Factors affecting the survival on freezing process of Lactobacillus delbrueckii subsp. bulgaricus suspension were investigated. At first, the survival rate as a function of cooling speed (from -1℃/min to -40℃/min) was examined. The results showed the least survival rate at -7℃/min, however, the differences in the all cooling rates were not significant. Subsequently, adding NaCl in medium, the effect of the final temperature (Tfa) from -15℃ to -50℃ on the damage of L. delbrueckii subsp. bulgaricus was investigated at a cooling rate of -7℃/min. It was found that the survival rate in the range Tfa> -21.1℃ ( eutectic temperature of NaCl solution) decreased significantly with Tfa, but it was constant and independent of Tfa below -21.1℃ These results suggested that the freeze concentration effect during freezing process damages L. delbrueckii subsp. bulgaricus significantly. Finally, we studied the change of survival rate when L. delbrueckii subsp. bulgaricus was immersed at room temperature in solution of NaCl and glucose with the same osmotic pressure as that observed during freezing. The results showed that there was no difference among solutions but the survival rate decreased by 70% in a short time even at room temperature. These results support that the main factor of damaging L. delbrueckii subsp. bulgaricus during freezing is the freeze concentration effect.
We simulated gas-liquid flow to predict the distribution ratio of a distributor. The computational region was divided into two regions: a bend pipe and a distributor. The boundary condition of the bend pipe outlet was connected to the distributor inlet with velocity and volume fraction of the liquid. The velocity at the inlet of the distributor was uniform with that at the inlet of the bend pipe. The volume fraction of the liquid was modified to conserve the mass flow rate of the liquid, because the liquid film inside the bend pipe disappeared with numerical diffusion. We used the volume of fluid (VOF) method for the gas-liquid interface calculation. Results of numerical analysis include profiles of the flow field, distribution ratio, and quality. Modified analysis results exhibit a higher quantity of retained liquid film than the unmodified one, meaning that the flow reproducibility was improved. Moreover, numerical analysis results of the distribution ratio and quality were closer to our experimental measurements than those obtained by unmodified analysis. The accuracy of the calculation in the distribution ratio of liquid was within 4% of computational error. These results demonstrate that the proposed calculation method is an effective means of predicting the distribution of the distributor.
In order to determine the characteristics of commercial vinegar-cured kamaboko gel, various qualitative aspects were evaluated and compared to those of commercial thermal kamaboko gel (i.e. mushi-kamaboko and hanpen). Commercial kamaboko gels were evaluated for textural properties (breaking strength, breaking strain, and gel stiffness) and chemical composition (moisture and crude protein, lipid, ash, carbohydrate). Additionally, SDS-PAGE analysis and microscopic observation were conducted. The breaking strength and gel stiffness of commercial vinegar-cured kamaboko gel were lower than those of the mushi-kamaboko gel, probably due to the degradation of the myosin heavy chain (MHC). The hanpen gel showed significantly lower breaking strength and gel stiffness than the other gels, possibly due to its large pore volume. Chemical composition did not differ significantly among the types of kamaboko. Microscopic observation showed that vinegar-cured kamaboko gel had a precise micro-structure compared with thermal kamaboko gel. The characteristics of vinegar-cured kamaboko originate from differences in processing; vinegar-cured kamaboko gel does not involve thermal processing and is instead soaked in cool vinegar.
There are many combinations of the piston stroke and the cylinder bore that yield a given suction volume in the reciprocating compressors. This study presents a fundamental optimal design concept to determine the combination of the piston stroke and the cylinder bore, which maximizes the mechanical efficiency of a compact “off-set type" single-cylinder reciprocating refrigerant compressor with a given ratio of the crank arm rotating radius to the connecting rod length. First, theoretical development of the equation of motion of the rotating crankshaft is briefly presented. Secondly, computer calculations are carried out to identify the mechanical efficiency for a variety of combinations of the major parameters, thereby permitting identification of the optimal combination for maximum mechanical efficiency. Finally, parametric study which search optimal non-dimensional off-set value of the compressor is carried out.
The relationship between the ice polycrystalline structure and the dielectric properties of a frozen gelatin gel were investigated. The cross-sectional images obtained by Micro-Slicer Image Processing System (MSIPS) were applied to the finite element method (FEM) to estimate the dielectric properties of the freeze concentrated gelatin gel. The overall dielectric properties of the frozen gelatin gel in this study were similar to that of pure water. Because the freeze concentrated gelatin gel contained water, and the relative effective permittivity, were different from those of gelatin powder. The results showed that the possibility of estimation of the dielectric properties in the freeze concentrated polymer gel utilizing with the MSIPS and FEM.