Effects of Oxygen Absorber and Temperature on ω3 Polyunsaturated Fatty Acids of Sardine Oil during Storage

To prevent loss of w3 polyunsaturated fatty acids over long-term preservation, the effects of temperature and oxygen absorber on the fatty acids of sardine oil stored in air-tight film were studied. The fatty acids of sardine oil and lipids in the diet of experimental animals rapidly decreased over 1 month at 22°C. The amounts in the diet decreased slowly at 2°C; however, no alterations in the oil samples were observed for 6 months. Also, the amounts did not change at -30°C. Significant changes in samples treated with oxygen absorber were not observed under all temperatures during 6 months storage (P > 0.05). These results indicate that treatment with an oxygen absorber and/or freezing can prevent ω3 polyunsaturated fatty acids of fish oil from decreasing during storage.     

Piezoelectric Properties of Pb(Mg1/3Nb2/3)O3 PbTiO3 -PbZrO3 Ceramics Modified with Certain Additives

Effects of additives on the piezoelectric properties of Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃-PbZrO₃ ceramics in a perovskite-type structure are described. The tetragonality of Pb(Mg_1/3Nb_2/3)_0.375-Ti_0.375Zr_0.25O₃ ceramics increased with the addition of NiO, Cr₂O₃, or Fe₂O₃ but decreased with the addition of MnO₂ or CoO. The dielectric and piezoelectric properties of the base composition were improved markedly through selection of additives in proper amounts. Addition of NiO yielded a high dielectric constant and planar coupling coefficient for compositions at the morphotropic transition boundary. High mechanical Q -factors and low electrical dissipation factors were obtained by addition of MnO₂. Addition of both NiO and MnO₂ produced a mechanical Q -factor of 2051 and a planar coupling coefficient of 0.553. The resonant frequency of Pb(Mg_1/2Nb_2/3)_0.4375Ti_0.4375 zr_0.125O₃ containing MnO₂ had very low temperature and time dependence. The microstructure indicated that ceramics with a high mechanical Q -factor had a fine, uniform grain structure. Addition of Cr₂O₃ retarded grain growth and addition of MnO₂, NiO, CoO, or Fe₂O₃ promoted grain growth in the ternary system.     

缓变弯道河道冲刷试验研究

有关弯道水流及其河道演变特性的研究一直为人们所关注。本文引入了在直线段和单一曲率圆弯道间插入曲率渐变的过渡段这一新的弯道型式，舒缓水流冲击力和离心力作用，以减轻水流对河床及堤身、堤脚的冲蚀破坏。作者首先对这一弯道和圆弯道的水流流速、副流强度进行了数值模拟的计算和比较；又通过变换床沙、流量及放水时间，进行了24组合的动床试验；最后，通过整理分析所有实验数据，对插有缓变曲线的弯道的减蚀作用进行了探讨。结果表明：插有缓变曲线的弯道可以减轻水流对两岸堤身和堤脚的冲蚀破坏；在弯道同一横断上的最大冲深与沙洲波高的比值最终稳定在0．58。     

Thawing Time of Frozen Food of a Rectangular or Finitely Cylindrical Shape

Through dual step simulations, theoretical regression formulae were obtained for estimating the dimensionless thawing time of rectangular or cylindrical food. These formulae contain independent variables related to an initial uniform food temperature, final central food temperature, thawing medium temperature, highest freezing point of food, empirical constant for estimating food enthalpy, shape factor of food and Biot number. The formulae were verified for their reliability by comparing thawing times estimated by these formulae with those determined experimentally. Error analyses were performed by using the formulae to examine the errors of thawing times due to uncertainty in parametric values.     

A Response Surface Method for the Estimation of Convective and Radiative Heat Transfer Coefficients during Freezing and Thawing of Foods

A procedure was developed to determine simultaneously convective and radiative heat transfer coefficients applicable to the nonsymmetric freezing or thawing of planar food. The transient state temperature distribution and transient state locations of thermal centers in a sample were used for this development together with computer programs for simulating heat transfer in the food. The coefficients were determined by minimizing squared residuals related to the temperature distributions and thermal centers. The developed method was used to determine the boundary coefficients of slabs made from a crystallized methyl cellulose gel subjected to freezing and thawing. The influence of thermophysical characteristics of the sample material on the determined coefficients was examined qualitatively.     

Entrance effect correction on the flow of moisturized soy protein isolate melt in an extrusion viscometer

A newly developed capillary viscometer, having an airtight sample cell and capillary system, was utilized to determine the flow properties of moisturized [70% dry basis (d.b.)] soy protein isolate (SPI) melt at 140°C. Pressure drop measurement with an orifice die was done to clarify the large end effect. An end effect correction method was performed by subtracting the orifice die data from the capillary tube data, and reasonable results were obtained. The flow properties of the SPI melt were thus elucidated and could be classified as those of a power law fluid with flow behaviour index of 0.35. It was concluded that SPI with 70% d.b. moisture is an extremely high pseudoplastic fluid at 140°C.     

Rheological Properties Including Tensile Fracture Stress of Semolina Extrudates Influenced by Moisture Content

Semolina extrudates were reshaped, immediately after extrusion to form 0.5 mm thick × 2 mm wide × 130 mm long strips. Moisture content (W) was adjusted to 5 to 39% (dry basis) equilibrating in desiccators containing saturated salt solutions. The following tensile rheological properties of the prepared samples were determined at room temperature (21-24°C) using a Rheometrics solid analyzer: Young modulus (E), yield stress (σ_y), fracture stress (σ_c) and fracture stain (?_c). Each of E, σ_y and σ_c was fitted by a semilogorithmically linear function of W with a negative slope. The property ?_c fitted two semilogarithmically linear functions: for W < 24.2% a line with a positive slope and for W > 24.2% a line with near zero slope. Such data for moisture ranges used in conventional pasta drying can help to optimize conditions for pasta production without stress cracking.     

Computerized Model for the Prediction of Thermal Responses of Packaged Solid-Liquid Food Mixture Undergoing Thermal Processes

A COMPUTERIZED MODEL for the prediction of thermal responses and lethality of packaged particles-liquid food was developed by assuming a statistical particle volume distribution for spherical, cylindrical, oblate spheroidal-shaped particles. For the model development, an overall heat balance equation was solved in combination with an equation for transient heat conduction. To solve the latter, Duhamel's theorem and empirical formulae containing f- and j-values were used. The reliability of the model was verified experimentally by processing canned potatoes-in-brine in an agitated cooker.     

Preparation of blood globin through carboxymethyl cellulose chromatography

A simple and inexpensive procedure for globin preparation from blood of various animals was developed in order to use globin as human food. Carboxymethyl cellulose was most effective among some cation exchangers tested, although amounts of haemoglobin applied to 1 g of the exchanger should be limited to less than 70 mg. The behaviour of adsorbing haem or haemin to the exchanger could not be explained only by a general theory of ion exchange chromatography. Yields and Fe contents of globin preparations from various haemoglobins by this procedure ranged from 67 to 80% and from 0.008 to 0.03% respectively, except for a chicken haemoglobin sample.     

Measurement of the Lattice Parameter of Wustite at High Temperatures

The lattice parameter of wustite (Fe₂O) single crystals was measured at high temperatures. Plots of both lattice parameter vs composition and lattice parameter vs temperature were linear, and no appreciable changes in slope were detected at the boundaries of the subphases suggested by Vallet and Raccah.