To examine the cryoprotective role of glycerol in preserving frozen red blood cells, we used a differential scanning calorimeter to study the thermal behavior of three kinds of glycerol-base cryoprotectants: a) the glycerol-water (binary) system, b) the glycerol-phosphate buffered saline (complex system), and c) the clinically used glycerol-based cryoprotective solutions. The results were as follows; (i) thermal characteristics for the binary system were the same as those previously reported, (ii) both the complex system and clinical-use cryoprotectants had the same characteristics as the binary system, (iii) a red cell suspension in the complex system showed the same tendency in hemolysis after freezing and thawing as that in the clinical-use cryoprotectants. (iv) the critical final glycerol concentration where hemolysis drops abruptly was 14% and 29% for rapid and slow freezing methods, respectively, (v) the final glycerol concentration where hemolysis becomes small was lower than that at which the glass transition occurs. This indicates that we must consider the microscopic cell behavior during freezing.

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The cryoprotectability of viable Lavandula vera cells after repetition of a freeze-thaw procedure one to three times was lowered after continuous subculture on nutrient medium for ten generations (ca. one year) without being subjected to the procedure. However, high cryoprotectability of viable cells after repeating the freeze-thaw procedure four times did not change after the continuous subculture. The frequency of redifferentiation of viable cells after one freeze-thaw procedure was high. These findings suggest that cells with stable high cryoprotectability could be selected by repeated freezing and thawing, and that the formation of shoots and/or roots was induced by the stress resulting from freezing.

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Autologous Blood (AB) transfusion is one of the most effective ways to avoid risks of homologous blood (HB) transfusion. Since the frozen red blood cells (RBCs) can be stored for a longer period, patients can predeposit the necessary amount of blood without their preoperative condition. We studied the frozen RBCs for AB transfusion use in elective surgery that performed from 1980 to 1996. A total of 1,355 patients undergoing surgical operation and participating in AB transfusion, which 699 cases for orthopedic surgery and 656 cases for cardiac surgery. From 90.7% (1,299/1,355) of patients were able to avoid HB transfusion. Patients who could avoid HB transfusion increased from 12.5% in 1980 to 100% in 1996 (p <0.05) and from 75.0% in 1987 to 89.6% in 1996 (p <0.05) in orthopedic surgery and cardiac surgery, respectively. No significant complications appeared during the donation periods and after retransfusion. Their average hemoglobin (Hb) level was remained above 11.0g/dl after one week of post-operative. We believe that the AB transfusion used in elective surgery is safe and effective, and its use should be widespread.

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Procedures of determining parameters of pre-freezing process are examined experimentally as well as analytically. The critical cell volume ratio of the endothelial cell and the smooth muscle cell of porcine arteries, which are closely related to the critical osmotic pressure, are measured from the view point of physiological functions. Also, the membrane permeability of endothelial cell is measured. By comparing two pre-freezing processes, that is, the direct immersion to the glycerol solution and the process in which the concentration of glycerol solution is increased stepwise, validity of the designing method is assessed experimentally.

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In this study, we examined the low temperature behavior and dehydration tolerance of xylem ray parenchyma cells from several hardwood species that grow from tropical to cold-temperate zones by observation using cryo-scanning electron microscopy and freeze-fracture replica technique in addition to differential thermal analysis (DTA). We found that the freezing behavior of ray parenchyma cells changed discontinuously from shallow supercooling (in the tropical zone), through deep supercooling (in the temperate zone) to extracellular freezing (in the cold-temperate zone) depending upon the temperature reduction in the growing areas. Conversely, dehydration tolerance increased continuously in parallel with the reduction of temperature in growing areas, despite the presence of supercooling ability. These results suggest that the responses of xylem ray parenchyma cells in wide variety of hardwood species to freezing temperatures can be explained as a continuum, the specifies of which depend upon the temperatures of growing conditions.

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Drying characteristics and the thermal conductivities as well as permeabilities have been measured for the dried layers of sliced and mashed apples undergoing freeze-drying. Both samples were frozen with a copper plate at its surface temperatures ranging from -27 to -44℃. They were freeze-dried at the constant surface temperatures ranging from -10 to 70℃. A mathematical model were applied to the drying data in order to determine the transport properties for the dried layer of the sample undergoing freeze-drying. The surface temperature of sliced samples was found to be impossible to set at more than 10℃, while that of mashed were allowed to heat up to 70℃. Values of thermal conductivity were found to be almost the same between sliced and mashed samples, but the permeability data for the mashed samples were more than 4 times greater than that for sliced ones. Both temperature and pressure dependence on these transport properties were not recognized apparently, and the effects of freezing rate on transport properties were critical for the mashed samples. The results indicated that the drying rate of sliced samples was limited by the transfer rate of water-vapor flowing through the dried layer.

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Recrystallization phenomena in frozen foods hurt the quality. In this study, rates of recrystallization of ice in frozen foods were determined for red meats of tuna and tofu cakes. These samples were frozen in methanol brine at -50℃ and stored at -50, -30, -20, -5℃ for maximum 80 days. Mean diameter of ice crystals in frozen foods were observed by microscope after these samples were fixed by freeze-substitution method and then sliced to very thin samples. The rates of recrystallization were k=135×10^3exp(-18.69/RT) and k=26×10^3exp(-1.6/RT) for tuna fish meat and tofu cake, respectively. These values were smaller by thousand times than the Zaritky's results. Zaritky's results were obtained at -20℃ final freezing temperature. The difference of final freezing temperature caused large difference in the recrystallization rates. The lower the final freezing temperature make the better storage conditions for frozen foods.

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The melting points, glass transitions and enthalpies of fusion of crystalline hydrates in binary water-raffinose mixtures have been studied by differential scanning calorimetry (DSC) over the accessible composition range. X-Ray diffraction was used to identify the crystalline forms. From the liquidus and solidus curves and shapes of the DSC scans, a raffinose trihydrate has been identified, and lower hydrates are also believed to exist. In the phase coexistence curve at higher raffinose concentrations a minimum point is observed, which is thought to be the eutectic of trihydrate and a lower hydrate. The glass-transition profile for the binary system has been measured over the experimentally accessible composition range and the data fitted to the Gordon-Taylor equation, from which the glass-transition temperature for anhydrous raffinose is obtained as 376.4 K.

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Water in polymer gels is known to remain sometimes unfrozen during cooling to turn into a glassy state, and to crystallise during subsequent warming. As the behaviour is likely to be influenced by the change in the polymer network, i.e., by the density of crosslinks, and freezing and drying are both dehydration processes from around the polymer moieties besides, drying and water adsorption of crosslinked dextran gels were investigated from the viewpoint of their dependency on the density of crosslinks. The adsorption isotherm indicated that the amount of adsorbed water is more for gels with lower crosslink density, and lay below the desorption isotherm. The extent of the hysteresis was more remarkable with gels with lower crosslink density. The rate of drying was slower with gels with lower crosslink density around the water content of 50 wt%. These results can be explained by considering that the polymer network in gels with lower crosslink density is more flexible than those with higher crosslink density and change easily during water adsorption or drying, and that water in gels with lower crosslink density is trapped readily by the polymer network as a result of its change during drying.

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