Air-drying Methods Research Articles

Drying Behaviour and Change in Colour and Textural Properties of Mushroom During Drying

Button mushroom in the form of whole and slices were dried using convective hot air drying and microwave drying methods. Main objectives were to study the drying behavior and change in colour and textural properties. To get moisture content of 0.08 g/g, hot air drying at 600C took 463 minutes and 350 minutes for whole and sliced mushroom respectively whereas these times were just 9 minutes and 8.5 minutes when the microwave oven was run at 60% of its maximum power (1350 W). The convective hot air drying process can be put into two falling rate periods. The decrease in brightness (indicated by L-value) in dried samples was about 44% as compared to the fresh ones. The variation within the differently dried samples was not much. Hardness was lowest (<2>N) in fresh samples and was highest (>5.5 N) in microwave dried samples with hot air dried samples in between. For most of the samples, the springiness were between 0.4 and 0.6 except for hot air dried sliced samples where it was 0.9. Except in hot air dried samples, the change in cohesiveness was not much. Adhesiveness was found in fresh mushroom only..

Effect of different drying methods on physicochemical properties and antioxidant activities of polysaccharides extracted from mushroom Inonotus obliquus

Inonotus obliquus is a kind of mushroom which has long been used as a folk remedy for curing various diseases such as cancers, heart disease and diabetes in Russian and Eastern Europe. Polysaccharides are one of the main bioactive constituents of Inonotus obliquus with health functions. Three drying methods, freeze drying, hot air drying and vacuum drying methods were comparatively studied on the physicochemical and antioxidant properties of Inonotus obliquus polysaccharide (IOPS) with chemical methods: gas chromatography, size exclusion chromatography, scanning electron micrograph, 1,1′-diphenyl-2-picrylhydrazyl (DPPH) assay, ferric reducing power assay and lipid peroxidation inhibition assay, respectively. Results showed that physicochemical and antioxidant properties of IOPS differed from each other after the treatment of the three drying methods. Compared with hot air drying and vacuum drying methods, freeze drying method resulted in the properties of IOPS with lower molecular weight distribution, a hyperbranched conformation with triple helix, higher antioxidant abilities on DPPH radical scavenging, ferric-reducing power and lipid peroxidation inhibition activity. Freeze drying was a good choice for the preparation of polysaccharides from Inonotus obliquus and could be used to produce antioxidants for food industry.

Karyotype differences among four species of Callosobruchus Pic (Coleoptera: Bruchidae)

Three species of the genus Callosobruchus are particularly common pests of stored legumes on an international scale. A fourth is closely associated with the most common. In this paper we show that they can all be separated quickly, easily and unambiguously by examination of their karyotypes. Karyotypes obtained from developing embryos of Callosobruchus analis (F.), Callosobruchus chinensis (L.), Callosobruchus maculatus (F.) and Callosobruchus subinnotatus (Pic) are illustrated and compared, using both plain (Giemsa-stained) and C-banded preparations. The karyotypes of all four species are distinctive, and the greater detail resulting from the use of hypotonic inflation, air-drying methods, compared with earlier squash techniques is shown to be crucial to revealing the differences between the species and to resolving some of the discrepancies in published information. We have found no evidence of intraspecific variation so the technique offers a quick and inexpensive way of confirming morphological distinctions.

The Effect of Pre-Treatments in Combination with Hot Air, Vacuum and Hot-a Microwave Drying Methods the Progress of the Drying Process, and Textural, and Colour and Rehydration Rate on Button Mushroom (Agaricus bisporus)

The effect of pre-treatments in combination with hot air, vacuum and hot-a microwave drying methods the progress of the drying process, and textural, and colour and rehydration rate on button mushroom (Agaricus bisporus) slices were investigated. In this work, one of the following methods: hot air, vacuum drying or microwave-assisted convective drying and also different pre-drying treatments, viz. blanching (with hot water or vapour) and sulphitation, were applied. Textural properties of button mushroom were measured during drying and rehydration using a texture analyser. The colour changes of samples during drying and rehydration were analysed applying a Hunterlab Colorimeter. During drying, hardness of mushrooms was increased. Sulphitation pre-treatment improved the structural and rehydration rate of the dried samples, but had varying effects on the colour. Microwave energy reduced drying time and can modify the structure, colour and texture strength of the final product. The effect of microwave treatment on colour varied with the type of pre-treatment applied before drying. Microwave samples showed also the highest rate of rehydration among all samples. Keywords: Microwave-assisted convective drying, Mushroom, Colour changes, Rehydration rate, Textural properties

The effect of solvent evaporation of dentin adhesive on bonding efficacy

Objectives: The purpose of this study is to evaluate bonding efficacy by means of measuring the effect of remained solvent on Degree of conversion(DC) and and FE-SEM examination. Materials and Methods: Two 2-step total etching adhesives and two single-step self etching adhesives were used in this study. First, volume weight loss of 4 dentin adhesives were measured using weighting machine in process of time in normal conditions and calculate degree of evaporation (DE). Reaction/reference intensity ratio were measured using micro-Raman spectroscopy and calculate DC according to DE. Then 2 experimental groups were prepared according to air-drying methods (under, over) and control group was prepared to manufacturer's instruction. Total 12 groups were evaluated by means of micro tensile bond strength and FE-SEM examination. Results: Degree of evaporation (DE) was increased as time elapsed but different features were observed according to the kind of solvents. Acetone based adhesive showed higher DE than ethanol and butanol based adhesive. Degree of conversion (DC) was increased according to DE except for bond. In evaluation, bond strength was increased by additional air-drying. Large gaps and droplets were observed in acetone based adhesives by FE-SEM pictures. Conclusions: Additional air-drying is recommended for single-step self etching adhesive but careful consideration is required for 2-step total etching adhesive because of oxygen inhibition layer. Evaporation method is carefully chose and applied according to the solvent type.

A Preliminary Study of Human Amniotic Membrane as a Potential Chondrocyte Carrier

Purpose: To investigate the feasibility of using processed human amniotic membrane (HAM) to support the attachment and proliferation of chondrocytes in vitro which in turn can be utilised as a cell delivery vehicle in tissue engineering applications. Methods: Fresh HAM obtained from patients undergoing routine elective caesarean sections was harvested, processed and dried using either freeze drying (FD) or air drying (AD) methods prior to sterilisation by gamma irradiation. Isolated, processed and characterised rabbit autologous chondrocytes were seeded on processed HAM and cultured for up to three weeks. Cell attachment and proliferation were examined qualitatively using inverted brightfield microscopy. Results: Processed HAM appeared to allow cell attachment when implanted with chondrocytes. Although cells seeded on AD and FD HAM did not appear to attach as strongly as those seeded on glycerol preserved intact human amniotic membrane, these cells to be proliferated in cell culture conditions. Conclusion: Preliminary results show that processed HAM promotes chondrocyte attachment and proliferation.

Compressive characteristics of cellular solids produced using vacuum-microwave, freeze, vacuum and hot air dehydration methods

Dried cellular solids were produced using different hydrocolloids such as locust bean gum, low methoxy pectin, methyl cellulose and tapioca starch. They were dried to less than 5% (w.b) moisture content using freeze-drying, vacuum drying, vacuum microwave drying or air-drying methods. The dry cellular solids were subjected to uniaxial compression using a Texture analyzer to study the compressive characteristics. True stress–strain relationship curves were developed for the dry cellular solids produced by different drying methods. Hencky’s strain was calculated for true strain. Comparisons of samples dried by different drying methods were done in terms of their compressive characteristics at various water activities. No matter the type of drying, the dried materials were brittle at low water activity, plastic at medium water activity and elastomeric at higher water activity levels. Due to non-uniformity in air-dried samples and more closed pores in vacuum dried samples as well as less mechanical strength, these two were considered inferior for production of strong elastomeric foams. Microwave vacuum dried foams were mechanically the strongest. All the microwave vacuum dried samples were close in their Young’s modulus. Increases in microwave power did not make any appreciable changes in pore structures although higher microwave power levels resulted in faster drying.

Effect of Dehydration Methods on Mechanical Strength of Nanohydroxyapatite/Collagen Composites

Hydroxyapatite/collagen composites were prepared in-situ synthesis. The composites were finally achieved by dehydration including air-drying and freeze-drying methods. FTIR, XPS and DSC were employed to investigate the composites dehydrated by two methods. The air-dried composites had better mechanical properties than those of the composites dried by freeze drying. Air-drying of the composite induced more bond formation and crosslink between collagen fibers and HA crystals compared with freeze-drying of the composite, as indicated by the shifting of amide A and I bands to the lower wavenumber and by the changes in the binding energy of O1s, Ca2p, and P2p, leading to the increase of the peak temperature of the composites. Collagen crosslink and bond formation in the air-dried composites were key factors to increase the bending strength of the composites. The results of this study confirm that in situ synthesis and air-dry method are effective ways to obtain nanoHA/COL composites with high mechanical properties.

Modeling Shrinkage and Density Changes During Microwave-Vacuum Drying of Button Mushroom

Shrinkage characteristics and apparent density of whole button mushrooms were determined at various moisture content levels (ranging from 5 to 92% wet basis) during microwave-vacuum drying at two different power (150 and 250 W) and pressure (10 and 20 kPa) levels. The above properties during convective hot air drying at 60°C were also measured for comparison. In both microwave-vacuum and air-drying methods, the shrinkage (volumetric and diametric) of mushroom showed a linear behavior with moisture content. Experimental data showed that the effect of the system pressure on shrinkage and density was more significant than the power level during microwave-vacuum drying. Moisture content and method of drying also affected shrinkage statistically. Microwave vacuum drying produced less shrinkage than air drying. Simple mathematical models were used to correlate the above properties with the material moisture content. The models were fitted to experimental data satisfactorily, and the parameters were estimated.

Influence of drying methods on drying of bell-pepper ( Capsicum annuum)

Drying of bell-pepper was carried out using sun solar and artificial air drying methods. The drying curves and rates obtained indicated that drying of bell-pepper was done in two drying rate periods, the constant drying rate period (mainly) and the falling drying rate period. The existence of the constant drying rate period was more pronounced in the artificial air-drying method than in the other two drying methods and the drying process was also faster. This was attributed to the effect of temperature of drying air on the diffusion of water from internal regions to the surface of the product.

Evaluation of drying technologies for retention of physical quality and antioxidants in asparagus ( Asparagus officinalis, L.)

The objective of this research is to evaluate drying methods that have the potential of adding value to green asparagus especially for use as ingredient in instant foods or as a nutraceutical product. Five drying methods were used: namely, tray drying (TD), spouted bed (SB) drying, combined microwave and spouted bed drying (MWSB), Refractance Window (RW) drying and freeze-drying. Asparagus spears with diameters between 9 and 12 mm were blanched in 85°C water-bath for 3 min, sliced into 2–4 mm thickness (or pureed for RW drying), then dried to moisture content less than 0.1 db. MWSB drying produced asparagus particles with good rehydration and color characteristics, and was the fastest among the methods where heated air was used. When using MWSB drying, the power level of 2 W/g and 60°C heated air resulted in highest retention of total antioxidant activity (TAA). TAA of asparagus was enhanced after RW and freeze-drying, with the TAA values being significantly higher than for heated air-drying methods. In all cases, the tip portion of asparagus retained more TAA after drying than either middle or basal parts. The highest amount of ascorbic acid was retained in the product after RW drying, followed by freeze-drying, MWSB and SB drying. TD resulted in the least retention of ascorbic acid.

Tensile strength of type IV dental stones dried in a microwave oven

Statement of Problem. It is known that drying dental stones in a microwave oven can save time, but the strength of the material may be affected by different drying methods. Purpose. This study evaluated the diametral tensile strength (DTS) of 5 type IV gypsum products at different time intervals using microwave and air-drying methods. Material and Methods. A total of 300 cylinder specimens were prepared from 5 type IV dental stones (Moldano, Amberok, Herastone, Shera-Sockel, and Fujirock; n = 60 per stone) in accordance with the manufacturers' recommendations. Half of the specimens of each stone (n = 30) were dried in open air within a temperature range of 20 ± 2°C; the other half (n = 30) underwent initial setting in a silicone rubber mold in open air for 10 minutes and then were dried in a microwave oven for 10 minutes. Within these groups, 10 specimens were tested under diametral compression at each of the following time periods: 30, 60, and 120 minutes after drying. Three-way analysis of variance and Scheffe's post hoc test were performed for statistical comparisons at a significance level of P<.05. Results. At all time intervals, the diametral tensile strength values for dental stones dried in a microwave oven (mean 2.99 MPa) were significantly higher (P<.01) than the values for specimens dried in open air (mean 2.53 MPa). Conclusion. Within the limitations of this study, microwave oven drying had a positive effect on the diametral tensile strength of 5 type IV dental stones. (J Prosthet Dent 2002;87:499-502.)

Electron probe microanalysis of permanent human enamel and dentine. A methodological and quantitative study.

Sample preparation of dental tissues for quantitative electron microprobe analysis has not been critically examined because of the highly mineralized nature of these structures. The present study was designed to establish the most suitable method for the electron probe quantitative determination of calcium in human permanent enamel and dentine while preserving the morphological features. Comparisons of quantitative data obtained with air-drying and freeze-drying methods showed that calcium in enamel was more accurately measured in specimens prepared with cryopreservation and freeze-drying. No significant differences between the methods tested were found in dentine although cryopreservation and freeze-drying yielded less statistical variability. Moreover this approach did not modify morphological features of interest. We recommend this combination of processing techniques for human permanent teeth not only because it was found the most accurate and least variable in determining calcium concentration, but also because of its potential usefulness in studies of alterations in tooth mineralization.

Comparison of air-drying methods for evaluating the desiccation tolerance of liquid culture-produced blastospores of Paecilomyces fumosoroseus

Various drying methods were tested to identify a standard procedure for evaluating the desiccation tolerance of liquid culture-produced blastospores of Paecilomyces fumosoroseus. Since our work is focused on optimizing fermentation conditions for the production of P. fumosoroseus, the criteria for selecting a drying method included ease of use, moderate spore survival after drying and limited variation in spore survival. Three air-drying methods were tested: P. fumosoroseus blastospores mixed with silica gel, with sand, or with diatomaceous earth. Humidity controlled drying was used in the diatomaceous earth drying method. Blastospore survivals after drying were 19% (C.V. range, 32 to 45%), 82% (C.V. range, 26 to 43%), and 2% (C.V. range 32 to 50%) for the silica gel, sand, and diatomaceous earth methods, respectively. Blastospores dried using the silica gel and sand methods had been rinsed in 0.7 m polyethylene glycol before drying and rehydrated in the same solution for determination of survival. The variation observed within each method was similar. The silica gel drying method was selected as most appropriate for our studies based on moderate blastospore survival (19%) and ease of use.

Chromosomal complements of two forms of Neanthes japonica (Polychaeta, Nereididae) with evidence of male-heterogametic sex chromosomes

Karyotypes of the brackish-water polychaeteNeanthes japonica (Izuka) collected from five rivers in Japan from 1984 to 1988 were examined with air-drying and flame-drying methods using materials consisting of regenerating tails, clumps of spermatogonia and youngN. japonica specimens (embryos, larvae or juveniles). A diploid number of 28 was determined in well-spread metaphase chromosomes of mitotic cells. The presence of an XX-XY (male heterogametic) sex chromosome system was established for the first time in polychaetes. The Y chromosome was larger than the X chromosome. Slight differences in karyotype were found between two forms (the small- and large-egg forms), which are very similar in adult morphology but can be distinguished by reproductive and developmental characteristics.

Ultrastructure of Epicuticular Wax in Canola

Ultrastructure of the epicuticular wax of four commercially grown Canadian cultivars of canola (Brassica campestris cvs. Tobin and Candle, B. napus cvs. Altex and Westar) was investigated. Freeze-drying and air-drying methods of specimen preparation for scanning electron microscopy were compared. The freeze-drying method resulted in disruption and possible washing away of wax crystals, whereas there was no visible damage with the air-drying method. The freeze-drying method provided evidence for an amorphous layer of wax beneath the wax crystals. Ultrastructure of wax in the four cultivars was generally similar. All cultivars had an evenly distributed layer of wax crystals superimposed on an amorphous layer of wax. Some trends such as density of wax on leaves and siliques appeared to be species-specific, whereas density of wax on stems did not. There appeared to be at least three types of wax crystals present. These included plate-like, filamentous, and rod-like crystals. The rods were present singly or in blocks.

Karyotypes of two species of genus Euhadra, Euhadra callizona and Euhadra peliomphala simodae (Bradybaenidae, Gastropoda).

Somatic chromosomes of two species in the genus Enhadra are studied using air-drying methods. The diploid numbers of both E. callizona and E. p. simodae are 2n=56, and are the same as other Euhadra species described in Inaba's report (1959) and in our previous papers (1984, 1987). From the karyotype analysis of the two species E. callizona is found to have 19 pairs of metacentric and 9 pairs of submetacentric chromosomes, E. p. simodae bears 18 pairs of metacentric and 10 pairs of submetacentric elements. The differences in the karyotypes of these two species suggest that they differ from each other cytogenetically. E. callizona is found to bear a karyotype resembling that of E. dixoni and E. amaliae (1984, 1987); the similarity of form suggests that it is closer to those two species cytogenetically. The karyotype of E. p. simodae is found to have some different elements to that of E. c. hickonis in the medium- sized and the small-sized chromosomes, and is therefore shown to be distinct from E. c. hickonis cytogenetically.

Comparative karyotypes of two land snails, Euhadra subnimbosa and Euhadra dixoni (Bradybaenidae, gastropoda).

Somatic chromosomes of two species in the genus Euhadra were observed using the air-drying methods supplying abundance of mitotic cells. The diploid numbers of E. dixoni and E. subnimbosa are confirmed to have 56 in each case. E. subnimbosa bears 21 pairs of metacentric and 7 pairs of submetacentric elements, while E. dixoni has 19 pairs of metacentric and 9 pairs of submetacentric chromosomes. They not only show the same fundamental number NF=112, but also have a secondary constriction in the approximal chromosomal position and in the same sized metacentric pairs. Consequently, the minor karyotypical difference found in the two suggests a close similarity cytologically, though they bear morphological differences.

INFLUENCE OF DRYING METHODS ON PROTEIN CONTENT AND AMINO ACID COMPOSITION OF THREE FORAGE LEGUMES

Forage samples of alfalfa (Medicago sativa L. ’Beaver’), sainfoin (Onobrychis viciaefolia Scop. ’Melrose’), and cicer milkvetch (Astragalus cicer L. ’Oxley’) were dried either in a forced-draft forage dryer, drying oven, or a microwave oven. The dry matter content, protein content, and amino acid composition were determined but the air-drying methods resulted in significant losses of dry matter compared with microwave drying, suggesting that the latter method is preferable for dry-matter determinations. Interactions between species and drying method were significant for some of the amino acid contents, but not for the limiting amino acids — methionine, isoleucine, and valine. Since protein scores, reflecting protein quality, and protein content of the three legumes were not affected by drying methods, any one of the drying methods would be satisfactory. However, large numbers of forage samples can be handled most conveniently in a forced-draft dryer.

Constitutive heterochromatin in mouse chromosomes treated with typsin.

Chromosome preparations from three sublines of mouse L-cells (A9, B82 L60) were made by conventional air-drying methods and the slides treated both by trypsin digestion and the C-banding methods, in order to investigate and compare the distribution of constitutive heterochromatin in these cells. Comparisons were also made with human and Chinese hamster cells. The mouse heterochromatic sites observed, including the interstitial sites found on the marker chromosomes, were similar for each line irrespective of the method used. The interstitial heterochromatic sites in the marker chromosomes 1 and 3 correspond to the locations of the secondary constrictions. The trypsin digestion method reveals the sites of constitutive heterochromatin in mouse chromosomes, but not in human or Chinese hamster chromosomes. All mouse chromosomes could be distinguished from those of Chinese hamster in the hybrid cells between mouse and Chinese hamster cell lines. The method is simple to use and therefore will facilitate the identification of mouse chromosomes within and between the cell populations of different origins and within cell hybrids.