苦瓜切片干制及其复水性的研究

通过热风干燥、微波干燥以及热风结合微波干燥三种不同的干燥方式,得到干制的苦瓜切片,并对其复水性进行研究。干制的苦瓜切片复水的最佳条件为,采用微波干燥方法,切片厚度为0.5 cm,复水时用水量为250 m L,水浴温度为55℃,此时复水比为6.25。微波干燥最佳工艺条件为干燥功率800 W,切片厚度0.5 cm,干燥量20 g。这些可为苦瓜切片干燥工艺的改进提供一定的理论依据。     

藕片干制及复水性研究

就干制温度、藕片厚度和β-环糊精对藕片干制及其复水性的影响进行了研究,实验表明,温度在50-70℃,藕片厚度小于0.8cm,β-环糊精浓度大于10%时,干制藕片性状及复水性较好,并确定了最佳干制条件为厚度0.3cm,温度60℃,β-CD浓度15%。     

干制条件与β-CD处理对藕片干制及复水性的影响

就干制温度、藕片厚度和β-环糊精对藕片干制及其复水性的影响进行了研究,实验表明,温度在50～70℃,藕片厚度小于0.8cm,β-环糊精浓度大于10%时,干制藕片性状及复水性较好,并确定了最佳干制条件为厚度0.3cm,温度60℃,β-CD浓度15%。     

pH值与温度对乳粉复水性的影响

用乳粉代替鲜乳生产酸奶的过程中,乳粉复水性对酸奶的质构有很大影响。为考察乳粉复水性,研究了pH值和温度对乳粉复水性的影响。以乳粉黏度、粒径和溶解度等为考察指标,获得了乳粉复水的最佳的pH值和温度条件。结果表明,脱脂乳粉的复水性优于全脂乳粉,温度对乳粉的黏度、粒径和溶解度影响差异显著,通过寻优分析确定了工业乳粉复水性的最佳条件:pH值为6.8,温度55℃,此条件能够显著提高工业乳粉的复水性。     

气体射流冲击干燥猕猴桃片的复水动力学特性及数学模型

为了研究不同干燥条件和复水温度对猕猴桃片复水动力学的影响,实验监测了不同条件干燥猕猴桃片在相同复水温度下的吸湿曲线,并采用不同复水温度(30、50、70℃)对干制猕猴桃进行复水。此外,采用Peleg、Weibull、Proposed三个经典模型对干燥猕猴桃片的复水动力学进行拟合及验证。结果表明,干燥风温、风速以及喷嘴高度对产品的复水特性均有影响;复水速率随着风温、风速的增加和喷嘴高度的降低而增加。不同复水温度下,复水温度越高复水速率越快。Peleg、Weibull和Proposed模型均能有效描述猕猴桃干片的复水过程,其中Weibull模型具有最好的拟合度,其预测值与实验值呈良好的一致性,更适合于描述猕猴桃干片的复水动力学。     

干制工艺对胡萝卜复水性的影响

探讨了温度，热烫，切分形状等干制胡萝卜复水性的影响，试验表明，较低干燥温度，不热烫，纵切，厚度薄的胡萝卜复水性较好，经方差分析，差异显著（Ｐ＝０．０５）。     

皱皮木瓜真空冻干工艺优化及基于LF-NMR技术的复水特性研究

目的:对皱皮木瓜片的真空冷冻条件进行优化,研究木瓜片复水过程中水分状态变化。方法:采用单因素试验结合Box-Behnken响应面法,分别以复水比和色差值为指标,考察木瓜片厚度,真空冷冻干燥机的隔板温度以及真空度3个因素对冻干工艺的影响,优化皱皮木瓜片冻干工艺;利用低场核磁共振技术比较真空冷冻干燥和热风干燥的木瓜片成品复水过程中水分状态的变化情况。结果:确定皱皮木瓜真空冷冻干燥的复水比最佳工艺条件:木瓜片厚度4 mm,隔板温度40℃,真空度2.4 mbar;色差值最优的组合为:木瓜片厚度7.45 mm,隔板温度28.37℃,真空度2.02 mbar。NMR试验表明,复水过程中进入木瓜片中的水很快转化为不易流动水,结合水和自由水变化不大,且真空冷冻干燥的木瓜片中不易流动水增加较快,说明冻干比热风干燥的木瓜片品质好。结论:本研究结果为优化的皱皮木瓜真空冷冻干燥工艺参数,低场核磁共振技术可用于表征皱皮木瓜复水过程中水分状态的变化。     

罗非鱼片热泵干燥时间及品质影响因素的初步研究

对罗非鱼片在不同干燥条件下的工艺进行了研究。结果表明,干燥温度、风速以及鱼片的厚度都是影响热泵干燥罗非鱼片的重要因素。在干燥温度35℃,风速1．6m／s,厚度0．4～0．5cm的工艺条件下,产品的干燥速度较快,在复水时间50min时复水率最高。     

胡萝卜热泵干燥工艺优化

目的:优化胡萝卜的热泵干燥工艺。方法:在单因素试验基础上,通过Box-Behnken试验设计,以色差、复水比和β-胡萝卜素含量为指标,研究初始温度、干燥温升和切片厚度对胡萝卜干燥品质的影响。建立回归方程,分析3个独立因素之间交互作用对响应值的影响,得到胡萝卜热泵干燥的最佳干燥工艺参数以及在此条件下的预测值,最后通过实验与预测值进行对比验证,确定最佳参数组合。结果:胡萝卜热泵干燥的最优工艺参数为:初始温度54.1℃,干燥温升9.25℃,切片厚度3.8 mm,此条件下的胡萝卜色差值为9.759,复水比为6.196,β-胡萝卜素含量为34.378 mg/100 g,其干制品色泽呈鲜亮橙红色,复水比高,β-胡萝卜素保留量高。结论:响应面法可确定胡萝卜热泵干燥的最佳工艺参数,使胡萝卜干制品的品质最佳。     

真空冷冻干燥过程对脱水胡萝卜品质的影响

为了满足我军对军用食品营养和品质的特殊需求,文中采用真空冷冻干燥技术对营养价值较高的胡萝卜进行加工,并对其冻干工艺参数进行研究。复水性能的好坏和颜色的变化是衡量冻干食品品质最重要的指标,文中研究了干燥过程中对复水性有较大影响的冷冻温度和加热温度。通过对胡萝卜冻干产品的冻干曲线,感官及复水率进行比较得出:冷冻过程决定冻干物料中的冰晶形成速度和大小,胡萝卜所需冷冻温度为—40℃左右,时间大约为2h;加热过程决定冻干物料中冰晶的升华,加热板温度设置为—20℃30min、0℃3h、20℃2 h、50℃3h4个梯度,所得产品品质最佳。     

Rehydration properties of dried onion

Abstract

The effect of pretreatment preceding convective drying and the mode of drying on reconstitution properties of dried onion was investigated. Soaking in water, dipping in starch solution and osmotic dewatering were used as pre‐drying treatments. Convective drying at 60, 70, and 80°C, infrared drying and convective drying assisted with microwaves were applied to remove water from raw onion. Rehydration was done in water at room temperature and in boiling water. In general amount of absorbed water and increase in mass during rehydration, both were higher for pretreated material than those observed with dried raw onion. The mode of drying seemed to affect the course of rehydration of dried onion, and to improve its reconstitution properties. However, this was observed at room temperature rehydration only. Pre‐drying treatment followed by convection drying affected much stronger reconstitution properties of dried onion than the mode of drying.     

复水温度对香菇复水特性及品质的影响

香菇是中国产量最高和市场消费量最大的食用菌。干制是香菇的主要加工方式,而干香菇需复水后才能作为原料被烹调或进一步加工。本研究将热风干燥的香菇分别在25,45,65℃和85℃下复水,研究香菇复水过程中复水比、外观、质构和风味品质的变化。结果表明,在45℃复水270 min,干香菇吸水后表面的褶皱较为舒展,微观结构显示其菌丝恢复膨胀且伸展。同时,其复水比稳定保持在3.88,剪切力(1 290.28 g)、弹力(0.66 g)和复原力(0.34 g)适中,咀嚼性(656.02 g)最大,说明香菇复水完全且质地柔软适中,易被切开。此外,45℃复水香菇所含特征含硫化合物的含量较高,以1,2,3,5,6-五硫杂环庚烷(67.02%)和1,2,4-三硫环戊烷(39.06%)为主,风味较浓郁。综上,复水温度显著影响香菇复水后的食用品质,将干香菇在45℃复水270 min可获得品质较好的复水香菇。     

Rehydration characteristics of freeze-dried tropical fruits

Rehydration behaviours of five freeze-dried fruits, namely, pineapple, mango, guava, acerola and papaya were investigated and related to the structural changes during drying and glass transition temperature. After freeze-drying performed under vacuum conditions (13 kPa) and initial sample temperature near to −30 °C, fruits were allowed to rehydrate at 25 °C in distilled water for 6 h. The Exponential, Peleg and Weibull equations were applied to fit the experimental data using non-linear regression analysis. The statistical criteria used to evaluate the goodness of fit of each equation were the coefficient of determination (R²), the standard error of estimate (SEE) and the mean relative percentage deviation modulus (MRD). The Weibull equation was found to be the most adequate for describing the rehydration kinetics, since it gave the higher R² values and lower SEE and MRD values for all fruits examined in this study. From indices that take into account the quantity of water absorbed and the losses of solutes, it was possible to fully characterize the rehydration process of the freeze-dried fruits. Their water uptake capacity was affected not only by injuries during moisture removal but also by structural collapse induced by the rehydration process itself, which was explained using the glass transition concept.     

Rehydration properties of dried plant tissues

Apples, carrots and potatoes cut in cubes were dried by convection and then subjected to rehydration in water at room temperature. Mass and volume changes were followed during rehydration. A minimal displacement gauge was used to record changes of height of individual cubes during wetting. Porosity of the dried material was calculated and its changes during rehydration were observed. Comparing volume increase with mass gain during rehydration it was found that the mechanism of water imbibing is strongly influenced by porosity and chemical composition of the dried material. Dried apple was very porous, hence its mass gain was much faster than the volume increase. On the other hand, gelatinised starch in dried potato strongly absorbed water and the volume increase outpaced the mass gain. Recording changes of height of the dried cubes upon rehydration evidenced phase changes and injury incurred to the tissue structure by dehydration. In apple a collapse of structure was observed, while potato cubes swelled from the very beginning of the wetting process. In carrot instantaneous changes of height of the cube were observed, which could be due to relaxation of shrinkage stresses and displacements of injured tissue structures.     

Rehydration kinetics of vacuum-dried Salicornia herbacea

Rehydration kinetics of Salicornia herbacea prepared by vacuum drying at 70 or 80°C was studied at water temperature of 30, 60, and 90°C, respectively. A 2-term 5-parameter exponential decay model was used to describe the rehydration process. The rehydration times for the S. herbacea to reach maximum water absorption (t _M ) at each rehydration condition varied depending on the rehydration temperature and the drying air temperature. The inverse of the time (1/t _M ) showed linear temperature dependency as described by the Arrhenius-type relationship. The activation energy values for the S. herbacea dried at 70 and 80°C were 17.66 and 21.06 kJ/mol, respectively.     

Rehydration of Freeze-Dried Cultures of Lactic Streptococci

Cell suspensions (0.2 ml each) of three lactic streptococci were freeze-dried from distilled water. In order to determine the optimum conditions of rehydration the effect of different factors such as composition, temperature, and pH of rehydrating media on viability of the freeze-dried cells of the lactic streptococci has been studied. Rehydration of freeze-dried cells with 10% solution of dextrose, sucrose or reconstituted skim milk at pH 6.5 and 22°C can be recommended as optimum conditions for maximum recovery of viable cells.     

Rapid Rehydration Methods for Dried Beans

Rapid methods of rehydrating dried kidney, pinto or navy beans by soaking at 82°C or 93°C for 5, 10 or 30 min were compared to standard 18 hr soaking at ambient temperature. Canned beans processed 21 min at 121°C had higher drained weights and softer texture with fewer split beans than those processed 41 min at 116°C. Kidney, pinto and navy beans soaked 30 min at 82°C had higher drained weight than those soaked 30 min at 93°C. Hydration coefficient (2.07) of controls (18-hr soak) and beans soaked 82°C (1.94) or 93°C for 30 min were not different. Pre soaking 30 min at 82°C provided adequate rehydration prior to canning.     

牡蛎冷冻干燥后复水特性及微观结构的研究

研究牡蛎冷冻干燥后的复水特性,将新鲜牡蛎分为直接冻干组(Fresh+FD组)、预煮处理后冻干组(Boiled+FD组)和自然干燥组(Fresh+ND组),考察干燥后牡蛎的干燥比、复水比、复水率和微观结构的差异。结果表明:两冻干组牡蛎的含水量远低于自然干燥组,在常温和沸水中的复水比和复水速率均大于自然干燥组,冷冻干燥更有利于牡蛎中水分的去除和复水;干燥后牡蛎闭壳肌微观形态优劣程度依次为Fresh+FD组>Boiled+FD组>Fresh+ND组,其中Fresh+FD组闭壳肌纤维细长、舒展,间隙均匀,Fresh+ND组闭壳肌纤维束堆叠,组织致密;常温复水80min,两冻干组牡蛎的复重系数和复水率均高于自然干燥组。     

Modeling Rehydration of Porous Biomaterials: Anisotropy Effects

ABSTRACT Based on the dynamics of capillary flow in partially saturated-porous media, a finite element model is developed to predict the infiltration of water into porous biomaterials, taking into account anisotropy effects. The model is formulated on the physically-based constitutive relationships of water activity and conductivity. These constitutive properties depend on temperature, moisture, and microstructure. This is in contrast to the constant transfer properties used in previous models developed for food materials. Rehydration of black leaf tea Assam has been simulated. The prediction agreed well with the experimental data of NMR measurements. The hydration rate from cut-edges is 45 to 200 times faster than that from top to bottom surfaces.