Viability of Two Freeze-dried Strains of Bifidobacterium and of Commercial Preparations at Various Temperatures During Prolonged Storage

ABSTRACT: Viability of bifidobacteria in freeze-dried probiotic products at various temperatures during prolonged storage was assessed. Bifidobacterium longum 1941 and B. longum 536 were freeze-dried and capsules were manufactured. Five commercial probiotic capsule products were also tested. The capsules were stored at -18 °C, 4 °C, and 20 °C. Cell counts were enumerated using MRS-NNLP agar at 37 °C for 72 h under anaerobic conditions at 0, 1, 2, 5, and 8 mo (commercial capsules) and at 0, 1, 2, 5, 8, 11, 14, 17, and 20 mo (laboratory capsules). Storage at 20 °C showed the greatest decline in the viability of bifidobacteria, whereas that at -18 °C showed the least decrease.     

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.     

Design of polymeric nanoparticles and its applications as drug delivery systems for acne treatment

Objective: The aim of this study was to evaluate a formulation made of poly(lactide-co-glycolide) (PLGA) nanoparticles containing azelaic acid for potential acne treatment.

Methods: Azelaic acid-loaded PLGA nanoparticles were prepared by spontaneous emulsification processes using poloxamer 188 as stabilizer. Several manufacturing parameters such as stirring rate, concentration of stabilizer and different recovery methods were investigated. Nanoparticles were evaluated in terms of size, zeta potential, encapsulation efficiency, release kinetics and permeation kinetics in vitro. Furthermore, in vitro toxicological studies were performed in Saccharomyces cerevisiae model.

Results: The results showed that by adjusting some formulation conditions it was possible to obtain nanoparticles with high loading and a controlled drug release. Freeze-dried recovery altered the nanoparticles structure by enhancing porous structures and mannitol was required to control the mean particle size. The centrifugation recovery was found to be the best approach to nanoparticles recovery. Similar toxicity profiles were observed for both drug-free and azelaic acid-loaded nanoparticles, with concentration-dependent decreases in cell viability.

Conclusion: These results indicate a potential formulation for controlled release delivery of azelaic acid to the follicular unit.     

甲醇、戊二醛交联剂对丝素蛋白/明胶多孔支架的性能影响

为了对比甲醇、戊二醛两种交联剂对丝素蛋白/明胶复合多孔支架的性能影响,采用冷冻干燥法等比例制备该支架,分两组分别用甲醇和戊二醛进行交联。通过观察支架的微观形貌,测量支架的孔隙率、吸水率、溶胀率,测试热稳定性及力学性能,比较经两种交联剂处理后支架结构和性能的变化。结果表明,经戊二醛交联后的支架孔隙分布更加规则、均匀,孔隙率、吸水率、溶胀率更高,力学性能更强。采用戊二醛交联丝素蛋白/明胶复合多孔支架,能够使支架性能更加优良。     

不同品种红枣冻干品质研究

选取木枣、梨枣、骏枣等六个品种的红枣进行真空冷冻干燥加工，然后对其冻干品的酸甜度、酥脆度、感观、苦涩味、焦味等五项指标，利用模糊矩阵法进行综合评价，将其结果进行归一化排序。结论是干制品种优于鲜食品种。     

真空冷冻干燥技术的应用研究

简要介绍真空冷冻干燥技术的原理、操作步骤和特点,对真空冷冻干燥技术在医药工业、食品工业、生物材料和新材料方面的应用与发展状况作一综述。     

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.     

冷冻干燥法在水电站中压气系统中的应用

主要分析在水电站工程中，中压压缩空气系统供气对象的变迁，中压压缩空气干燥方法的选择．着重对热力干燥法和冷冻干燥方式进行必要的比较，希望引出对水电厂中压气干燥方式的探讨和思考。     

青蒜真空冷冻升华干燥技术的研究

本文主要研究了青蒜的真空冷冻升华干燥的工艺流程。并通过对物料冻干曲线的分析，从真空度、物料体积的大小和预冻速度等方面探讨了对冻干速率和冻干成品品质的影响，还测定了冻干品的复水性、得率等。研究发现在一定范围内，真空度越低，冻干速率越慢。物料体积的大小，会影响物料的冻干速率。物料不能太厚，也不能太薄，应在保证质量的前提下，选择一个能耗最低的物料厚度。青蒜冻干的得率为10．55％。青蒜冻干产品的复水率为85％～87％。     

Effect of stabilisation treatment of rice bran on functional properties of protein concentrates

The functional properties of differently dried protein concentrates prepared from unstabilised, acid-stabilised, heat-stabilised and parboiled rice bran were evaluated. Freeze-dried protein concentrates from all types of bran exhibited similar nitrogen solubilities. Both cabinet-and roller-dried protein concentrates had lower nitrogen solubilities than freeze-dried samples except for cabinet-dried concentrate from heat-stabilised bran. The functional properties (bulk density, water and fat absorption, emulsification and foaming capacity) of protein concentrates prepared from acid-stabilised rice bran were not significantly different from those prepared from untreated bran. Freeze-dried protein concentrates from both heat-stabilised and parboiled rice bran had low water absorption capacity and high fat absorption capacity. Cabinet-dried samples did not exhibit any foaming or emulsification capacity, thereby indicating a greater extent of denaturation. Thus, the study indicated that in addition to stabilisation treatment functionality was also influenced by the drying technique employed.