小麦粮堆降温冷却过程中温度变化研究

采用风冷制冷机组对模拟仓进行冷却通风,在粮层中间形成明显的温度梯度后停机,探究制冷时和停机后粮温的变化规律。结果表明:在冷却通风过程中,靠近冷源的底层(7层)温度变化最快,于通风38 h时温度先达到平衡,平均降温速率约为0.04℃/h,5、6层粮温通风50 h后达到平衡。停机3个月,各层温度变化不一致:上层粮温先上升后下降,与仓温和气温的变化趋势一致,上层粮温高于表层中部,而低于仓墙两侧粮温;中、下层粮温以接近抛物线形式缓慢上升,前期速率依次约为0.31、0.179、0.115、0.115℃/d,远低于冷却时的平均降温速率(0.02~0.26℃/h),且制冷前后粮堆平均水分没有明显变化。     

配合饲料水分含量和贮藏温度对脂质酸败的影响

采用 3× 3因子试验设计 ,研究了配合饲料的水分含量在 12 %、14 %、16 %和贮藏温度 2 4、30、37℃时对脂质酸败的影响。试验结果表明 :脂质水解酸败随着温度和水分含量的升高 ,极显著增强 (P <0 .0 1)。水分含量在 16 %以下 ,随着水分含量的降低和温度的升高 ,脂质氧化酸败迅速增强 ,12 %的水分组脂质的氧化酸败极显著的高于 16 %组 (P <0 .0 1)。     

鱼松中水分含量和水分活度的探讨

以鱼为原料加工的鱼松属于调味熟食品,容易被人体消化吸收,特别适合婴幼儿及老年人食用。鱼松的口感与加工过程调味及其产品自身水分含量有关。了解鱼松中水分含量和水分活度,便于控制加工过程,进行合理的贮藏食品。     

面制品干燥过程中水分迁移机制及影响因素分析

内外水势差是水分迁移的动力。水分由高水势向低水势迁移是机制。通过综述了水势差及差值对水分迁移过程的影响,以确证该机制,为研究低能耗干燥提供数据和理论支撑。内部水势可以用水分活度表征,外部水势可以用环境相对湿度表征。内外水势差越大,水分迁移的动力越大。内部水势会随着水分含量、淀粉占比、孔隙率、外界环境温度的增加而升高;外部水势随着环境相对湿度的增加而升高。不同的水势调控方案可实现相同的水分迁移量,但对面制品的质量和能耗影响不同,为高质量面制品低能耗干燥工艺提供了设计思路。     

高水分小麦通风干燥过程中加工品质变化规律研究

将刚收获的高水分小麦放置在就仓干燥模拟仓内进行通风干燥,测定小麦粮堆各层水分含量变化,及小麦粗蛋白含量、湿面筋含量、粉质特性、降落值等指标。结果表明：含水量超过20%的小麦在模拟仓中采用纵向通风技术可以在短期内将小麦水分含量降低至安全水分,对其加工品质没有显著不良影响。使用通风技术可有效降低小麦水分含量,但各粮层降水存在一定不均匀性,在实仓干燥中可辅以其他技术予以改善。     

房式仓粮堆温度和水分变化的模拟研究

基于计算流体动力学理论,对"F"型网络冷却通风时房式仓粮堆内部的温度和水分变化规律进行了三维数值模拟,通过分析得到了就仓通风时粮堆内部热量和水分迁移的基本规律,并与实验测试数据进行了比较。     

基于Fortran程序对储粮通风温度水分和害虫演替的模拟研究

世界各国因储粮害虫对粮食造成的损失非常严重,为了降低粮食在储藏期间的损耗,所以研究储粮通风过程中害虫增长量的变化至为重要。文章基于多孔介质热湿耦合理论,建立了浅圆仓的粮堆内部热湿传递和流动的数学模型以及害虫和熏蒸经验模型,并基于Fortran语言编程,模拟分析了通风状态下粮堆温度、水分含量、储粮害虫增长量以及杀虫剂浓度衰减的变化。结果表明：通风对粮堆内部温度和水分以及害虫生长影响明显。粮堆的水分含量近似对称分布,而受太阳辐射的影响,粮仓不同方向壁面的温度分布并不对称。储粮害虫在粮仓内的数量分布与温度、水分等因素有关,在壁面附近害虫分布较多,且在筒仓中心区域出现分层现象。杀虫剂浓度衰减也受温度的影响,温度高会影响杀虫剂的降解,导致杀虫剂浓度较低     

仓储粮堆机械通风时压力场的模拟研究

以仓储粮堆机械通风试验为基础,以实仓试验相关数据为依据,建立了仓储粮堆机械通风过程中内部压力场分布的计算流体动力学(CFD)模型,并进行了不同通风风量条件下开环流熏蒸口和开人孔时的数值模拟计算。最后通过实仓试验数据和模拟结果进行验证。结果表明,仓储粮堆机械通风过程CFD模型能够真实反映机械通风过程中粮堆内部压力场的分布情况,将计算流体力学模拟技术应用于仓储粮堆压力场的预测分析是可行的。     

初始水分含量与温度对油炸香蕉片贮藏稳定性的影响

为研究油炸香蕉片在不同贮藏条件下的贮藏特性,采用静态平衡将样品水分稳定到高、低两种初始水分含量,分别贮藏于0、25、37 ℃的避光环境,通过测定过氧化值、酸值、茴香胺值和介电常数等指标评价油炸香蕉片贮藏期间的氧化状况。结果表明,相同的贮藏温度和时间条件下,高初始水分含量油炸香蕉片的过氧化值、酸值、茴香胺值、介电常数均高于低初始水分含量的样品,降低油炸香蕉片的初始水分含量可以提高其贮藏稳定性。高初始水分含量油炸香蕉片的过氧化值随贮藏时间的延长而升高,低初始水分含量样品达到峰值后逐步降低;样品的酸值、茴香胺值在贮藏期间均升高;高初始水分含量样品介电常数在贮藏期间变化不大,低初始水分含量样品介电常数随贮藏时间的延长,整体呈上升趋势。     

水分含量对新鲜干酪贮藏特性的影响

对水分含量不同的4组干酪进行贮藏期水分含量、水分活度、pH、酸价、TBA值测定和感官评定。结果表明:干酪水分含量与水分活度随贮藏期呈递减趋势,并且呈正相关关系;酸价随着贮藏期的延长先增加后减少;pH则相反,呈先下降后上升的趋势;TBA值呈逐渐上升趋势。表明水分含量低的干酪,其耐贮藏性较好。感官特征测定在贮藏的第18d开始,干酪逐渐开始出现腐败特征,水分含量较低的干酪感官评分高。     

粮堆表层通风控温试验研究

采用负压通风原理,对150 cm以内表层局部发热、水分偏高的粮堆进行粮堆表层通风控温试验,试验表明:当气温不超过25℃时,采用粮堆表层通风控温法处理局部发热点温度30～38℃的粮堆,可在1.5h内将粮温降到27℃左右,使其接近于正常粮堆的粮温,较好地解决了粮堆表层局部发热的难题.     

高温高湿地区偏高水分玉米的筒仓储藏试验

针对高温高湿地区筒仓中粮食储藏安全的问题,进行了偏高水分玉米控温的试验.结果表明:偏高水分玉米初春入仓后,应首先将粮食水分降至14.5％左右;然后启动内环流系统将内圈筒仓的粮温维持在20℃以下、外围筒仓维持在25℃左右;盛夏期间当偏高水分粮或杂质分级点引起局部发热时,可利用谷冷机进行降温散湿.另外,可将偏高水分玉米储于不受外部环境影响的内圈筒仓,配以加强入仓粮食清杂和提前进行预防性熏蒸等措施,以提高湿粮储藏的稳定性.     

Effect of temperature and relative humidity on yellowing rate of paddy

The effects of temperature and relative humidity (or water activity) in storage chambers on yellowing rate of paddy were investigated and then an empirical equation for predicting the yellowing rate was developed. Paddy was conditioned using saturated salt solutions at relative humidities ranging from 0.80 to 0.95 and temperatures of 35, 45, 55, 60 and 65°C. The yellowing rate was found to follow the zero order kinetics. The yellowing constant value (k) increased exponentially with temperature and increased linearly with water activity. The magnitude of apparent activation energy varied from 130–145 kJ/mol. A predictive equation for determining yellowing rate was ln k=−δa_w−/T+(γa_w)/T where a_w was water activity (valid from 0.80 to 0.95), T was absolute temperature (valid from 308 to 338 K) and , δ, and γ were constants. The results of variance analysis showed that temperature, water activity and their interaction significantly influenced the yellowing rate of paddy.     

Effects of increasing air temperature on physiological and productive responses of dairy cows at different relative humidity and air velocity levels

This study determined the effects of increasing ambient temperature (T) at different relative humidity (RH) and air velocity (AV) levels on the physiological and productive responses of dairy cows. Twenty Holstein dairy cows were housed inside climate-controlled respiration chambers, in which the climate was programmed to follow a daily pattern of lower night and higher day T with a 9°C difference, excluding effects from sun radiation. Within our 8-d data collection period, T was gradually increased from 7 to 21°C during the night (12 h) and 16 to 30°C during the day (12 h), with an incremental change of 2°C per day for both nighttime and daytime T. During each research period, RH and AV were kept constant at 1 of 5 treatment levels. A diurnal pattern for RH was created, with lower levels during the day and higher levels during the night: low (RH_l: 30–50%), medium (RH_m: 45–70%), and high (RH_h: 60–90%). The effects of AV were studied during the day at 3 levels: no fan (AV_l: 0.1 m/s), fan at medium speed (AV_m: 1.0 m/s), and fan at high speed (AV_h: 1.5 m/s). Effects of short and long exposure time to increasing T were evaluated by collecting data 2 times a day: in the morning [short: 1 h (or less) ? exposure time] and afternoon (long: 8 h ? exposure time). The animals had free access to feed and water and both were ad libitum. Respiration rate (RR), rectal temperature (RT), skin temperature (ST), dry matter intake, water intake, milk yield, and composition were measured. The inflection point temperatures (IPt) at which a certain variable started to change were determined for the different RH and AV levels and different exposure times. Results showed that IPt under long exposure time for RR (first indicator) varied between 18.9 and 25.5°C but was between 20.1 and 25.9°C for RT (a delayed indicator). The IPt for both RR and RT decreased with higher RH levels, whereas IPt increased with higher AV for RR but gave a minor change for RT. The ST was positively correlated with ambient T and ST was not affected by RH but significantly affected by AV. For RR, all IPt was lower under long exposure time than under short exposure time. The combination of higher RH levels and low AV level negatively affected dry matter intake. Water intake increased under all treatments except RH_l-AV_l. Treatment RH_h-AV_l negatively affected milk protein and fat yield, whereas treatments RH_m-AV_m and RH_m-AV_h reduced milk fat yield. We concluded that RH and AV significantly affected the responses of RR, RT, ST, and productive performance of high-producing Holstein cows. These responses already occurred at moderate ambient T of 19 to 26°C.     

醒发温湿度对馒头感官评定影响

选择对馒头醒发起关键作用两个关健因素:温度和相对湿度,以感官评分作为指标,找出较佳醒发温度和醒发相对湿度;结果表明,馒头醒发时最佳条件为:醒发温度40℃,醒发相对湿度85%。     

环境湿度对植物蛋白膜的影响研究

研究了环境湿度对小麦蛋白膜、大豆蛋白膜以及小麦-大豆复合膜机械性能、通透性等的影响。结果表明,由于蛋白腹为亲水性膜,受环境湿度的影响,其水分含量、分子间作用力有所不同,从而导致蛋白膜的机械性能、透湿性和吸湿率也随之发生变化。膜的阻止水蒸汽渗透的能力下降,吸湿率降低,透氧率呈上升趋势。     

基于Fortran程序的储粮通风温度和水分变化的模拟研究

小麦储藏过程中,温度和水分是安全储粮的关键因素。迄今为止,相关研究人员设计了多种数学模型来预测通风过程中小麦堆的温度和水分,然而这些模型一般需要占用大量的内存且计算周期很长。基于局部热质平衡原理采用Fortran程序设计了一套新的数学模型,有效地解决了以上问题,并且首次提出R值,使水分传递更加接近实际情况,通过与实验结果的比较,验证了该模型的准确性与可行性,对以后指导安全储粮具有非常重要的意义。