Process Parameter Effects on Particle Residence Time in a Vertical Scraped Surface Heat Exchanger

Residence times of 1.0-2.0 cm potato cubes with 0.4-1.2% aqueous solutions of sodium carboxymethyl cellulose flowing at 453-599 mli sec were investigated in a vertical scraped surface heat exchanger rotating at 60 160 rpm. Minimum and maximum normalized particle residence times (NPRTs) standard deviation of mean NPRTs, and characteristic parameter for tanks-in-series models were not significantly affected by particle concentration. Mean NPRT for 40% particle concentration was significantly higher than those of single particle - 20% particle concentrations. Mean NPRTs were significantly influenced by process parameters and 2-way interactions.     

NONENZYMATIC BROWNING IN DRIED RED PEPPER PRODUCTS

The nonenzymatic browning of dried red peppers was studied under various water activities, storage temperatures, and packaging atmospheres. Whole pepper and pepper powders-coarse and fine, with and without seeds-were compared. The browning can be described by the zero order reaction, and the rate constant is strongly affected by water activity and temperature. Flushing the package with nitrogen did not have a significant effect on the browning rate. For minimum browning, the peppers should be stored at water activities below 0.3 and in the form of whole pods or coarse powder with seeds.     

CHANGES IN 'DELICIOUS' APPLE BROWNING AND SOFTENING DURING CONTROLLED ATMOSPHERE STORAGE

High CO₂ conditions offered no advantage over normal CA storage in terms of reduced ‘Delicious’ apple browning or softening during a 28 week storage period. After approximately 7–14 weeks in CA storage, ‘Delicious’ apples showed significant losses in PPO activity, browning tendency and firmness. Electrolyte leakage reached a maximum at 11.5 weeks and declined, while total phenolics remained fairly constant. The changes observed may indicate a loss in membrane integrity and decompartmentalization after 7–14 weeks of storage, which may in turn allow for increased enzymatic browning. Polygalacturonase activity was only detectable at harvest. Holding apples for additional time in air following removal from CA storage appears to accelerate changes in these characteristics.     

Minced Meat Crabcake from Blue Crab Processing Byproducts—Development and Sensory Evaluation

Quantitative and qualitative characteristics of minced meat, mechanically separated from blue crab processing by-product, were determined. Sensory evaluation was performed on crabcakes with various combinations of claw mince/meat (CMM), surimi, and functional soy protein concentrate (SPC). Separation produced 50–58% food-grade mince from picking table by-products and 49% from undersized claws. Claw mince had lower microbial concentrations than the composite picking table by-products. Crabby and beany flavors were influenced (p<0.05) by the CMM ratio but not by SPC. No significant differences were observed for textural characteristics using various levels of CMM. Sensory firmness and cohesiveness scores marginally correlated (p<0.1) with Instron compressive force measurements. Food-grade undersized crab claw mince can be used in value-added products.     

Linear Programming and Response Surface Methodology to Optimize Surimi Gel Texture

A formulation optimization study was conducted on surimi gels prepared with starch, and/or raw egg white employing the stepwise method (SM), linear programming (LP), and response surface methodology (RSM). At 78% moisture, the greatest gel strengthening and reduction of expressible moisture occurred at 8% starch, 6% egg white, or a combination of 5% starch and 5% egg white for SM, 5.33% starch and 4.33% egg white for LP, and 3.5% starch and 5% egg white for RSM. RSM resulted in gels with the greatest strength (compressive and penetration forces), followed by LP and SM. The RSM enabled more accurate prediction of textural behavior of final product at various ingredient combinations than the SM or LP.     

Evaluation of Time-Intensity Sensory Responses using a Personal Computer

A method is presented which utilizes a personal computer to measure time-intensity (T-I) sensory responses. The judge uses a game paddle which moves an “X” along a fixed scale appearing on the monitor screen to indicate the attribute intensity at each instant in time. A clicker device on the game paddle can be used to record the occurrence of events such as initial mouth entry and time of swallowing. Data acquisition is continuous with the data stored on discs. This technique has advantages over strip chart recorder methods. Disc storage allows rapid and efficient data analysis. Judges can perform the evaluations virtually unsupervised with only minimal training.     

Heating Cruciferous Vegetables Increases in Vitro Dialyzability of Intrinsic and Extrinsic Iron

Iron dialyzability (ID) from three Cruciferae (broccoli, kale and cabbage) was determined by an in vitro digestion method. The effect of added Crucifers on the ID of extrinsic nonheme iron as well as effects of heating were studied. Uncooked Crucifers contained iron of moderate ID (7–9%); cooking resulted in substantial ID increase (200%). Cooked Crucifers increased extrinsic ID three- to fourfold. Time and temperature relationships for the increase suggested that organic acids released after partial cell wall degradation combined with protein denaturation and iron solubilization from fiber were major reasons for differences between raw and cooked vegetables. Cruciferous vegetables can contribute to improved iron nutrition.     

Tenderization of Meat with Ginger Rhizome Protease

Beef steaks and sliced beef marinated with different levels of crude ginger extract were evaluated for the tenderness and structural changes. A significant (P<0.05) enhancement of tenderness with increasing amounts of ginger extract was observed at low levels of extract (0, 0.05, 0.1, and 0.2 mL/6.5 cm² for the steaks; 0, 0.25, 0.5, and 1 mL/lOOg for the sliced beef), whereas further improvement of tenderness at more than 0.2 mL/6.5 cm² or 1 mL/lOOg was minimal. Electron microscopy of the treated beef revealed the preferential degradation of thin filaments in the I-bands, resulting in extensive fragmentation of myofibrils. Thus, ginger rhizome protease is an effective meat tenderizer and the tenderization is achieved through preferential degradation of thin filaments.     

弹性基体磨具的磨抛轨迹与表面加工质量研究

目的 解决以光学玻璃为代表的硬脆材料加工效率与表面质量难以同时得到保证的共性问题。方法 以弹性基体工具磨削抛光技术为基础,分析弹性接触区域内有效工作磨粒的运动行为。基于Preston方程材料去除模型,研究磨抛过程中磨抛接触区域的接触面积、速度分布、多颗磨粒的运动轨迹。基于运动学模型,探究磨抛过程中磨具的运动学参数、磨粒浓度及排布特征等因素对磨粒磨抛轨迹的影响,采用磨具与工件接触区域磨粒运动轨迹相对面积占比和变异系数表征磨粒运动轨迹分布的均匀性,并建立基于轨迹均匀性的加工表面质量评价方法,优化工艺参数。以石英玻璃为加工对象,以硅橡胶中混入金刚石磨粒为基体,通过正交实验研究不同参数对工件表面质量的影响。结果 仿真结果表明,选取自转速度为300 r/min、进给速度为1 mm/s、磨抛进动角为15°,磨粒浓度及排布采用1 mm磨粒理论间距,此时获得的最大磨粒运动轨迹相对面积占比为96.46%,最小变异系数为0.375。通过实验,得到了选取磨抛工艺参数中的最佳参数组合,自转速度为1 200 r/min,进给速度为1 mm/s,磨抛进动角为15°~20°,磨粒浓度及排布采用磨粒间距1 mm,该组合可将工件的表面粗糙度由1.078 μm降至0.057 μm,材料去除率为3.8×10⁸ μm³/min。结论 磨粒运动轨迹的密集程度与自转速度、磨粒浓度及排布呈正相关,与进给速度呈负相关,在考虑加工成本的前提下,采用高自转速度、高磨粒浓度、低进给速度及15°~20°的进动角可以获得密集且均匀的磨粒运动轨迹,提高了工件的表面质量和材料去除效率。