vital elements affect lubriion of grinding mill

grinding mills - an overview | sciencedirect topics

grinding mills - an overview | sciencedirect topics

Grinding circuits are fed at a controlled rate from the stockpile or bins holding the crusher plant product. There may be a number of grinding circuits in parallel, each circuit taking a definite fraction of the feed. An example is the Highland Valley Cu/Mo plant with five parallel grinding lines (Chapter 12). Parallel mill circuits increase circuit flexibility, since individual units can be shut down or the feed rate can be changed, with a manageable effect on production. Fewer mills are, however, easier to control and capital and installation costs are lower, so the number of mills must be decided at the design stage.

The high unit capacity SAG mill/ball mill circuit is dominant today and has contributed toward substantial savings in capital and operating costs, which has in turn made many low-grade, high-tonnage operations such as copper and gold ores feasible. Future circuits may see increasing use of high pressure grinding rolls (Rosas et al., 2012).

Autogenous grinding or semi-autogenous grinding mills can be operated in open or closed circuit. However, even in open circuit, a coarse classifier such as a trommel attached to the mill, or a vibrating screen can be used. The oversize material is recycled either externally or internally. In internal recycling, the coarse material is conveyed by a reverse spiral or water jet back down the center of the trommel into the mill. External recycling can be continuous, achieved by conveyor belt, or is batch where the material is stockpiled and periodically fed back into the mill by front-end loader.

In Figure 7.35 shows the SAG mill closed with a crusher (recycle or pebble crusher). In SAG mill operation, the grinding rate passes through a minimum at a critical size (Chapter 5), which represents material too large to be broken by the steel grinding media, but has a low self-breakage rate. If the critical size material, typically 2550mm, is accumulated the mill energy efficiency will deteriorate, and the mill feed rate decreases. As a solution, additional large holes, or pebble ports (e.g., 40100mm), are cut into the mill grate, allowing coarse material to exit the mill. The crusher in closed circuit is then used to reduce the size of the critical size material and return it to the mill. As the pebble ports also allow steel balls to exit, a steel removal system (such as a guard magnet, Chapters 2 and 13Chapter 2Chapter 13) must be installed to prevent them from entering the crusher. (Because of this requirement, closing a SAG mill with a crusher is not used in magnetic iron ore grinding circuits.) This circuit configuration is common as it usually produces a significant increase in throughput and energy efficiency due to the removal of the critical size material.

An example SABC-A circuit is the Cadia Hill Gold Mine, New South Wales, Australia (Dunne et al., 2001). The project economics study indicated a single grinding line. The circuit comprises a SAG mill, 12m diameter by 6.1m length (belly inside liners, the effective grinding volume), two pebble crushers, and two ball mills in parallel closed with cyclones. The SAG mill is fitted with a 20MW gearless drive motor with bi-directional rotational capacity. (Reversing direction evens out wear on liners with symmetrical profile and prolongs operating time.) The SAG mill was designed to treat 2,065t h1 of ore at a ball charge of 8% volume, total filling of 25% volume, and an operating mill speed of 74% of critical. The mill is fitted with 80mm grates with total grate open area of 7.66m2 (Hart et al., 2001). A 4.5m diameter by 5.2m long trommel screens the discharge product at a cut size of ca. 12mm. Material less than 12mm falls into a cyclone feed sump, where it is combined with discharge from the ball mills. Oversize pebbles from the trommel are conveyed to a surge bin of 735t capacity, adjacent to the pebble crushers. Two cone crushers with a closed side set of 1216mm are used to crush the pebbles with a designed product P80 of 12mm and an expected total recycle pebble rate of 725t h1. The crushed pebbles fall directly onto the SAG mill feed belt and return to the SAG mill.

SAG mill product feeds two parallel ball mills of 6.6m11.1m (internal diameterlength), each with a 9.7MW twin pinion drive. The ball mills are operated at a ball charge volume of 3032% and 78.5% critical speed. The SAG mill trommel undersize is combined with the ball mills discharge and pumped to two parallel packs (clusters) of twelve 660mm diameter cyclones. The cyclone underflow from each line reports to a ball mill, while the cyclone overflow is directed to the flotation circuit. The designed ball milling circuit product is 80% passing 150m.

Several large tonnage copper porphyry plants in Chile use an open-circuit SAG configuration where the pebble crusher product is directed to the ball mills (SABC-B circuit). The original grinding circuit at Los Bronces is an example: the pebbles generated in the two SAG mills are crushed in a satellite pebble crushing plant, and then are conveyed to the three ball mills (Mogla and Grunwald, 2008).

Pulverizer systems, which integrate drying, grinding, classification, and transport of the ground fuel to the burners, can present the greatest problems when switching coals/fuels (Carpenter, 1998). Low quality fuels may have grinding properties that are markedly different from the pulverizer design coal (Kitto and Stultz, 2005; Vuthaluru et al., 2003). Consequently, problems are experienced with pulverizer capacity, drying capacity, explosions, abrasive wear of the pulverizer grinding elements, erosion of the coal classifiers and/or distributors, coal-air pipes, and burners.

Whenever there is a loss of a pulverizer, the operator should light oil burner/s to help the operating group of pulverizers to stabilize the flame. At the same time, the operator should bring down the load matching to the capability of the running puverizer/s. Effort should be made to cut in standby pulverizer/s depending on draft fan group capability. Faults in electric supply, if there are any, can then be inspected and rectified. In the case of jamming in the pulverizer internals, the affected pulverizer should be cooled and cleaned and prepared for the next operation.

a pulverizer that is tripped under load will be inerted as established by equipment manufacturer, and maintained under an inert atmosphere until confirmation that no burning or smouldering fuel exists in the pulverizer or the fuel is removed. Inerting media may be any one of CO2, Steam or N2. For pulverizers that are tripped and inerted while containing a charge of fuel, following procedure will be used to clear fuel from the pulverizer:1.Start one of the pulverizers2.Isolate from the furnace all shut-down or tripped pulverizers3.Continue to operate the pulverizer until empty4.When the operating pulverizer is empty, proceed to another tripped and inerted pulverizer and repeat the procedure until all are cleared of fuel

NFPA 85 recommends the pulverizer system arrangement should be such as to provide only one direction of flow, i.e., from the points of entrance of fuel and air to the points of discharge. The system should be designed to resist the passage of air and gas from the pulverizer through the coal feeder into the coal bunker. To withstand pulverizer-operating pressures and to resist percolation of hot air/gas, a vertical or cylindrical column of fuel at least the size of three coal-pipe diameters should be provided between the coal-bunker outlet and the coal-feeder inlet as well as between coal-feeder outlet and the pulverizer inlet. Within these cylindrical columns there will be accumulation of coal that will resist percolation of hot air/gas from the pulverizer to the coal bunker. All components of the pulverized coal system should be designed to withstand an internal explosion gauge pressure of 344kPa [9].

Number of Spare Pulverizers: To overcome forced outage and consequent availability of a number of operating pulverizers it is generally considered that while firing the worst coal one spare pulverizer should be provided under the TMCR (Turbine Maximum Continuous Rating) operating condition. In certain utilities one spare pulverizer is also provided even while firing design coal, but under the BMCR (Boiler Maximum Continuous Rating) operating condition. Practice followed in the United States generally is to provide one spare pulverizer for firing design coal, in larger units two spare pulverizers are provided. However, provision of any spare pulverizer is not considered in current European design [5].

Pulverizer Design Coal: The pulverizer system should be designed to accommodate the fuel with the worst combination of properties that will still allow the steam generator to achieve the design steam flow. Three fuel properties that affect pulverizer-processing capacity are moisture, heating value, and HGI, as discussed earlier.

Unit Turndown: The design of a pulverizer system determines the turndown capability of the steam generator. The minimum stable load for an individual pulverizer firing coal is 50% of the rated pulverizer capacity. Normally in utility boilers, the operating procedure is to operate at least two pulverizers to sustain a self-supported minimum boiler load. Thus, the minimum steam generator load when firing coal without supporting fuel is equal to the full capacity of one pulverizer. Therefore, a loss of one of the two running pulverizers will not trip the steam generator because of loss of fuel and/or loss of flame.

Pulverizer Wear Allowance: A final factor affecting pulverizer system design is a capacity margin that would compensate for loss of grinding capacity as a result of wear between overhauls of the pulverizer (Figure 4.6). A typical pulverizer-sizing criterion is 10% capacity loss due to wear.

The grinder consists of a body with a conical inner surface in which is arranged an internal moving milling cone. The two cones form the milling chamber. On the axle of the internal moving milling cone a debal-ancing vibrator is fitted, which is driven through a flexible transmission. During vibrator rotation, the centrifugal force is generated, leading the internal cone to roll along the inner cone surface of the grinder body without clearance, if material is absent in the milling chamber or across a material layer. Such innercone movement difference is possible owing to the absence in these machines of kinematic limitation of inner cone amplitude. Thus, KID does not have a discharging gap as for eccentric crushers, therefore, the diametric annular between cones is received by coincidence of their axes.

The idea of using the vibrator drive of the cone crusher appeared as long ago as 1925 (US Patent 1 553 333) and then its later versions (German Patent 679 800, 1952; Austrian Patent 200 598, 1957; and Japanese Patent 1256, 1972) were published. In the Soviet Union, the first experimental KID specimens had been created by the early 1950s. Now, in the various branches of industry in the Commonwealth of Independent States, KIDs with capacity from 1 to 300 t/h are produced.

The basic KID feature absence of rigid kinematic bondings between the cones allows the inner moving cone to change its amplitude depending on the variation of grindable material resistance or to stop if a large non-grindable body is encountered; but this is not detrimental and does not lead to plugging. Another KID feature is the nature of the crushing force. In KID, the crushing force is the sum of the centrifugal force of debalance of the inner cone by its gyrating movement. Such force is determined by mechanics and does not depend on the properties of the processed material. The crushing force acts as well on idle running as the result of gapless running in of cones. Therefore, the stability of the inner cone on its spherical support during idle running is ensured.

The grinder consists of a body with a conical inner surface in which is arranged an internal moving milling cone. The two cones form the milling chamber. On the axle of the internal moving milling cone, an unbalanced vibrator is fitted, driven through a flexible transmission. During vibrator rotation, centrifugal force is generated, leading the internal cone to roll along the inner cone surface of the grinder body without clearance if a material that is being grinded is absent in the milling chamber or on this material layer. Such inner cone varying movement is possible owing to the absence in these machines of kinematic limitation of inner cone amplitude. KID does not have a discharging gap as do ordinary cone crushers; therefore, the diametric annular between cones is received by coincidence of their axes.

The idea of using the vibrator drive of the cone crusher appeared as long ago as 1925 (US Patent 1,553,333) and then its later versionsGerman Patent 679,800 (1952), Austrian Patent 200,598 (1957), and Japanese Patent 1256 (1972)were published. The first experimental KID specimens were created in Russia in the early 1950s. Subsequently, in the various branches of industry in the Soviet Union, KIDs with a capacity from 1 to 300t/h were produced. The manufacture of KIDs under license from Soviet Union was developed in Japan in 1981.

The basic KID featurethe absence of rigid kinematic bonding between the conesallows the inner moving cone to change its amplitude, depending on the variation of grindable material resistance, or to stop if a large nongrindable body is encountered. This is not detrimental and does not lead to stopping the debalance. Another KID feature is the nature of the crushing force. In KID, the crushing force is the sum of the centrifugal force of debalance and the inner cone by its gyrating movement. Such force is determined by mechanics and does not depend on the properties of the processed material. This characteristic in combination with the resilient isolation of KID from the foundation allows a two-fold increase in the inner cone vibration frequency.

henan mining machinery and equipment manufacturer - ikman lk leaves grinding machines

henan mining machinery and equipment manufacturer - ikman lk leaves grinding machines

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Ore beneficiation equipment, sand making equipment, crushing equipment and powder grinding equipment, which are widely used in various industries such as metallurgy, mine, chemistry, building material, coal, refractory and ceramics.

milling and flour quality - sciencedirect

milling and flour quality - sciencedirect

Flour quality is vitally important to improvements in breadmaking, and this in turn means that the milling process is critical to bread quality. Even though flour milling is mankinds oldest continuously practised industry, transformative developments have taken place within the last 15 years that have led to significant implications for breadmaking improvements. After reviewing the modern flour milling process and recent innovations, we examine how flour milling governs flour quality and the technological developments that a mill will employ to holistically integrate process and product. Because research is key to technology developments, a review of some milling research highlights since the last edition is followed by some thoughts on the future of flour milling.

redesign of impact plates of ventilation mill based on 3d numerical simulation of multiphase flow around a grinding wheel - sciencedirect

redesign of impact plates of ventilation mill based on 3d numerical simulation of multiphase flow around a grinding wheel - sciencedirect

This paper presents results of the impact plate surface modification of the ventilation mill in the Kostolac B power plant (Serbia). The modification is based on 3D numerical simulation of multiphase flow around a grinding wheel. High velocity of sand particles in the ventilation mill causes strong wear of the impact plates. The multiphase flow simulations of dilute gassolid are performed in order to obtain the sand particle paths and velocity vectors for a different surface geometry of the mill impact plates. The mixture model of the EulerEuler approach is used. The results obtained in the numerical simulation serve for the selection of an optimal redesign of the impact plates. The experimental tests of the revitalized mill wearing parts in real exploitation conditions show that the proposed modification, surfacing technologies and (coating) materials give good results. The relative weight loss of the base plate after 1440h period of exploitation in real conditions is 8%, while the weight loss for the hardfaced plate is 5.9% for the second filler. The application of this approach can reduce the number of possible repairs and extends the period between them, resulting in significant economic effects.

CFD simulations of the multiphase flow in a thermo power plant mill are performed. The impact plate parts, exposed to wear, due to sand movement, are defined. Distribution and velocity vectors of gas mixture and sand particles are presented. Optimal surfacing technology and material are used to optimize the surface hardness. Modified plates tested in exploitation conditions have reduced wearing.

particle size of ginseng ( panax ginseng meyer) insoluble dietary fiber and its effect on physicochemical properties and antioxidant activities | applied biological chemistry | full text

particle size of ginseng ( panax ginseng meyer) insoluble dietary fiber and its effect on physicochemical properties and antioxidant activities | applied biological chemistry | full text

Dietary fibers (DFs) and associated phytochemicals in ginseng species are known to provide various functional and health benefits. The incorporation of ginseng insoluble dietary fiber (IDF) in food products often result in undesirable physicochemical properties. Thus, to overcome such demerits, micronization of IDF has been considered. This study investigated the effect of particle size on the physicochemical properties, antioxidant activities, structure and thermal analysis of ginseng IDF. Micronized IDF powder with median particle diameter of 15.83m was produced through fine grinding. Reduction of ginseng IDF resulted in increased brightness, water holding capacity and solubility. Decreasing particle sizes also lowered bulk, tapped density, Carr index and Hausner ratio. Reduction of particle size caused greater extractability of mineral and phenolic content and thereby increasing the DPPH radical scavenging activity and ferric reducing antioxidant power. Increased polyphenol extraction with smaller particle size also lowered the mice erythrocytes hemolysis percentage while the hemolysis inhibition rate was increased. Particle size also influenced the thermal stability of ginseng IDF powders. FTIR spectra revealed lack of impact on the major phenolic structures due to superfine grinding. Hence,micronized ginseng IDF powders with improved physicochemical properties and antioxidant activities possess the potential to be used in food and pharmaceutical industries.

Several studies have elucidated various functional and health benefits of dietary fibers (DFs) including reducing postprandial glycemic index while maintaining gastrointestinal function and lowering the risk of cardiovascular diseases, diabetes and colon cancer [1]. The other functional effects of DFs include influences on water holding capacity (WHC) and oil holding capacity (OHC), which could be potentially utilized in the development or reformulation of food products. DFs are defined as carbohydrate polymers primarily derived from the cell walls of plants with two or more monomeric units [2]. DFs can be directly obtained from natural sources such as cereals, vegetables, and fruits. For the enrichment of foods, fibers with particular properties have been extracted, isolated and modified from various sources. Fibers are derived mainly from natural raw materials via chemical, physical and enzymatic methods [3]. DFs are classified based on some parameters that include major source, chemical structure and water solubility [4].

DFs are usually non-starch polysaccharides that possess the ability to withstand digestion and absorption in the small intestine, undergoing full or partial fermentation in the large intestine of humans [4]. DFs are also classified based on water solubility as water soluble DFs (pectin and some hemicelluloses) and water in-soluble DFs (cellulose or lignin). It is the insoluble dietary fibers (IDF) that regulate the intestinal function via improving the intestinal peristalsis and fecal volume and removing heavy metals, grease, and other unwanted substances [2, 5]. To achieve best activity of DFs, about 5075% of IDF in daily meals is recommended [4]. Furthermore, soluble DF (SDF), which are higher in fruits and vegetables than cereals, are also required along with IDF. DFs can also act as prebiotics, which function as sources of carbon for the growth of gastrointestinal microbiota. Inulin, galactooligosaccharides and fructooligosaccharides, are the well-known prebiotics [6]. However, it is important to note that the functional benefits of DFs are contingent upon the structural and chemical composition of DFs [4].

Panax ginseng Meyer, which usually refers to the root of the Panax genus, has long been widely used as a curative agent in Eastern Asia, North America, and Europe [7]. The utilization of ginseng root is more favored due to the presence of pesticide residue in other parts such as leaf or stem [8]. Ginseng has been shown to exhibit immunomodulatory properties that promote a wide range of antimicrobial functions. However, immunomodulatory properties are highly affected by factors such as type and source of ginseng, and extraction method [9]. The variation in such properties is attributed to the various phytochemicals that include ginsenosides, carbohydrates, phytosterols, polyacetylenes, polyphenolic compounds, sugars, acidic polysaccharides, organic acids, amino acids, vitamins, nitrogenous substances, and minerals. In particular, ginsenosides are known to provide various health benefits that include antioxidant, anti-inflammatory and immunity enhancing activities. Owing to the aforementioned bioactive agents along with dietary fibers, ginseng is used as nutritional supplement, herbal remedy [10] and adjuvants during vaccination [11]. However, acceptability of DFs in final product is dependent upon the interaction of DFs with components and ingredients utilized [4]. In particular, IDF has been shown to negatively impact the color, texture and flavor of the final product. To overcome such demerits, DFs have been modified using sulfuric acid (low concentration) and blasting extrusion. However, the most effective method was found to be with enzymatic treatment [12].

Micronization involves the reduction of average particle size of raw materials [13]. Particle size reduction of raw materials has been shown to modify structural characteristics and improve technological properties [14]. Particle size is known to influence physico-chemical properties such as waterholding capacity, solubility and flowability. However, a major constraint in production of superfine powders is the nature of raw materials. Particularly, hardness and rough texture of materials can influence the average particle size of its powders [13]. Furthermore, health benefits derived from ginseng are dependent on dietary fibers, making it necessary to evaluate the impact micronization on ginseng IDF. In addition, functional properties, such as adsorption to cholesterol and oil, are mostly due to IDF than SDF [5]. As a result, micronization of IDF has gained increased attention [15]. Since studies pertaining to micronization of ginseng IDF are limited, this study focused on the structural characteristics and technological functionalities of micronized ginseng IDF. This study systematically analyzes composition, structure, physicochemical, and technological properties of IDF as influenced by micronization.

Dried ginseng roots were purchased from a local supermarket in Jillin city (longitude 125 40~127 56, latitude 42 31~44 40), China. The ginseng roots cultivated for 5years were collected in November 2019. All chemicals and reagents used in this study were of analytical grade. Trichloroacetic acid, hydrogen peroxide, ferric chloride, potassium ferricyanide, sodium carbonate, methanol were supplied by Zhengda Chemical Company, Jilin, China. -amylase, amyloglucosidase, protease, gallic acid, 1,1-Diphenyl-2-picrylhydrazyl were obtained from Sigma-Aldrich (St. Louis, MO, USA).

Ginseng residue was prepared according to Hua et al. [5]. Briefly, Ginseng residue was formed after ginseng polysaccharides were extracted by boiling. The residue was then washed with ethanol and distilled water for the removal of water-soluble oligosaccharide and inorganic salts. The residue was dried (60C for 24h), sieved (60 mesh), packaged in a self-sealing bag, and stored at 20C until further analysis.

The obtained ginseng residue was then used for the preparation of the IDF as described by Bunzel et al. [16] with some modification. Ginseng residue (60g) was treated with 1.8mL heat-stable -amylase in 1.5 L of buffer (pH 6.0) using a water bath at 95C for 20min. The pH of reactants was adjusted to 7.5, protease (3.0mL) was added at 60C and incubated for 1h. Later, amyloglucosidase (1.2mL) was added to the reaction mixture with pH adjusted to 4.5 at 60C for the removal of starches and proteins. Finally, the reaction mixture was centrifuged at 5000rpm for 20min, and the residue was then washed twice with distilled water and 95% ethanol. Precipitate was dried at 50C for 24h to yield IDF. The ginseng IDF was then packaged in an aluminum-laminated bag and stored at 20C until further analysis.

The ginseng IDF was milled coarsely using a disc-mill (FZ102, Taisite Instrument Co., Ltd., Tianjin, China), and then the powders were passed through 2060 mesh, 6080 mesh and 100160 mesh sieves, such that three different particle size ginseng IDF were obtained. The superfine powders passed through mesh sized less than 400 mesh was prepared using a superfine mill (HMB-700S, Hongquan Machinery Co., LTD, Taiwan) by regulating the grinding time. The particle size of samples between 20 and 60 mesh, 60 and 80 mesh, 100 and 160 mesh and less than 400 mesh were designated as M20, M60, M100 and M400, respectively. All samples were sealed in aluminum-laminated bags and stored at 20C until use.

Particle size distributions of the ginseng IDF powders were analyzed using a Matersizer 3000 laser diffraction instrument (Malvern Instruments Ltd., Malvern, UK). The powder was dispersed in methanol prior to measurements. Dv 50 is considered the median particle diameter, which is the equivalent volume diameter at 50% cumulative volume. Correspondingly, Dv 10 and Dv 90 denote the volume diameter at 10 and 90% cumulative volume, respectively. Powder morphology was observed using an environmental scanning electron microscopy (ESEM; Quanta 250 FEG, FEI Company, USA) at 15kV. Powders were coated with gold, attached to a double-sided adhesive tape, and observed at 200magnification.

WHC and water solubility index (WSI) were determined according to a method reported by Phat et al. [17]. For WHC quantification, 0.5g (H) of sample was added to 10mL of distilled water and mixed in a 15mL centrifuge tube (W1). Afterwards, the reaction mixture was subjected to incubation in a water bath (DK500, Jing Hong Laboratory Instrument Co., Ltd., Shanghai, China) at 60C for 30min and subsequently centrifuged at 3000rpm for 15min (TD5A-WS, Xianglu Centrifuge Apparatus Co., Ltd., Changsha, China). The sediment tubes were then weighed (W2) and WHC was calculated based on the formula:

For WSI quantification, About 10mL of distilled water was mixed with 0.2g of powder in a tube, which was placed in a water bath at 80C for 30min. After centrifugation at 3000rpm for 10 min, the supernatant was transferred to a pre-weighed dish (S1) and dried at 105C to constant weight (S2). WSI was calculated using the formula:

Ginseng IDF samples of color properties (L*, a* and b* values) were measured by colorimeter (CM-3600A, Konica Minolta, Osaka, Japan). The sample (powder) was placed on a glass plane and the colorimeter was placed directly on to the sample to measure the color values. The calibration of the equipment was performed by a white tile prior to recording sample color values and standard values were these: L*=86.90, a*=0.3170, and b*=0.3240.

The bulk and tapped densities were measured according to the method described by Ramachandraiah and Chin [18]. The flowability and cohesiveness of the samples were evaluated by the Carr index (%) [19] and Hausner ratio [20], respectively. The Carr index and Hausner ratio were calculated as shown below;

Samples with Carr index values<15% very good, 1520% were considered good, 2035% fair, 3545% bad, and very bad if>45% [21]. Hausner ratio values<1.2 were considered to have low cohesiveness, Hausner ratio values 1.2 to 1.4 were intermediate, and the Hausner ratio value>1.4 were considered to have high cohesiveness [21].

Each ginseng IDF (0.5g) was added with 10mL deionized water and boiled for 15min. Each sample was then centrifuged at 3500rpm for 10min and filtered using Whatman filter paper no. W1. After that, liquid solution (1mL) was transferred to a 50mL volumetric flask with deionized water and analyzed. An atom absorption spectrophotometer (AFS-8230, Titan Instruments Co., Ltd, Beijing, China) was used to determine the elemental composition (K, Ca, Na, Mg, Zn, Fe, Mn and Cu) in ginseng IDF samples.

The ginseng IDF samples were extracted according to a method by Jiang et al. [22]. The samples (2g) were homogenized with 20mL methanol (80%) for 5min and then extracted by sonication for 20min. Homogenization and sonication treatments were performed repeatedly followed by filtration with a No 1. filter paper (Whatman Ltd., Cambridge, UK). The supernatant of each sample was collected, concentrated in vacuum, and stored at 20C before being analyzed.

TPC was determined for each sample based on the method described by Eghdami and Sadeghi [23]. Diluted extract (200L) was added to Folin-Ciocalteu reagent (800L) and 7.5% sodium carbonate (2mL). Distilled water used to dilute the mixture before being incubated at room temperature under dark condition for 2h.The absorbance values were measured at 765nm using a UV spectrophotometer (UV-1800, Shimadzu Instruments Mfg. Co., Ltd, Kyoto, Japan). The TPC was expressed as gallic acid equivalents (mg GAE 100g1) on dry weight (DW) basis.

The DPPH-RSA of the samples was determined using the method described by Kang et al. [24]. Methanolic extract (50L) was added to 80% methanol (50L), and mixed with 0.2mM DPPH radical solution (2mL). The vortexed mixture (30s) and stored at 25C for 30min. Sample absorbance of the mixture was measured at 517nm using a spectrophotometer.

RP was determined as described by Huang et al. [25]. Methanolic extract (0.3mL) was added with 1.1 mL phosphate buffer (0.2M, pH 6.6) and mixed. To this mixture, 0.6mL of 1% potassium ferricyanide was added and incubated at 50C for 20min. Following incubation, 10% trichloroacetic acid (1 mL) was added and centrifuged at 2016gfor 15min. The supernatant was separated and mixed with distilled water (1 mL) and 0.1% ferric chloride (0.5 mL).Sample absorbance was measured at 700nm; increased absorbance corresponded to higher RP.

The maintenance of mice was carried out using a laboratory diet and water ad libitum until they were 6weeks old. Experimental female mice weighing 1820gwere fed in an environment of temperature 2024C, humidity 5070%, and 12h alternate light and dark. All of the animal procedures were conducted in adherence to the animal welfare guidelines and ethical committee compliance. Whole blood collected from experimental mice was added with anticoagulant heparin sodium and then centrifuged at 5000rpm for 10min. The plasma was discarded, and the erythrocytes isolated were washed with cold phosphate-buffered saline three times. Each phenolic extract (0.3mL) from the different particle sizes (M20, M60, M100 and M400) was added with 0.1mL mice erythrocytes suspension (0.5%), followed by the addition of 0.1mL of 100mmol/L H2O2. The test tubes were incubated at 37C for 1h, and then added with 5.2mL normal saline [26]. The samples were then centrifuged at 4000rpm for 10min, and the absorbance measured at 415nm (Optizen 2120 UV; Mecasys Co., Daejon, Korea).

Ginseng IDF powder samples (1020mg) were weighted accurately, sealed in aluminum pans and analyzed using DSC (Cph60, Netzsch, Germany). Temperature scans were conducted from 20 to 200C at a heating rate of 10C/min. Each sample was measured at least in triplicate. The Universal Analysis 2000 software (TA Instruments Co., New Castle, USA) was applied to analyze the curve of each sample.

The organic functional groups of ginseng IDF samples were analyzed using a FT-IR spectrophotometer (FTIR/NIR 400, PerkinElmer Inc., Waltham, MA, USA). The spectrum wavelength was 4004000cm1 at 4cm1 resolution with 4 scans at a scan speed of<10s.

All analyses were performed in triplicate and values were presented as meanstandard deviation. One-way analysis of variance (ANOVA) was used to determine differences between treatments and were carried out in SPSS version 18.0 (Chicago, IL, USA). The differences in means were evaluated using the Duncans multiple-range tests for means with 95% confidence limit (p0.05).

It is known that the reduction in particle size and increased surface area could influence several powder properties. Particle sizes of ginseng IDF as affected by disc mill and superfine grinding are shown in Table1. Although the difference in the average particle size of M20 and M60 was large, the specific surface was not (p>0.05) affected. However, when ginseng IDF was subjected to vibrating superfine mill treatment, powder with highly (p0.05) reduced particle size and increased specific surface area was formed. This is because vibrating superfine mill treatment caused greater breakage of the physical structure than disc mill. Similar reduction in particle size was observed in a study by Wen et al. [12], wherein rice bran dietary fibers were modified using enzyme-ball mill treatments. In another study, superfine powder was formed when rice bran IDFs were milled in a vibrating superfine mill [15]. However, the span values, which indicate the width of the particle size distribution was increased upon superfine grinding. Similar increases in span values were also observed in rice bran IDF [15]. On the other hand, decreased span values were observed in Lentinus edodes mushroom powder [14]. Apart from the nature of the materials, the milling method and time also influence span values. It is important to note that micronization is a dynamic process that encompasses physical forces of fracture, breakage, and aggregation [27].

Changes in the microstructure of ginseng IDF powders are illustrated in Fig.1. As shown in Table1, the particle size of M20, M60, and M100 are considerably larger than M400. Superfine powders (M400) show smaller particles of varying sizes as opposed to large blocky particles in the other three powders. Smaller particles that seem to have broken off from larger particles indicate the impact of superfine grinding on ginseng IDF. Large particles of ginseng IDF with porous surface was also shown in another study [5]. The lack of smooth surface is attributed to the loss of water soluble components during processing [3].

Hydration properties of ginseng IDF powders with different particle sizes are shown in Table2. Although disc milling of ginseng IDF reduced the particle size, it had no impact on WHC. However, superfine grinding resulted in increased WHC. Increased WHC of superfine powders was also seen with rice bran IDF [13]. Likewise, WSI increased significantly only for superfine powders. Improved hydration properties of superfine powders are due to increased surface area, which causes higher exposure of polar groups to water. Increased polar groups present as binding sites for water. Studies have indicated the increased porosity of particles could also affect its ability to hold water via hydrogen bonding [15]. Particle size reduction resulting in increased solubility was also seen in other study with Hericium erinaceum powders [17]. Increased solubility has been attributed to shorter cellulose chains and higher exposure of hydrophilic cellulose and hemicellulose groups as a result of superfine grinding [28]. When products such as instant food are developed, the hydration property, WSI, is a major consideration.

The color values of ginseng IDF powders as affected by different particle sizes are given in Table2. The L* (lightness) and b* (yellowness) values of powders showed significant (p0.05) increases with corresponding rises in powder mesh sizes from M20 to M400. It was found that reduction of particle size conferred more degree of brightness to powder product. On the other hand, the a* (redness/greenness) values showed significant decreases with increases in mesh sizes. This implied that superfine grinding led to decreasing tendency of redness in powdered products. The increases in degree of yellowness might be attributed to the aggregation phenomenon of phenolic compounds after exposure to superfine grinding. These results are in correspondence with the findings of previously reported study in which decreases in particle sizes led to increases in lightness and yellowness during superfine grinding of celery stalk powders [18].

Bulk and tapped densities as well as flowability are also shown in Table3. Decreasing particle sizes resulted in decreasing bulk and tapped density. This is contrary to other studies wherein particle size reduction caused increased bulk density [17]. However, decreased bulk and tapped density indicates open packed structures of powders subjected to superfine grinding. Studies show that bulk density is associated with particle size distributions, surface weighted mean D (3, 2), and fineness. Lower surface weighted mean is associated with higher cohesiveness [29]. However, in this study, D (3, 2) values of M20, M60, M100 and M400 were 583.34.6m, 555.04.3m, 87.22.7m and 8.00.02m, respectively. As shown in Table3, reduced particle sizes resulted in increased cohesiveness of ginseng IDF powders. This is based on the Hausner ratio, which increased with reduced particle size indicating higher cohesiveness. Nonetheless, particles within cohesive superfine powders tend to aggregate and form larger particles that are held together by interparticle forces. Cases in which external force is unable to break such interparticle forces between larger particles can cause loose packing of powders, which in turn decreases the bulk density [30]. Bulk and tap densities are considered in the development of aqueous food products, such as instant beverages or soup mixes [17]. However, in this study, lower particle size increased the Carr values, which in turn lowered the flowability of ginseng powders from very good to fair to poor. Carr index values should be considered when powders are poured, sieved, and mixed during processing [31].

The results of mineral content analysis for ginseng IDF with different particle are shown in Table4. Ginseng residue insoluble dietary fibers have been shown to contain mineral elements such as calcium, sodium, magnesium, potassium, copper, manganese, and zinc etc. [3]. Mineral and inorganic components are essential for several purposes and play a vital role in metabolism [32]. However, in this study, the mineral elements detected were calcium, potassium, magnesium, manganese, zinc, copper and iron. Powders with the largest particle size contained Ca, K and Mg. However, as the particle size reduced, the mineral content of Ca, K and Mg were increased. The particles with the smallest size was found to contain Mn, Zn and Fe. These results indicate that particle size reduction caused higher extraction of mineral content.

Effect of particle size on TPC is shown in Fig.2a. Decreasing particle size resulted in increasing TPC. Particles of superfine ginseng powders had the highest TPC. Increased TPC due to superfine grinding has also been reported in other studies on wine grape pomace [33] and rice bran IDF [15]. Ginseng has been reported to contain a variety of phenolic compounds. In a study, 23 different types of phenolic compounds were identified. Particularly, gentisic acid, rutin, p- and m-coumaric acid, and chlorogenic acid were reported to be the main phenolic compounds present in Panax ginseng [34]. In a previous investigation, 12 different free, esterified, and insoluble-bound forms of phenolic acids were identified. The predominant free phenolic acid was trans-Ferulic acid, esterified phenolic acids were cis-ferulic acid and trans-ferulic acid and the main insoluble-bound phenolic acid was Ferulic acid (cis and trans isomers) [35]. However, in this study, smaller particles due to increased surface and improved extraction caused an increase in TPC. DPPH-RSA, which relates to the antioxidant activity of ginseng IDF is shown in Fig.2. Similar to the trend of TPC values, DPPH-RSA also increased with decreasing particle size. DPPH-RSA for M20, M60, M100 and M400 was 13.29%, 23.88%, 25.54% and 39.21%, respectively. The smallest particle size IDF exhibited the highest RSA. Elevated levels of RSA could be directly associated with increased TPC. These results are consistent with another study on rice bran IDF [15]. However, higher DPPH-RSA is not always related to increased TPC. Despite the decrement in particle size, DPPH RSA was not increased, as seen in other studies [33]. Likewise, RP assay is also employed to measure the antioxidant activities of ginseng IDF. RP, as shown in Fig.2, was also consistent with the TPC. Ginseng IDF with the largest particle size had the lowest activity. When compared with M20, reducing power increased by 28.8%, 36.6% and 90% for M60, M100 and M400, respectively. The antioxidant potential of ginseng has been demonstrated in a clinical study, wherein level of serum ROS and methane dicarboxylic aldehyde activity were reduced in healthy volunteers [36]. However, in this study, with decrement in particle size, increases in surface area could have caused greater exposure and release of phenolic contents from fibrous matrix, which in turn could have improved antioxidant activity. Since several traditional materials have been adopted as modern medicines, it is likely that ginseng powders can also be utilized in the development of new therapeutic agents [37].

Total phenol content (TPC), DPPH radical scavenging activity and reducing power (antioxidant activities) of ginseng powders (A) and hemolysis of mice erythrocytes (B) by ginseng powders as affected by different particle size. MeanSD (n=3) with different letters (ad) indicating significant difference (p0.05)

It is known that oxidative damage by reactive oxygen species occurs through the peroxidation of erythrocyte membranes. Oxidative damage induced by H2O2 can elevate erythrocyte hemolysis and the inhibition rate [26]. In this study, RBC hemolysis percentage decreased with decreasing particle size (Fig.2b). Contrarily, hemolysis inhibition rate increased with decreasing particle size. This is likely due to the increased extraction of polyphenols with the decreasing particle size of ginseng powders. Studies have shown that polyphenols binding to RBC membrane matrix, particularly to tryptophan residues, can inhibit oxidation of lipids and induce antihemolytic activity [38]. In this study, the smallest particle size (M400) had the highest erythrocyte hemolysis inhibition rate of 86.6%, which was higher than other ginseng IDFs. As shown in Fig.2a, increased TPC with decreasing ginseng particle size could have contributed to such inhibition rates. A similar effect of the concentration of polyphenols from mulberry fruit on the hemolysis rate and inhibition rate of red blood cells from mice induced by H2O2 was observed in another study. Increasing polyphenol concentration decreased the mice erythrocytes hemolysis rate and increased the inhibition rate [26].

The transition temperature (Tp1) and melting peak temperatures (Tp2) of ginseng IDF with different particle sizes in shown in Table5. The transition temperature (Tp1) tended to reduce with decreasing particle size. The smallest particle size powder (M400) had the lowest Tp1. Endothermic peaks (Tp2) for all the samples were observed to be between 80 and 125C. The peak temperatures also decreased with decreasing particle size. Similar results were observed for sugar beet pulp powders [39]. These results are in contrast with another study on white winter wheat bran, wherein decreasing particle size resulted in a decreasing tendency for peak temperatures [40]. In this study, it is likely that the reducing particle size could have caused greater exposure of polysaccharide and protein groups, thereby lowering the peak temperatures.

FT-IR spectra of ginseng IDF with different particle sizes are shown in Fig.3. Functional groups such as OH, NH, and CO can be qualitatively evaluated via FT-IR analysis [41]. The OH group stretching at 33003500 is associated with phenolic structures [41]. In this study, the peaks formed at 3301cm1 correspond to OH stretch vibration, which indicates the presence of phenolic structures. The FT-IR spectra in this study was similar to that of ginseng IDF [5]. However, the decrease in intensity in this region of spectra for different powders could be attributed to the breakdown of intermolecular bonds due to the physical force of milling [42]. Similar bands formed at these frequency ranges were also observed in another study [43]. The major absorption peak at 2923cm1 is due to the CH stretching indicating the presence of cellulose [42, 44]. Similarly, in an earlier study, peak at 2924cm 1 was assigned to CH stretching of grape pomace powders [13]. The major peak at 1619cm1 can be attributed to the esterified and ionized carboxyl groups of galacturonic acid [3]. The peak corresponding to CH bonds indicate the presence the aromatic molecules as also shown in another study [13, 43]. The weak peaks at 1317cm1 and 1239cm1 can be ascribed to the cellulose and hemicellulose structures, respectively. The peaks formed around 1027cm1 for ginseng IDF with different particle size distributions indicated stretching vibration of CO [43]. Furthermore, the decrease in absorbance intensity of peaks is associated with the changes in the surface properties of the finer powders. Similar decrement in the intensity associated with lower particle size was also observed in a recent study on Moringa Oleifera leaf powders [45]. The lack of disappearance of the major phenolic compounds in the profiles of different ginseng powders suggested that the particle size reduction did not affect the major structure of phenolics.

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Jiang, G., Wu, Z., Ameer, K. et al. Particle size of ginseng (Panax ginseng Meyer) insoluble dietary fiber and its effect on physicochemical properties and antioxidant activities. Appl Biol Chem 63, 70 (2020). https://doi.org/10.1186/s13765-020-00558-2

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