Vacuum Drying Methods Research Articles

Drying kinetics and quality parameters of pumpkin slices dehydrated using different methods

Drying of pumpkin slices was carried out using convective, vacuum-microwave, vacuum and freeze drying methods. The aim of our study was to determine the drying shrinkage and bulk density, as well as to measure the colour and carotenoid content for the slices of 12 pumpkin cultivars. Another major objective was to establish the moisture content, specific density and cutting strength of the slices before dried, as well as the kinetics of their dehydration by the convective and vacuum-microwave methods. The application of the vacuum-microwave method has approximately tenfold shortened the time of pumpkin slice drying as compared to the convective method. In the hot air stream, the slices of the species Cucurbita pepo were dehydrated faster than those of the species Cucurbita maxima. When use was made of the vacuum-microwave process, the slices of C. maxima dried at a faster rate. Each of the drying methods used was more effective than the convective method.

Improved Stability of OPALMON Tablets under Humid Conditions. III: Application of the Rotary Vacuum Drying Method to Dry Opalmon Tablets

In stability studies on moisture-resistant Opalmon tablets in press-through-packages (PTP), which were placed in aluminum bags, we found that the degradation rate of the dextran formulation is faster than that of the lactose formulation. The fast degradation of the dextran formulation is attributed to residual moisture in the package because drying the tablets before packaging suppressed the degradation and there is a good correlation between the stability of the drug and the water-activity of the tablets. Therefore, we developed a new drying method for the tablets, i.e. the rotary vacuum drying method, and investigated the effects of the operating conditions such as heating temperature, rotation speed, and vacuum degree on the drying time, and the appearance of the tablets. Using the rotary vacuum drying method, the tablets were dried over a short time (30 min) on a mass production scale so that the water activity was less than 0.03. Furthermore, the tablets suffered negligible damage such as breaking and chipping during the drying process. These results indicate that the rotary vacuum drying method is useful for drying tablets on mass production scales.

Variation in Drying Behavior and Final Moisture Content of Wood during Conventional Low Temperature Drying and Vacuum Drying of Betula pendula Timber

Conventional and vacuum drying experiments were conducted on Betula pendula timber, which was sawn from trees felled during three different seasons. The influence of the wood procurement season on drying behavior differed, on the one hand, between the drying phases above and below 30% moisture content in the conventional drying, and, on the other hand, between the conventional and vacuum drying methods. During the first steps of the conventional drying process, relative humidity in the kiln, as well as drying time and drying rate, varied according to the felling season. Variations in environmental conditions outside the kiln and the seasonal variation in the physical properties of the wood were presumed to be the reasons for differences in drying behavior. The difference in moisture content gradient, i.e., the difference in final moisture content between the inner wood and the surface layer of boards, was greater in conventionally dried timber than in vacuum-dried timber. In conventionally dried timber there was a clear seasonal variation in the gradient of final moisture content, which was greatest for winter-felled wood. The premature drying of the surface layer during the first steps of the conventional drying process of winter-felled wood was the reason for the higher gradient of moisture content. Storage of wood as logs decreased the standard deviation of the final moisture content.

Low water uptake content and low water/methanol transport in CP/Nafion hybrid membrane with high non-hydrogen bonding

We investigated the relation between water uptake content and water/methanol transport and non-hydrogen bonding ratio for the cast Nafion and calcium phosphate (CP)/Nafion composite membranes. The water/methanol uptake content was evaluated with FT-IR, vacuum-drying method and thermogravimetry (TG). It was found that composite membranes have lower water/methanol uptake content with increasing CP compared to cast Nafion. We evaluated the non-hydrogen (NH) bonding ratio ( R A), representing the ratio of the non-hydrogen bonding to the sum of NH-bonding and H-bonding. As a result, R A increased in the CP/Nafion composite membrane compared to the cast Nafion. It is due to the formation of new non-hydrogen bonding interaction between CF main backbone and OH − in the incorporated CP. On the other hand, water/methanol permeability, measured by water sorption/desorption and methanol permeation tests, decreased in the CP/Nafion composite membranes. Finally, we can conclude that lower water/methanol uptake and water/methanol transport in the composite membranes result from the formation in new non-hydrogen bonding due to the incorporation of CP.

Comparison of near infrared reflectance analysis of fecal fat, nitrogen and water with conventional methods, and fecal energy content

Objectives: To evaluate Near-Infrared Analysis (NIRA) method for determining fecal fat, water and nitrogen. Design and methods: The results of fecal fat, water and nitrogen by NIRA were compared with results of van de Kamer and Acid Steatocrit (AS), Dumas and vacuum drying methods for fat, nitrogen and water respectively. Results of fat determining methods were also compared with total fecal energy as obtained by bomb calorimeter. Results: NIRA results correlated significantly ( p < 0.001) with standard methods for nitrogen (r = 0.79), fat (r = 0.84 and r = 0.88 for van de Kamer and AS respectively) and water (r = 0.91). The limits of agreement for nitrogen and fat results were too wide for the methods to be used interchangeably. The fecal fat results correlated significantly ( p < 0.001) with fecal energy results. Conclusion: NIRA may be valuable for monitoring malabsorption but the diagnostic value remains to be determined.

Preservation of salicaceae leaves for phytochemical analyses: Further assessment

The chemistry of the plant family Salicaceae has been of interest to researchers as diverse as chemical ecologists, chemosystematists, and paper chemists. Continuing the debate on proper methods for preservation of plant material prior to analysis, vacuum-drying was recently advocated, because freeze-drying may cause degradation of phenolic glycosides. This study was conducted to clarify the consequences of freeze-drying for foliar secondary chemicals and to evaluate the consequences of vacuum-drying for primary compounds (protein and carbohydrates). Leaves of quaking aspen (Populus tremuloides) were flash-frozen in liquid nitrogen and freeze-dried or vacuum-dried at room temperature. We then analyzed samples for levels of salicortin and tremulacin (phenolic glycosides), condensed tannins, nitrogen, soluble protein, sugars, and starch. Freeze-drying did not alter the concentrations of phenolic glycosides or tannins, relative to vacuum-drying. Freeze-drying did cause a small and inexplicable decline in nitrogen and soluble protein. Vacuum-drying, however, reduced starch concentrations by 38%. We suggest that the vacuum-drying method be used in studies in which carbohydrates are of no interest. For studies measuring carbohydrates, however, freeze-drying is a better alternative, and should effect no changes in levels of secondary compounds if samples are not allowed to thaw during the drying process.

金属射出成形で作製したＮｄ‐Ｆｅ‐Ｂ磁石の磁気特性

The Nd-Fe-B alloy powder was kneaded at 283K with the binder of methylcellulose dissolved in water. The mixture was injected at temperature 293K in a die of 353K, which is slightly above the sol-gel transformation temperature of methylcellulose. The magnetic field of 1.35 (MA/m) was applied to produce the alignment of easy magnetization direction of alloy powder in a molded body. The molded body was dehydrated by the vacuum-drying method to suppress the oxidation of alloy powder. By heating it in H2 at 573K for 0.5H, about 80% of carbon in binder was removed, although the oxygen in binder remained unremoved. With the molded body added 2wt% methylcellulose, these treatments can allow to suppress the residual contents of oxygen and carbon in the resulted sintered Nd-Fe-B alloy within less than 9000ppm and 800ppm, respectively. The highest coercive force (iHc) and maximum energy product (BH) m ?? x for a sintered anisotropic magnet prepared by the above mentioned process are 1.10(MA/m) and 287.2(kJ/m3), respectively.

Comparison of Sodium Sulfate and Vacuum Drying Methods in Preparing Fish Tissue Samples for PCB Analysis

Comparison of Sodium Sulfate and Vacuum Drying Methods in Preparing Fish Tissue Samples for PCB Analysis

A simple method for preservation of some non-sporing fungi.

A method of vacuum drying is described for the preservation of fungal cultures which are difficult to freeze dry. Approximately 80% of cultures so far tested have survived with this technique.

Influence of Short Term Fasting on Chicken Alimentary Canal Mucosa

Little is known about the physiological effects of short-term fasting in avian species. The present study was developed to examine the alimentary mucosal changes in fasted birds by scanning and transmission electron microscopy. Chickens of various ages were fasted for periods of 3, 5, and 7 days. Water was provided ad libitum. At the end of the fasting periods the birds were sacrificed along with ad libitum fed controls. Tissue samples from crop, duodenum, and ileum were processed by standard methods for scanning and transmission electron microscopy (SEM and TEM). The SEM samples were prepared by vacuum drying methods. The TEM samples were embedded in Spurrs embedding medium. Mucosal sloughing was observed in the crop and small intestine with SEM only in fasted birds. With TEM, separation was observed between the mucosal cells of fasted birds with membranous whorls in these spaces. Sloughed cells may be an endogenous protein source for the fasting bird.