Oxidation of Ascorbic Acid in Copper-Catalyzed Sucrose Solutions

The effect of sucrose on the oxidation of ascorbic acid (A) in Cucatalyzed (1, 2.5, and 5 ppm) and noncatalyzed solutions was studied at 30°C in samples shaken at various speeds. In unbuffered solutions, all sucrose levels tested (10–40%) were protective of A without shaking; however, all sucrose levels tested were destructive of A at the highest speed of shaking. This observation was much more pronounced in Cu-catalyzed reactions. Sucrose enhanced the catalytic action of Cu on the oxidation of A. In 0.1M acetate-buffered sucrose solutions this destructive effect of sucrose was slightly diminished due to the Cu-complexing effect of the buffer salt.     

SELECTIVE GAS ABSORPTION UNDER PRESSURE

For selective removal of H2S from much larger quantities of CO₂ under pressure, an industrial prototype spray column has been constructed. Sodium hydroxide solution was atomized by a pressure nozzle of special design and entered the scrubber as fine spray to contact the sour gases.

Several operating variables were examined in order to indicate optimal operating conditions for maximum selectivity of H₂S over CO₂. Fine mist and short contact time favor this selective absorption process. An optimum inlet reactant concentration was found dependent upon the H₂S content relative to CO₂ in the inlet sour gas mixture. A special nozzle/shield configuration to avoid contact of sour gas with highly turbulent liquid during droplet formation significantly improved the selectivity.     

岩石变形记忆效应:应用、试验与理论

基于岩石变形记忆效应DMEDRA法,为准确便捷测量初始地应力提供了全新的思路,国际上及中国台湾的一系列实践应用证明了其巨大的潜力。但是,岩石变形记忆效应的研究和工程应用在中国(除中国台湾外)刚起步,同时,试验及理论的系统性研究整体上落后于工程应用,成为制约DMEDRA法成熟和普及的瓶颈问题。因此,开展岩石变形记忆效应的应用、试验、理论的研究进展综述具有重要意义。首先给出岩石DMEDRA法的基本概念,然后给出在国际上的应用实践现状;从7个方面的内容对试验研究进展进行系统性评述:(1)岩石变形记忆DRA曲线特征;(2)岩石变形记忆效应的失忆性;(3)人工记忆与地应力记忆;(4)初始加载保持时间;(5)初始加载重复次数;(6)记忆存在应力区域;(7)三维应力记忆特征;详细探讨各方面成果及不足;探讨了岩石变形记忆效应形成机理的两种认识及相应的理论模型,深入剖析现有研究结论与进展揭示存在的挑战,最终给出研究方向与建议。为推动国内开始开展岩石变形记忆效应的研究与应用提供基础。     

MODELING PROTEIN GELATION AND APPLICATION OF ENTROPY ELASTICITY TO UNDERSTAND PROTEIN GEL PROPERTIES

The theory of rubber elasticity is reviewed to study several properties of the three dimensional protein gels, e.g., the number of sulfhydryl binding sites per protein polypeptide. Alternatively, the theory of gelation can be used to explore the protein aggregating reactions, to evaluate the required number of protein aggregates and the rate that the different size proteins aggregate when gelling.     

Rapid Species Identification of Cooked Red Snapper Using Isoelectric Focusing

A rapid method using isoelectric focusing (IEF) was developed to identify species of cooked snapper. The IEF protein band patterns of red snapper as impacted by two extraction systems (water and 8M urea), various cooking times (raw, 5, 10, 15, 20, 25 and 30 min) and cooking methods (microwave, bake, steam, broil, deep fry, and pan fry) were investigated. Samples were desalted and cleaned using a 10-sec rinsing procedure. The characteristic IEF protein pattern of red snapper was reproducible for various cooking conditions. Both 8M urea and water could be used as extractant of snapper sarcoplasmic proteins. IEF protein bands in the acidic region of the polyacrylamide gel (pH 3.5-9.5) were useful as markers for species identification.     

PREDICTION OF FREEZING TIMES FOR FOODS AS INFLUENCED BY PRODUCT PROPERTIES

This investigation utilizes a computer simulation technique to predict the freezing times and temperature history curves for food products. The input information consists of the product properties for temperatures above the initial freezing point, freezing medium conditions and the initial product temperature. It has been established that food products with lower initial freezing points, higher initial water contents and higher initial product densities will have longer freezing times. The prediction of freezing time is most sensitive to the accuracy of the measurement of the product density and the initial freezing point if the freezing point is above ?0.5°C. The influence of the accuracy of unfrozen product thermal conductivity data on the freezing time is not important in the range of 0.45 to 0.55 W/m°K investigated. The combined influence of inaccuracy in measuring these product properties on the freezing time prediction will be significant even if the influence of an individual product property is small.     

DETECTION OF SPECIES ADULTERATION IN PORK PRODUCTS USING AGAR-GEL IMMUNODIFFUSION AND ENZYME-LINKED IMMUNOSORBENT ASSAY

Mixing undeclared species in meat products is illegal under food labeling regulations. This study compared the conventional agar-gel immunodiffusion (AGID) with the Enzyme-Linked Immunosorbent Assay (ELISA) for detecting species adulteration and assessed the species adulteration problem in raw ground pork products in Alabama retail markets. Forty-two ground pork and 87 fresh pork sausage samples collected throughout Alabama were examined by AGID and ELISA for four species: pork, beef, poultry and sheep. Using ELISA, 91 % of the ground pork samples were found to contain other meats while 71 % were found to be contaminated using AGID. Using ELISA, 54% of the sausage samples were found to contain undeclared species while none were found to be contaminated using AGID. The major adulterating species in the pork products was beef followed by poultry and sheep. Reliable analytical methods, such as ELISA, must be used as a regulatory tool to discourage the meat species adulteration problem in retail markets.