Use of rosemary extract in preventing oxidation during deep-fat frying of potato chips

The effect of using a rosemary extract on the stability of oil used for frying potato chips has been evaluated. Sliced potatoes were fried intermittently in soybean oil containing a natural extract from rosemary. The conditions used for frying were 185°C for 90 s. Two separate experiments, with and without replenishment of oil, were carried out. Oil samples were taken each day, not only from the frying pans but also by extraction with hexane from the chips. Changes in the induction period of the oil samples (Rancimat method) were determined. The induction period decreased as frying progressed. The reduction in the induction period was higher in the oil free of rosemary extract, and the chips were much darker in color. The oil containing the extract showed greater antioxidant activity, and reduced darkening and rancidity of the oil. Potato chips fried in the oil with added rosemary extract were more acceptable than chips fried in oil containing no extract until the last frying. The free radical scavenging activity of rosemary extract in comparison to other natural antioxidants was also determined by the reduction of O₂ ^.- in a hypoxanthine/xanthine oxidase system.     

FLOW OF LIQUOR THROUGH WOOD CHIPS IN A MODEL DIGESTER

Electrical resistance tomography was used to evaluate liquid flow trough a 40 L model digester filled with wood chips. Tests were made with cooked and uncooked chips, both uncompressed and at two levels of chip compression (giving external liquid void fractions of 0.53, 0.43, and 0.33). The chips were stationary in all tests. Flow situations (symmetrical and asymmetrical liquid upflow, symmetrical liquid downflow) were studied with liquor recirculated through the downcomer-screen circulation loop. The creation of distinct liquor flow zones both above and below the screen section depended on the ratio of liquor flow in the downcomer-screen circuit to the axial liquor flow (either upflow or downflow) and did not depend on the level of chip compaction attained. Asymmetrical flows created by closing one-half of the screen set established nonuniform zones within the model digester. The significance of these findings for operating digesters is discussed.     

STEAM DRYING OF WOOD CHIPS IN PNEUMATIC CONVEYING DRYERS

ABSTRACT

A model for a pneumatic conveying dryer is presented. Although the main emphasis is put on superheated steam drying of wood chips, it can be used for other porous materials as well

The model includes a comprehensive two-dimensional model for the drying of single wood chips which accounts for the main physical mechanisms occurring in wood during drying. The external drying conditions in a pneumatic conveying dryer were calculated by applying the mass, heat and momentum equations for each incremental step in dryer length. A plug flow assumption was made for the dryer model and the single particle and dryer models were solved in an iterative manner. The non-spherical nature of wood chips were accounted for by measuring the drag and heat transfer coefficients

Model calculations illustrate the complex interactions between steam, particles and walls which occur in a flash dryer. The drying rate varies in a very complex manner through the dryer. The internal resistance to mass transfer becomes very important in The drying of less permeable wood species such as spruce. Two effects were observed as the particle size was increased: firstly the heat transfer rate decreased, and secondly the residence time increased. To some extent, these effects compensate for each other, however, the net result is that larger chips have a higher final moisture content.     

Addition of ferulic acid,ethyl ferulate,and feruloylated monoacyl- and diacylglycerols to salad oils and frying oils

To determine antioxidative effects of ferulic acid and esterified ferulic acids, these compounds were added to soybean oils (SBO), which were evaluated for oxidative stability and frying stability. Additives included feruloylated MAG and DAG (FMG/FDG), ferulic acid, ethyl ferulate, and TBHQ. After frying tests with potato chips, oils were analyzed for retention of additives and polar compounds. Chips were evaluated for hexanal and rancid odor. After 15 h frying, 71% of FMG/FDG was retained, whereas 55% of ethyl ferulate was retained. TBHQ and ferulic acid levels were 6% and <1%, respectively. Frying oils with ethyl ferulate or TBHQ produced significantly less polar compounds than SBO with no additives. Chips fried in SBO with TBHQ or ferulic acid had significantly lower amounts of hexanal and significantly less rancid odor after 8 d at 60°C than other samples. Oils were also aged at 60°C, and stability was analyzed by PV, hexanal, and rancid odor. Oils with TBHQ or FMG/FDG had significantly less peroxides and hexanal, and a lower rancid odor intensity than the control. FMG/FDG inhibited deterioration at 60°C, whereas ethyl ferulate inhibited the formation of polar compounds in frying oil. Ferulic acid acted as an antioxidant in aged fried food. TBHQ inhibited oil degradation at both temperatures. Presented at the 94th AOCS Meeting & Expo, Kansas City, MO, May 4–7, 2003.     

Seed Oils of Five Black Tartary Buckwheat Cultivars with Biochemical Characterization and Antioxidant Properties

Black tartary buckwheat oils (BTBOs) were extracted from five major industrial tartary buckwheat cultivars grown under similar agronomical activities and environmental conditions. These oils were characterized for the bioactive compounds containing fatty acids, β‐carotene, lutein, α‐, β‐, δ‐ and γ‐tocopherol, and for their antioxidant properties. The total tocopherol contents that were obtained ranged from 704.66 to 1156.19 mg/kg, with γ‐tocopherol (588.98–977.91 mg/kg) as the main component. The concentration of lutein ranged from 253.14 to 429.63 mg/kg, which was almost ten times higher than that of β‐carotenoid (46.71–69.2 mg/kg), indicating that black tartary buckwheat seed oils were a good source of lutein. The predominant fatty acids were unsaturated oleic acid (C18:1) (35.27–40.61 %) and linoleic acid (C18:2) (38.25–42.90 %). Excellent values of 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH), diammonium salt (ABTS) radical scavenging activities were obtained and the highest oxygen radical absorbance capacity (ORAC) value of 13.89 mmol Trolox equiv/g oil was detected in the variety of Chuanqiao No. 1, which was clearly separated by principal component analysis (PCA) on the basis of the highest content of tocopherols and carotenoids. Moreover, the correlation analysis showed that tocopherols and carotenoids were the major contributors to the antioxidant activities of the BTBOs. This study demonstrates that lipophilic extraction in the tartary buckwheat seed contains many interesting bioactive compounds, which are beneficial for human health.     

化学气相沉积生长氧化铪薄膜研究进展

氧化铪薄膜具有高介电常数、大击穿场强、高热稳定性、高力学强度等优势,是新一代高集成芯片中的理想介质材料。本文总结了氧化铪薄膜的主要特性、制备技术及在芯片介质层中的应用。针对芯片介质层的电、热、力学性能与生产要求,以氧化铪薄膜制备技术的发展历程为主线,重点介绍各类化学气相沉积方法的特点与典型研究成果,讨论了氧化铪薄膜制备技术存在的问题,并对该领域未来的发展趋势进行了展望。     

曲柄滑块机构最优解的解析计算方法

用优化设计方法,以曲柄滑块机构最小传动角为最大作为目标函数,给出了最优解的解析计算方法,从而得到机构的最佳设计。     

高分子表面活性剂的合成

以丙烯酸、丙烯酰胺和丙烯酸丁酯为单体,采用瞬时聚合法合成了高分子表面活性剂。表面活性研究表明,制备的高分子表面活性剂有良好的表面活性,表面张力可低至42 mN/m。红外光谱表明,产物没有发生交联,黏度法测定产物的分子量为2×104～4×104。     

PTT长丝瞬时拉伸回弹性能研究

在相同条件下对比研究了PET ,PTT和PBT 3种芳香族聚酯长丝的瞬时拉伸回弹性能 ,分析了测定条件对PTT长丝瞬时拉伸回弹性能的影响 ,并初步讨论了 3种芳香族聚酯长丝的瞬时拉伸回弹机理。结果表明 ,PTT长丝的瞬时拉伸回弹性能明显优于PBT长丝 ,更优于PET长丝 ,PTT长丝在低伸长率和高伸长率下均具有优异的瞬时拉伸回弹性能 ;测定PTT长丝瞬时拉伸回弹率时 ,建议采用 0 .5cN/tex的预张力 ,5 0 0mm/min的拉伸速率和 2 0 %的定伸长率等条件     

瓶级PET切片的研究及分析

介绍了固相缩聚反应的工艺流程及瓶级PET切片的反应过程,从IPA和添加剂的用量,PET切片大小和形状,PET切片特性黏度,反应温度、结晶,氮气的影响等方面分析了固相缩聚的影响因素。