超临界萃取技术的应用研究进展

综述了超临界萃取技术的原理、特点及其在食品和医药中的研究进展，并介绍了超临界萃取技术在天然香料、色素的生产条件，油脂的提取分离，中药有效成分的提取，并对今后的发展趋势作了预测。     

超临界流体提取技术及其在食品工业中的应用

超临界流体提取(SFE)技术开辟了分离工业的新领域,是一种新型的分离技术。本文对SFE技术的原理、特征,超临界流体的性质及超临界流体的选择,SFE技术在食品工业中的应用情况作一综述。     

浆料中的空气对纸张抄造的影响及其消除

浆料中的空气是造成流送系统不稳定的最主要的原因之一,也是影响出纸质量的一个因素。浆料进湿部系统前必须考虑浆料的脱气。     

超临界流体萃取技术在农产品加工业中的应用进展

超临界流体萃取技术是一种清洁、高效的分离方法,具有操作条件温和、无溶剂残留、分离效率高等特点,正受到越来越广泛的关注。本文简要介绍了超临界流体萃取的基本原理、影响超临界流体萃取的因素以及超临界流体萃取技术在农产品加工业中的应用,并对超临界流体萃取技术与其他高新技术联用情况进行了概述与展望,以期为超临界流体萃取技术在农产品加工业的进一步研究与应用提供参考和借鉴。     

葡聚糖水溶液流变性研究

本实验研究了葡聚糖水溶液的流变性能,选取了五种不同分子量的葡聚糖,分别考查了分子量、溶液浓度、溶液温度等因素对葡聚糖水溶液流变性的影响。结果显示,多数葡聚糖水溶液表现出牛顿流体的特性,而当葡聚糖分子量为531000,溶液浓度为30%时,溶液则表现出假塑性流体的性质,黏度随着剪切速率的提高而降低。当葡聚糖浓度较低时(≤1%),水溶液均表现出一种特殊的流变性,即黏度随着剪切速率增加先降低后升高,本研究对出现这一现象的原因进行了分析。     

凉粉草胶的稳剪切流变学性质

研究了凉粉草胶在不同质量浓度、温度、pH、盐的种类及盐浓度和不同蔗糖浓度下的流体行为以及固定剪切速率下的表观粘度随不同条件的变化情况。结果表明,凉粉草胶溶液在不同的条件下呈牛顿流体或假塑性流体行为,在剪切速率52.8s-1下,10 g/dL凉粉草胶溶液的表观粘度随胶质量分数(1~20 g/dL)的增加而递增,随温度(25~70℃)的升高而递减,随pH(5~12)的变化则不具有单调性,随NaCl(0~3.0 g/dL)的添加而递减,随CaCl2(0~3.0 g/dL)的添加则先减小后增大,随蔗糖(10~50 g/dL)的添加则递增。     

Regulation of fluid flow through the mammary gland of dairy cows and its effect on milk production: a systematic review

Dairy milk consists of more than 85% water. Therefore, understanding the regulation of fluid absorption in the mammary gland is relevant to improving milk production. In recent decades, studies using different approaches, including blood flow, transmembrane fluid flow, tight junction, fluid flow of the paracellular pathway and functional mammary epithelial cell state, have been conducted aiming to investigate how mammary gland fluid absorption is regulated. However, the relationship between regulation mechanisms of fluid flow and milk production has not been studied systematically. The present review summarizes a series of key milk yield regulatory factors mediated by whole‐mammary fluid flow, including milk, mammary blood flow, blood/tissue fluid–cell fluid flow and cell–alveolus fluid flow. Whole‐mammary fluid flow regulates milk production by altering transporter activity, ion channels, local microcirculation‐related factors, driving force of fluid transport (osmotic pressure or electrochemical gradient), cellular connection state and a cell volume sensitive mechanism. In addition, whole‐mammary fluid flow plays important roles in milk synthesis and secretion. Knowledge gained from fluid flow‐mediated regulatory mechanisms of the dairy mammary gland will lead to a fundamental understanding of lactation biology and will be beneficial for the improvement of dairy productivity. © 2017 Society of Chemical Industry     

纸页成形中的牵连作用

在脱水前,纸浆属于牛顿流体。在纸浆上网进入脱水过程后,浆层经历了逐层脱水的过程。经过一定程度脱水的浆层由于水分减少,转变为宾汉流体,并由于力学性质的突变而获得了附加的加速度,从而使得浆层在这个水分发生转变的区域内产生了速度的差别。这个差别对纸页的形成具有特定的影响。本文从浆料在成形过程中的流体性质变化的视角,探讨这种变化对纸页中纤维取向和再絮聚倾向可能发生的作用。     

ER/MR智能材料及其在土木工程结构振动控制中的应用

综述了电流变体/磁流变体(ER/MR)智能材料的基本性能,ER/MR智能减振驱动器的工作原理、力学模型,介绍了其在我国土木工程结构振动控制中的应用,提出了未来的研究方向.     

玉米黄浆中蛋白的回收研究

降低玉米浆的酸度和调节黄浆的ｐＨ值为３，５－４，５之间，有利于提高玉米蛋白的回收率。     

CFD技术在流体机械中的应用与发展

流体机械在轻工行业、化工行业等多种行业都得到广泛应用,通过分析CFD技术在流体机械的应用现状和发展趋势,针对湍流模型的选择、网格的分类及使用、计算域和边界条件的确定、计算模型的验证等方面,指出了CFD技术计算结果的可信度和二次开发应该引起重视。提出CFD技术发展方向应该是:既具有高适应、高速度、集成化和易用性的特点,又有正确合理的VV评价体系。     

超临界流体萃取在食品工业中的应用

本文简要介绍了超临界二氧化碳萃取技术,概括了近十年来它在食品工业中的应用和最新研究动态,并对超临界二氧化碳萃取技术作了展望。关键词 超临界流体 萃取 食品工业     

Analysis of viscosity measurements obtained using the short back extrusion method. Part 1: Theory of short back extrusion in viscometry

The back extrusion (BE) method is a well-known translational concentric cylinder viscometry that can analyze viscosity from the force–time curve of a cylindrical plunger pushed into a cylindrical cup filled with a sample fluid. It can analyze Newtonian, power-law, and Herschel–Bulkley flows. However, the plunger must be moved 100 mm or more from the sample surface toward the cup bottom, any sample fluid adhering to the plunger must be removed. Moreover, given the complexity of the calculation steps, the BE method is not as widely. The short back extrusion (SBE) method proposed in this study is an improved immersed-type BE method. By setting the measurement position inside the sample, the upflow in the annular space is smooth even over a short distance (5–15 mm). Measurement over a short distance decreases the amount of sample adhered to the plunger, mitigating the need to remove any sample from the plunger after each measurement, thereby facilitating repeated measurements. A program automatically determines flow type and, using novel mathematical formulas, it calculates the measured characteristics of the flow. In addition, the greatest advantage of the SBE method is that it can measure samples containing solids. It can be measured in a state in which a person usually eats, because the larger the stress required for the flow, the wider the gap. Moreover, its measurement accuracy is comparable to cone-plate analysis, and the linear region of the analysis area is wide with less destructive movement.     

Flavor and flavor chemistry differences among milks processed by high-temperature,short-time pasteurization or ultra-pasteurization

Typical high-temperature, short-time (HTST) pasteurization encompasses a lower heat treatment and shorter refrigerated shelf life compared with ultra-pasteurization (UP) achieved by direct steam injection (DSI-UP) or indirect heat (IND-UP). A greater understanding of the effect of different heat treatments on flavor and flavor chemistry of milk is required to characterize, understand, and identify the sources of flavors. The objective of this study was to determine the differences in the flavor and volatile compound profiles of milk subjected to HTST, DSI-UP, or IND-UP using sensory and instrumental techniques. Raw skim and raw standardized 2% fat milks (50 L each) were processed in triplicate and pasteurized at 78°C for 15 s (HTST) or 140°C for 2.3 s by DSI-UP or IND-UP. Milks were cooled and stored at 4°C, then analyzed at d 0, 3, 7, and 14. Sensory attributes were determined using a trained panel, and aroma active compounds were evaluated by solid-phase micro-extraction or stir bar sorptive extraction followed by gas chromatography-mass spectrometry, gas chromatography-olfactometry, and gas chromatography-triple quad mass spectrometry. The UP milks had distinct cooked and sulfur flavors compared with HTST milks. The HTST milks had less diversity in aroma active compounds compared with UP milks. Flavor intensity of all milks decreased by d 14 of storage. Aroma active compound profiles were affected by heat treatment and storage time in both skim and 2% milk. High-impact aroma active compounds were hydrogen sulfide, dimethyl trisulfide, and methional in DSI-UP and 2 and 3-methylbutanal, furfural, 2-heptanone, 2-acetyl-1-pyrroline, 2-aminoacetophenone, benzaldehyde, and dimethyl sulfide in IND-UP. These results provide a foundation knowledge of the effect of heat treatments on flavor development and differences in sensory quality of UP milks.     

CFD simulation of ozone gas flow for controlling Sitophilus zeamais in rice grains

Ozone gas (O₃) is a prominent alternative for the integrated pest management of stored products. The present study fitted a computational fluid dynamics (CFD) model to elucidate the ozone gas flow dynamics in an aeration system, at a lethal concentration for Sitophilus zeamais Mots in rice grains. First, an experiment was carried out to understand the flow of ozone gas (2.2 mg L⁻¹; 2 L min⁻¹) in a cylindrical PVC column filled with 4 kg of rice grains. The ozone gas concentration was monitored every 12 h, at a point immediately above the grains. The gas flow was modeled using the CFD technique. The parameters used to feed the model and adjust it to the experimental data were the mass transfer coefficient and ozone-rice grain reaction constant. Then, a simulation of ozone gas injection in a silo with a static capacity of 69.6 tons of rice was performed. In the ozone gas injection experiment, 100% of insect mortality was observed on the sixth day, when the O₃ concentration reached 0.1 mg L⁻¹. In this case, the mass transfer coefficient was 0.55 m s⁻¹, and the reaction constant was 0.78 s⁻¹. At the concentration of 0.8 mg L⁻¹, it is possible to treat 69.6 tons of rice grains within 9 days.     

Design of a magnetorheological robot gripper for handling of delicate food products with varying shapes

Natural food products are often variable in shape and easily bruised, making them difficult to handle for a robot. In this paper, a novel robot gripper that utilizes the effects of a magnetorheological (MR) fluid is described and evaluated. In the gripping process pouches filled with MR fluid are molded around the product’s contours. Through the activation of an electromagnet in the gripper arm, a large increase in the MR fluids yield stress confines the product in the mould produced by the gripper surfaces, allowing it to be lifted. Mounted on a six axis KUKA robot products such as apples, carrots, strawberries, broccolis and grapes have been handled without bruising or denting and without the tool changes that would typically be needed. The paper presents data regarding the forces exerted on products during gripping as well as data on maximum payloads and graspable product shapes.     

Flavan‐3‐ol C‐glycosides – Preparation and model experiments mimicking their human intestinal transit

In order to study the human intestinal transit of flavan‐3‐ol C‐glycosides, several C‐glycosyl derivatives were prepared by non‐enzymatic reaction of (+)‐catechin with α‐D ‐glucose, α‐D ‐galactose and α‐D ‐rhamnose, respectively. In contrast to literature data, we propose that the reaction mechanism proceeds in analogy to the rearrangement of flavan‐3‐ols during epimerization under alkaline conditions. Four of the 12 synthesized flavan‐3‐ol C‐glycosides were incubated under aerobic conditions at 37°C using saliva (2 min) and simulated gastric juice (3 h). To simulate human intestine, the C‐glycosides were also incubated under anaerobic conditions at 37°C both in human ileostomy fluid (10 h) and colostomy fluid (24 h), respectively. The flavan‐3‐ol C‐glycosides under study, i.e. (+)‐epicatechin 8‐C‐β‐D ‐glucopyranoside (1a), (+)‐epicatechin 6‐C‐β‐D ‐glucopyranoside (1d), (+)‐catechin 6‐C‐β‐D ‐galactopyranoside (2b), (+)‐catechin 6‐C‐β‐D ‐rhamnopyranoside (3b) were analyzed in the incubation samples by HPLC‐DAD and HPLC‐DAD‐MS/MS. They were found to be stable in the course of incubation in saliva, simulated gastric juice and ileostomy fluid and underwent degradation in colostomy fluid. While the 6‐C‐β‐D ‐glucopyranoside 1d was completely metabolized between 2 and 4 h, decomposition of the 6‐C‐β‐D ‐galactopyranoside 2b reached only 16±2% within 4 h of incubation. Linear degradation rates of 1d and 2b in colostomy fluid differed significantly. As microbial metabolism of flavan‐3‐ols is known not to be influenced by the stereochemistry of the aglycon, varying degradation rates are ascribed to the effect of the sugar moiety. Based on these results we assume that flavan‐3‐ol C‐glycosides pass through the upper gastrointestinal tract (oral cavity, stomach and small intestine) unmodified and are then metabolized by the colonic microflora.     

液池中牵引辊表面的流场分析——幂律流体和Maxwell流体情况

运用Polyflow有限元计算软件包分析了非牛顿流体在牵引辊表面的流场.流体模型采用幂律流体和Maxwell流体.结果表明:非牛顿流体的剪切稀化特性明显压抑涡的形成;而其弹性和拉伸特性则导致大涡的产生.