基于升华和解析干燥结束点杨梅冻干工艺优化

以东魁杨梅为研究对象,利用自制在线测量系统,实时测量和采集杨梅在冷冻干燥过程中的重量和温度及其变化曲线,对采集的数据进行分析,再结合杨梅冻干制品的吸湿率变化,判断升华干燥时间终结点,根据样品中心温度变化率或重量变化率趋于零时判断为解析干燥结束点。研究结果表明,杨梅冻干工艺优化条件为:杨梅共晶点平均温度-20.5℃,共熔点平均温度-17.7℃,升华干燥阶段搁板温度-20.0℃,升华时间30.0h,解析干燥阶段搁板温度50.0℃。该条件下生产的冻干杨梅色泽为紫红色,形态完整,质密松脆,具有杨梅的浓郁气味,便于贮藏。     

Freeze-drying and mechanical redispersion of aqueous PEDOT:PSS

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films are attracting famous applications in antistatic coating, energy storage and conversion, printed electronics, and biomedical fields due to their conductivity, optical transparency and flexibility. However, PEDOT:PSS has poor dispersion stability during long-term storage and transport. Moreover, the dried PEDOT:PSS films are insoluble in any solvent and cannot be redispersed again. In comparison to bake drying, here, a feasible strategy to achieve mechanically redispersed PEDOT:PSS with the help of freeze-drying process was reported. The redispersed PEDOT:PSS can recover not only the initial characters such as pH, chemical composition, viscosity, and particle size under similar solid contents, but also conductivity and surface morphology of treated films. In addition, the treated film exhibits self-healing properties similar to pristine film in terms of mechanical and electrical properties. This technology enables reuse and overcomes the technical problems of PEDOT:PSS dispersion, realizing real-time processing to meet variable applications.     

Influence of pressurised cryogenic nitrogen technology on Arthrospira platensis (spirulina) preservation during storage

In this study, preservation of spirulina using the new pressurised cryogenic nitrogen technology (PCN) was compared to classical methods used in laboratories and industry. Spirulina morphology was better preserved by PCN compared to unpressurised cryogeny and classical freezing at −20 °C that led to cells fragmentation. A 25% loss of Phycocyanin-C content against 60% were measured after 98 days storage for 6-Bar PCN process and frozen samples, respectively. The Total AntiOxidant Power (PAOT Liquid Technology^®) was used for determination of total antioxidant and oxidant power of spirulina extracts. PAOT value of PCN samples was 50% higher than the frozen sample. From ABTS measurements on PCN spirulina fractions sonicated or not, it was suggested that pressurisation at 6 bars allowed a better preservation of free antioxidants (outside the cells) due to replacement of oxygen by nitrogen in the frozen beads. After dehydration, phycocyanin-C content variation during storage at 20 °C and 33% RH showed higher loss for freeze-dried spirulina treated at 0 compared to 6 Bars.     

Stabilizing and destabilizing effects of drug-excipient interactions in spray-dried,freeze-dried,and granulated Sennae fructus extracts

Abstract

The objective of this study was to compare spray-dried and freeze-dried extracts of Sennae fructus regarding the stability of the sennosides. Therefore, the influence of the addition of maltodextrin (MD) not only before the drying processes but also during fluidized bed granulation was investigated. Analysis of the hygroscopicities, the simultaneous TGA-DSC-MS data, and the influence of storage revealed that spray-dried extracts are more stable than freeze-dried extracts. The addition of MD led to an even better stability of the extracts. Lower amounts of MD are sufficient if applied onto the surface of the native extract during fluidized bed granulation.     

Lactic fermentation of cooked navy beans by Lactobacillus paracasei CBA L74 aimed at a potential production of functional legume-based foods

In recent years, scientific interest in the development of non-dairy-based functional foods is increasing progressively and the fermentation of cereals, legumes, fruits and vegetable-based foods is becoming an important scientific research topic for the production of new probiotic products. In particular, legumes represent a possible alternative to protein foods from animal origins and an adequate fermentation substrate as they contain high amount of nutrients, such as proteins, carbohydrates, fibres, vitamins, and minerals, which are all useful to the growth and metabolic activity of certain microorganisms. This work focuses on the feasibility of developing a dry legume-based functional product using a fermentation process carried out on a 10% w/v navy bean suspension, in a lab-scale stirred batch reactor. After soaking and cooking dried navy beans, the fermentation tests performed on the resulting medium using Lactobacillus paracasei CBA L74 showed a maximum bacterial count of 10⁹ CFU/mL after 20 hours and a maximum lactic acid concentration of 1.9 g/L after 16 hours of process time. A freeze-drying process was performed on the fermented bean suspension, showing a 2-log microbial reduction and a bacterial viability in the resulting probiotic powder of 3.7 × 10⁸ CFU/g.     

纤维素纳米纤维/纳米蒙脱土复合气凝胶制备及其结构与性能

针对纤维素纳米纤维(CNF)气凝胶易燃、强力低等问题,利用纳米蒙脱土(MMT)共混改性纤维素纳米纤维,基于冷冻干燥的方法制备阻燃隔热的CNF/MMT复合气凝胶。研究了MMT质量分数对CNF/MMT复合气凝胶形貌结构、压缩性能、热稳定性、热导率和阻燃性能的影响。结果表明:MMT的引入使气凝胶具有更加紧密的片层结构,气凝胶力学性能、热稳定性和阻燃性能得到改善;在MMT质量分数为50%时,CNF/MMT复合气凝胶的表观密度最大且仅为0.016 8 g/cm³,应变为10%的应力最大为12.45 kPa,应变为70%的应力最大为77.93 kPa,导热系数最大为 0.04 W/(m·K); 气凝胶中MMT质量分数不低于42.9%时,复合基气凝胶的极限氧指数得到明显提升。     

Effects of the drying method on the oxidative stability of the free and encapsulated fractions of microencapsulated sunflower oil

The influence of the drying method, freeze-drying and spray-drying, on the oxidative stability of microencapsulated sunflower oil depended on the type of encapsulation matrix. For a dairy-type matrix, formed by sodium caseinate and lactose, greater losses of tocopherols were detected during spray-drying, but both the free and encapsulated oil fractions were more stable against lipid oxidation than their freeze-dried counterparts. Results suggested that the free oil was also constituted by droplets that preserved their interfacial membrane and were protected by the matrix. Therefore, the free oil was not necessarily the non-encapsulated fraction. For a matrix constituted by gelatine, maltodextrin and sucrose, the emulsion showed low stability and a great destabilisation during spray-drying. No significant effect of the drying method on the oxidative stability of the encapsulated fraction was found with this matrix, but the free oil of the spray-dried sample oxidised faster, probably due to the emulsion destabilisation observed, which gave rise to a great amount of oil on the particle surface as a consequence of large droplets poorly stabilised.