Physical and Functional Properties of Blackberry Freeze- and Spray-Dried Powders

The aim of the present work was to develop two products from blackberry juice by freeze and spray drying with potential use as food colorants or healthy ingredients. A characterization of the physical and functional properties of the powdered juices was done. Maltodextrin or a mixture of trehalose and maltodextrin were assessed as carrier matrices. Freeze-dried, maltodextrin-containing powders presented the best retention of bioactive compounds and antiradical activity; however, they showed a narrow relative humidity range for storage in the glassy state. Spray-dried powders showed better physical properties, bearing higher glass transition temperature and lower molecular mobility than freeze-dried formulations.     

Water Sorption,Glass Transition,and Microstructures of Refractance Window– and Freeze-Dried Mango (Philippine “Carabao” Var.) Powder

Water sorption isotherms, glass transition, and microstructures of Refractance Window (RW)– and freeze-dried Philippine “Carabao” mango powders were investigated. Water sorption isotherms were developed by the isopiestic method, while thermal transition of the powders, at various water activities (a _w  = 0.11–0.86), was determined using differential scanning calorimetry (DSC). The sorption isotherms of RW- and freeze-dried (FD) mango powders exhibited a type III sigmoidal curve, showing higher and lower adsorption capacities above and below 0.5 a _w , respectively. A significant difference (p < 0.05) in water content of RW- and freeze-dried mango powders for equivalent water activities was obtained above 0.5 a _w . The onset glass transition temperature (T _gi ) of RW- and freeze-dried mango powder solids decreased as the water content increased. There were no significant differences (p ≥ 0.05) in T _gi of RW- and freeze-dried mango powder solids at constant water activities, except for a _w  = 0.86. Microscopic examination of mango powders indicated that freeze-dried mango powders exhibited greater surface area and porosity in comparison to RW-dried mango powders.     

Study on a Combination Drying Technique of Sea Cucumber

To develop a highly efficient drying technique for sea cucumber, the effects of different drying methods on the drying procedure and product quality were investigated. FD could lead to the best quality but took the longest time, and AD product quality was too poor. VMD was introduced to combine with FD to get acceptable quality and reduce drying time. In order to get optimal technique parameters, an RSA experiment was carried out. The optimal technique parameters of combination drying of FD-VMD were 45% conversion point, 20-30 kPa chamber pressure, and 350-450 W microwave power. Compared with Freeze Drying (FD), Air Drying (AD)-Vacuum Microwave Drying (VMD) could reduce the drying time to half and maintain good product quality.     

Study on a Combination Drying Technique of Sea Cucumber

To develop a highly efficient drying technique for sea cucumber, the effects of different drying methods on the drying procedure and product quality were investigated. FD could lead to the best quality but took the longest time, and AD product quality was too poor. VMD was introduced to combine with FD to get acceptable quality and reduce drying time. In order to get optimal technique parameters, an RSA experiment was carried out. The optimal technique parameters of combination drying of FD-VMD were 45% conversion point, 20–30 kPa chamber pressure, and 350–450 W microwave power. Compared with Freeze Drying (FD), Air Drying (AD)-Vacuum Microwave Drying (VMD) could reduce the drying time to half and maintain good product quality.     

Self-Reinforcing Composite Based on Ethylene Acrylic Elastomer (AEM)/Liquid Crystalline Polymer (LCP) Blend

Abstract

Blends of ethylene acrylic elastomer (AEM) and thermotropic liquid crystalline polymer (TLCP) have been prepared by melt mixing technique. Processing studies indicated a decrease in the viscosity of the blends with the addition of liquid crystalline polymer (LCP). At lower level of LCP the tensile strength and tear strength increased. However, at higher level of LCP tensile strength values decreased due to insufficient adhesion between two phases. The modulus of the samples increased with the LCP content. The degree of crystallinity increased with increasing LCP content. This improvement in crystallinity is associated with the increase in crystallite size. For the blends, thermal studies indicated, the endothermic signals which were more prominent at all the peak temperatures. The heat of degradation values increased with the LCP content. Scanning electron microscope (SEM) study suggested the fibril formation, which affected the failure mechanism under DMA studies. Storage modulus and loss modulus of the blends increased with increasing LCP content. At above glass transition temperature (Tg) improvement in storage modulus is nearly five times higher than that of the pure AEM.     

Effect of drying treatments on texture and color of vegetables (pumpkin and green pepper)

The present work evaluates the effect of different drying treatments on the color and textural attributes of green bell peppers and pumpkin, which were dried using two different methods: air drying and freeze-drying. The treatments in air drying were carried out at 30 °C and 70 °C.From the results it is possible to conclude that the increase in drying temperature reduced drastically the hardness of green peppers and the freeze drying had an intermediate effect between vegetables dried at 30 °C and 70 °C. Moreover, the springiness was higher in dried green peppers but an opposite effect was observed on chewiness. With respect to pumpkin, any dependence between the fiber orientation and the hardness of the fresh vegetable was not found. In addition, increasing temperature from 30 °C to 70 °C particularly reduced the hardness and the chewiness of dried product and maintained cohesiveness and springiness approximately constant.Regarding the color, it was possible to conclude that air drying at 30 °C produced small changes in color of green pepper whereas air drying at 70 °C and freeze drying originated more intense color changes. The increase of temperature on air drying augmented the color saturation of dried pumpkin while decreased the hue angle by a linear relationship. In addition, the chroma of dried pumpkin decreased significantly with the freeze drying, while the hue angle was maintained constant as compared with the fresh vegetable.     

The drying strategy of atmospheric freeze drying apple cubes based on glass transition

Freeze drying (FD) yields the best quality of dried apple cubes but at the cost of long drying time and also the overall cost. To achieve economical freeze drying along with a high quality product an atmospheric freeze drying (AFD) technique was developed to dry apple cubes. The effect of different air temperature loading scheme on product quality and drying process was studied during AFD. According to the glass transition temperature of apple, a step-up temperature loading strategy for AFD process was developed to reduce the drying time by almost half and provided a similar good product quality.     

Evolution of particle properties during spray drying in relation with stickiness and agglomeration control

Spray drying consists in atomizing a solution into liquid drops in a hot air flow to get dry solid particles after solvent evaporation. The convective drying at the drop surface leads to a very fast evolution of temperature and water content due to initial high differences of temperature and water vapour pressure between the drop surface and the drying air. During drying, the drop surface viscosity is increasing due to potentially amorphous polymers reaching a rubbery state. The drop surface is becoming sticky with consequences on wall deposit. This sticky behaviour which appears in the range of 10 to 30 °C above the glass transition temperature Tg, may be utilized in a positive way for agglomeration of drying particles with dry powders, either recycled fines or new dry powder, to improve instant properties.The evolution of water content of drops along drying, is deduced from measurements of air temperature and relative humidity, at different places in the dryer and used to predict the drying and sticky behaviour of two maltodextrin solutions (DE12 and DE21) with different Tg. The studied parameters in a co-current spray dryer were the inlet air temperature (144, 174, 200 °C) and flow rate (80 and 110 kg h^− 1), the liquid flow rate (1.8, 3.6 and 5.4 kg h^− 1) and the rotation speed of the wheel atomizer. The results on particle water content combined with the evolution of Tg showed that particles are sticky close to the atomiser for the two maltodextrins, and also along the chamber for maltodextrin DE21 due to its lower Tg. The introduction of dry particles at different places in the chamber allowed validating the method to control agglomeration.     

The Effect of Glass Transition Temperature on the Procedure of Microwave–Freeze Drying of Mushrooms (Agaricus bisporus)

Freeze drying (FD) yields the best quality of dried mushroom but at the cost of a long drying time and high overall cost. Air drying (AD) gives an unacceptably poor quality product. To achieve faster drying along with a high-quality product, a microwave–freeze drying (MFD) technique was developed to dry mushrooms. The relationship between dried mushroom quality and the glass transition temperature during the MFD process was studied to optimize the MFD process. According to the change tendency of the glass transition temperature of mushroom during MFD, a step-down microwave loading scheme for the MFD process was developed to obtain good product quality.     

A Combination of Freeze Drying and Microwave Vacuum Drying of Duck Egg White Protein Powders

High energy consumption during freeze drying (FD) is a major concern that limits its application on common food product manufacturing. In this research, fresh duck egg white protein (FDEWP) powder and desalted duck egg white protein (DDEWP) powder were obtained by a combined two-stage tandem drying technologies (FD and microwave–vacuum drying [MVD]) in order to reduce energy consumption while maintaining good product quality. The results showed that the drying time for the FDEWP and DDEWP powders was significantly decreased by FD + MVD compared to those obtained by the FD-only process. The FDEWP powders dried by FD + MVD had a better color (higher L* and lower b*), lower apparent density, and lower foaming stability but higher emulsifying index than those dried by FD only. The DDEWP powder dried by FD + MVD had a product quality similar to that of FDEWP powder, suggesting that the DDEWP powder could be widely used as a food ingredient.     

Surface Stickiness of Drops of Carbohydrate and Organic Acid Solutions During Convective Drying: Experiments and Modeling

Abstract

Drying kinetics of low molecular weight sugars such as fructose, glucose, sucrose and organic acid such as citric acid and high molecular weight carbohydrate such as maltodextrin (DE 6) were determined experimentally using single drop drying experiments as well as predicted numerically by solving the mass and heat transfer equations. The predicted moisture and temperature histories agreed with the experimental ones within 6% average relative (absolute) error and average difference of ± 1°C, respectively. The stickiness histories of these drops were determined experimentally and predicted numerically based on the glass transition temperature (T _g ) of surface layer. The model predicted the experimental observations with good accuracy. A nonsticky regime for these materials during spray drying is proposed by simulating a drop, initially 120 µm in diameter, in a spray drying environment.     

Surface Stickiness of Drops of Carbohydrate and Organic Acid Solutions During Convective Drying: Experiments and Modeling

Drying kinetics of low molecular weight sugars such as fructose, glucose, sucrose and organic acid such as citric acid and high molecular weight carbohydrate such as maltodextrin (DE 6) were determined experimentally using single drop drying experiments as well as predicted numerically by solving the mass and heat transfer equations. The predicted moisture and temperature histories agreed with the experimental ones within 6% average relative (absolute) error and average difference of ± 1°C, respectively. The stickiness histories of these drops were determined experimentally and predicted numerically based on the glass transition temperature (T_g) of surface layer. The model predicted the experimental observations with good accuracy. A nonsticky regime for these materials during spray drying is proposed by simulating a drop, initially 120 µm in diameter, in a spray drying environment.     

Drying Kinetics and Quality of Shrimp Undergoing Different Two-Stage Drying Processes

An innovative two-stage drying concept is presented in this article. The work considered drying of shrimp using a superheated steam dryer followed by a heat pump (SSD/HPD) or a hot air dryer (SSD/AD) both from drying kinetics and dried product quality points of view. The experiments were performed using the first-stage superheated steam drying temperature of 140°C while the second-stage heat pump drying (or hot air drying) was performed at 50°C. The moisture content of shrimp at the end of the superheated steam drying stage was varied between 30 and 40% (w.b.). The effect of tempering between SSD/HPD was also investigated. Shrinkage, color, rehydration behavior, texture (toughness and hardness), and microstructure of dried shrimp were measured. The results showed that SSD/HPD dried shrimp had much lower degree of shrinkage, higher degree of rehydration, better color, less tough and softer, and more porous than single-stage SSD dried shrimp. It was also found that SSD/AD gave redder shrimp compared to shrimp dried in a single-stage superheated steam dryer. No improvement in terms of shrinkage and rehydration behavior was observed, however.     

Drying Kinetics and Quality of Shrimp Undergoing Different Two-Stage Drying Processes

Abstract

An innovative two-stage drying concept is presented in this article. The work considered drying of shrimp using a superheated steam dryer followed by a heat pump (SSD/HPD) or a hot air dryer (SSD/AD) both from drying kinetics and dried product quality points of view. The experiments were performed using the first-stage superheated steam drying temperature of 140°C while the second-stage heat pump drying (or hot air drying) was performed at 50°C. The moisture content of shrimp at the end of the superheated steam drying stage was varied between 30 and 40% (w.b.). The effect of tempering between SSD/HPD was also investigated. Shrinkage, color, rehydration behavior, texture (toughness and hardness), and microstructure of dried shrimp were measured. The results showed that SSD/HPD dried shrimp had much lower degree of shrinkage, higher degree of rehydration, better color, less tough and softer, and more porous than single-stage SSD dried shrimp. It was also found that SSD/AD gave redder shrimp compared to shrimp dried in a single-stage superheated steam dryer. No improvement in terms of shrinkage and rehydration behavior was observed, however.     

Dried Food Properties: Challenges Ahead

In the last few decades, the knowledge of the properties of dried-food has increased tremendously. In fact drying research and development has extended beyond its limited chemical and mechanical engineering approach of heat and mass transfer. In the past drying was performed to preserve foods with less emphasis on multidimensional quality attributes. A recent trend is to develop dried-foods maintaining its quality, such as flavor, texture, convenience, and functionality with increased nutritional contents and reduced anti-nutritional factors or toxins. At present drying of foods has extreme focus on maintaining its bioactive and structural functionality. The main purpose of this paper is to give an overview on the food properties and to provide basic concepts of food properties and quality. A critical assessment is presented with emphasis on classifications, measurement techniques, data generation, prediction models and applications of food properties. An attempt is also made to answer the following questions: where are we now and where do we need to go or reach? What vicious circle needs to be broken? What efforts are being made around the globe?     

冷冻干燥过程的数学模型

本文以物料衡算和热量衡算为基础，作适当的简化，导出了所需参数较少，但能准确地预测冷冻干燥全过程时间的数学模型，通过对胡萝卜和土豆的实验研究，检验了模型的适用性和准确性。     

Effects of Different Drying Methods on the Quality Changes of Granular Edamame

In this article, the quality changes of the granular fruits and vegetables dried by vacuum microwave drying, freeze drying, hot air drying, and combined hot air-vacuum microwave drying are investigated, and the quality parameters compared on the basis of vitamin C and chlorophyll contents, shrinkage and rehydration capacity, color, texture, and microstructure changes. The quality parameters of products dried by vacuum microwave drying are slightly lower than those obtained by freeze drying, but much better than those obtained using conventional hot air drying. The quality characteristics of product dried by combined hot air-vacuum microwave are significantly improved compared to those simply hot air-dried.     

冻干魔芋胶性能的实验研究

介绍了采用冻干工艺获取的优质魔芋胶（KGM）的主要性能及其实验研究。该工艺方法具有成胶薄、韧性好、保存容易而且时间长、复水性好等优点。魔芋胶可广泛用于食品保鲜与储藏以及保健、医疗等方面；由于它价格低，可进一步拓展其应用领域，深受医疗保健人员的关注。