VISCOELASTIC PROPERTIES OF HEAT-SET WHEY PROTEIN EMULSION GELS

The viscoelastic properties of heat-set whey protein gels and whey protein-stabilized emulsion gels have been studied using the dynamic oscillatory rheometry technique. The storage modulus was monitored and analysed for pure protein gels and emulsion gels over a wide range of protein concentrations. The dependence of storage modulus on protein concentration is different for gels of low and high modulus. At low protein concentrations, the increase of storage modulus is much more sensitive to the increase of protein concentration. The protein-coated oil droplets behave as active filler particles and dramatically enhance the gel strength. The effect of the oil volume fraction on the rheology has been investigated for emulsion gels containing 11 vol. %, 20 vol. % and 45 vol. % Trisun oil. The formula of van der Poel fails to describe the experimental results. This is attributed to the strongly flocculated state of the emulsion system.     

Humidity Drying of Plastic Clay

The humidity drying cycle gives rise to surface and body cracks in plastic clay. The cracks appear in the initial stages when the clay is being heated in a saturated atmosphere. Various factors affecting cracking in this initial heating stage were studied using a purified kaolin in the plastic state, and appropriate experimental models were used to isolate certain aspects for study. It is shown that the condensation of moisture on the clay surface is the major factor influencing the cracking of the plastic clay. The effect of thermal diffusion is insignificant and the loss of mechanical strength is of secondary importance. The balance af evidence from the literature and from this study indicates that capillarity plays a major part in the movement of moisture and the production of stresses during drying. When air spaces are present in the body, thermal capillarity may become important. Stresses caused by thermal expansion oppose those caused by drying shrinkage, while the thermal expansion of capillaries will have a negligible effect.     

Biological Evaluation of Protein Quality of Radiation-Pasteurized Haddock, Flounder and Crab

SUMMARY— The effects of radiation sub-sterilization or heat-treatment on the protein quality of haddock, crab and flounder were evaluated by determining the protein efficiency ratio (PER). The PER value of haddock radiated at either level was statistically equal to that of non-radiated haddock. The PER value of crab radiated at either level was statistically equal to non-radiated crab in one replication and significantly higher than non-radiated crab in another replication. The PER value of flounder radiated at the low level was significantly less than that of non-radiated flounder, whereas the PER value of flounder radiated at the high level was statistically equal to that of non-radiated flounder. Low PER values were obtained for heat-treated marine products and these values were significantly lower than those for all other marine product treatments investigated. The protein quality of haddock, crab and flounder was not significantly changed as a result of radiation pasteurization.     

专用硅胶在油脂精炼生产中的应用研究

利用专用硅胶对油脂进行吸附脱胶、吸附脱皂、吸附脱色及脱除氯离子,通过对工艺条件和脱除效果的研究,评价其在油脂精炼生产中应用的可行性。结果表明:利用SORBSILR92硅胶对浓香花生油进行吸附脱胶,在硅胶添加量0. 5%、吸附温度80℃、吸附时间15 min条件下,磷脂脱除率为96. 2%,且脱胶油色泽清亮、风味保留好;利用SORBSILR92硅胶对碱炼脱酸后的大豆油进行脱皂处理,可使大豆油含皂量从130. 7 mg/kg降至未检出,与水洗脱皂相比,不仅能明显降低含皂量,还实现了脱皂过程的废水零排放,减少了脱皂过程的油脂损耗;利用SORBSILR40F在优化条件下对大豆油脱色(先向待脱色油中添加0. 08%的SORBSILR40F硅胶,吸附反应后再添加1. 57%的活性白土)后,其含磷量明显低于单纯活性白土脱色油,并且脱臭油的色泽、氧化稳定性也优于单纯活性白土脱色脱臭油;利用SORBISILR40F硅胶和SORBSILR92硅胶在100℃、20 min条件下对大豆油进行吸附处理,大豆油中氯离子含量分别降低28. 47%和18. 98%,这对防范和降低油脂脱臭过程3-氯丙醇酯和缩水甘油酯的形成是有利的。综上,专用硅胶SORBSILR92和SORBSILR40F在油脂精炼工艺技术的改进发展方面具有很好的应用前景。     

Superfine and Ultrafine Grinding— A Literature Survey

The growing demand for ultrafine powders, coupled with stringent quality requirements, calls for continuous improvements in all aspects of fine particles production. The high energy costs involved in comminution is also an additional motivator. The equipment most commonly used in fine particles processing and the related process parameters is described. Tumbling ball, stirred, vibratory and fluid energy mills are the most commonly used mill types. A number of factors influence the choice of equipment, including the end-use of the product, required product size distribution, sensitivity of the material to heat, and purity requirements. Stirred ball mills are used in ultrafine grinding because of their high unit outputs, while the low amplitude vibro-energy mills are used because of their low specific energy. Fluid energy mills are economic only in some specific applications as in treating heat sensitive materials, materials for plastics and ceramics where purity and delamination are the most important criteria.     

The Aqueous and Surface Chemistry of Activation in the Flotation of Sulphide Minerals—A Review. Part I: An Electrochemical Model

The activation of sulphide minerals by heavy metal ions in acidic pH solutions has been reviewed from an electrochemical point of view. It is shown that the well-documented ion-exchange model is oversimplified. Surface oxidation of the mineral and reduction of the activator metal ions occur during the activation processes. Activation in an oxygen-deficient system leads to the formation of a sulphur-rich surface and results in activation-induced flotation. The overall process of activation is controlled by a mixed-potential mechanism.     

Autoclave Soda Leaching: A Case Study on Uludag Flotation Scheelite Concentrate

Laboratory scale autoclave leaching of Uludag scheelite flotation concentrate containing 24.5% WO₃ obtained from Etibank Corporation of Turkey was carried out. The effects of experimental parameters—amount and initial concentration of Na₂CO₃, temperature, particle size and time—on the recovery of WO₃ were studied. The concentrate had to be heated to around 650°C initially to drive off the organic flotation chemicals. To achieve 99% WO₃ recovery four limes the stoichiometric amount of Na₂CO₃ was necessary within four or five hours at 220°C. Lower temperatures and lower Na₂CO₃ amounts decreased the recovery. Highest recoveries were obtained with around 200 g/𝓁 initial Na₂CO₃ concentration. It was possible to leach the concentrate with +93% WO₃ recovery using three times the stoichiometric Na₂CO₃ amount at 220°C when particle size was reduced. Iso-extraction contour diagrams were drawn to illustrate the effects of various parameters on leaching.