Retention of Antioxidant Capacity of Vacuum Microwave Dried Cranberry

ABSTRACT: In this study, cranberries were dried by vacuum-microwave drying (VMD), freeze-drying (FD), or hot air-drying (AD), to compare the effects of different drying processes on both physical changes as well as the retention of bioactive components in dried samples. Total porosity (%) and average pore radius of dehydrated cranberries were greater using VMD compared to FD and AD (P < 0.05). Crude methanol cranberry powdered extracts were fractionated by solid phase extraction (SPE) into organic acid-, total phenolics-, anthocyanin-, or proanthocyanidin-enriched extracts, respectively. The chemical composition of the 60% acidified methanol fractions contained cyanidin-3-galactoside, cyanidin-3-arabinoside, peonidin-3-galactoside, and peonidin-3-arabinoside, as assessed by HPLC. Antioxidant activities of cranberry fractions were measured using chemical ORAC and ABTS methods. The 60% acidified methanol fraction had a significantly higher (P < 0.05) antioxidant potential than the other chemical fractions, which was largely attributed to the relatively higher anthocyanin content. In general, vacuum-microwave drying and freeze-drying resulted in similar retention of anthocyanins and antioxidant activity, which were both relatively higher (P < 0.05) than that recovered from cranberries dried by hot air drying.     

芦荟凝胶的真空冻干研究

为了对芦荟凝胶进行真空冷冻干燥,首先通过简单的电阻装置测定了芦荟凝胶的共晶点与共融点.然后按照一定的升温程序对芦荟凝胶进行了冻结与升华干燥,并得到了芦荟凝胶的真空冻干曲线.最后通过对真空冻干芦荟凝胶与喷雾干燥芦荟凝胶的指标测定,将两种加工方法下芦荟凝胶所含的矿物质、蛋白质、有机酸、外观等指标进行了对比,结果表明,真空干燥能较好地保持芦荟凝胶的生物活性与特征.     

A comparison of drying operations on the rheological properties of whey protein thickening ingredients

An existing procedure for the alteration of whey proteins into a cold‐set thickening agent was modified by developing a spray‐drying operation to replace the prohibitively expensive freeze‐drying step. The original and the modified derivatization procedures were used with a commercial whey protein concentrate (WPC). The freeze‐dried and spray‐dried derivatized WPC powders, along with polysaccharide thickeners, were reconstituted in water and evaluated by using a range of rheological studies. The effects of temperature, concentration, and shear on viscosity as well as the mechanical spectra were assessed to characterize the ability of the powders to function in food systems. Rheological characterization revealed the modified derivatization procedure yielded an ingredient having the same cold‐set thickening and gelling ability as the original derivatized powder. The modified whey proteins were also able to achieve, at higher usage levels, textural properties similar to several polysaccharide thickeners. Use of a spray‐drying technique created a more economical process for the production of a whey protein ingredient that was suitable for contributing viscosity and texture to a wide range of food systems.     

Comparison of Nonenzymatic Browning Kinetics in Spray-dried and Freeze-dried Carbohydrate-based Food Model Systems

ABSTRACT: Nonenzymatic browning (NEB) rates of amorphous, carbohydrate-based, freeze-dried and spray-dried food model systems containing L-lysine and D-xylose as reactants (5% w/w) were investigated at different temperatures (40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C). Samples were exposed to various relative vapor pressure levels (11%, 23%, and 33%) to adjust water contents. Water sorption was determined gravimetrically, and data were modeled using the Brunauer-Emmett-Teller and Guggenheim-Anderson-deBoer equations. Glass transition, T_g, was observed by differential scanning calorimetry. NEB was followed spectrophotometrically. The surface structures of freeze-dried and spray-dried models were observed by scanning electron microscopy. The freeze-dried samples and the spray-dried samples showed different surface structures and slight differences in thermal behavior. Crystallization of component sugars in the freeze-dried samples was slightly more delayed than in spray-dried samples. The glass transition temperatures in spray-dried samples were higher than those of the freeze-dried samples at the same water activity. The temperature dependence of NEB rate in both systems followed the Arrhenius kinetics, but the activation energies were different. Williams-Landel-Ferry equation could be used to model the NEB kinetics in the freeze-dried system, but for the spray-dried system, negative constant values were not within the allowable range.     

无糖型茅岩莓速溶茶的加工技术

以茅岩莓 (学名显齿蛇葡萄 )为原料 ,经提取、过滤、真空浓缩得茅岩莓浓缩汁 ,再配以其他原料经干燥而得茅岩莓速溶茶。研究表明 ,茅岩莓提取温度为 85℃ ,提取时间为 2 0min ,加水质量为 1 5倍时 ,所得提取液具有较高的得率和较好的品质 ;当茅岩莓速溶茶的配方为茅岩莓浓缩汁(3 0 % ) :麦芽糊精∶麦芽糖醇 :低聚果糖 :阿斯巴甜∶VC∶柠檬酸∶天然茶香精质量比为 3 5∶2 0∶3 0∶1 0∶0 7∶1∶1 3∶2时 ,采用低温冷冻干燥 ,所得茅岩莓速溶茶产品的溶解性和风味良好。     

芫荽真空冷冻干燥的研究

本文采用真空冷冻干燥技术,探讨了搁板温度、物料重量对芫荽冻干时间、品质及设备生产能力的影响。试验结果表明,搁板设置温度每提高10℃,冻干时间缩短15.68%以上,但温度过高芫荽风味下降,出现干草味;芫荽每增加100g/层,冻干时间延长2.5～3h左右。在温度40℃、芫荽重量400g/层条件下冷冻干燥,冻干时间为12.5h,产品质量优于单纯的真空干燥样品;复水后与新鲜芫荽相对较为接近。     

全营养冻干方便米饭的配方设计与研究

采用线性规划法(LP),结合SPSS进行配方设计,得到冻干方便米饭的最佳配方为:主食大米650 g;配菜分别为猪肉140.195 g(20.67％)、豌豆167.740 g(24.73％)、菠菜186.946 g(27.56％)、土豆96.184 g(14.18％)、带鱼47.749 g(7.04％)、绿油菜39.465 g(5.82％).结合真空冷冻干燥技术,从营养和感官两个角度与四川得益方便米饭和贵州伊妹方便米饭进行比较,对产品进行综合评价.结果表明,方便米饭配方产品较四川得益和贵州伊妹具有一定的优势.     

A STUDY OF VACUUM FREEZE-DRYING OF FROZEN WET PAPERS

Vacuum freeze-drying of frozen wet papers was investigated experimentally. A freeze-drying facility was built to study the process by monitoring the various physical parameters (pressure, sample temperature, heater temperature, water content of the sample and cold panel temperature). A simple phenomenological model was developed to explain experimental results. The values of the physical parameters were optimized to make the process cost effective.     

药品冷冻干燥过程的退火机理分析

运用热力学和动力学理论分析了药品冷冻干燥过程中的退火操作改变冻结药品结构的机理。通过对化学势随晶粒曲率半径变化、重结晶过程中冰晶半径随时间变化、非晶态基质的粘度随温度变化几个关系式的分析,得出退火温度必须要高于冻结药品的玻璃化转变温度;最佳退火持续时间与重结晶的速率紧密相关,且是退火温度的函数;退火后再冷却过程的冷却速率不影响升华干燥速率等结论。     

初始非饱和多孔物料对冷冻干燥过程的影响

提出了“初始非饱和多孔物料冷冻干燥”的思想,从实验上验证具有一定初始孔隙的非饱和多孔物料对液体物料冷冻干燥过程的强化作用。设计、加工和组装了一套实验室规模的多功能冷冻干燥装置。采用“液氮制作冰激凌法”,将以甘露醇为主要溶质的液体物料制备成具有不同初始孔隙的冷冻物料。对于相同质量和相同湿含量的非饱和冷冻物料,在相同的操作条件下,进行冷冻干燥实验,并与常规冷冻干燥相比较。结果表明,初始非饱和物料对冷冻干燥过程确实具有显著的强化作用。非饱和冷冻物料(初始饱和度0.28)的干燥时间比常规冷冻物料(初始饱和度1.00)能够节省36.4%。初始饱和度越小,干燥时间越短,干燥产品的含水率越低。