不同壁材对超声波喷雾-冷冻干燥制备香味缓释微胶囊的影响

为研究不同微胶囊壁材包埋挥发性风味物质的差异,使用超声波喷雾-冷冻干燥技术制备微胶囊,并采用冷场发射扫描电子显微镜、电子鼻和顶空固相微萃取-气相色谱-质谱技术,评价7种常见壁材制备的微胶囊表观形态及包埋缓释32种挥发性风味物质的能力。结果显示,不同壁材对不同挥发性物质的包埋能力呈现一定的选择性。总体而言,β-环糊精包埋能力更强,且对挥发性物质的包埋率和释放量普遍更高,可作为较理想的包埋壁材。挥发性物质经β-环糊精包埋后,当孵育时间达到30 min时,电子鼻雷达图中风味释放轮廓与未包埋样品相近,表明本研究所制得的微胶囊具有良好的风味缓释效果。研究结果为食品领域使用微胶囊化产品增强风味和提高风味稳定性提供了理论依据。

鲜南瓜片冷冻-真空干燥工艺优化

为了优化鲜南瓜片冷冻-真空干燥工艺,通过Design-expert软件的Central Composite Design方法设计,研究冷冻后原料含水率、真空干燥温度和真空脱水时间对产品含水量、膨化度、色泽的影响,在此基础上由试验数据推导出描述三个响应值的二次回归模型,并对变量进行响应面分析。结果表明:南瓜冷冻后原料含水率、真空干燥温度、真空脱水时间对南瓜脆片的含水率、膨化度、色差值均有极显著的影响。得出非油炸南瓜脆片最佳冷冻-真空干燥工艺条件为:冷冻后原料含水率70%,真空干燥温度为90℃,真空脱水时间为120min。该研究为开发休闲食品南瓜脆片的产业化生产提供理论依据。

热风-真空冷冻联合干燥对脆性龙眼果干品质及益生活性的影响

[目的]研究热风-真空冷冻联合干燥对脆性龙眼果干品质及益生活性的影响,为高品质龙眼果干工业化节能干燥模式提供理论依据.[方法]以热风干燥、真空冷冻干燥龙眼果干为对照,比较分析热风-真空冷冻联合干燥对脆性龙眼果干水分含量、水分活度、皱缩率、复水比等理化特性和总糖、多糖等营养品质的影响.同时采用GC-MS测定风味物质变化,电量表测定能源消耗量.并选用植物乳杆菌和嗜酸乳杆菌发酵龙眼果干,比较发酵过程中活菌数、总糖、还原糖以及短链脂肪酸的变化,评价热风-真空冷冻联合干燥对龙眼体外益生活性的影响.[结果]热风-真空冷冻联合干燥龙眼果干的水分含量、水分活度和皱缩率显著低于热风干燥,而复水比显著高于热风干燥.在总糖、多糖含量以及挥发性风味物质种类和总量上,热风-真空冷冻联合干燥低于真空冷冻干燥而高于热风干燥.在能源消耗上,热风-真空冷冻联合干燥比真空冷冻干燥节约干燥时间12.16%,节约单位能耗25.40%.在益生活性方面,植物乳杆菌和嗜酸乳杆菌均能通过发酵龙眼干增加活菌数量,利用龙眼干中的总糖产生短链脂肪酸,降低发酵液pH,且益生效果受干燥方式和菌株种类的影响较大.当植物乳杆菌发酵热风-真空冷冻干燥的龙眼果干48 h后,活菌数生长最多可达12.40 lg cfu/mL,高于真空冷冻干燥、热风干燥和新鲜龙眼.嗜酸乳杆菌发酵48 h后,热风-真空冷冻联合干燥活菌数达11.84 lg cfu/mL,与真空冷冻干燥接近,低于热风干燥,但高于新鲜龙眼.[结论]热风-真空冷冻联合干燥结合了热风干燥和真空冷冻干燥两种干燥方式的特点,可以显著缩短干燥时间,节约能耗,提高干燥效率和果干品质.

蚕豆冷冻-真空干燥工艺的优化

为了优化蚕豆冷冻-真空干燥工艺,通过Design-expert软件的Central Composite Design方法设计,研究原料(冷冻)含水率、真空干燥温度和真空脱水时间对产品含水量、膨化度、色泽的影响,在此基础上由实验数据推导出描述3个响应值的二次回归模型,并对变量进行响应面分析,结果表明:蚕豆原料冷冻后含水率、真空干燥温度、真空脱水时间对蚕豆脆片的含水率、膨化度、色泽均有极显著的影响。得出蚕豆最佳冷冻-真空干燥工艺条件为:原料冷冻后含水率50%,真空干燥温度为85℃,真空脱水时间为120 min。

兰州百合冷冻-压差膨化干燥工艺优化

为有效解决市售百合干硬度大、适口性差的问题,开发兰州百合脆片生产新技术,筛选兰州百合片冷冻后的含水率、压差膨化干燥温度和压差膨化干燥时间为影响因子。以兰州百合脆片膨化产品的含水量、酥脆度、色泽为响应值,在单因素实验的基础上,采用Box Behnken试验设计构建二次多项式回归方程的模型,进行响应面分析,并利用扫描电子显微镜对兰州百合冷冻-压差膨化干燥前后的结构进行比较。结果表明:原料冷冻后的含水率、压差膨化干燥温度和压差膨化干燥时间对兰州百合脆片膨化产品的含水量、酥脆度、色泽的影响程度依次为冷冻后的含水率>压差膨化温度>压差干燥时间,兰州百合脆片冷冻-压差膨化干燥最佳工艺条件为:原料冷冻处理后干基含水率70%、压差膨化干燥温度65℃、压差膨化干燥时间120 min,在此条件下,加工的兰州百合脆片膨化产品的含水量为4.75%、酥脆度为1.78、色差值为10.63,产品外观形态及口感最佳;扫描电子显微镜显示,压差膨化干燥对兰州百合结构的影响较小,组织结构未发生皱缩、塌陷,冷冻-压差膨化干燥后的百合形态较好,该工艺可以获得品质较好的兰州百合膨化脆片产品。

超声喷雾-冷冻干燥制备高汤微胶囊粉体工艺优化

为开发新型高汤微胶囊粉体调味料,设计搭建了用于高汤粉体加工的超声波喷雾-冷冻干燥实验装置。通过扫描电镜分析和粒度分析,对雾化阶段进样体积流量、超声波功率、料液比、退火温度和时间等影响高汤微胶囊粉体包埋的5种因素进行了优化。以麦芽糊精为壁材,对高汤中的风味物质、滋味物质等进行包埋,经由超声波喷雾-冷冻干燥实验装置,制成微胶囊粉体。结果表明,通过对微胶囊粉体微观结构及粒度指标的分析,确定在进样体积流量3 mL/min、超声波功率3 W、物料固形物浓度5%,退火时间5 h,退火温度为-40℃时,所得到的微胶囊粉体的形态和粒度最好,粉体平均粒径23.11μm。

超声波喷雾-冷冻干燥与传统干燥技术制备高汤粉体的比较

以传统佛跳墙高汤为原料,分别采用超声波喷雾-冷冻干燥、真空冷冻干燥、喷雾干燥3种工艺制备高汤粉体。通过粉体理化性质和微观结构对比,结果显示超声波喷雾-冷冻干燥制备的粉体具有水分质量分数低(4.79%)、堆积密度小(102 mg/mL)、粒径小(平均粒径23.11μm)以及溶解性好的特点。超声波喷雾-冷冻干燥制备的粉体大多呈规则球型颗粒状,颗粒平滑、均匀、尺寸可控、多孔,有利于水分从颗粒内部向外扩散;冷冻干燥制备的粉体呈现多种状态,如针型、扁片型等;经喷雾干燥制备的粉体颗粒大都呈现扁球状。利用感官评定对不同干燥方式的样品进行气味的综合性比较,结果表明超声波喷雾-冷冻干燥样品综合评分8.8分,更符合未干燥传统高汤的风味标准。顶空固相微萃取-气相色谱-质谱联用考察不同干燥方式对高汤挥发性化合物的保留情况,结果表明超声波喷雾-冷冻干燥处理的样品检测出39种挥发性风味物质,其中醇类7种、醛类7种、酮类1种、酯类4种、杂环类8种和烷烃类12种,说明超声波喷雾-冷冻干燥制备的粉体能更好地保留高汤总体风味。

溶胶-冷冻干燥法制备La_(1-x)Ca_xCo_(0.8)Ni_(0.2)O_3及其性能研究

采用溶胶-冷冻干燥法制备了La1-xCaxCo0.8Ni0.2O3(x=0.1、0.2、0.3、0.4、0.5)催化剂。用X射线衍射(XRD)、比表面测定仪(BET)和扫描电子显微镜(SEM)等分析手段对催化剂的结构和形貌进行了表征,并探讨Ca2+掺杂对催化剂结构和催化活性的影响。结果表明,溶胶-冷冻干燥法可制得单一的钙钛矿型氧化物,最佳焙烧温度为600℃。Ca2+掺杂取代La3+后,当x≤0.3时,催化剂可形成单一的钙钛矿结构,x=0.4、0.5时,催化剂以钙钛矿相和CaO相共存。x=0.2、0.3时,催化剂对CO的催化活性最高(T100%=160℃)。

响应面法优化青椒微波-真空冷冻联合干燥工艺及品质分析

该研究采用微波-真空冷冻联合干燥方式对青椒进行干制,研究微波功率、中间转换点含水率及真空冷冻干燥时间对青椒干燥产品维生素C含量、感官评分、复水比及a*的影响。通过单因素试验和响应面试验优化微波-真空冷冻联合干燥工艺,并对青椒联合干燥产品的营养成分、风味进行了比较分析。最后研究了微波-真空冷冻联合干燥、微波干燥、真空冷冻干燥对青椒干燥品质的影响。结果表明,联合干燥的最佳工艺条件为微波功率381.17 W,中间转换点含水率61.81%,真空冷冻干燥时间12.04 h。3种青椒联合干燥产品在营养成分和风味上分别具有一定差异性。微波-真空冷冻联合干燥和真空冷冻干燥的青椒产品在质构、青椒组织微观结构、部分理化指标方面均优于微波干燥的青椒产品。

冷冻真空-热风联合干燥技术对金花茶花朵品质的影响

采用冷冻真空-热风联合干燥技术对金花茶花朵进行干燥,以微波干燥、冷冻真空干燥作为对照,对3种不同方法干燥的金花茶花朵的感官品质、内含成分、贮藏过程中品质变化、干燥效率等指标进行综合评价。结果表明:冷冻真空-热风联合干燥所制的金花茶花朵综合品质明显优于其他两种干燥工艺,并能较好地保留花朵中茶多酚活性成分,在室内常温下(18~22℃)贮藏时间长、不易变质,且干燥效率高于冷冻真空干燥。

一种新型水溶性单体聚合-冷冻干燥联用法在饱水木质文物脱水定型应用中的研究

为了改善饱水木质文物脱水定型技术保护的定型效果、操作周期以及环保经济性,本研究以田螺山遗址、河姆渡遗址和茅山遗址出土的3种饱水木材试样为实验对象,进行了以水溶性单体丙烯酰胺(AM)和N-乙烯基吡咯烷酮(NVP)为反应物的单体聚合-冷冻干燥联用法的研究。首先在水体系中选取不同比例的AM和NVP在水溶液中聚合,并根据聚合和冷冻前后的体积变化率控制在±5%以内的标准进行聚合体系的筛选。然后选取其中5组符合条件的聚合体系对3种饱水木材进行脱水定型处理,当在聚合体系中AM和NVP的质量分数总和不高于7.5%时,经单体聚合-冷冻干燥联用法处理后的试样的尺寸变化率可控制在±5%以内,达到良好的脱水定型的效果。

溶胶-凝胶-冷冻法制备纳米TiO2及其表征

为解决纳米TiO2粉体易产生团聚的问题,采用溶胶-凝胶与冷冻干燥法制备纳米TiO2粉体.通过X射线衍射、扫描电子显微镜和紫外分光光度计对纳米TiO2粉体的物相组成、形貌和光催化活性进行了表征.实验结果表明:在400℃下所制得的TiO2纳米粉体的粒径约为6 nm,且粒度分布均匀,呈球形;所制得的TiO2纳米粉体在投加量为2 g/L时可使质量浓度为20 mg/L的甲基橙溶液在2.5 h内几乎全部降解.溶胶-凝胶与冷冻干燥法再结合阶段升温焙烧法可得到分散性好、粒径小和光催化活性好的粉体.

国内外果蔬联合干燥技术的研究进展

阐述了联合干燥的定义和技术特点,介绍了各种联合干燥方式在国内外的研究和应用现状,探讨了该技术在果蔬干燥加工中存在的问题和应用前景.

制作工艺及干燥方法对速食小米粥品质的影响探究

对速食小米粥的制作工艺进行探究,通过正交实验确定了最佳工艺参数,并对其干燥方法进行了比较分析。结果表明:单甘脂与β-环状糊精添加比为3 g/kg∶5 g/kg,浸泡温度为55℃,浸泡时间为40 min,蒸煮时间为10 min是速食小米粥的最佳制作参数;冷冻辅助热风-微波干燥法是制备速食小米粥的最佳干燥方法,具体为:先在-20℃条件下冷冻20 h,再置于80℃热风干燥40 min,最后用240 W微波处理5 min。此方法能明显提高复水性,复水时间为6.5 min,产品感官品质达到最优。

Preparation of highly dispersed iron species over ZSM-5 with enhanced metal-support interaction through freeze-drying impregnation

Supported metal catalysts play a vital role in the chemical industry, and the metal-support interaction is an important property of the catalyst. However, in the traditional impregnation method, it is difficult to obtain sufficient metal-support interactions owing to the mobility of the metal precursor during evaporation drying. Here, freeze drying is applied during impregnation instead of evaporation drying for enhancing the metal-support interactions. 57 Fe ZSM-5 was chosen as a representative catalyst. A quantitative analysis was conducted based on Mossbauer spectroscopy. Compared with traditional evaporation-drying catalyst, freeze-drying catalyst has stronger metal-support interactions. In addition, more iron species are confined in the channel and smaller metal sizes and less diversity are obtained. The compositional change is also proved because of the superior performance of the freeze-drying catalyst during N2O decomposition. This method can be extended to other supported metal catalysts prepared through an impregnation method, which can be used to tune the metal-support interactions and metal sizes.

Optimizing the Chemical Compositions of Protective Agents for Freeze-drying Bifidobacterium longum BIOMA 5920

Freeze drying has a deleterious effect on the viability of microorganisms. In front of this difficulty, the present study adopts response surface methodology to optimize the chemical compositions of protective agents to seek for maximum viability of Bifidobacterium longum BIOMA 5920 during freeze-drying. Through the compara- tive analysis of single protectant, the complex protective agents show better effect on the Bifidobacterium viability. Human-like collagen (HLC), trehalose and glycerol are confirmed as significant factors by Box-Behnken Design. The optimized formula for these three variables is tested as follows: HLC 1.23%, trehalose 11.50% and glycerol 4.65%. Under this formula, the viability is 88.23%, 39.67% higher in comparison to the control. The viable count is 1.07×10 9 cfu·g-1 , greatly exceeding the minimum viable count requirement (10 6 cfu·g-1 ).

Numerical investigation on freeze-drying of aqueous material frozen with pre-built pores

Freeze-drying of the initially porous frozen material with pre-built pores from liquid material was found experimentally to save drying time by over 30% with an initial saturation being 0.28 compared with the conventional operation with the initial saturation being 1, using mannitol as the solid material. In order to understand the mass and heat transfer phenomena of this novel process, a two-dimensional mathematical model of coupled mass and heat transfer was derived with reference to the cylindrical coordinate system. Three adsorption–desorption equilibrium relationships between the vapour pressure and saturation value namely, power-law, Redhead's style and Kelvin's style equation, were tested. Kelvin's style in exponential form of adsorption equilibrium relation gave an excellent agreement between the model prediction and experimental measurement when the equation parameter, γ, of 5000 was applied. Analyses of temperature and ice saturation profiles show that additional heat needs to be supplied to increase the sample temperature in order to promote the desorption process. Simulation also shows that there is a threshold initial porosity after which the drying time decreased with the increase in the initial porosity. Enhanced freeze-drying is expected to be achieved by simultaneously enhancing mass and heat transfer of the process.

Optimization of Protectant, Salinity and Freezing Condition for Freeze-Drying Preservation of Edwardsiella tarda

Novel preservation condition without ultra-low temperature is needed for the study of pathogen in marine fishes. Freeze-drying is such a method usually used for preservation of terrigenous bacteria. However, studies using freeze-drying method to preserving marine microorganisms remain very limited. In this study, we optimized the composition of protectants during the freeze-drying of Edwardsiella tarda, a fish pathogen that causes systemic infection in marine fishes. We found that the optimal composition of protectant mixture contained trehalose(8.0%), skim milk(12.0%), sodium citrate(2.0%), serum(12.0%) and PVP(2.0%). Orthogonal and interaction analyses demonstrated the interaction between serum and skim milk or sodium citrate. The highest survival rate of E. tarda was observed when the concentration of Na Cl was 10.0, 30.0 and between 5.0 and 10.0 g L^(-1) for preparing TSB medium, E. tarda suspension and protectant mixture, respectively. When E. tarda was frozen at-80℃ or-40℃ for 6 h, its survival rate was higher than that under other tested conditions. Under the optimized conditions, when the protectant mixture was used during freeze-drying process, the survival rate(79.63%–82.30%) of E. tarda was significantly higher than that obtained using single protectant. Scanning electron microscopy(SEM) image indicated that E. tarda was embedded in thick matrix with detectable aggregation. In sum, the protectant mixture may be used as a novel cryoprotective additive for E. tarda.

Technological Study on Instant Date Powder in Natural Ziziphus jujuba through Vacuum Freeze-drying

[Objective] The aim was to get optimized conditions for date powder with good color and taste.[Method] The pectinase enzymolysis and vacuum freeze-drying technology were used in the extract process of date powder.[Result] The production boasts of superior quality were with rich fragrance and uniform particle under certain process conditions.The optimized conditions for pectinase enzymolysis were:the amount of pectinase reached to 0.1% of that of date syrup,enzymolysis temperature and time were 50 ℃ and 50 min respectively,the pH value was 4.0.The optimized conditions for vaccum freeze-drying were:10% altodextrin,three times volumn of water with the thickness of 7 mm.[Conclusion] The optimized conditions were obtained in this study to produce instant date powder from Ziziphus jujuba.