升温方式对真空冷冻干燥过程的影响

为了在保证冻干样品品质的同时缩短冻干时间,以猪主动脉为研究对象进行真空冷冻干燥。采用阶段升温方式与传统地一次干燥和二次干燥方式进行对比,结合脱水率、外观形态和力学性能,探讨阶段升温方式对缩短冻干时间的影响。实验结果表明,采用阶段升温方式明显缩短了干燥时间,且脱水率同样达到较高水平、外观形态和力学性能与采用传统方式所得样品无明显差异。实验结果为研究真空冷冻干燥过程降低能耗提供参考。     

Optimization of Oxygen Parameters for Determination of Carbon and Nitrogen in Biochar Materials

Recently, there has been increased focus on biochar materials due to their ability to sequester carbon for long-term in soil. In the production of biochar or charcoal, plant biomass is heated in a low or no oxygen environment. This process results in a product with unique characteristics. But there is limited research on the standardization of methods for determining total carbon (C) and nitrogen (N) in the biochar materials whose properties vary by feedstock type and pyrolytic conditions. The objective of this study was to determine the oxygen dosing time (OT) and dose (OD) for total organic carbon (TC) and nitrogen (TN) analysis in biochar materials by dry combustion method (using Vario Max CNS analyzer). Central composite rotatable design was used to determine the effect of five levels of oxygen dosing time (OT) and dosing level (OD) on measurement of total carbon and total nitrogen in four types of plant originated biochars. OT and OD level interaction had significant impact on the measurement of TC and TN in all types of biochar materials. Optimum levels of OT and OD were determined as 103 to 110 sec and 180 to 232 ml/min, respectively.     

Influence of homogenization and drying on the thermal stability of microfibrillated cellulose

Homogenization has been used to release microfibrils from cellulose fibres to produce microfibrillated cellulose (MFC). Oven drying, atomization or freeze-drying were used to dry MFC. Morphological differences were observed linked to the compaction of the system and the formation of microfibril agglomerates. Thermal stability of the dried MFC, checked by TGA, decreased after homogenization and drying. Char level at the end of the pyrolysis was higher than for cellulose fibres. Derivative TGA (dTGA) showed a shoulder around 250 °C for the dried MFC. Volatile degradation product detection by FTIR spectroscopy (FTIR) coupled to TGA and DSC showed that the shoulder corresponds to expected dehydration reactions of the cellulose. Increasing the contacts between microfibril(s) (bundles) and agglomerates of the freeze-dried MFC by compression promoted dehydration reactions. Homogenization and drying modified the thermal properties of the MFC. No significant influence of freeze-drying kinetics on the thermal behaviour of the MFC was observed.     

Synthesis and characterization of new copolymers of ethyl methacrylate grafted on tapioca starch as novel excipients for direct compression matrix tablets

In last years, the introduction of new materials for drug delivery matrix tablets has become more important. This paper evaluates the physicochemical and mechanical properties of new graft copolymers of ethyl methacrylate (EMA) on tapioca starch (TS) and hydroxypropylstarch (THS), synthesized by free radical polymerization and dried in a vacuum oven (OD) or freeze-dried (FD). Infrared and ¹³C NMR spectroscopies confirm the change of chemical structure of the copolymers and X-ray diffraction shows up the higher amorphization of copolymers respect to the carbohydrates. Particle size analysis and SEM indicate that graft copolymerization leads to an increase of particle size and a more irregular shape. Graft copolymerization implies decrease of density and moisture content values. Heckel equation shows that copolymers have less densification by particle rearrangement and fragmentation than carbohydrates. Concerning the drying methods, FD products have larger plasticity and lower elasticity than OD copolymers. Graft copolymerization produces a decrease of the applied pressure necessary to obtain tablets, ejection force and friction work. Furthermore, graft copolymers show longer disintegration time than tablets from raw starches. These qualities suggest that these copolymers could be used as excipients in matrix tablets obtained by direct compression, and with a potential use in controlled release.     

Effect of Filtrated Osmotic Solution Based on Concentrated Chokeberry Juice and Mint Extract on the Drying Kinetics,Energy Consumption and Physicochemical Properties of Dried Apples

Background: Filtration of osmotic solution affects selective penetration during osmotic dehydration (OD), and after drying is finished, this can influence the chemical composition of the material, which is also modified by OD. Methods: Osmotic dehydration was carried out in filtrated and non-filtrated concentrated chokeberry juice with the addition of mint infusion. Then, this underwent convective drying, vacuum-microwave drying and combined convective pre-drying, followed by vacuum-microwave finishing drying. Drying kinetics were presented and mathematical models were selected. The specific energy consumption for each drying method was calculated and the energy efficiency was determined. Results and Discussion: The study revealed that filtration of osmotic solution did not have significant effect on drying kinetics; however, it affected selective penetration during OD. The highest specific energy consumption was obtained for the samples treated by convective drying (CD) (around 170 kJ·g⁻¹ fresh weight (fw)) and the lowest for the samples treated by vacuum-microwave drying (VMD) (around 30 kJ·g⁻¹ fw), which is due to the differences in the time of drying and when these methods are applied. Conclusions: Filtration of the osmotic solution can be used to obtain the desired material after drying and the VMD method is the most appropriate considering both phenolic acid content and the energy aspect of drying.     

Adsorption of some toxic elements from water samples on modified activated carbon,activated carbon and red soil using neutron activation analysis

A simple and sensitive method for the determination of some metalloids and heavy metals in water samples is presented. The method is based on the preconcentration of the attachment of chelating functionalities with metalloids and toxic metals irreversibly and targeted towards toxic metals adsorbed on modified activated carbon, activated carbon and red soil particles at pH 3.0–9.0±0.2, followed by quantitative determination using instrumental neutron activation analysis (INAA), on the absorbers. Attachment results from attraction that may be physical, chemical, electrical, or a combination of all three. The efficient removal of metalloids and toxic metals, especially arsenic, chromium and mercury is anticipated. The adsorption capacity of the chemically modified activated carbon materials was evaluated for the above mentioned metalloid and toxic metal ions in the presence of iron ions and simulated water samples. Red soil particles containing iron was utilized in the control of oxidation-reduction reaction with metalloids and toxic metals. The preconcentration of the elements of interest on red soil particles, activated carbon and modified activated carbon at different depths, pH and oxidation states was investigated. The results obtained showed good agreement with certified values giving relative errors of less than 10%.     

Production of salvianolic acid B in roots of Salvia miltiorrhiza (Danshen) during the post-harvest drying process

Drying is the most common and fundamental procedure in the post-harvest processing which contributes to the quality and valuation of medicinal plants. However, attention to and research work on this aspect is relatively poor. In this paper, we reveal dynamic variations of concentrations of five major bioactive components, namely salvianolic acid B (SaB), dihydrotanshinone I, cryptotanshinone, tanshinone I and tanshinone IIA, in roots of Salvia miltiorrhiza (Dashen) during the drying process at different oven temperatures. A minor amount of SaB was found in fresh materials while an noticeable increase in SaB was detected in drying at 50~160 °C. The maximal value occurred after 40 min of drying at 130 °C and its variation showed a reverse V-shaped curve. Production of SaB exhibited a significant positive correlation with drying temperatures and a significant negative correlation with sample moistures. The amounts of tanshinones were nearly doubled in the early stage of drying and their variations showed similar changing trends with drying temperatures and sample moistures. The results supported our speculation that postharvest fresh plant materials, especially roots, were still physiologically active organs and would exhibit a series of anti-dehydration mechanisms including production of related secondary metabolites at the early stage of dehydration. Hence, the proper design of drying processes could contribute to promoting rather than reducing the quality of Danshen and other similar medicinal plants.     

Drying cellulose nanofibrils: in search of a suitable method

Increasing research activity on cellulose nanofibril-based materials provides great opportunities for novel, scalable manufacturing approaches. Cellulose nanofibrils (CNFs) are typically processed as aqueous suspensions because of their hydrophilic nature. One of the major manufacturing challenges is to obtain dry CNFs while maintaining their nano-scale dimensions. Four methods were examined to dry cellulose nanocrystal and nanofibrillated cellulose suspensions: (1) oven drying, (2) freeze drying (FD), (3) supercritical drying (SCD), and (4) spray-drying (SD). The particle size and morphology of the CNFs were determined via dynamic light scattering, transmission electron microscopy, scanning electron microscopy, and morphological analysis. SCD preserved the nano-scale dimensions of the cellulose nanofibrils. FD formed ribbon-like structures of the CNFs with nano-scale thicknesses. Width and length were observed in tens to hundreds of microns. SD formed particles with a size distribution ranging from nanometer to several microns. Spray-drying is proposed as a technically suitable manufacturing process to dry CNF suspensions.     

Integration of biomass drying with combustion/gasification technologies and minimization of emissions of organic compounds

Moisture content (MC) of green biomass or raw biomass materials (wood, bark, plants, etc.) commonly exceeds 50 mass % (wet basis). The maximum possible MC of biomass fuel for big scale combustion (e.g. fluidized bed combustion with low external heat losses) is approximately 60–65 mass %. Higher biomass MC generally causes operational problems of biomass combustors, lower stability of burning and higher CO and VOC emissions. Gasification of biomass with higher MC produces fuel gas of lower effective heating values and higher tar concentrations. In this review, various technological schemes for wood drying in combination with combustion/gasification with the assessment of factors for possible minimization of emissions of organics from the drying processes are compared. The simple direct flue gas biomass drying technologies lead to exhaust drying gases containing high VOC emissions (terpenes, alcohols, organic acids, etc.). VOC emissions depend on the drying temperature, residence time and final MC of the dried biomass. Indirect biomass drying has an advantage in the possibility of reaching very low emissions of organic compounds from the drying process. Exhaust drying gases can be simply destroyed as a part of the total combustion air (gas) in a combustion chamber or a gasifier. Liquid, condensed effluents have to be treated properly because they have relatively high content of organic compounds, some of them accompanied by odor. Drying of biomass with superheated steam offers more uniform drying of both small and bigger particles and shorter periods of higher temperatures of the dried biomass, particularly if drying to the final MC below 15 mass % is required. In practical modern drying technologies, biomass (mainly wood) is dried in recirculated gas of relatively high humidity (approaching saturation) and the period of constant rate drying is longer. Drying of moist wood material (saw dust, chips, etc.) is required in wood pellet production. Emissions of organics in drying depend on biomass properties, content of resins, storing time and on operational aspects of the drying process: drying temperature, drying medium, final MC, residence time, and particle size distribution of the dried biomass (wood). Integration of biomass drying with combustion/gasification processes includes the choice of the drying medium (flue gas, air, superheated steam). Properties of the drying media and operational parameters are strongly dependent on local conditions, fuel input of the combustion/gasification unit, cleaning of the exhaust drying media (gas, steam, wastewater), and on environmental factors and requirements.     

In Vitro Anti-Diabetic Activities and UHPLC-ESI-MS/MS Profile of Muntingia calabura Leaves Extract

Anti-diabetic compounds from natural sources are now being preferred to prevent or treat diabetes due to adverse effects of synthetic drugs. The decoction of Muntingia calabura leaves was traditionally consumed for diabetes treatment. However, there has not been any published data currently available on the processing effects on this plant’s biological activity and phytochemical profile. Therefore, this study aims to evaluate the effect of three drying methods (freeze-drying (FD), air-drying (AD), and oven-drying (OD)) and ethanol:water ratios (0, 50, and 100%) on in vitro anti-diabetic activities of M. calabura leaves. In addition, an ultrahigh-performance-liquid chromatography–electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS) method was used to characterize the metabolites in the active extract. The FD M. calabura leaves, extracted with 50% ethanol, is the most active extract that exhibits a high α-glucosidase and α-amylase inhibitory activities with IC₅₀ values of 0.46 ± 0.05 and 26.39 ± 3.93 µg/mL, respectively. Sixty-one compounds were tentatively identified by using UHPLC-ESI-MS/MS from the most active extract. Quantitative analysis, by using UHPLC, revealed that geniposide, daidzein, quercitrin, 6-hydroxyflavanone, kaempferol, and formononetin were predominant compounds identified from the active extract. The results have laid down preliminary steps toward developing M. calabura leaves extract as a potential source of bioactive compounds for diabetic treatment.     

Determination of alkylphenols and alkylphenol ethoxylates in sewage sludge: effect of sample pre-treatment

A complete characterization of sewage sludge collected from five biological waste water treatment plants was done to determine physico-chemical parameters, heavy metals and alkylphenols, making special emphasis on sampling, homogenization, and sample pre-treatment. Ultrasonic extraction followed by gas chromatrography coupled with mass spectrometry was used to evaluate the effect of sample pre-treatment (untreated sample, freeze-drying, drying at 40 °C or drying at 100 °C) on the concentration of octylphenol (OP), nonylphenol (NP) and nonylphenol ethoxylates (NP₁EO, NP₂EO). Untreated samples and samples dried at 100 oC gave concentration levels up to 62% and 89% lower, respectively, than freeze-dried samples. In 50% of cases, freeze-dried samples led to significantly higher concentrations than those obtained by drying at 40 °C. Thus, freeze-drying is the recommended sample pre-treatment to prevent possible losses of OP, NP, and NP₁EO. Using this methodology, concentrations detected were from 3.2 to 199 mg kg⁻¹ being NP followed by NP₁EO found in highest concentration. The total concentration of NP and NP₁EO exceeded the limit of 50 mg kg⁻¹ proposed by the draft European directive on sewage sludge in three out of five samples studied. Contrarily, heavy metals were below the legislated values.     

Uranium biosorption under dynamic conditions: Preliminary tests with Sargassum filipendula in real radioactive wastewater containing Ba, Cr, Fe, Mn, Pb, Ca and Mg

The biosorption of uranium by the seaweed Sargassum filipendula was investigated under dynamic conditions at various bed heights. Our results indicate that a bed height of 40.0 cm (111.9 g biomass) was the most efficient for long-term operation of the continuous system. Our results also indicate that the effluent solutions produced are in accordance with Brazilian legislation for safe discharge of uranium in aqueous streams. The efficiency of the process increased with an increase in bed height from 5.0 to 40.0 cm due to changes in the transfer zone. In treatment of a real effluent contaminated with uranium, stable heavy metals and essential metals, 64% of the uranium was biosorbed, as well as the stable heavy metals chromium, lead and barium. The essential metals calcium, magnesium, iron and manganese were not biosorbed by the seaweed, in fact, their concentrations in the solution increased due to ion-exchange mechanisms with the constituent polysaccharides of the biomass. Another important result was the 85–87% reduction of mass obtained after drying and calcination of the biomass. This is a relevant indication that long-term storage of biomass loaded with radionuclides and heavy metals is possible after concentration of the contaminants. In the present work, the reduction in total mass of the loaded biomass was considerable, thus facilitating storage of the contaminated seaweed.     

A comparative analysis of gold-rich plant material using various analytical methods

During 2003 a field demonstration of gold phytoextraction technology was conducted in Brazil. As there is no commercially available biogeochemical standard reference material with an elevated concentration of gold, the trial biomass was analysed for its gold content using five analytical methods, at five laboratories, to confirm the concentration of gold in the harvested plant material. Nitric and hydrochloric acid digest followed by ICP-OES solution analysis of a doré bead prepared through fire assay of vegetative material was considered the benchmark analytical method to which the other results were compared. The gold concentrations reported by the five laboratories varied widely. Flame atomic absorption analysis of a solution prepared through the digest of plant ash by aqua regia proved the most accurate analytical method relative to fire assay. Gold concentrations reported by a New Zealand commercial laboratory using ICP-MS and a standard ‘biological materials digest’ procedure were affected by the digest method employed. X-ray fluorescence results may have been affected by synthetic standards that were prepared specifically for this investigation. Alternatively, matrix effects may not have been fully corrected for using XRF. Analysis of metal-rich biomass is becoming more common due to the popularity of studies that use plants to absorb heavy metals. The results of our comparative investigation emphasise that due care and consideration must be given to the selection of the analytical method chosen to analyse such plant material. Our results also highlight the need for standard reference materials that are suitably enriched in metals, such that these may be of use to phytoextraction studies.     

Improvement of technology for producing pure pyrolusite from carbonate ores

The kinetics of the infrared drying of the solution of sulfonol in the foam state was studied on the basis of experimental-analytical studies. Curves of dehydration and velocity of drying were get, their mathematical simulation was executed. As a result of the analysis of the curves of the drying speed we made conclusion about the mechanism of the transfer of water inside the product in the process of dehydration.     

Characterization of thermostructural damages observed in a seaweed used for biosorption of cadmium

The effect of drying Sargassum filipendula on the kinetics and uptake of cadmium was studied. The maximum uptake was not reduced when ovendried biomass was used for cadmium concentrations from 10.0 to 500.0 mg/L. Kinetics indicated better performance of the in natura biomass. Drying at 333 K affected the uptake capacity. Results fit the Langmuir model better than the Freundlich. This process followed pseudo-second-order kinetics. Thermogravimetric and infrared analysis confirmed that no structural damage occurred after drying, and no differences between the biomasses were observed. Temperatures from 303 to 328 K affected cadmium uptake capacity.     

Extreme dehydration of plant tissues irreversibly converts the major and variable phyA' into the minor and conserved phyA'

Effect of dehydration of plant tissues on the two native phenomenological phytochrome A (phyA) pools - major, variable and soluble phyA' and minor, relatively conserved and presumably membrane(protein)-associated phyA' - was investigated on etiolated seedlings of barley and maize. With the use of in situ low-temperature fluorescence spectroscopy and photochemistry, it was found that even a considerable loss of water (up to 75-85% of the initial fresh weight) by coleoptiles does not bring about noticeable alterations of the spectroscopic and photochemical parameters of phytochrome pointing to a relative stability of the phyA'/phyA' system in this regard. However, extreme dehydration (loss of weight 90%) of plant tissues including freeze-drying caused dramatic changes of the phytochrome properties - blue shift of the emission maximum and its widening and reduction in the extent of the Pr photoconversion into lumi-R at 85 K and into Pfr at 273 K. Rehydration of the dried tissues did not reverse the spectroscopic changes and did not recover the Pr-->lumi-R phototransformation at 85 K but restored the ability of Pr to photoconvert into Pfr at ambient temperatures. At the same time, the total phytochrome content was not affected by these treatments. These effects were interpreted as an irreversible transformation of phyA' into phyA' upon extreme loss of water by plant tissues suggesting that water may play a role in stabilizing the conformation of the major and soluble phyA' species. The data also imply that phyA in dry and imbibing seeds is likely represented primarily by its phyA' isoform.     

Assessment of the impact of a phosphatic fertilizer plant on the adjacent environment using fuzzy logic

The impact of a phosphatic fertilizer plant on the adjacent environment was examined. Selected rare earth elements, heavy metals and metalloids were determined in substrates and products, waste by-product, and grass and soil samples. Concentration gradients of elements in grass and soil samples along the southerly and easterly directions were examined and compared with the content of interior soil and grass samples, substrates, and products. Results were compared with available data on soil permissible element concentration levels. Two fuzzy principal component analysis (FPCA) methods for robust estimation of principal components were applied and compared with classical PCA. The efficiency of the new algorithms is illustrated. The investigation explored the impact of the plant on the adjacent environment. The most reliable results, in good agreement with types of samples, were produced using the FPCA-O algorithm     

Carbon Aerogel Films Synthesized at Ambient Conditions

Carbon aerogels derived from organic sol-gel process and supercritical drying are novel porous materials with interconnect structures and higher electrical conductivity, which are considered to be ideal electrode materials for supercapacitors and rechargeable batteries. The objective of the research was to synthesize carbon aerogel films at ambient conditions. Resorcinol formaldehyde (RF) and carbon aerogel films have been produced with extremely high RC ratio (molar ratio of resorcinol to catalyst) followed by subcritical drying. The structure of the porous films was investigated using electron scanning microscope. The specific surface area was measured by using nitrogen adsorption (BET) and electrical conductivity was measured with four-probe method. It was found that with extremely high RC ratio, the porous structure of RF and carbon aerogel films can be controlled from micro to macro porous at ambient conditions. With respect to the application as electrodes for fuel cells, carbon aerogel films with different porous structures on the two surfaces have been also obtained through optimizing the sol-gel process.     

Effect of Additives on Freeze-Drying and Storage of Yarrowia lipolytica Lipase

The extracellular lipase of Yarrowia lipolytica presents numerous potentialities for biotechnological applications. This work describes the development and storage of powders obtained from supernatants containing Y. lipolytica lipase by freeze-drying as downstream process that is important in obtaining a stable lipase powder with high enzymatic activity. Lipase was produced by Y. lipolytica U6 mutant strain in 20-L bioreactor. Non-concentrated cell-free culture supernatant samples were supplemented with different concentrations (0.5?C1?%) of maltodextrin and glycerol as additives to freeze-drying. Effects of additives, temperature, pH, and storage time on lipase powders were determined. After addition of additives, freeze-drying yield increased 3.5-fold compared to supernatant without additive. Maltodextrin with 0.5?% concentration gave the best protection of lipase during dehydration treatment and its freeze-drying yield (77?%) is better than other formulations. Lipase powders were stored at 4 and 25?°C for 46?weeks without loss of lipase activity. A common impediment to the production of commercial enzyme is their low-stability aqueous solutions. The present study shows that freeze-dried lipase powders of Y. lipolytica have good stability for storage and various applications.     

Changes in Physicochemical Properties and Volatile Compounds of Roselle (Hibiscus sabdariffa L.) Calyx during Different Drying Methods

Fresh roselle are high in moisture and deteriorate easily, which makes drying important for extending shelf-life and increasing availability. This study investigated the influence of different drying methods (oven-drying, freeze-drying, vacuum-drying, and sun-drying) on the quality of roselle calyx expressed as physicochemical properties (moisture content, water activity, soluble solids, color), volatile compounds, and microstructure. Oven-drying and freeze-drying reduced moisture content most while vacuum-drying and sun-drying were not as efficient. All drying methods except sun-drying resulted in water activities low enough to ensure safety and quality. Vacuum-drying had no impact on color of the dry calyx and only small impact on color of water extract of calyx. Drying reduced terpenes, aldehydes, and esters but increased furans. This is expected to reduce fruity, floral, spicy, and green odors and increase caramel-like aroma. Sun-drying produced more ketones, alcohols, and esters. Scanning electron microscopy revealed that freeze-drying preserved the cell structure better, and freeze-dried samples resembled fresh samples most compared to other drying techniques. The study concludes that freeze-drying should be considered as a suitable drying method, especially with respect to preservation of structure.