Dynamic Optimization of Dehydration Processes: Minimizing Browning in Dehydration of Potatoes

A simulation-optimization procedure based on the complex method was used to determine optimal drying schemes for minimizing browning during dehydration of white potatoes. Browning kinetics were obtained from the literature, and the heat and mass transfer characteristics of the potatoes were based on experimental data obtained previously. The optimal dryer temperature control path reduced the temperature while the sample disk moisture content was in the range 0.1–0.2 g/g-solids, where the browning rate is maximal. Excellent agreement was obtained between optimal dryer temperatures based on local moisture and those based on average moisture contents.     

Dehydration of carrots.

The effect of blanching, sulphiting, starching, freezing and sucrose and sodium
chloride dipping before air drying on moisture transport during carrot cube dehydration was studied. The results, interpreted in terms of existing theories combined with physical considerations, provide evidence that factors such as blanching, freezing and sucrose dipping affect moisture transport and product quality.     

蓖麻油催化脱水研究

以NaHSO4为催化剂，NaHSO3为助催化剂，在减压下对蓖麻油催化脱水进行了研究。考察了反应温度、反应时间、催化剂用量、助催化剂用量、真空度对脱水反应的影响。利用正交实验得出的最佳工艺条件为：反应温度250℃、反应时间50min、催化剂用量1．0％、助催化剂用量0％、真空度690mmHg。在该工艺条件下制得的脱水蓖麻油平均碘值达到136，且色泽较浅。     

Catalytic Infrared Dehydration of Onions

ABSTRACT:  Dehydrated onions are commonly dried with convection heating, which is inefficient and costly. This study compared the drying and quality characteristics of onion dried with catalytic infrared (CIR) heating and forced air convection (FAC) heating. Sliced high-solids onions were dehydrated under 9 conditions: CIR heating with and without air recirculation, and FAC each operated at 60, 70, and 80 °C. In general, CIR both with and without air recirculation had higher maximum drying rates, shorter drying times, and greater drying constants than FAC at moisture contents greater than 50% (d.b.). Dried onion quality, measured as pungency degradation, was similar for both the drying methods at 60 and 70 °C. The color analysis showed better product color (whiter and less yellow) at lower temperatures for CIR and higher temperatures for FAC. The browning could have been caused by the higher surface heat flux of the CIR heating and longer process times of FAC drying. Aerobic plate counts and coliform counts were not significantly different for either product from the CIR or FAC drying. However, samples dried by the CIR had significantly lower yeast and mold counts than those dried by the FAC. It is recommended that CIR be used in the early stages of onion drying.     

Heats of Dehydration of Starch Gels

Integral heats of dehydration have been measured by simultaneous differential thermal analysis (D.T.A.) and thermogravimetric analysis (T.G.A.) for gels of wheat starch. The results are interpreted on the basis that removal of water involves three structural changes: (a) Breakdown of starch-water interaction (endothermic); (b) Breakdown of water-water interaction (endothermic); (c) Increase in starch-starch interaction (exothermic). On balance, the overall process is endothermic. It has also been shown qualitatively that the formation of gels from starch and water is an endothermic process. It is suggested that the energy required to disrupt the structure of the starch granules during gelation is greater than the energy released by increased starch hydration.     

微波生产咸干花生的失水特性及工艺优化

采用微波干燥技术代替传统加热烘烤,研究不同微波功率、载物量条件下花生果的失水特性,结果显示,花生果样品在微波干燥条件下的失水特性表现为两个阶段,即出现两个失水高峰,出现高峰的时间、最大失水速率随载物量、微波功率不同而不同。以微波功率、载物量、微波时间为3因素,咸干花生果终产品的失水速率、耗电量、感官评定为3指标,根据Box-Benhnken中心组合试验设计原理,利用Design expert7.0.1软件分析优化微波生产咸干花生的工艺条件并建立回归模型。结果表明:微波功率、载物量、微波时间对失水速率和单位耗电量均有极显著的影响,载物量对产品感官评定有显著的影响;优化的最佳工艺条件为:微波功率800W、载物量54.25g、微波处理时间3.5min,此时失水速率为5.79g/min,单位耗电量为0.76kW·h/kg,感官评定为9.17分。     

Dehydration Artefacts in Gelatinized Starches

Scanning electron microscopy of swollen starch granule systems is valuable for interpretation of structural changes, but the results obtained must be interpreted with caution. The two major drying systems used, solvent exchange and lyophilization, both produce artefacts but of different types. The presence of pores on specimens prepared by lyophilization has often been interpreted as a true feature of the granule structure, but our experience suggests that this is incorrect. Furthermore, we consider that the fibrillar structure present in preparations of lyophilized starch solubles results from ice crystal formation effectively concentrating, in the remainder of the solution, solute which is subsequently preserved as a dry web.     

蓝莓渗透脱水的研究

在不同的渗透温度 ( 4 5～ 65℃ )条件下 ,高果糖浆和蔗糖的有效水分扩散率 (Dm)分别为( 4 90 60～ 5 2 3 66)× 1 0 - 10 m2 /s和 ( 3 5 5 1 8～ 4 0 1 0 9)× 1 0 - 10 m2 /s,有效固形扩散率 (Ds)分别为( 2 7740～ 3 691 5 )× 1 0 - 10 m2 /s和 ( 1 3 1 63～ 2 691 5 )× 1 0 - 10 m2 /s的规律。在渗透脱水处理过程中Dm 和Ds 随处理温度升高而增加。经高果糖浆 ( 70°Brix)渗透脱水的蓝莓的平均体积比随温度升高而稍微下降。其相对密度随温度的升高也略有增加     

脱水蓖麻油的研究

研究了脱水蓖麻油的制取中,催化剂 Ｃｕ Ｓ Ｏ４, Ｈ３ Ｐ Ｏ４ , Ｎａ Ｈ Ｓ Ｏ４ 的催化效果及助剂 Ｎａ Ｈ Ｓ Ｏ３ 对防止副产物发生,提高产品质量的作用,并通过条件优化得到了以 Ｎａ Ｈ Ｓ Ｏ４ 为催化剂的最佳工艺条件,产品最终指标符合美国 Ａ Ｓ Ｔ Ｍ 标准。     

Dehydration of membrane-coated foods by osmosis

Preliminary studies have shown that pieces of fruit, meat, fish, and whole shellfish can be dehydrated osmotically. Fifty percent invert sucrose was used as a solute; edible semipermeable membranes maintained osmotic differential and reduced solute contamination of the product. The greatest weight loss was observed with component items of high molecular weight such as meats and fish. Some of the products when re-hydrated show a marked similarity to the fresh food. Calcium pectate membranes gave the best results.     

Use of Ultrasound for Dehydration of Papayas

This work evaluated the production of dehydrated papayas (Carica papaya L.) with low sugar content. The product was obtained applying ultrasonic waves to enhance the loss of sugar from the fruit. To achieve this goal, this paper examined the influence of the ultrasonic pre-treatment before air-drying on dehydration of papaya. Ultrasonic pre-treatment for air-drying of fruits was studied and compared with osmotic dehydration. This study allowed estimate of the effective diffusivity water in the air-drying process for papayas submitted to ultrasonic pretreatment. Results show that the water effective diffusivity increases after application of ultrasound causing a reduction of about 16% in the drying time. During ultrasonic treatment the papayas lost sugar (13.8% in 30 min), so such a pre-treatment stage can be a practical process to produce dried fruits with lower sugar content.     

脱水菊花菜生产工艺关键技术研究

本试验根据菊花菜原料特性,对热风干燥脱水工艺中烫漂浸液pH值、烫漂温度、烘干温度时间组合等工艺关键技术进行单一因子对比试验,并设计脱水菊花菜干燥质量评分标准做为综合判断指标,确定添加碳酸氢钠调整烫漂浸液pH值为9,烫漂温度95℃,烫漂时间2.5miq,烘干温度时间组合为75℃(0.5h)→70℃(2h)→60℃(2h)→48(2h)的工艺效果较佳.脱水菊花菜成品呈墨绿色,短段卷曲状,具有浓郁的菊花香味,水分含量≤8%,保质期达到12个月以上,理化卫生指标均达到脱水蔬菜标准要求.     

蓖麻油催化脱水的研究

以硫酸氢钠为催化剂，亚硫酸氢钠为助剂对蓖麻油进行催化脱水，考察了催化剂、反应温度和反应时间对脱水效果的影响，采用正交试验法优化的脱水工艺条件为：反应温度为200℃，硫酸氢钠用量为1.5%，亚硫酸氢钠用量为1％，反应时间为2h。得到的脱水蓖麻油羟值低，而且色泽较浅。     

蘑菇渗透脱水规律的研究

对蘑菇片在糖溶液中的脱水规律进行初步的试验研究。通过多因素正交试验，得出影响蘑菇渗透脱水因素的主次顺序及因素间交互作用的关系；通过应用均匀试验，建立了蘑菇渗透脱水的回归数学模型，其理论值与实测值具有很好的一致性；利用回归模型，建立了不同条件下的渗透脱水规律预测表。     

Osmotic Dehydration of Tropical Fruits and Vegetables

Because of the microstructural complexity of plant tissue, osmotic dehydration cannot simply be explained as a pure osmotic process in which cell membranes act as a semipermeable barrier allowing water to pass through. Instead, osmotic dehydration is considered a process in which many simultaneous mechanisms, acting at different levels, are responsible for mass transport. Different compositional and structural profiles are induced in fruits and vegetables, depending on process variables and the tissue microstructure. Compositional-structural profiles that are developed with gas-liquid exchanges in the tissue during osmotic process have a significant impact on physical (optical), textural and chemical properties (e.g., flavour profile) of the final product, which is in part influenced by the differences in the number of cells that are altered and unaltered during the treatment. This review focuses on changes in the physical, chemical, and cellular structure of fruits and vegetables, some technologies commonly applied to increase mass transfer during osmotic dehydration (OD), potentials and industrial applications of OD, and the challenges of osmo-drying technology.     

干燥脱水法在肉类保藏中的应用

本文介绍了肉类保藏中常用的一种方法即干燥脱水法,其中包括干燥脱水法的原理、常用方式以及此法目前的应用现状,并在此基础上对干燥脱水法在肉类保藏中的应用前景进行了预测.     

Apple Pectic Gel Produced by Dehydration

A novel, flexible sheet-like food formed by the high methoxyl pectin–sugar–acid gelation during drying of apple puree was investigated to characterize drying-related properties. Product volume was reduced by 68% over the process, and this shrinkage was successfully modeled by assuming the volume reduction equal to the volume of water evaporated. The sorption isotherm at 25 °C was determined, and a new expression for the moisture content, W, as a function of water activity, a _w, of the type resulted as the most accurate for this J-shaped isotherm. The drying kinetics was studied at 50, 60, and 80 °C in a tray dryer. No constant drying rate period was found, and the drying curve was divided in high- and low-moisture zones. For high moistures, an internal–external mixed control diffusive model coupling mass and heat transfer was applied to obtain a mass transfer Biot number of 2.1. In the low-moisture zone, a diffusive, isothermal drying model for strict internal control was utilized. Diffusivities varied around 1 × 10–9 m²/s for high moistures and were about ten times lower at low moistures, although the activation energies were comparable (15,259 and 16,800 J/mol, respectively). The drying time at 60 °C was 6.67 h. The product scored four points out of five in a sensory evaluation of general acceptability.     

马铃薯淀粉的提取与直链淀粉的制备

为解决商品淀粉成本高的问题,以绵阳本地鲜马铃薯为原料,通过设计正交实验研究马铃薯淀粉提取工艺,以马铃薯淀粉得率为参考指标筛选出马铃薯淀粉提取最佳工艺参数为:粉碎时间2 min,静置时间3 h,洗涤次数3次。在最佳工艺条件下,鲜马铃薯的平均淀粉得率为13.5%。以国标法为基础,采用热碱法和正丁醇-异戊醇结晶法制备直链淀粉纯品,对其进行品质鉴定,结果表明实验室自制的直链淀粉可以作为标准品使用。