two different drying methods, i.e., freeze drying and hot-air drying. Olive pomace was produced using the two most common industrial olive oil production processes, one based on the two-phase (2P) decanter and one based on the three-phase (3P) decanter. Our results show that freeze drying more efficiently preserves phytocompounds such as α-tocopherol, carotenoids, chlorophylls, and polyphenols, whereas hot-air drying does not compromise the β-sitosterol content and the extraction of squalene is not dependent on the drying method used. Moreover, higher amounts of α-tocopherol and polyphenols were extracted from 2P olive pomace, while β-sitosterol, chlorophylls, and carotenoids were more concentrated in 3P olive pomace. Finally, tocopherol and pigment/polyphenol fractions exerted antioxidant activity in vitro and in accelerated oxidative conditions. These results highlight the potential of olive pomace to be upcycled by extracting from it, with green methods, functional phytocompounds for reuse in food and pharmaceutical industries.

Fruit seeds and their oils as promising sources of value-added lipids from agro-industrial byproducts: oil content, lipid composition, lipid analysis, biological activity and potential biotechnological applications

Thousands of tons of fruit seeds are discarded every year worldwide as agro-industrial byproducts. Fruit seeds have a high oil content, are rich in monounsaturated fatty acids (FA) and in n-6 and n-3 polyunsaturated essential FA. Sterols, phospholipids, glycolipids, carotenoids, tocopherols and polyphenols are other seed phytochemicals that make them interesting from a commercial viewpoint. Fruit seeds have high potential as raw material for several industries, but their lipid profile remains poorly studied. Current analytical approaches for the analysis of lipids that are based on high-performance liquid chromatography and high-resolution mass spectrometry allow the separation and analysis of compounds with the accurate identification and structural characterization of molecular species in very small quantities. Even though lipidomic analysis of fruit seeds' lipids is still in its infancy, it will bring a new look over these value-added byproducts. This review covers the following topics: (a) the lipid content of various fruit seed oils; (b) their lipid composition (FA, triacylglycerol, sterol, phospholipid and glycolipid profiles), (c) current and future analytical methodologies for the analysis of lipids in fruit seeds; (d) biological activities of fruit seeds' extracts; and (e) potential biotechnological applications of fruit seed oils for their commercial valorization based on lipids.

In-situ extraction and impregnation of black walnut husk into polyethylene film using supercritical carbon dioxide with an ethanol modifier

Walnuts are commonly cultivated for their kernel, which is a rich source of antioxidant phenolic compounds. The husk likewise contains antioxidant and antimicrobial compounds, but is typically discarded without further processing. Antioxidant compounds are useful in creating active packaging films, but typically decompose at melt extrusion temperatures in polymer processing. Due to carbon dioxide's low critical point and ability to swell polymer films, supercritical carbon dioxide may be used to impregnate phenolic compounds into polymers. For this study, a novel technique is used to simultaneously produce walnut husk extracts and impregnate the extract into polymer films in the same batch extractor using supercritical carbon dioxide with a 15 wt-% ethanol modifier at 60°C at 19.4 MPa. The effect of varying the loading of walnut husk in the extractor upon impregnation mass was evaluated with the impregnation mass of the film increasing with walnut husk loading. It was determined by FTIR, as well as the reduction of the protein cytochrome c, that antioxidant compounds may be extracted from walnut husks and impregnated into low-density polyethylene film (LDPE) by this technique.

Consecutive high-pressure and enzyme assisted fractionation of blackberry (Rubus fruticosus L.) pomace into functional ingredients: Process optimization and product characterization

In this study supercritical carbon dioxide (SFE-CO₂) and pressurized liquid (PLE) extractions were optimized for the recovery of valuable fractions from blackberry pomace. Consecutively applied SFE-CO₂ and PLE at optimized parameters yielded 9.9, 26.3 and 5.1 g/100 g of CO₂, ethanol (EtOH) and water-soluble extracts, respectively. Oil of lipophilic fraction was composed mainly of healthy polyunsaturated fatty acids (linoleic 64.1%, α-linolenic 12.9%), while polar solvents effectively recovered antioxidants (up to 29.1 mg gallic acid and 168.7 mg Trolox equivalents from g pomace). PLE-EtOH extract contained 12.2 mg/g of cyanidin-3-glucoside, while other anthocyanins were detected in significantly lower quantities (0.5-0.7 mg/g). SFE-CO₂ and PLE reduced the antioxidant capacity of starting plant material by 86-93%. In terms of extraction time, solvent consumption, total yields, and phytochemical characteristics, high-pressure fractionation was more efficient for obtaining valuable pomace constituents as compared to conventional and enzyme-assisted extractions.

Enzyme-Assisted Extraction of Bioactive Compounds from Raspberry (Rubus idaeus L.) Pomace

Industrial processing of raspberries into juice and jam results in the production of with high content of lipophilic and hydrophilic phytochemicals. Usually considered as waste, raspberry pomace is occasionally cold-pressed to recover specialty oil. However, the resulting pomace press-cake (PPC) still contains 30% to 35% of lipophilic compounds, such as essential fatty acids, tocols, phytosterols, and ellagitannins initially present in pomace. In a perspective of sustainable development, we investigate an eco-friendly process using an aqueous enzyme-assisted extraction (AEAE) to simultaneously and effectively recover lipophilic compounds and polyphenols from the PPC. The performance of different combinations of carbohydrases and proteases was compared. After selecting the best enzymatic system, a definitive screening design involving six factors was then implemented to optimize the process. Under optimized conditions, 1.2 units of thermostable alkaline protease/100 g PPC, pH 9, 60 °C, and 2 hr hydrolysis, more than 38% of total PPC lipophilic content were recovered in the aqueous medium. The recovery of polyphenols and antioxidant activity was, respectively, 48% and 25% higher than obtained by extraction with methanol/acetone/water mixture. Such an AEAE extract might prove useful in food and nutraceutical applications. PRACTICAL APPLICATION: Raspberry pomace, a food industrial by-product, is often considered as waste. However, it is a rich source of phytochemicals, such as tocols, polyphenols, and polyunsaturated fatty acids. To overcome the drawbacks of organic solvent use, an enzyme-assisted extraction process was developed as an eco-friendly alternative to recover these bioactive compounds. Definitive screening design experimental design was used to enhance polyphenols and lipophilics extraction yields while reducing process costs. This extract is an oil-in-water emulsion, with high content in antioxidant phytochemicals, which might have potential for use in nutraceutical applications. Therefore, this green process developed for the valorization of raspberry pomace is considered as a perspective of sustainable development.

Composition and physicochemical properties of dried berry pomace

BACKGROUND

Berry pomace is a valuable but little used by-product of juice manufacturing. When processed to a stable fruit powder, the composition differs from that of the whole fruit. To facilitate application in foods, a detailed knowledge of its composition and physicochemical properties is essential.

RESULTS

Blackcurrant, redcurrant, chokeberry, rowanberry and gooseberry were selected for analysis. All pomace powders had a high fibre content (> 550 g kg^-1 ) and a fat content of up to 200 g kg^-1 . Despite identical milling conditions, the particle sizes of the pomace powders varied. This can be traced back to seed content and brittleness, which also becomes apparent with respect to surface characteristics. Blackcurrant pomace powder differed from other varieties in terms of its low water-binding capacity (3.2 g g^-1 ) and a moderate moisture uptake, whereas chokeberry pomace powder showed the highest polyphenol content and rowanberry pomace powder was rich in flavonols.

CONCLUSION

The results obtained in the present study provide a comprehensive overview of the properties of berry pomace powder and allow conclusions to be made regarding their applicability for use in complex food systems. © 2018 Society of Chemical Industry.

Physicochemical and rheological characterization of pectin-rich fraction from blueberry (Vaccinium ashei) wine pomace

Blueberry wine pomace is rich in pectin, which has been extensively used as a functional dietary fiber and a rheological modifier in the food industry. This paper reports a method to extract the pectin-rich fraction (PF) with a mediate degree of esterification of 51.66% from blueberry wine pomace and provides insight into its relationship between the structure and rheological properties. The impacts of related extrinsic factors, such as sucrose, ions and pH, were also studied in view of food applications. The viscosity of PF aqueous dispersion gradually increased with its concentration. The addition of sucrose, CaCl₂ or NaCl to the solution resulted in increased viscosity. However, the elevations in temperature and pH led to decrease in solution viscosity. The viscoelastic property of PF dispersion displayed strong temperature dependence but weak frequency dependence. This was largely due to PF concentration, sucrose, CaCl₂ and solution pH. The present study revealed the unique characteristic of medium-methoxylated pectin fraction and the obtained results are helpful in value-added utilization of blueberry wine pomace.

UV-C inactivation of foodborne bacterial and viral pathogens and surrogates on fresh and frozen berries

Outbreaks of foodborne illness associated with berries often involve contamination with hepatitis A virus (HAV) and norovirus but also bacteria such as Escherichia coli O157:H7 and parasites such as Cyclospora caytanensis. We evaluated the applicability of UV-C to the inactivation of pathogens on strawberries, raspberries and blueberries. Our three-step approach consisted of assessing the chemical safety of UV-C-irradiated berries, evaluating the sensory quality after UV-C treatment and finally studying the inactivation of the target microorganisms. Treatments lasting up to 9 min (4000 mJ cm^-2) did not produce detectable levels of furan (<5 μg/kg), a known photolysis product of fructose with genotoxic activity and thus were assessed to be toxicologically safe. No effect on taste or appearance was observed, unless treatment was excessively long. 20 s of treatment (an average fluence of ~ 212 mJ cm^-2) reduced active HAV titer by >1 log₁₀ unit in 95% of cases except on frozen raspberries, while 120 s were required to inactivate murine norovirus to this extent on fresh blueberries. The mean inactivation of HAV and MNV was greater on blueberries (2-3 log₁₀) than on strawberries and raspberries (<2 log₁₀). MNV was more sensitive on fresh than on frozen berries, unlike HAV. Inactivation of Salmonella, E. coli O157:H7 and Listeria monocytogenes was poor on all three berries, no treatment reducing viable counts by >1 log₁₀ unit. In most matrices, prolonging the treatment did not improve the result to any significant degree. The effect was near its plateau after 20 s of treatment. These results provide insight into the effectiveness of UV-C irradiation for inactivating bacterial and viral pathogens and surrogates on fresh and frozen berries having different surface types, under different physical conditions and at different levels of contamination. Overall they show that UV-C as single processing step is unsuitable to inactivate significant numbers of foodborne pathogens on berries.

Organic Acids, Antioxidants, and Dietary Fiber of Mexican Blackberry (Rubus fruticosus) Residues cv. Tupy

Blackberry fruit processing generates residues comprised of peel, seeds, and pulp that are abundant in flavonoids, colorants, and organic acids. The objective of this study was to determine the organic acids, antioxidants, and dietary fiber content of blackberry residues and compare antioxidants and dietary fiber content of a prune-based commercial product. The ABTS, DPPH, and FRAP methodologies were used for antioxidant capacity. The blackberry residues exhibited a high amount of malic acid (5706.37 mg/100 g db), phenols (4016.43 mg GAE/100 g db), and anthocyanins content (364.53 mg/100 g db) compared with the commercial product. These compounds contributed to the antioxidant capacity (by ABTS) of both products but were 20 times higher in blackberry residues. The fruit residues were able to reduce iron (by FRAP) 4.4 times compared to the prune-based product. Total dietary fiber (44.26%) and functional properties as water retention capacity (2.94 g/g), swelling capacity (5.00 mL/g), and fat absorption capacity (1.98 mL/g) of blackberry residues were significantly higher than those of the commercial sample. The results demonstrated that, due to its antioxidant compounds and functional properties, the blackberry residue can be considered a source of components with potential benefit to human health.

Current technologies and new insights for the recovery of high valuable compounds from fruits by-products

The recovery of high valuable compounds from food waste is becoming a tighten issue in food processing. The large amount of non-edible residues produced by food industries causes pollution, difficulties in the management, and economic loss. The waste produced during the transformation of fruits includes a huge amount of materials such as peels, seeds, and bagasse, whose disposal usually represents a problem. Research over the past 20 years revealed that many food wastes could serve as a source of potentially valuable bioactive compounds, such as antioxidants and vitamins with increasing scientific interest thanks to their beneficial effects on human health. The challenge for the recovery of these compounds is to find the most appropriate and environment friendly extraction technique able to achieve the maximum extraction yield without compromising the stability of the extracted products. Based on this scenario, the aim of the current review is twofold. The first is to give a brief overview of the most important bioactive compounds occurring in fruit wastes. The second is to describe the pro and cons of the most up-to-dated innovative and environment friendly extraction technologies that can be an alternative to the classical solvent extraction procedures for the recovery of valuable compounds from fruit processing. Furthermore, a final section will take into account published findings on the combination of some of these technologies to increase the extracts yields of bioactives.

Red Fruits: Extraction of Antioxidants, Phenolic Content, and Radical Scavenging Determination: A Review

Red fruits, as rich antioxidant foods, have gained over recent years capital importance for consumers and manufacturers. The industrial extraction of the phenolic molecules from this source has been taking place with the conventional solvent extraction method. New non-conventional extraction methods have been devised as environmentally friendly alternatives to the former method, such as ultrasound, microwave, and pressure assisted extractions. The aim of this review is to compile the results of recent studies using different extraction methodologies, identify the red fruits with higher antioxidant activity, and give a global overview of the research trends regarding this topic. As the amount of data available is overwhelming, only results referring to berries are included, leaving aside other plant parts such as roots, stems, or even buds and flowers. Several researchers have drawn attention to the efficacy of non-conventional extraction methods, accomplishing similar or even better results using these new techniques. Some pilot-scale trials have been performed, corroborating the applicability of green alternative methods to the industrial scale. Blueberries (Vaccinium corymbosum L.) and bilberries (Vaccinium myrtillus L.) emerge as the berries with the highest antioxidant content and capacity. However, several new up and coming berries are gaining attention due to global availability and elevated anthocyanin content.

Application of Ultrasound in a Closed System: Optimum Condition for Antioxidants Extraction of Blackberry (Rubus fructicosus) Residues

Blackberry processing generates up to 20% of residues composed mainly of peel, seeds and pulp that are abundant in flavonoids. The objective of this study was to optimize the ultrasound conditions, in a closed system, for antioxidants extraction, using the response surface methodology. Blackberry (Rubus fructicosus) residues were analyzed for total phenolics, total anthocyanins, and antioxidant activity by ABTS and DPPH. The selected independent variables were ultrasound amplitude (X₁: 80%-90%) and extraction time (X₂: 10-15 min), and results were compared with conventional extraction methods. The optimal conditions for antioxidants extraction were 91% amplitude for 15 min. The results for total phenolic content and anthocyanins and antioxidant activity by ABTS and DPPH were of 1201.23 mg gallic acid equivalent (GAE)/100 g dry weight basis (dw); 379.12 mg/100 g·dw; 6318.98 µmol Trolox equivalent (TE)/100 g·dw and 9617.22 µmol TE/100 g·dw, respectively. Compared to solvent extraction methods (water and ethanol), ultrasound achieved higher extraction of all compounds except for anthocyanins. The results obtained demonstrated that ultrasound is an alternative to improve extraction yield of antioxidants from fruit residues such as blackberry.

Adding Value to Fruit Processing Waste: Innovative Ways to Incorporate Fibers from Berry Pomace in Baked and Extruded Cereal-based Foods-A SUSFOOD Project

This article communicates the set-up of BERRYPOM, a European research project established in the second call of the SUStainable FOOD Production and Consumption (SUSFOOD) network. The project deals with the by-product from berry processing, which is frequently recycled as animal feed, composted or utilized for biogas production. With BERRYPOM it is proposed to analyze the value of berry pomace, to optimize the recovery of bioactive compounds from pomace material, and to incorporate processed berry pomace in cereal-based foods to take advantage of nutritional benefits that originate from its fiber and the content of bioactive substances. Additionally, extraction methods will be evaluated to obtain products rich in phytochemicals, and the influence of processing steps on the antioxidant capacity of pomace will be analyzed. The fiber extracts will then also be utilized in different cereal-based foods and extruded products. As project outcome we expect a substantial increase of knowledge concerning fiber and phytochemicals extraction from berry pomace, its suitability for enhancing nutritional and sensory properties of cereal-based foods, and its effects on the sustainability of the food chain.

Supercritical fluid extraction (SFE) of cranberries does not extract oligomeric proanthocyanidins (PAC) but does alter the chromatography and bioactivity of PAC fractions extracted from SFE residues

Supercritical fluid extraction (SFE) removed lipophilic compounds and low molecular weight flavonoids from cranberries. However, SFE did not extract proanthocyanidins (PAC). The SFE PAC-enriched residue was submitted to fractionation on Sephadex LH-20 using ethanol, ethanol/methanol, and 80% acetone. PAC degree of polymerization (DP) and ratios of "A-type" to "B-type" interflavan bonds were compared with those of PAC fractions without SFE. Mass spectrometry showed that when SFE was used, PAC distribution was shifted toward higher DP and contained higher amounts of two and three "A-type" bonds compared to PAC fractions without SFE. The 80% acetone fraction with SFE had significantly greater extraintestinal pathogenic Escherichia coli (ExPEC) agglutination and significantly lower ExPEC invasion of enterocytes than the fraction without SFE. Cranberry PAC with higher numbers of "A-type" interflavan bonds are more bioactive in agglutinating ExPEC and inhibiting ExPEC enterocyte invasion.

Colloidal interactions in liquid CO2--a dry-cleaning perspective

Liquid CO(2) is a viable alternative for the toxic and environmentally harmful solvents traditionally used in dry-cleaning industry. Although liquid CO(2) dry-cleaning is being applied already at a commercial scale, it is still a relatively young technique which poses many challenges. The focus of this review is on the causes of the existing problems and directions to solve them. After presenting an overview of the state-of-the-art, we analyze the detergency challenges from the fundamentals of colloid and interface science. The properties of liquid CO(2) such as dielectric constant, density, Hamaker constant, refractive index, viscosity and surface tension are presented and in the subsequent chapters their effects on CO(2) dry-cleaning operation are delineated. We show, based on theory, that the van der Waals forces between a model soil (silica) and model fabric (cellulose) through liquid CO(2) are much stronger compared to those across water or the traditional dry-cleaning solvent PERC (perchloroethylene). Prevention of soil particle redeposition in liquid CO(2) by electrostatic stabilization is challenging and the possibility of using electrolytes having large anionic parts is discussed. Furthermore, the role of different additives used in dry-cleaning, such as water, alcohol and surfactants, is reviewed. Water is not only used as an aid to remove polar soils, but also enhances adhesion between fabric and soil by forming capillary bridges. Its role as a minor component in liquid CO(2) is complex as it depends on many factors, such as the chemical nature of fabrics and soil, and also on the state of water itself, whether present as molecular solution in liquid CO(2) or phase separated droplets. The phenomena of wicking and wetting in liquid CO(2) systems are predicted from the Washburn-Lucas equation for fabrics of various surface energies and pore sizes. It is shown that nearly complete wetting is desirable for good detergency. The effect of mechanical action and fluid dynamic conditions on dry-cleaning is analyzed theoretically. From this it follows that in liquid CO(2) an order of magnitude higher Reynold's number is required to exceed the binding forces between fabric and soil as opposed to PERC or water, mainly due to the strong van der Waals forces and the low viscosity of CO(2) at dry-cleaning operational conditions.

Supercritical carbon dioxide extraction of bioactive compounds from Ampelopsis grossedentata stems: process optimization and antioxidant activity

Supercritical carbon dioxide (SC-CO₂) extraction of bioactive compounds including flavonoids and phenolics from Ampelopsis grossedentata stems was carried out. Extraction parameters such as pressure, temperature, dynamic time and modifier, were optimized using an orthogonal array design of L₉ (3⁴), and antioxidant activities of the extracts were evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay and ferrous ion chelating (FIC) assay. The best conditions obtained for SC-CO₂ extraction of flavonoids was 250 bar, 40 °C, 50 min, and with a modifier of methanol/ethanol (1:3, v/v), and that for phenolics extraction was 250 bar, 40 °C, 50 min, and with a modifier of methanol/ethanol (1:1, v/v). Meantime, flavonoids and phenolics were found to be mainly responsible for the DPPH scavenging activity of the extracts, but not for the chelating activity on ferrous ion according to Pearson correlation analysis. Furthermore, several unreported flavonoids such as apigenin, vitexin, luteolin, etc., have been detected in the extracts from A. grossedentata stems.