悬浮烘干机干燥系统设计的初步研究

悬浮烘干技术与喷动床烘干技术原理相象,都是用于粗大颗粒物料干燥的一种新型流化技术。本文采用内部加热和普通喷动床相结合的方式设计了悬浮干燥系统,物料在烘干过程中处于悬浮状态,实现了在烘干过程中以每颗被烘干物料个体为脱水量检测因子控制烘干质量和烘干时间,与传统喷动床相比,强化了传热传质,提高了热效率,减少了空气用量,降低了能量消耗。     

红外—喷动床联合干燥设备研制与分析

为较好地解决单一红外干燥均匀性差的问题,利用红外加热高效节能的特点,结合喷动床流动性好、传热均匀的特点,设计了红外联合喷动床干燥设备。该装置包括喷动床干燥系统、红外辐射加热系统、回风式空气调节系统、动力循环系统和控制系统等。并以新鲜毛豆为物料,对该装置干燥均匀性和产品品质进行试验验证。结果表明,单一红外干燥耗时270 min,而红外—喷动床联合干燥耗时160 min,与单一的红外干燥相比,红外—喷动床联合干燥时间缩短了40.7%;同时,红外—喷动床联合干燥设备减轻了毛豆仁干瘪皱缩现象,使干制品具有较好的豆香味和感官品质。     

脉冲喷动微波真空干燥器内喷动流化动力特性的数值研究

为探索脉冲喷动微波真空干燥系统(PSMVD)中气固喷动流化床的动力特性,采用基于无粘性两相流理论,使用计算流体力学欧拉-欧拉方法(CFD)对二维喷动流化床中喷动流化特性进行了数值研究,对喷动流化床的动力特性和颗粒运动分布特征进行了揭示,这些因素影响颗粒空间位置分布和其微波加热的均匀性。结果表明,采用欧拉-欧拉双流体模型,成功获得脉冲喷动微波真空干燥腔内的二维喷动流化床的喷动流化动力特性;喷动流化过程在特定气流喷动速度下有一个初始阶段和准稳态流化阶段;喷动速度是控制颗粒在喷动床中颗粒位置的重要因素,存在一个影响流化模式转变的关键喷动速度;射流穿透深度和喷射速度之间存在线性关系。     

微波联合干燥方法的发展趋势及展望

微波联合干燥即微波干燥与其他干燥方法的联合应用。例如微波热风干燥,微波真空干燥,微波冷冻干燥及微波喷动床干燥等。随着人们对干燥产品的品质提出了更高要求,各种联合干燥方法应运而生。微波联合干燥以其如下几方面的优点倍受研究者的青睐:大量缩短干燥时间,提高产品干燥质量,灵活生产出各种类型的干燥产品。简要阐述了微波干燥的基本原理,概述了微波联合干燥在果蔬干燥方面的研究状况及不同联合干燥方法的特点及其试验设备,为缩小实验室研究和工业生产之间的差距提供参考。     

莴苣微波喷动均匀干燥工艺

通过单因素实验和正交实验确定莴苣微波喷动干燥的最佳工艺参数,并将产品和热风、喷动、真空冷冻、真空微波干燥的产品进行比较,旨在发现微波喷动干燥的优势所在。产品的质量主要通过复水率、叶绿素质量分数、色泽、能耗、感官评定等方面来衡量。实验结果表明,莴苣最佳微波喷动干燥参数为干燥前期(10min),微波功率为300W,热风温度为68～78℃,喷动风速为8m/s;干燥后期(45min)微波功率为200W,热风温度为68～78℃,喷动风速为6m/s。检测结果表明,微波喷动干燥产品的复水性、叶绿素质量分数、色差值和感官评定均优于热风干燥、喷动干燥和真空微波干燥产品,复水性和叶绿素质量分数略低于真空冷冻干燥产品,微波喷动干燥在节约能耗方面有显著效果。     

载能微波在不同负压水平的干燥模式与应用

为回顾近年来载能微波在农产品干燥中的研究进展,并解析负压环境对干燥行为的影响,文章以微波干燥的负压水平和干燥模式为主线,阐述高水分农产品物料在低真空度的负压微波脉冲喷动干燥(pulse-spouted microwave vacuum drying,PS-MVD),中真空度的微波真空干燥(microwave vacuum drying,MVD),高真空度的微波真空冷冻干燥(microwave vacuum freeze drying,MVFD)的干燥模式及物料特性,同时对农产品物料“热风-微波真空”组合干燥、“微波真空-真空含浸”加工、“脉冲喷动微波真空冷冻干燥”工艺的创新应用展开讨论。     

谷物干燥方法的研究

介绍了谷物的各种干燥技术和方法,以及干燥方法的研究进展。目前谷物干燥方法主要有微波干燥、红外线辐射干燥、顺溜干燥、流化床干燥、低温真空干燥、热风干燥和喷动床干燥。     

喷动床最小喷动速度的计算颗粒流体力学数值模拟

为了进一步研究喷动床的操作参数和结构参数对最小喷动速度Ums的影响,以及建立最小喷动速度的预测关联式,课题组建立了二维喷动床数理模型,床的高度为800 mm、宽度为200 mm和厚度为20 mm,喷动气入口底部是夹角为60°的V形结构。采用计算颗粒流体力学(CPFD)方法模拟计算了5种颗粒在3种喷口宽度和在不同静止床高时最小喷动速度变化情况。结果表明:喷动床的结构参数和操作参数对最小喷动速度有着极大的影响,最小喷动速度随着静止床高和颗粒粒径增大而增大,而随着喷口宽度的增大而减小;综合所有数据进行多因素影响回归,得到了新的最小喷动速度预测关联式。研究结果对于喷动床实际操作条件的确定和工艺设计提供了借鉴。     

土豆片脉冲喷动微波负压干燥特性及品质

在干燥腔内真空压力范围为11.8~15.0 kPa的条件下,研究微波功率、脉冲喷动频率、预处理及不同组合方式对脉冲喷动微波负压干燥(PSMVD)土豆片的干燥特性及色泽、质构、均匀性等品质的影响。结果表明:Midilli传质薄片模型优于其它三个模型;未漂烫处理及提高微波功率可以增加土豆片在干燥过程中水分扩散系数Deff,从而缩短土豆片脉冲喷动微波负压干燥时间。与传统的干燥相比,脉冲喷动微波负压干燥具有干燥周期短、产品干燥均匀性及品质较好等优点。     

茭白热风-微波联合喷动干燥的复水性研究

以茭白为原料,复水率为评价指标,采用响应面法优化干燥工艺参数,探讨茭白颗粒热风-微波联合喷动干燥的效果。不同喷动干燥方式研究表明:热风-微波联合喷动干燥条件对茭白复水率影响显著(p<0.05)。响应面优化最佳参数表明,进风温度52℃,颗粒大小8mm,微波功率2.7W/g。在此最佳条件下,茭白复水率达到3.05,试验结果与模型预测值吻合度达99%。方差分析表明,颗粒大小、微波功率对茭白复水性影响极显著(p<0.01),温度(A)与颗粒大小(B)交互项对复水率影响显著(p<0.05)。优化后的工艺参数为茭白微波喷动干燥技术的工业化应用提供理论依据。     

Low-cost drying methods for developing countries

Low-cost drying technologies suitable for rural farming areas are presented. Some of the important considerations with regard to their suitability include: 1. Low initial capital; 2. easy-to-operate with no complicated electronic/mechanical protocol, and 3. effective in promoting better drying kinetics. The drying technologies that were selected include fluidized bed, spouted bed, infrared, solar, simple convective and desiccant drying. A brief introduction on each drying technology has been presented followed by some technical details on their working operations. Examples of farming crops suitable for the employment of individual drying technology are provided to illustrate their potential application in agricultural product drying.     

Physical properties of parboiled wheat and bulgur produced using spouted bed and microwave assisted spouted bed drying

The main objective of this study was to compare the spouted bed and microwave assisted spouted bed drying on affecting physical properties of parboiled wheat and bulgur. Drying was performed at different temperatures (50 °C, 70 °C, 90 °C) and microwave powers (288 W, 624 W). Bulk and apparent density, bulk and apparent porosity, sphericity, color, microstructure and pore size distribution of parboiled wheat were investigated after drying. Yield and water absorption capacity were determined in bulgur samples. The effect of air temperature on physical properties of product except color was not significant in spouted bed drying. More porous structure was observed in wheat samples dried in microwave assisted spouted bed compared to air dried ones. Sphericity and bulk density were higher when high temperature was combined with high microwave power. In microwave assisted spouted bed drying, similar yield value but lower water absorption capacity of bulgur were observed as compared to spouted bed drying.     

低温等离子体在农产品加工保藏中应用的研究进展

低温等离子体技术是一种新兴的非热处理技术,具有安全、高效、无毒副作用等特点,在农产品加工、环保、医药以及纺织等领域具有十分广阔的前景。近年来,将低温等离子体技术应用于农产品保藏的研究正在兴起。本文综述了等离子体的分类,分析了低温等离子体灭菌的应用、影响因素以及作用机理,此外还分析了低温等离子体在脱除农残和包装材料中的不同应用研究进展,探讨了低温等离子体用于农产品保藏的优点以及存在的问题,并对低温等离子体技术应用于食品工业的前景进行了展望,为低温等离子体技术在农产品加工中的应用研究提供参考。     

农产品能源循环节能干燥工艺智能实验系统的研究

热风干燥是大宗粮食以及农产品加工的关键环节,当前农产品热风干燥节能工艺的研究与开发多限于实际作业跟踪和经验设计,通过传热传质理论进行数值计算等,都存在一定的局限性。实物模拟是一种潜在的比较有效的研究方法。在研究冷凝增效节能工艺过程中,开发了可以模拟实际热风干燥、能源循环利用的实验系统,具有多参数可调、图形化显示干燥状态、能耗监测等功能,可为农产品热风干燥节能工艺的研究提供有效手段。利用该系统开展的玉米干燥实验表明,能源循环节能干燥比普通开放式热风干燥节能32%～56%。     

Conical spouted bed drying of Baker's yeast: Experimentation and multi-modeling

Baker's yeast drying experiments in a conical spouted bed are used to characterize the effects of operating conditions on drying behavior. A novel multiscale model, describing Baker's yeast drying in a conical spouted bed, is presented; it is based on an intrinsic drying model developed for a single pellet, combined with a gas–solid flow model developed for a conical spouted bed. The resulting phenomenological model, which has only one adjustable parameter, is in good agreement with the experimental results. The model is capable of adequately predicting the drying rate of Baker's yeast pellets during the entire drying period in a conical spouted bed: from the beginning, where the water removal rate is limited by the air saturation with vapor during its residence time in the bed; to the end, where the water removal rate is dictated by internal resistance within the yeast pellets.The quality of dried Baker's yeast was characterized by measuring the gassing power in bread dough. This parameter was monitored during the conical spouted bed drying experiments. It was found that yeast degradation is linked to intracellular water removal (type D, end of the drying below a moisture content of around 0.5 (d.b.)) and it is mostly the rate of this water removal that controls the final quality of the product. Intercellular water removal (type E, beginning of the drying) was found to have no significant influence on yeast degradation. In all the cases, degradation is amplified when solid temperature is higher than 40 °C.     

水产品干燥技术研究进展

干燥是水产品加工工艺中不可或缺的环节之一,但采用不同的干燥技术会导致最终产品风味和质地的差异。因此,本文从传统干燥技术和新型干燥技术的角度出发对水产品干燥技术的研究进展进行总结,综述了自然晾晒、热风干燥、真空冷冻干燥、真空干燥、冷风干燥、热泵干燥、微波干燥和红外干燥技术的研究情况,概述了各种干燥技术的研究应用现状,指出水产品干燥技术今后的研究方向和发展趋势,旨在有效提高水产品干燥效率,并促进水产品的加工利用和经济效益,从而为干燥技术的进一步研究利用提供参考。     

微波辅助热风干燥预处理对油炸紫薯片品质的影响

为研究微波辅助热风干燥预处理对油炸紫薯片品质的影响,以厚度为3 mm的新鲜紫薯片为对象,首先采用不同微波功率(259、280、358 W)辅助热风(50、60、70 ℃)干燥方式对紫薯片进行预干燥,对不同微波功率(259、280、358 W)干燥后的紫薯片油炸8、3.5、2.5 min,研究紫薯片预处理过程的干燥特性及花青素含量,以及油炸紫薯片产品的色泽、脆度、硬度和脂肪含量等。结果表明:随着微波预处理功率的升高,紫薯片达到干燥终点的时间缩短(90 min以上),平均干燥速率显著提高;并且热风干燥温度越高,微波预处理对干燥效率的促进作用也越明显。而低功率(259 W)的微波辅助50 ℃热风干燥联用更有利于干燥紫薯片花青素的留存;较低功率(259、289 W)的微波预处理不仅在保护产品颜色上具有优势,还可以使得油炸紫薯片更高的硬度和更好的脆性。在不同微波预处理功率下,油炸紫薯片的脂肪含量最低值基本一致。本研究可为微波辅助热风技术在干燥紫薯及其他农产品干燥中的应用提供参考。     

THIN LAYER METHOD ANALYSIS OF SPOUTED BED DRIED MALAYSIAN PADDY – CHARACTERISTIC DRYING CURVES

A lab‐scale spouted bed dryer was used for the drying of paddy. The Malaysian grown paddy is a sample of Geldart's Group D particle. Drying was carried out in the dryer at two different internal configurations, namely with or without the installation of a draft tube, and at several drying temperatures (60–90C), air flow rates (1.14–1.45 m/s) and bed heights (30–45 cm). Drying kinetics of paddy in spouted bed showed only induction and falling rate periods, without constant drying rate period. Thin layer method analysis shows characteristic drying rate curves of linear and exponential functions for the first and second falling rate period, respectively, in conventional spouted bed drying. A single power function was observed in spouted bed drying with a draft tube, mainly as a result of a better tempering effect that gave a lower drying rate gradient.     

银川:宁夏大学,2017. [45]Alaejos M S,Afonso A M. Factors that affect the content of heterocyclic aromatic amines in foods[J]. Comprehensive Reviews in Food Science & Food Safety,2011,10(2):52-108. [46]姚瑶. 酱牛肉中常见杂环胺化合物的形成与控制研究[D]. 南京:南京农业大学,2013. 稳定同位素技术 在农产品产地溯源中的应用

农产品溯源技术是为保护地区品牌和特色产品,防止食品掺假和食源性疾病扩散,确保食品安全,降低公司召回成本而建立起来的一项追踪检测技术。建立高效的食品溯源体系是保证食品质量安全的关键,近年来稳定同位素技术因没有放射性、灵敏度高、可靠性强等优点,已广泛用于鉴别不同产地、不同食源的各种农产品,成为追溯食品来源的一种有效手段。文中系统阐述了稳定同位素技术在谷物、肉制品、果蔬、果汁饮料、葡萄酒、乳制品、水产品等各类食品在产地溯源方面的应用,进一步剖析了稳定同位素技术在我国农产品产地溯源中的优势及局限性,并对其发展前景进行展望,以期为我国农产品溯源体制的建立提供借鉴,推动稳定同位素技术在食品溯源中的应用。