The shrinkage in dehydration of root vegetables such as carrots, potatoes, sweet potatoes and radishes was investigated. The samples were dried in flowing hot air. The surface areas were measured by photographing the samples. Three drying models were postulated for the formulation of the relation between the changes of the surface area and the moisture contents. The uniform drying model, which in the case of drying is that the shrinkage in volume equals the volume of water lost by the evaporation, agreed with the measured values during the early stages of the drying. The core drying model by assuming the formation of the dried layer at outer side of material was better in agreement with the experimental results. The semicore drying model, which is the intermediate model between the uniform and the core drying model, and the empirical equations of the shrinkage were also considered.

The mechanism of cooking rice was investigated in this study. The rheological method using the parallel plate plastometer was adopted for measurement of the degree of cooking. The range of temperatures measured ran from 75-150°C. Experimental results showed that cooking rate followed the equation of a first order chemical reaction. We designated the proportional constant as the cooking rate constant, but the slope of Arrhenius plots of the cooking rate constants changed around 110°C. The activation energy of cooking at temperatures below 110°C and above 110°C was about 19,000 and 8,800 cal/mol respectively. The influences of water soaking time before cooking were also studied. We concluded that the cooking process comprises two mechanisms; at temperatures below 1 10°C the cooking rate is limited by the reaction rate of rice components with water; and at temperatures above 110°C it is limited by the rate of diffusion of water through the cooked layer toward the interface of uncooked core where the reaction occurs. The reaction rate constant and the diffusion coefficient of water were calculated by assuming the core model or shell-type model.

The gelatinization rate of rice and potato starches were investigated. The rheological method, using a capillary tube viscometer, was applied for the measurement of the gelatinization degree. The gelatinization rates were measured for the rice and potato starches at temperature ranges of 70-85 and 60~63°C respectively. The rate parameter in the rate equation was given as the Arrhenius equation. The equivalent values of the activation energy for the rice and potato starches were about 14 and 230 k&/g-mol respectively. We concluded that the gelatinization rate of starches is limited by the chemical reaction rate and/or the physical transforming rate of starch components wi-ih water.

The soaking and the cooking mechanisms of rice were investigated in terms of the mathematical rate equations in this study. The soaking and the cooking rate were measured by using the weighing method, and the soaking rate was examined at temperatures from 8 -SO"C, and the cooking rate from 70 -98.5"C. The rate equation involved two rate parameters: the reaction rate parameter of the rice component with water and the diffusion rate parameter of water, was assumed. The results showed that the cooking rate was mainly limited by the reaction rate of rice components with water at temperatures from 70 -98S"C, and the equivalent value of the activation energy of the reaction rate was nearly equal to 20 kcal/mol, though the cooking rate was relatively influenced by the diffusion rate of water in the cooked rice layer at 98S"C. In the soaking of rice, the values of the diffusion rate parameter at from 8.0 -50°C were smaller than the values at from 110 -150°C.

Two open reading frames (nhpS and acsA) were identified immediately downstream of the previously described Pseudomonas chlororaphis B23 nitrile hydratase (NHase) gene cluster (encoding aldoxime dehydratase, amidase, the two NHase subunits, and an uncharacterized protein). The amino acid sequence deduced from acsA shows similarity to that of acyl-CoA synthetase (AcsA). The acsA gene product expressed in Escherichia coli showed acylCoA synthetase activity toward butyric acid and CoA as substrates, with butyryl-CoA being synthesized. From the E. coli transformant, AcsA was purified to homogeneity and characterized. The quality of the recombinant protein was verified by the NH 2 -terminal amino acid sequence and the results of matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The apparent K m values for butyric acid, CoA, and ATP were 0.32 ؎ 0.04, 0.37 ؎ 0.02, and 0.22 ؎ 0.02 mM, respectively. AcsA was shown to be a short-chain acyl-CoA synthetase, according to the catalytic efficiencies (k cat /K m ) for various acids. The substrate specificity of AcsA was similar to those of aldoxime dehydratase, NHase, and amidase, the genes of which coexist in the same orientation in the gene cluster. P. chlororaphis B23 grew when cultured in a medium containing butyraldoxime as the sole carbon and nitrogen source. The activities of aldoxime dehydratase, NHase, and amidase were detected together with that of acyl-CoA synthetase under the culture conditions used. Moreover, on culture in a medium containing butyric acid as the sole carbon source, acyl-CoA synthetase activity was also detected. Together with the adjacent locations of the aldoxime dehydratase, NHase, amidase, and acyl-CoA synthetase genes, these findings suggest that the four enzymes are sequentially correlated with one another in vivo to utilize butyraldoxime as a carbon and nitrogen source. This is the first report of an overall "nitrile pathway" (aldoxime3nitrile3amide3acid3acyl-CoA) comprising these enzymes.

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Particles were dried in a vibro-fluidized bed and the drying characteristics in a constant drying rate period are discussed. Ion exchange resin particles were used for sample because they were fluidized smoothly even at a somewhat high moisture content.The effects of vibration on the uniformity of moisture content in the bed were remarkable when air velocities become lower than the minimumfluidization velocity umf. The bed could be dried uniformly and it had no moisture content distributions under the appropriate vibrational conditions, even whenair velocities were lower than umf.The uniformity of moisture content in the bed depended upon air velocity, vibrational intensity, and height of bed. IntroductionGenerally, air velocities more than several tens of times larger than the minimumfluidization velocity are used for the fluidized bed dryer12K This is required for good fluidization and for the uniformity of quality of the dried products. But these air conditions are undesirable from the standpoint of heat and other energy consumption and for the entrainment of undried particles. For the drying of oxygensensitive materials such as medicines and foods, the use of a large amount of air is undesirable for fear of oxidation and denaturation. Therefore, fluidized bed drying is expected to be operated at as low air velocities as possible. In this respect, the vibro-fluidized bed, which enhances the fluidity of the bed through addition of vibration to the bed, is considered as one of the more useful types of drying equipment and is in practical use in drying processes75.Onthe effects of vibration, some research workers have already reported that it increases the circulation rate of the particles2>8) and the heat transfer coefficient3'6>15'16). In this study, we investigated the drying results of ion exchange resin particles that are fluidized smoothly even whentheir moisture contents are rather high, up to 0.5 kg-H2O/kg-d.m. In the study of drying rates and moisture content distributions of the bed that depend upon the vibrational conditions, an analytical model that includes the particle circulation rate as a parameter was applied. The air velocities used in the experiments were mainly near or lower than the minimumfluidization velocity for the purpose of studying the effects of vibration in especially low air velocity regions.

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