Dehydration Techniques Research Articles

EFFECT OF OSMOTIC TREATMENT WITH CONCENTRATED SUGAR AND SALT SOLUTIONS ON KINETICS AND COLOR IN VACUUM CONTACT DRYING

ABSTRACT An experimental study of osmotic dehydration (OD) of selected heat-sensitive products was carried out in a laboratory-scale vacuum contact dryer. Cubes of potato and apple were examined as model heat-sensitive objects. Experiments were conducted at different conduction heat input levels with wall temperatures in the range 35–45C under vacuum and also in pure vacuum without any external heat input. Detailed investigations were carried out of OD on drying performance, product temperature and color of the dried product. PRACTICAL APPLICATIONS Osmotic treatment of potato and apple samples using concentrated sugar solution shows better osmotic dehydration as well as drying rate in a vacuum contact drying system. This information may help to select the osmotic agent in any industrial application for faster drying rate in vacuum contact drying specially for food products. Moreover this work shows the analysis to find out the starting point of precipitation of osmotic agent inside the products in terms of drying time, temperature and moisture content. This information will be helpful for critical analysis in osmotic dehydration technique which in turns may help for optimum design.

Process development of Gac powder by using different enzymes and drying techniques

New products from Gac, an indigenous fruit of Vietnam have been recently found in the worldwide markets as the aril part of the fruit has a high content of lycopene and β-carotene. These carotenoids are currently in special demand as they are natural antioxidants with potential to prevent and treat cancers. This study investigated some processing approaches for the production of powder from Gac arils and used currently developed analytical methods to measure the product qualities. The process development focused on the selection of a pre-treatment method before seed removal and a dehydration technique to minimise the degradation of the carotenoids after processing. The heat and enzymatic pre-treatments could be applied in an industrial-scale seed removal. However, using the same drying method the powder produced without enzymatic pre-treatment had a higher carotenoid content than the enzymatic-treated powder. Constant drying rates and critical moisture contents on a solid basis were measured for oven drying, air drying and vacuum drying. Spray drying and freeze drying were also attempted. Freeze-drying resulted in the Gac powder with the brightest colour and the highest level of carotenoids. The average loss of carotenoids of five Gac powder samples after pre-treatment and dehydration was 35%. These samples stored in vacuo below 25 °C could retain the red colour and 70% of carotenoids after 4 months. They were found to be acceptable in some trial food products.

Presence of negative charge on the basal planes of New York talc

Potentiometric titration measurements as well as rheological measurements of talc aqueous suspensions indicate that the behavior of the New York talc particles is consistent with the presence of a negative charge on their basal planes. The possibility of the presence of a negative electrical charge on the basal planes of talc particles is analyzed in this paper. Samples of New York talc were studied using electron microprobe analysis and dehydration techniques and the exact chemical formula of New York talc was determined. It was found that there exists a deficiency of protons in the tetrahedral layers of talc, resulting from substitution of Si 4+ ions with Al 3+ and Ti 3+ ions. The comparison of the level of substitution of Si 4+ ions with ions of a lower valency was found to be of a similar order of magnitude as that found in other talc deposits. This strongly points to the presence of a negative charge on the talc basal planes.

Production and Characterization of Xanthosoma sagittifolium and Colocasia esculenta Flours

The physical proximate composition and physicochemical characteristics, microbiological stability, and in vitro alpha-amylolysis rate of flours produced by conventional dehydration techniques of the edible portions of the aroids Xanthosoma sagittifolium and Colocasia esculenta were investigated. Flours from the edible portion of both tubers did not show significant statistical differences in moisture, Aw, crude protein, total sugars, amylose, and amylopectin contents. C. esculenta flour showed higher crude fat, total, soluble, and insoluble dietary fiber, and mineral (P, Ca, Fe, and Zn) contents, whereas X. sagittifolium flour showed higher starch, ash, and reducing sugar content than its counterpart. With regard to physical and physicochemical characteristics, X. sagittifolium flour showed higher titratable acidity and relative density values, being darker and more yellowish than its counterpart. On the other hand, X. sagittifolium flour showed higher gelatinization temperature than C. esculenta flour. Parameters such as viscosity during the holding time (95 degrees C for 30 min), viscosity at 50 degrees C, setback, and consistency were lower in C. esculenta flour than X. sagittifolium flour. The viscosity peak and breakdown indexes were higher in C. esculenta flour than in the X. sagittifolium sample. The colony forming units (CFU) of the microorganisms were much lower than those reported in the literature for similar products. Moreover, due to their moisture content and water activity, these flours could be classified as dry foods and they are shelf-stable foods. The results reflect that flours with good chemical, physicochemical, and nutritional quality and satisfactory microbiological stability may be produced from these aroids.

Microporous, Demineralized Collagen Matrices in Intact Radicular Dentin Created by Commonly Used Calcium-depleting Endodontic Irrigants

The use of calcium-depleting solutions in restorative dentistry results in demineralization of intact coronal dentin beneath smear layers. Likewise, application of calcium-depleting irrigants as final rinses might create demineralized collagen matrices in intact radicular dentin after removal of root canal wall smear layers created during canal shaping. These unsupported collagen matrices collapse on desiccation and might be difficult to detect in scanning electron microscopy dehydration techniques traditionally used in endodontic research. Demineralized collagen matrices were identified, by using a hexamethyldisilazane dehydration protocol, on the surface of smear layer-depleted radicular dentin when NaOCl was used as initial rinse, followed by the use of 17% ethylenediaminetetraacetic acid or BioPure MTAD as the final rinse. Compaction of conventional root filling materials over a demineralized collagen matrix in instrumented dentin is analogous to performing the same procedure against the predentin collagen network in the uninstrumented parts of root canals. The potential consequences of this process are, however, unknown.

Renewable energy source—Dehydrated ethanol

Abstract Ethanol produced from renewable energy sources—biomass, is the most promising future biofuel. In the article, a pervaporation membrane technique for ethanol dehydration is presented. Experimental results and semi-empirical and empirical models calculated on their basis are discussed. The data determined by mathematical models and experimental calculations are compared.

Crystallization, dehydration and preliminary X-ray analysis of excisionase (Xis) proteins cooperatively bound to DNA.

This paper describes the crystallization, dehydration and preliminary X-ray data analysis of a complex containing several bacteriophage lambda excisionase (Xis) [Bushman et al. (1984). Cell, 39, 699-706] proteins cooperatively bound to a 33-mer DNA duplex (Xis-DNA(X1-X2)). Xis is expected to recognize this regulatory element in a novel manner by cooperatively binding and distorting multiple head-to-tail orientated DNA-binding sites. Crystals of this complex belonged to space group P3(1)21 or P3(2)21, with unit-cell parameters a = b = 107.7, c = 73.5 angstroms, alpha = beta = 90, gamma = 120 degrees. Based on the unit-cell parameters for the asymmetric unit, V(M) is 3.0 A(3) Da(-1), which corresponds to a solvent content of approximately 59%. The approaches used to crystallize the unusually long DNA fragment in the complex and the dehydration technique applied that dramatically improved the diffraction of the crystals from 10 to 2.6 angstroms are discussed.

Drying of cherry tomato by a combination of different dehydration techniques. Comparison of kinetics and other related properties

Dehydration of tomatoes is a process commonly used to preserve the product and extend shelf-life. However, the quality of the dehydrated product is often poor. Collapse of the structure, discoloration and a tough texture are frequent quality problems. No less important, although not visually apparent, is the lack of flavour and nutritional value. The combination of osmotic dehydration and microwave drying is a potential new process that could improve the quality of dried tomatoes. In the present work, various osmotic solutions formulated with salt, sugar and calcium lactate were used in an osmotic treatment prior to microwave assisted air drying. The influence of microwave energy on the kinetics was analyzed and correlated with the dielectric properties of the samples. The results showed that osmotic dehydration with ternary solutions (27.5% sucrose, 10% salt and water (w/w)) with the addition of 2% of calcium lactate combined with microwave assisted air drying makes it possible to obtain dried and intermediate moisture tomato products that are shelf stable and have better quality than the traditional product.

Trends in microwave-related drying of fruits and vegetables

Microwave (MW)-related (MW-assisted or MW-enhanced) combination drying is a rapid dehydration technique that can be applied to specific foods, particularly to fruits and vegetables. Increasing concerns over product quality and production costs have motivated the researchers to investigate and the industry to adopt combination drying technologies. The advantages of MW-related combination drying include the following: shorter drying time, improved product quality, and flexibility in producing a wide variety of dried products. But current applications are limited to small categories of fruits and vegetables due to high start-up costs and relatively complicated technology as compared to conventional convection drying. MW-related combination drying takes advantages of conventional drying methods and microwave heating, leading to better processes than MW drying alone. This paper presents a comprehensive review of recent progresses in MW-related combined drying research and recommendations for future research to bridge the gap between laboratory research and industrial applications.

Ammoniation Technology for Dehydration of Hydrated Magnesium Chloride in China

Ammonination technique for dehydration of hydrated magnesium chloride is a special kind of method for preparation of high-pure anhydrous magnesium chloride, which is requisite for electrolytically manufacturing metal magnesium. The technique has been developing for decades in the west world. China has now been exploiting the technique for his magnesium ore, especially the magnesium resource in the west of China. We started investigation of the method for several years, and several new progresses were arrived for preparation of anhydrous magnesium chloride. From our study, ethanol, methanol and water solution can be used for the method, and each had an advantage over the others; the ammonia used in the technique for preparation of anhydrous magnesium chloride is less corrosive for the equipment, and friendly for environment. The method gives great potential application in industry of metal magnesium and magnesium matrix materials.

Effects of SEM Preparation Techniques on the Appearance of Bacteria and Biofilms in the Carter Sandstone

Abstract When biofilms (aggregations of bacteria and extracellular polymer secretions) in samples from the Carter Sandstone of Alabama were prepared for scanning electron microscopy (SEM) using different dehydration techniques, the organic material had visibly different textures and distributions. In order to assess whether the variation was attributable to sample preparation or to inherent biofilm heterogeneity, each of five techniques were tested 3 to 10 times on small (1 cm) pieces of the Carter Sandstone containing either a strain of bacteria cultured from and reintroduced into the rock, or an in situ biofilm grown by injection of nutrients through core samples. The techniques tested were (1) air drying alone; (2) fixation in 10% glutaraldehyde with air drying; (3) ethanol dehydration with hexamethyldisilazane (HMDS) drying [2.5% glutaraldehyde, ethanol dehydration, and HMDS]; (4) ethanol dehydration with critical-point drying; and (5) ethanol and acetone dehydration with critical-point drying. Unpreserved control samples were either imaged wet in an environmental scanning electron microscope (ESEM) or vacuum-dried for SEM. Observations were based on SEM microscopy of over 60 samples and study of over 150 photomicrographs. In both experiments, the original morphology of individual bacteria was best preserved by ethanol dehydration with HMDS drying, ethanol dehydration with critical-point drying, or ethanol-acetone dehydration with critical-point drying. Critical-point drying preserved bacteria but stripped away mucilaginous material, revealing filamentous structures within the biofilm. These filaments, along with masses of microspheres (nannobacteria?) and the smooth mucilaginous outer layer, also occur in wet samples studied by ESEM, and are, therefore, not dehydration artifacts. However, different sample preparation techniques accentuated different components of the heterogeneous biofilm, thus resulting in vastly different textures. The cultured bacteria produced a biofilm that had a different surface texture and was more susceptible to sample preparation artifacts than the in situ biofilm. Use of more than one sample preparation technique is recommended in order to avoid bias.

Dehydration Techniques Affect Phytochemical Contents and Free Radical Scavenging Activities of Saskatoon berries (Amelanchier alnifolia Nutt.)

ABSTRACT: Saskatoon berries (Amelanchier alnifolia Nutt., cv. Thiessen and Smoky) were dehydrated using freeze‐drying (FD), vacuum microwave drying (VMD), air‐drying (AD), and a combination of air‐drying and vacuum microwave drying (CD) methods. All processed berries had significantly reduced (P < 0.05) total phenolics and anthocyanin contents in addition to reduced antioxidant activities, as compared with fresh frozen (FF) berries. FD berries rendered the highest amount (P < 0.05) of anthocyanin and antioxidant activities, followed by VMD berries. The CD dehydration resulted in intermediate results between VMD and AD. The substantial decrease in both total phenolics and anthocyanin content in berries was corresponded to significant (P < 0.05) losses in antioxidant capacities measure in different model systems.

Cryopreservation by encapsulation-dehydration of ‘Christmas bush’ (Ceratopetalum gummiferum) shoot tips

Abstract Christmas bush (Ceratopetalum gummiferum Sm) is a shrubby tree species of the east coast of New South Wales in Australia. It is much prized as a cut flower crop because of its bright, pinky red floral calyces. New varieties are being developed, the storage of which is an important issue. In this study, it was shown that shoot tips sampled from in vitro plantlets withstood cryopreservation using the encapsulation–dehydration technique. The protocol leading to optimal regrowth was the following: excised shoot tips were pretreated for 1 d in the dark on hormone-free Murashige and Skoog (MS) medium with 0.3 M sucrose, then encapsulated in 3% calcium alginate and precultured in liquid MS medium with 0.5 M sucrose for 3 d. Precultured beads were dehydrated for 6 h in the air current of the laminar flow cabinet to 24.3% moisture content (fresh weight basis) before rapid immersion in liquid nitrogen. Under these conditions, regrowth of shoot tips after cryopreservation reached 61.4%. Regrowth of cryopres...

Growth response and carcass composition of rabbitfish, Siganus canaliculatus (Park) fed diets supplemented with dehydrated seaweed, Enteromorpha sp.

A trial to incorporate dehydrated Enteromorpha in the diet of rabbitfish fry averaging 0.25 ± 0.04 g was undertaken for a period of 12 weeks. Four isonitrogenous (39% crude protein) and isoenergetic (19 kJ/g) diets were fed to fish. The dehydrated Enteromorpha was incorporated in the diets at a rate of 0 (control), 10, 20 and 30%. A fifth group of fish was fed control diet and supplemented with known weight of fresh Enteromorpha placed in plastic baskets at the bottom of the rearing tanks. The survival rate, growth performance and feed utilization efficiency were observed to decrease with increasing inclusion levels of dehydrated algae (p < 0.05). The best results of all parameters were achieved by fish fed control diet and fresh Enteromorpha (P< 0.05). Carcass protein was not affected by the different treatments while lipid content was observed to increase inthe group of fish supplemented with fresh Enteromorpha (P< 0.05). It is concluded that further studies are needed on the dehydration techniques of Enteromorpha as well as on the digestibility and assimilation of diets containing dehydrated algae.

Water status and thermal analysis of alginate beads used in cryopreservation of plant germplasm

Encapsulation and dehydration techniques using alginate beads are used increasingly for the pre-treatment of various plant materials for cryopreservation to improve survival post-cryogenic storage. This study reports the effects of the water content of beads (formed with 3% (w/v) alginic acid in liquid S-RIB), polymerisation time (in 100 mM calcium chloride solution), osmotic dehydration (in 0.75 M sucrose solution), and evaporative air desiccation on the thermal properties of alginate beads used in cryopreservation protocols. Experimental beads were assayed using a differential scanning calorimeter (DSC) with a cooling programme to −150 °C, followed by re-warming. Resultant thermograms were evaluated with particular reference to the onset temperature and enthalpy of the melt endotherm from which the quantities of frozen and unfrozen water were calculated. Treatments were applied sequentially to samples of beads and their thermal features evaluated at each stage of the protocol. Using ‘standard’ beads (40–55 mg fresh weight), formed using plastic disposable pipettes, the degree of polymerisation (>10 min) proportionally reduced their dry weight and increased their water content. Thermal characteristics of the beads were unaffected by polymerisation times >10 min, but the maximum level (23%) of unfrozen (osmotically inactive) water was achieved after 15 min polymerisation. Osmotic dehydration using 0.75 M sucrose significantly lowered bead water content and mean dry weight approximately doubled with 20–24 h immersion time. Bead desiccation in still air reduced their water content by 83% of fresh weight, whilst dry weight remained constant. After 8 h desiccation in air between 27 and 37% of the water in the bead was osmotically inactive (unfrozen) in DSC scans. Desiccation >18 h reduced this fraction to zero. The melt onset temperature and the enthalpy of melting were directly related to bead water content. The unfrozen water fraction increased substantially with reduced water content of the beads (from 23 to 37% of total water content), concomitant with a reduction in the ratio of unfrozen to frozen water from 1:3 to 1:2. For successful vitrification and the production of a glass that did not destabilise on rewarming, a bead water content of ca. 26% of fresh weight (0.4 g water g −1 dry weight) was required, much of which was osmotically inactive water. These data are discussed in relation to optimal pre-treatments for alginate bead encapsulation techniques used in the cryopreservation of a range of plant germplasm. It is proposed that increased standardisation of alginate beads, in terms of volume, fresh weight, and water content, is required to reduce the variability in physical and thermal features, which in turn will improve survival of plant samples post-cryopreservation.

Food Matrix Engineering: The Use of the Water-Structure-Functionality Ensemble in Dried Food Product Development

The structured food systems (i.e. cellular tissues) are dissipative structures whose functionality mainly concerns their properties (physico-chemical properties, chemical and biochemical reactions), external interactions with surroundings (interactions with micro-organisms, heat and mass transport pathway) and especially, their interactions with consumers (nutritional value, quality, taste and flavour, texture, appearance: size, shape, colour). Dehydration or rehydration processes concern heat and mass transport phenomena (water, solutes) coupled with micro and macrostructure changes both producing important effects on food functionality. Control of these changes is the major concern in food product development. This control must be applied not only to the changes in physico-chemical properties but also to those related with consumers' issues. Food matrixengineering is a branch of food engineering which aims to apply the knowledge of the food matrixcomposition, structure and properties to promote and control adequate changes which can improve some sensorial and/or functional properties in the food. These changes, which are caused by some basic operations, are related to the phenomena of heat and mass transfer, vaporization-condensation, internal gas or liquid release, structure deformation-relaxation and phase transitions in matrixcomponents, and are usually coupled throughout the operation's progress. The final product may be a new product with improved composition and sensorial properties and/or more stability. All these concepts are discussed in this paper using several examples related to the application of combined food dehydration techniques.

Optimisation of a freeze-drying process of high purity Factor VIII and Factor IX concentrates

The infusion of high purity Factor VIII and Factor IX concentrates represent one of the best alternatives in the treatment of haemophilia A and haemophilia B respectively. Among the dehydration techniques, freeze-drying is considered as the reference process preserving biological activity and, consequently, it is utilised for manufacturing high-quality pharmaceutical products. The aim of this work was to study the influence of the freezing and the drying conditions on the final quality of both freeze-dried high purity Factor VIII and Factor IX concentrates. The biological activity of both Factor VIII and Factor IX was not influenced by the freezing rates and, considering the experimental conditions that led to uncollapsed products, by the drying rates studied. Moreover, according to other previous works and to the industrial experience, no remarkable difference on their biological activities depending on the freezing and primary drying conditions was noticed for both factors. From these results, a new optimised cycle that permitted to reduce considerably the duration of the freeze-drying process, was defined. The freeze-dried products obtained had a relative biological activity in line with the actual industrial standards, were good rehydratable and showed a stability of at least 1 month at +4 °C.

Postsynthesis, Characterization, and Catalytic Properties in Alkene Epoxidation of Hydrothermally Stable Mesoporous Ti-SBA-15

Mesoporous Ti-SBA-15 has been postsynthesized by the titanation of pure silica SBA-15 in glycerol with the assistance of quaternary organic ammonium hydroxides, and has been extensively characterized by various techniques to investigate the mesostructural and catalytic properties, and the chemical nature of the incorporated Ti species, in comparison with those of Ti-MCM-41. To incorporate tetrahedral Ti species into the silica walls of SAB-15, the titanation needs to be carried out at elevated temperature and using an optimum amount of organic ammonium hydroxide. Ti-SBA-15 samples with a Si/Ti ratio ranging from 376 to 16 are successfully prepared with the retention of hexagonal mesostructure by elaborately conducting the titanation. The nature of the Ti species depends greatly on the Ti loading. At Si/Ti ratios higher than 50, the Ti species are mainly tetrahedrally coordinated in isolated states, while poorly dispersed Ti species of octahedral coordination are formed at higher Ti incorporation levels; however, no anatase phase is formed in all cases. The IR band at 948 cm-1 due to Si−O−Ti bonds can be used to characterize the tetrahedral Ti species in mesoporous materials, but the techniques of dehydration or trimethylsilylation should be adopted to get rid of the influence of silanol groups. In an actual catalytic reaction, Ti-SBA-15 exhibits not only extremely high thermal stability but also outstanding endurance against Ti leaching not observed for Ti-MCM-41. Ti-SBA-15 is thus presumed to be a promising liquid-phase oxidation catalyst.

Performances of crosslinked asymmetric poly(vinyl alcohol) membranes for isopropanol dehydration by pervaporation

Asymmetric poly(vinyl alcohol) (PVA) membranes crosslinked with glutaraldehyde (GA) were prepared by phase inversion technique for pervaporation dehydration of isopropanol (IPA). The crosslinking solutions contain sodium sulfate, sulfuric acid and different contents of GA, wherein sulfuric acid serves as a catalyst. The effects of three variables involved in the membrane preparation, including PVA molecular weight, PVA concentration and GA concentration on pervaporation characteristics were investigated. The results showed that the permeation flux decreases with the increase of these three factors, whereas the selectivity has an opposite trend. The influence of feed IPA concentration and temperature on pervaporation performances was also studied to find optimum operating conditions.

Microwave-enhanced dehydration and solvent washing purification of penicillin G sulfoxide

In the present study, a new microwave-enhanced dehydration and solvent washing purification of penicillin G sulfoxide technique has been developed. The results show that microwave irradiation can dehydrate penicillin G sulfoxide from a water content of 14–26 to below 0.5% in 40–60 min in N 2 or air. After washing with ethyl acetate to remove impurities and residual water, the penicillin G sulfoxide can be used to synthesize cephalosporanic acid. The recovery of cephalosporanic acid was equal to and the purity of cephalosporanic acid was higher by 2% than that of the current dehydration technique. FTIR spectroscopy was used to study the process of microwave-enhanced dehydration and solvent washing purification of penicillin G sulfoxide.