通风过程中进风相对湿度对仓储粮堆温度和水分的影响研究

温度和水分含量是两个重要的物理变量,在研究谷物储存时品质变化起到很大作用。通风用于冷却粮堆并保持温度恒定,以防止水分迁移。良好的通风条件对粮仓内存储安全有显著影响。目前,通风空气相对湿度对粮堆水分影响的研究相对较少。采用数值模拟和实验研究相结合的方式,探索和比较因不同进风相对湿度而引起的通风过程中仓储的小麦温度和水分变化规律。结果表明:进风相对湿度较低时冷却干燥效率更高,小麦粮堆降温更快速,并将昆虫和霉菌的活动保持在较低水平。     

枸杞平衡含水率的测定及其干燥工艺的优化

枸杞的平衡含水率是研究枸杞干燥特性和干燥工艺优化的基础。本文采用静态称重法,利用LHS-250HC-II型恒温恒湿试验箱和DHG-9240A型电热鼓风干燥箱,测得枸杞在温度为40℃、50℃、60℃、70℃,相对湿度为40%、50%、60%、70%的平衡含水率。通过对干燥特性曲线的分析,得出干燥快速阶段干燥工艺参数为温度40℃,相对湿度40%,干燥恒速阶段干燥工艺参数为温度50℃,相对湿度40%,干燥降速阶段干燥工艺参数为温度60℃,相对湿度40%的工艺参数组合,此干燥工艺干燥时间最短,干燥品质最好。     

超细纤维合成革基布的制备及其性能

为提高聚酯/聚酰胺6(PET/PA6)中空超细纤维合成革基布的透湿性、柔软性,将聚丙烯腈(PAN)纳米纤维与PET/PA6超细纤维混合,通过水刺固网的方法制备出PAN-PET/PA6微/纳米超细纤维合成革基布并进行碱处理,分析了PAN纳米纤维质量分数对革基布透气性、透湿性、吸湿性、柔软度及力学性能的影响。结果表明:当革基布面密度一定时,随着PAN纳米纤维质量分数的增加,革基布的透湿性、吸湿性、柔软度、撕裂性能提升,而透气性能和断裂强力有所下降;当PAN纳米纤维质量分数为20%时,革基布的透湿率提升了15.19%,吸水量提高了23.53%,柔软度增加了38.17%;经碱处理后,革基布的亲水性有了明显改善,透湿率提升了23.81%,吸水量提高了42.26%,柔软度提高了23.20%。     

海藻糖部分替代蔗糖对猪肉脯品质特性的影响

为改善传统猪肉脯的品质特性,采用不同比例（10%、20%、30%、40%）的海藻糖部分替代猪肉脯配料中的蔗糖,测定其总糖含量、pH值、水分、质构特性、色泽、脂肪氧化情况及感官品质等的变化。结果表明：海藻糖部分替代蔗糖,在降低总糖含量的前提下,显著提高猪肉脯的亮度值、红度值和黄度值（P＜0.05）,并延缓猪肉脯贮藏期间的褪色,显著降低硫代巴比妥酸反应物值（P＜0.05）;随着海藻糖替代比例的增大,猪肉脯水分含量显著提高,且其中的结合水和不易流动水含量总体呈降低趋势,自由水含量显著提高（P＜0.05）,猪肉脯的硬度、咀嚼性和坚实度显著下降（P＜0.05）;海藻糖替代蔗糖比例10%时,猪肉脯的感官品质较佳。     

不同储藏条件下玉米挥发性成分研究

为通过挥发性物质变化来探究玉米储藏期间品质变化,并找出相关性特征挥发物,为玉米安全储藏提供参考。本实验模拟不同仓储条件,通过电子鼻(E-NOSE)和顶空固相微萃取-气质联用(GC-MS)对玉米挥发性物质进行检测,结合主成分分析法和样品得分图对结果进行分析。结果表明,随储藏周期变化,不同水分、温度条件下玉米样品,雷达图有明显区别,对应传感器显示15%高水分样品比低水分样品更易出现霉味。高温高水分样品在储藏3个月后在主成分分析图上与其余样品有明显区分,表明气味变化较大。气质检测中共检出醇类物质15种,芳香烃25种,醛类23种,酸酯类59种,酮类18种,烷烃53种,烯烃22种,杂环类27种。贡献率较大的是酸酯类、芳香烃和醇类物质。氧气浓度较低时,酸酯类物质挥发量减少,氧气浓度对醇类、芳香烃等影响较小,且只在浓度极低(2%~5%)时,2,6-二叔丁基对甲酚和1-氯二氟甲氧基-4-硝基-苯挥发量会增加。在低水分条件下苯甲醇挥发量较大;alpha-戊基-gama-丁内酯、壬酸和烯醛类物质在低温低水分条件下挥发量较大;酰胺类物质则在高温高水分条件下产生较多;香兰素在高温高水分下挥发量较小;不饱和烯烃与烯醇类物质都随着储藏时间的推移而增加。电子鼻和GC-MS能有效对不同储藏条件下的玉米样品进行区分,亦可通过特定挥发物质的多少来判别玉米品质的好坏,水分与温度两个条件对挥发物质影响较大,氧气浓度影响较小,当水分含量低于13%,温度低于20℃时在常压下储藏就能有效防止玉米品质劣变。     

变性淀粉对肌原纤维蛋白凝胶特性的影响

分别将0%、4%、6%、8%、10%和12%的玉米原淀粉、玉米乙酰化二淀粉磷酸酯、木薯乙酰化双淀粉己二酸酯淀粉(acetylated distarch adipate,ADA)、木薯醋酸酯变性淀粉(starch acetate,SA)添加到肌原纤维蛋白溶液中,制备淀粉-蛋白复合物并测定流变特性、凝胶强度、保水性和水分子弛豫时间等指标。结果表明:添加淀粉可显著提高肌原纤维蛋白的储能模量G′,G′在42℃左右开始增加,此时肌原纤维蛋白开始变性形成凝胶,添加变性淀粉可显著延迟肌原纤维蛋白的变性温度(43~46℃)。变性淀粉添加量为8%时淀粉-蛋白复合物凝胶强度均达到最大,而原淀粉对肌原纤维蛋白的凝胶强度影响不显著(P>0.05)。添加变性淀粉的复合凝胶保水性比原淀粉保水性高约13%(P<0.05),SA-蛋白复合物与ADA-蛋白复合物保水性最高。核磁共振分析表明T2弛豫时间随变性淀粉添加量增大而减小,T22向快弛豫方向移动,说明变性淀粉的添加降低了水分子的移动性。因此,ADA-蛋白复合物对肌原纤维蛋白的流变性、凝胶强度、保水性和水分迁移影响最显著,添加10%以内变性淀粉可显著提高肌原纤维蛋白的G′和保水性,同时增大凝胶强度,降低水分迁移速率。     

羊毛与37.5涤纶混纺针织物的热湿舒适性研究

选择8种不同的羊毛与普通涤纶、37.5涤纶混纺针织物试样,测试试样的密度、面密度、未充满系数和厚度等基本参数,以及回潮率、透气率、芯吸高度、瞬间接触凉感(Q-max)及恒定加热条件下的干、湿态升温性能等织物的热湿舒适性能,分析和评价了针织物的基本参数对其热湿舒适性能的影响。试验结果显示,与普通涤纶相比,采用37.5涤纶有助于提高织物的回潮率、芯吸高度和Q-max;透气率随针织物未充满系数的增大而增大;当织物的纤维组成成分基本一致,组织结构相同时,针织物的面密度越大,透气性越差;含37.5涤纶的纬平针织物的瞬间接触凉感性能较好。     

An effective method of bulk materials moisture measurement using capacitive sensors

When we speak about capacitance moisture meters for bulk materials we have to face with different values of dielectric permittivity for different bulk materials in dehydrated state, what causes a method error that can be named ‘type uncertainty’. Besides, different varieties of the same material have different values of dielectric permittivity, which depend from geographical origin, processing conditions etc. It can be hardly predicted automatically and type uncertainty can be compensated only in separate situations with the help of preliminary calibration. Main tasks of the research are to develop new comparison principle of moisture measurement with better accuracy due to effective compensation of physical, chemical and granulometric composition influence on the result of moisture measurement, develop new primary and secondary instrument transducers. Moisture sensor consists of four measuring capacitors. Two of them should be filled with a sample, which moisture content should be determined, and other pair of measuring capacitors should be filled with a same substance, but previously dehydrated. Mathematical models, developed to take into account granulometric composition of a bulk material were used to carry out a comparison analysis for three types of instrument measuring transducers. Obtained results proved that suggested principle of moisture measurement provides effective compensation of granulometric composition influence. Developed measuring principle had been experimentally tested what helped to confirm that it provides two times better compensation of different physical and chemical composition for different materials in comparison with the direct comparison method.     

聚酯织物的防紫外-吸湿快干复合整理

对聚酯织物正面采用防紫外线涂层整理,反面采用吸湿排汗差别化功能整理,赋予织物防紫外线和吸湿快干功能。结果表明,整理聚酯织物同时具有较高的防紫外线作用和较强的吸湿快干效应,经过多次洗涤后效果仍能保持,且对染色聚酯织物的色光基本无影响。     

Moisture sorption and thermodynamic properties of cassava starch and soy protein concentrate based edible films

Moisture sorption isotherms and thermodynamic properties of cassava starch and soy protein concentrate–based edible films were investigated. Equilibrium moisture content was determined at various temperatures (10, 20, 30 and 40 °C) and relative humidities (17–83%) using gravimetric method, and the results were analysed using four sorption isotherm models. The equilibrium moisture of edible films (both adsorption and desorption modes) decreased with soy protein concentrate addition and temperature at constant water activity. The monolayer moisture content values of cassava starch–soy protein concentrate edible films decreased with increase in temperature and soy protein level. GAB and Oswin models (%RMS ≤10) best described the isotherms of the biofilms with the monolayer moisture contents, isosteric enthalpy and entropy higher for adsorption with significant kinetic compensations. The moisture sorption and thermodynamic properties of cassava starch–soy protein concentrate edible films showed that they are suitable for packaging applications.