Drying of Probiotics: Optimization of Formulation and Process to Enhance Storage Survival

This work describes how probiotic bacteria can be dried at low temperature in two steps, combining spray drying and vacuum drying, in order to enhance their survival during storage. A sufficient number of dried probiotics survived storage for more than 3 months at 30°C, if an appropriate combination of protein and carbohydrate was selected as carrier and storage conditions were maintained optimal. The use of soy protein and maltodextrin or skim milk and arabic gum resulted in the best survival rates of probiotics during storage. No evident difference was found between different spray dryer configurations, although a cocurrent flow was preferred.     

Spray Drying of Yogurt: Optimization of Process Conditions for Improving Viability and Other Quality Attributes

Plain yogurt was subjected to spray drying to determine the optimum processing conditions that yield maximum survival ratio of lactic acid bacteria, maximum overall sensory attributes, minimum color change, and acceptable moisture content. The inlet (150–180°C) and outlet air temperatures (60–90°C) and the feed temperature (4–30°C) were the independent factors. A pilot-scale spray dryer was used to conduct a set of drying experiments where the process conditions were selected according to central composite rotatable design (CCRD). The resulting yogurt powder at each condition was also subjected to the measurement of some physical properties (water activity, titratable acidity [lactic acid, %] and pH) to determine the effects of spray-drying conditions. The morphological structure of the powder was inspected by scanning electron microscopy (SEM) analysis. Optimization by the application of the desirability function method resulted in air inlet temperature of 171°C, air outlet temperature of 60.5°C, and feed temperature of 15°C as the optimum processing condition. The mathematical optimum condition was experimentally verified.     

Injury Mechanisms of Lactic Acid Bacteria Starter Cultures During Spray Drying: A Review

Lactic acid bacteria (LAB) starter cultures can be processed by many drying techniques, among which spray drying has great potential. However, injuries of LAB during spray drying lead to a low survival rate. The microbial injuries of LAB during spray drying are specifically induced by dehydration inactivation, thermal inactivation, and balance between the two. To reduce the drying temperature, new drying techniques based on spray drying were tried; that is, low-temperature vacuum–spray drying and spray–freeze drying.     

Establishing Guidelines to Retain Viability of Probiotics During Spray Drying

We present the application of a model-based approach to map processing conditions suitable to spray dry probiotics with minimal viability loss. The approach combines the drying history and bacterial inactivation kinetics to predict the retention of viability after drying. The approach was used to systematically assess the influence of operational co-current spray drying conditions on residual viability. Moreover, two promising alternative drying strategies for probiotics were evaluated involving encapsulation in a hollow particle and using an “ideal-mixed” dryer system. Finally, a graph was constructed with the model to provide visual guidelines to optimize spray dying for probiotics in terms of viability and drying efficiency.     

Spray Drying of Biopharmaceuticals: Stability and Process Considerations

Spray drying represents an elegant one-step process for producing biopharmaceutical formulations with unique particle characteristics. However, the full potential of spray drying of therapeutic/proteins/peptides has yet to be fully exploited. The reluctance of utilizing spray drying for formulation development may stem from the fact that the process oftentimes subjects the therapeutic actives to temperatures in excess of 100°C, which is a concern for thermally labile drugs as spray drying was performed primarily on co-current spray dryer in a single-stage mode. In this review we discuss the respective dehydration mechanisms of spray drying and the appropriate formulation strategies that can be taken to minimize detrimental effects on biomolecules.     

Spray Drying of Biopharmaceuticals: Stability and Process Considerations

Spray drying represents an elegant one-step process for producing biopharmaceutical formulations with unique particle characteristics. However, the full potential of spray drying of therapeutic/proteins/peptides has yet to be fully exploited. The reluctance of utilizing spray drying for formulation development may stem from the fact that the process oftentimes subjects the therapeutic actives to temperatures in excess of 100°C, which is a concern for thermally labile drugs as spray drying was performed primarily on co-current spray dryer in a single-stage mode. In this review we discuss the respective dehydration mechanisms of spray drying and the appropriate formulation strategies that can be taken to minimize detrimental effects on biomolecules.     

Spray Drying and Process Optimization of Unclarified Pomegranate (Punica granatum) Juice

In this study, production of pomegranate juice powder using a spray dryer was investigated. To prevent stickiness, maltodextrin dextrose equivalent 6 (DE6) was used as a drying agent. While feed flow rate, feed temperature, and air flow rate were kept constant, air inlet temperature (110–140°C), percentage maltodextrin (MD; maltodextrin dry solids/100 g feed mixture dry solids; 39.08–64.12%), and feed mixture concentration (19.61–44.11 °Brix) were chosen as the independent variables. Product properties investigated included moisture content, hygroscopicity, anthocyanin content, color change, solubility, bulk density, total phenolics content, antioxidant capacity, and sensory properties. The products were produced with high yield (86%) and high antioxidant activity (77%). MD and drying temperature were found to be the most important variables in production of pomegranate juice powders. Because total color change (ΔE), bulk density, antioxidant capacity, and powder yield were affected strongly by the independent variables, these parameters were used in optimization of the process. The optimum temperature, feed mixture concentration, and percentage maltodextrin were 100°C, 30.8 °Brix, and 53.5% MD, respectively. This study revealed that by applying these optimal conditions, pomegranate juice powder with a 55% dry solids yield, 9.78 total color change, 0.35 g/mL bulk density, and 57.8% antioxidant capacity were produced.     

太阳能-除湿-常规分段组合木材干燥工艺优化

为降低木材干燥能耗,通过对杨木进行太阳能-除湿-常规分段组合干燥,即含水率40%以上采用太阳能进行预干,25%—40%采用除湿干燥,25%以下采用常规干燥,并与常规干燥进行干燥能耗和木材质量的对比。结果表明,分段组合干燥比常规干燥节能19%左右,而且干燥质量和常规干燥基本一致。分段组合干燥充分利用了三者各自的优势,从而达到节能的目的。     

Effects of Drying Methods on Functionality of a Native Potato Protein Concentrate

Pulp and dilute fruit water (PFW) are by-products from the potato starch processing industry. Potato protein obtained from an expanded bed adsorption (EBA) process is a value-added protein concentrate that can offer special technical properties in food systems. The influence of drying techniques on the physiochemical, quality, and functional properties (color, water content, bulk density, rehydration properties, sorption isotherms, specific enzyme activity, solubility, protein denaturation) of dehydrated potato water effluent was investigated. The results indicate that atmospheric freeze drying (AFD) is a more gentle drying process than spray drying and vacuum freeze drying. Both enthalpy measurements and sorption isotherms indicate reduced protein denaturation of AFD samples, while specific enzyme activity is at the same level for all dried samples.     

Effects of Drying Methods on Functionality of a Native Potato Protein Concentrate

Pulp and dilute fruit water (PFW) are by-products from the potato starch processing industry. Potato protein obtained from an expanded bed adsorption (EBA) process is a value-added protein concentrate that can offer special technical properties in food systems. The influence of drying techniques on the physiochemical, quality, and functional properties (color, water content, bulk density, rehydration properties, sorption isotherms, specific enzyme activity, solubility, protein denaturation) of dehydrated potato water effluent was investigated. The results indicate that atmospheric freeze drying (AFD) is a more gentle drying process than spray drying and vacuum freeze drying. Both enthalpy measurements and sorption isotherms indicate reduced protein denaturation of AFD samples, while specific enzyme activity is at the same level for all dried samples.     

Optimization of Spray Drying of Ginger Extract

Ginger (Zingiber oficinale) has many applications in the food and pharmaceutical sectors as an additive in a number of commercial foods and beverages. It is valued both for its aromatic volatile constituents and its spicy, pungent constituents. Ginger, if taken in a proper dosage, has high medicinal value because it is useful in preventing motion sickness and has a calming effect on upset stomach. Dehydration helps to achieve longer shelf life and easier transportation and storage, enabling wider distribution of the product. But it is important to retain the 6-gingerol, the active component, during drying of ginger extract. The present work pertains to the optimization of spray drying of ginger extract using response surface methodology (RSM). A central composite method was used to design the experiments. Different parameters investigated include inlet temperature (120–160°C), air flow rate (40–60 Nm³/h), feed rate (2.5–4 mL/min), and atomization pressure (1.5–2.25 kg/cm²). Optimum drying conditions for spray drying were decided on the basis of different responses such as moisture content, water activity (a_w), flowability, porosity, and percentage retention of gingerol.     

Optimization of Fish Oil Spray Drying Using a Protein:Inulin System

The aim of this work was to investigate the use of an unconven-tional polymeric material, inulin, in fish oil spray drying. The influence of inlet air temperature, oil load, and carrier substitution (whey protein isolate by inulin) on the physical properties of particles containing fish oil was investigated. Increasing the oil load caused an increase in the surface oil; however, the presence of inulin favorably decreased the particle surface oil when a high oil lad was applied. The parameters hygroscopicity and wettability were also influenced by the inulin fraction. The higher inlet air temperature produced larger particles with lower densities. The best operating conditions were determined to be an air temperature of 185°C, a 40% inulin fraction, and a 6% oil load. The results indicate that inulin is an alternative carrier in the fish oil spray-drying process.     

Microencapsulation of Gac Oil by Spray Drying: Optimization of Wall Material Concentration and Oil Load Using Response Surface Methodology

The objective of this study was to optimize the wall material concentration and the oil load on the encapsulation of Gac oil using spray drying by response surface methodology. Results showed that the quadratic polynomial model was sufficient to describe and predict encapsulation efficiencies in terms of oil, β-carotene, lycopene, peroxide value (PV), moisture content (MC), and total color difference (Δ E) with R ² values of 0.96, 0.95, 0.86, 0.89, 0.88, and 0.87, respectively. Under optimum conditions (wall concentration of 29.5 % and oil load of 0.2), the encapsulation efficiencies for oil, β-carotene, lycopene, PV, MC, and Δ E were predicted and confirmed as 92 %, 80 %, 74 %, 3.91 meq/kg, 4.14 % and 12.38, respectively. The physical properties of the encapsulated oil powders obtained by different formulations were also determined. It was concluded that the protein-polysaccharide matrix as the wall material was effectively used for spray-drying encapsulation of Gac oil.     

Experimental Study and Modeling of Crystalline Powders Vacuum Contact Drying with Intermittent Stirring

Modified literature models were successfully applied to simulate the evolution of the average solvent content (ethanol) of potassium chloride bed during vacuum contact drying with intermittent stirring. Our new modeling approach incorporated the following modifications: the introduction of a jacketed vessel heat transfer coefficient and an accumulation term for the heating wall temperature; the application of alternate static bed and stirred bed conditions; and modeling of all the three drying phases, namely the constant rate phase, the transition phase, and the falling rate phase. Moreover, several validation experiments were carried out with different operating conditions to identify the values of the unknown model parameter. The optimal stirring conditions were investigated by calculating total drying times for different sequences of stirring and no stirring periods.     

Experimental Study and Modeling of Crystalline Powders Vacuum Contact Drying with Intermittent Stirring

Modified literature models were successfully applied to simulate the evolution of the average solvent content (ethanol) of potassium chloride bed during vacuum contact drying with intermittent stirring. Our new modeling approach incorporated the following modifications: the introduction of a jacketed vessel heat transfer coefficient and an accumulation term for the heating wall temperature; the application of alternate static bed and stirred bed conditions; and modeling of all the three drying phases, namely the constant rate phase, the transition phase, and the falling rate phase. Moreover, several validation experiments were carried out with different operating conditions to identify the values of the unknown model parameter. The optimal stirring conditions were investigated by calculating total drying times for different sequences of stirring and no stirring periods.     

纳米颗粒的干燥及其研究进展

由于纳米粒子的表面效应，用湿法制备了纳米粉体的前驱－胶体的干燥已不能采用传统的干燥方法，本文根据胶体干燥的一般理论，综述了用于纳米颗粒干燥的各种干燥技术，给出了具体实例并分析了不同因素产生的效应。     

Process Design of a Multistage Drying Process via Flowsheet Simulation

Multistage drying processes including spray drying and fluidized bed unit operations are challenging to design due to the dependencies of the preceding process steps. Flowsheet simulation offers the possibility to simulate a complete process by the application of suitable short-cut models. In this contribution a novel model for a spray dryer based on a population balance approach is presented. Furthermore, a dynamic model for a fluidized bed dryer is introduced. Experimental data is used for validation and parameter optimization. The calibrated models are then used to design an industrial drying process of multiple drying stages.     

Drying of Foamed Biological Materials: Opportunities and Challenges

An overview is provided on hot air drying of foamed materials in a thin layer (foam-mat drying), foam-spray drying, microwave-assisted drying of liquid foams, as well as microwave drying of frozen foams with and without dielectric solid inserts, used as complementary heat sources. In particular, the mechanisms of heat and moisture transport during the drying of foams are identified. The effects of foam characteristics (e.g., foam density and stability) and drying conditions (temperature, air velocity) on drying kinetics and product quality are examined, and the differences between the drying of non-foamed and foamed materials are discussed.     

Spray Drying of Skim Milk Mixed with Milk Permeate: Effect on Drying Behavior, Physicochemical Properties, and Storage Stability of Powder

The possibility of using milk permeate (MP) to lower the protein level of skim milk powder (SMP) in producing powders of 34% and lower protein is explored. Skim milk suspensions with various levels of MP were prepared by mixing SMP and MP powder (MPP) at the ratios of 1:0, 7:3, 3:7, and 0:1: from 34 to 5.3% protein. The suspensions were dried in a spray dryer with inlet and outlet temperatures of 180 and 80°C, respectively. Increasing permeate concentration in the mixture showed a greater tendency to stickiness manifested by lowered the cyclone recovery of the powder as more powder stuck on the wall of the dryer. Increasing permeate concentration in the resultant powder did not significantly affect the bulk density but led to a reduction in the particle size and also made the powder slight green and yellowish in color. It also found to lower the glass transition temperature (T_g) of the skim milk powder (SMP) and induce crystallization of lactose at lower water activity (a_w ≥ 0.328 for SMP:MPP of 3:7 and 0:1 compared to a_w ≥ 0.0.432 for SMP:MPP of 1:0 and 3:7). Addition of MP in SMP lowered the T_g values of the resulting powders. The permeate fraction in spray-dried SMP/MPP mixtures found to lower the critical a_w and moisture content, suggesting the SMP mixed with MPP is more likely to become sticky than SMP alone (at 34% protein) when stored at a similar water activity and moisture content.     

Spray Drying of Skim Milk Mixed with Milk Permeate: Effect on Drying Behavior,Physicochemical Properties,and Storage Stability of Powder

The possibility of using milk permeate (MP) to lower the protein level of skim milk powder (SMP) in producing powders of 34% and lower protein is explored. Skim milk suspensions with various levels of MP were prepared by mixing SMP and MP powder (MPP) at the ratios of 1:0, 7:3, 3:7, and 0:1: from 34 to 5.3% protein. The suspensions were dried in a spray dryer with inlet and outlet temperatures of 180 and 80°C, respectively. Increasing permeate concentration in the mixture showed a greater tendency to stickiness manifested by lowered the cyclone recovery of the powder as more powder stuck on the wall of the dryer. Increasing permeate concentration in the resultant powder did not significantly affect the bulk density but led to a reduction in the particle size and also made the powder slight green and yellowish in color. It also found to lower the glass transition temperature (T_g ) of the skim milk powder (SMP) and induce crystallization of lactose at lower water activity (a_w  ≥ 0.328 for SMP:MPP of 3:7 and 0:1 compared to a_w  ≥ 0.0.432 for SMP:MPP of 1:0 and 3:7). Addition of MP in SMP lowered the T_g values of the resulting powders. The permeate fraction in spray-dried SMP/MPP mixtures found to lower the critical a_w and moisture content, suggesting the SMP mixed with MPP is more likely to become sticky than SMP alone (at 34% protein) when stored at a similar water activity and moisture content.