scholarly journals Structural Changes During Air Drying of Fruits and Vegetables

2003 ◽  
Vol 9 (3) ◽  
pp. 201-206 ◽  
Author(s):  
I. N. Ramos ◽  
T. R.S. Brandão ◽  
C. L.M. Silva
Keyword(s):  
Physical Properties ◽  
Structural Changes ◽  
Fruits And Vegetables ◽  
Particle Density ◽  
Drying Process ◽  
Air Drying ◽  
New Approach ◽  
Volume Porosity ◽  
Textural Attributes ◽  
Kinetics Of

This work aims at reviewing structural changes occurring in convective air drying of fruits and vegetables. These include changes in physical properties, such as volume, porosity and bulk and particle density, which directlyaffect textural attributes of the products. Models relating with water content physical properties are also summarised. At microscopic level, the phenomena observed byprevious authors is described, focusing on shrinkage. In particular, a new approach on modelling kinetics of microstructural modifications is presented. Although the air drying process is relatively well studied, there is a lack of research concerning changes in structural properties. Modelling mass transfer during drying frequently does not include those effects and, there has not been established a standard methodologyfor predictive purposes. Correlating microstructure, texture measurements and sensoryanalysis would be an attractive area to be exploited for drying processes of fruits and vegetables. Although this is a wide working field, much is still to be done.

scholarly journals Physical Properties and Non-Isothermal Crystallisation Kinetics of Primary Mechanically Recycled Poly(l-lactic acid) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3396
Author(s):  
Luboš Běhálek ◽  
Jan Novák ◽  
Pavel Brdlík ◽  
Martin Borůvka ◽  
Jiří Habr ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Physical Properties ◽  
Structural Changes ◽  
The Other ◽  
Half Time ◽  
Crystallisation Kinetics ◽  
Isothermal Crystallisation ◽  
Melt Crystallisation ◽  
Kinetics Of ◽  
Crystallisation Rate

The physical properties and non-isothermal melt- and cold-crystallisation kinetics of poly (l-lactic acid) (PLLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) biobased polymers reprocessed by mechanical milling of moulded specimens and followed injection moulding with up to seven recycling cycles are investigated. Non-isothermal crystallisation kinetics are evaluated by the half-time of crystallisation and a procedure based on the mathematical treatment of DSC cumulative crystallisation curves at their inflection point (Kratochvil-Kelnar method). Thermomechanical recycling of PLLA raised structural changes that resulted in an increase in melt flow properties by up to six times, a decrease in the thermal stability by up to 80 °C, a reduction in the melt half-time crystallisation by up to about 40%, an increase in the melt crystallisation start temperature, and an increase in the maximum melt crystallisation rate (up to 2.7 times). Furthermore, reprocessing after the first recycling cycle caused the elimination of cold crystallisation when cooling at a slow rate. These structural changes also lowered the cold crystallisation temperature without impacting the maximum cold crystallisation rate. The structural changes of reprocessed PHBV had no significant effect on the non-isothermal crystallisation kinetics of this material. Additionally, the thermomechanical behaviour of reprocessed PHBV indicates that the technological waste of this biopolymer is suitable for recycling as a reusable additive to the virgin polymer matrix. In the case of reprocessed PLLA, on the other hand, a significant decrease in tensile and flexural strength (by 22% and 46%, respectively) was detected, which reflected changes within the biobased polymer structure. Apart from the elastic modulus, all the other thermomechanical properties of PLLA dropped down with an increasing level of recycling.

scholarly journals Sustainable Development of Apple Snack Formulated with Blueberry Juice and Trehalose

2021 ◽  
Vol 13 (16) ◽  
pp. 9204
Author(s):  
Juan Manuel Castagnini ◽  
Silvia Tappi ◽  
Urszula Tylewicz ◽  
Santina Romani ◽  
Pietro Rocculi ◽  
...  
Keyword(s):  
Control Sample ◽  
Solid Matrix ◽  
Vacuum Impregnation ◽  
Drying Process ◽  
Air Drying ◽  
Blueberry Juice ◽  
Drying Kinetic ◽  
Kinetics Of ◽  
Impregnation Solution ◽  
Novel Products

Novel products that carry concrete and relevant health benefits, with texture and flavor not substantially different from already available products, are generally well accepted by consumers. Vacuum impregnation is a non-thermal technology that allows the enrichment of fruit with different ingredients in solution. The characteristic of the resulting product is a combination of both the solid matrix and the impregnation solution. This work aimed at: (i) evaluating the effect of trehalose on anthocyanin retention after drying of apple snacks vacuum impregnated with blueberry juice; (ii) modelling the air-drying kinetic, proposing an image analysis approach to monitor the drying process. Four mathematical models successfully fitted the drying experimental data, obtainingequations that could be used in the implementation of this process at industrial scale. The drying kinetics of samples impregnated with blueberry juice and trehalose were faster when compared to the control sample. Samples impregnated with blueberry juice and 100 g/kg of trehalose retained nearly four times more anthocyanin after drying when compared to the control.

Drying and Denaturation Kinetics of Whey Protein Isolate (WPI) During Convective Air Drying Process

2013 ◽  
Vol 31 (13-14) ◽  
pp. 1532-1544 ◽  
Author(s):  
M. Amdadul Haque ◽  
Aditya Putranto ◽  
Peter Aldred ◽  
Jie Chen ◽  
Benu Adhikari
Keyword(s):  
Whey Protein ◽  
Whey Protein Isolate ◽  
Protein Isolate ◽  
Drying Process ◽  
Air Drying ◽  
Denaturation Kinetics ◽  
Kinetics Of

Influence of Drying on the Properties of Pears of the Rocha Variety (Pyrus communis

2013 ◽  
Vol 9 (2) ◽  
pp. 197-207 ◽  
Author(s):  
Sandra C. R. V. L. Santos ◽  
Raquel P. F. Guiné ◽  
Ana I. A. Barros
Keyword(s):  
Physical Properties ◽  
Pyrus Communis ◽  
Air Drying ◽  
Drying Temperature ◽  
Total Solids ◽  
Different Temperatures ◽  
Textural Attributes ◽  
Maturation Index ◽  
Solids Content

AbstractRocha pear (Pyrus communis L.) is the main cultivar produced in Portugal, usually consumed in fresh. However, the drying of the pear can be an opportunity for development and enables the provision of alternative products to consumers. This work evaluates the effect of drying on some chemical and physical properties of pears of the Rocha variety. Furthermore, the origin of the pears was also a variable studied. For the completion of this work, pears from five different locations were analysed in fresh and after convective air drying at two different temperatures, 40 and 60°C. The properties analysed were dimensions of pears in terms of height and diameter, total solids content, acidity, maturation index, processing yields, colour and textural attributes.The results showed that the peel had lower acidity and higher maturation index, when compared to the pulp and that drying greatly reduced acidity, either in the pulp or in the peel. However, this variation was not influenced by the drying temperature. With respect to colour, total colour differences between 25 and 50 were observed (for the dried pears in relation to the fresh) and in this case increasing the drying temperature caused evident variations in the peel but not in the pulp. As to the textural attributes, hardness and chewiness were the ones that showed the higher changes with drying, increasing considerably with drying temperature.

Fruits & Vegetables Drying Combining Hot Air, DIC Technology and Microwaves

2008 ◽  
Vol 4 (6) ◽  
Author(s):  
M. Al Haddad ◽  
S. Mounir ◽  
V. Sobolik ◽  
K. Allaf
Keyword(s):  
Fruits And Vegetables ◽  
Drying Process ◽  
Hot Air Drying ◽  
Air Drying ◽  
Physical Mechanisms ◽  
Microwave Assisted ◽  
Hot Air ◽  
Air Dehydration ◽  
Instant Controlled Pressure Drop

Dehydration of fruits and vegetables is one of the most ancient and efficient preservation methods. The quality of the product and its cost depend mainly on the final stage of drying. In the present paper we analyze physical mechanisms occurring during drying throughout heat and mass transfer for defining an efficient and economic three stage drying process of hot air drying combined to a texturing stage by DIC (Instant Controlled Pressure Drop) and finally using microwave assisted by ambient temperature air dehydration.

scholarly journals The Effect of Vacuum Impregnation Pretreatment on Air-Drying Kinetics of Pears

2020 ◽  
Vol 8 (11) ◽  
pp. 2248-2254
Author(s):  
Şeyma Uysal ◽  
Fikret Pazır
Keyword(s):  
Effective Diffusion ◽  
Solution Concentration ◽  
Drying Kinetics ◽  
Vacuum Impregnation ◽  
Drying Process ◽  
Drying Time ◽  
Air Drying ◽  
Pyrus Communis L ◽  
Experimental Values ◽  
Kinetics Of

The aim of this study was to examine the drying kinetics of pears (Pyrus communis L.) with and without vacuum impregnation and under the different temperature by using tray dryer. Vacuum impregnation were applied to the the pears (15 mm thickness, 65 mm outer and 20 mm inner dimensions respectively) with the conditions of 50⁰ Brix impregnation solution concentration, 225 mbar vacuum pressure and 45 min vacuum time. Drying process was carried out at temperatures of 55, 65 and 75°C. Drying time of non-vacuum impregnated pears was determined 640, 500 and 340 min and vacuum impregnated pears was determined 700, 540 and 560 min respectively. Page, Exponential, Henderson and Pabis, Diffusion Approach were examined for testing the drying kinetics. Experimental values are in accordance with the expected values resulted Page and Difussion models of with and without vacuum impregnated pears. Effective diffusion coefficient (Deff) was varying 2.74×10-11 to 7.31×10-11 m2/s. m2/s with respect to the drying temperatures. The activation energy for the non-vacuum impregnated and vacuum impregnated pears was 32.93 kJ / mol and 24.25 kJ / mol, respectively.

scholarly journals Effects of Osmotic Dehydration on the Hot Air Drying of Apricot Halves: Drying Kinetics, Mass Transfer, and Shrinkage

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 202
Author(s):  
Ivan Pavkov ◽  
Milivoj Radojčin ◽  
Zoran Stamenković ◽  
Krstan Kešelj ◽  
Urszula Tylewicz ◽  
...  
Keyword(s):  
Activation Energy ◽  
Osmotic Dehydration ◽  
Effective Diffusivity ◽  
Drying Process ◽  
Air Velocity ◽  
Hot Air Drying ◽  
Drying Time ◽  
Air Drying ◽  
Hot Air ◽  
Kinetics Of

This study aimed to determine the effects of osmotic dehydration on the kinetics of hot air drying of apricot halves under conditions that were similar to the industrial ones. The osmotic process was performed in a sucrose solution at 40 and 60 °C and concentrations of 50% and 65%. As expected increased temperatures and concentrations of the solution resulted in increased water loss, solid gain and shrinkage. The kinetics of osmotic dehydration were well described by the Peleg model. The effective diffusivity of water 5.50–7.387 × 10−9 m2/s and solute 8.315 × 10−10–1.113 × 10−9 m2/s was calculated for osmotic dehydration. Hot air drying was carried out at 40, 50, and 60 °C with air flow velocities of 1.0 m/s and 1.5 m/s. The drying time shortened with higher temperature and air velocity. The calculated effective diffusion of water was from 3.002 × 10−10 m2/s to 1.970 × 10−9 m2/s. The activation energy was sensitive to selected air temperatures, so greater air velocity resulted in greater activation energy: 46.379–51.514 kJ/mol, and with the osmotic pretreatment, it decreased to 35.216–46.469 kJ/mol. Osmotic dehydration reduced the effective diffusivity of water during the hot air drying process. It also resulted in smaller shrinkage of apricot halves in the hot air drying process.

Processing Immunoperoxidase Labeled Cell Monolayers and Cryostat Sesctions For Electron Microscopy

1985 ◽  
Vol 43 ◽  
pp. 714-715
Author(s):  
K. Chien ◽  
R. Van de Velde ◽  
I.P. Shintaku ◽  
A.F. Sassoon
Keyword(s):  
Cell Monolayer ◽  
Cell Types ◽  
Surface Antigens ◽  
Immunoperoxidase Method ◽  
Reaction Step ◽  
Hot Plate ◽  
Air Drying ◽  
New Approach ◽  
Cell Monolayers ◽  
Glass Slides

Immunoelectron microscopy of neoplastic lymphoma cells is valuable for precise localization of surface antigens and identification of cell types. We have developed a new approach in which the immunohistochemical staining can be evaluated prior to embedding for EM and desired area subsequently selected for ultrathin sectioning.A freshly prepared lymphoma cell suspension is spun onto polylysine hydrobromide- coated glass slides by cytocentrifugation and immediately fixed without air drying in polylysine paraformaldehyde (PLP) fixative. After rinsing in PBS, slides are stained by a 3-step immunoperoxidase method. Cell monolayer is then fixed in buffered 3% glutaraldehyde prior to DAB reaction. After the DAB reaction step, wet monolayers can be examined under LM for presence of brown reaction product and selected monolayers then processed by routine methods for EM and embedded with the Chien Re-embedding Mold. After the polymerization, the epoxy blocks are easily separated from the glass slides by heatingon a 100°C hot plate for 20 seconds.

Studies on the Behavior Some Paints in Electro-insulating Fluid Based on Vegetable Esters

2018 ◽  
Vol 69 (5) ◽  
pp. 1139-1144
Author(s):  
Iosif Lingvay ◽  
Adriana Mariana Bors ◽  
Livia Carmen Ungureanu ◽  
Valerica Stanoi ◽  
Traian Rus
Keyword(s):  
Structural Changes ◽  
Oxidation Processes ◽  
High Oleic ◽  
Painting Materials ◽  
Insulating Paper ◽  
Different Types ◽  
Mechanism And Kinetics ◽  
Kinetics Of ◽  
Natural Ester

For the purpose of using three different types of painting materials for the inner protection of the transformer vats, their behavior was studied under actual conditions of operation in the transformer (thermal stress in electro-insulating fluid based on the natural ester in contact with copper for electro-technical use and electro-insulating paper). By comparing determination of the content in furans products (HPLC technique) and gases formed (by gas-chromatography) in the electro-insulating fluid (natural ester with high oleic content) thermally aged at 130 �C to 1000 hours in closed glass vessels, it have been found that the presence the investigated painting materials lead to a change in the mechanism and kinetics of the thermo-oxidation processes. These changes are supported by oxygen dissolved in oil, what leads to decrease both to gases formation CO2, CO, H2, CH4, C2H4 and C2H6) and furans products (5-HMF, 2-FOL, 2 -FAL and 2-ACF). The painting materials investigated during the heat treatment applied did not suffer any remarkable structural changes affecting their functionality in the electro-insulating fluid based on vegetable esters.

Biofilm Structure – An Important and Neglected Parameter in Waste Water Treatment

1989 ◽  
Vol 21 (8-9) ◽  
pp. 805-814 ◽  
Author(s):  
F. R. Christensen ◽  
G. Holm Kristensen ◽  
J. la Cour Jansen
Keyword(s):  
Wastewater Treatment ◽  
Structural Changes ◽  
Waste Water Treatment ◽  
Experimental Investigations ◽  
Biofilm Reactors ◽  
Substrate Removal ◽  
Treatment Processes ◽  
Laboratory Reactor ◽  
Biofilm Structure ◽  
Kinetics Of

Experimental investigations on the kinetics of wastewater treatment processes in biofilms were performed in a laboratory reactor. Parallel with the kinetic experiments, the influence of the biofilm kinetics on the biofilm structure was studied at macroscopic and microscopic levels. The close interrelationship between biofilm kinetics and structural changes caused by the kinetics is illustrated by several examples. From the study, it is evident that the traditional modelling of wastewater treatment processes in biofilm reactors based on substrate removal kinetics alone will fail in many cases, due to the inevitable changes in the biofilm structure not taken into consideration. Therefore design rules for substrate removal in biofilms used for wastewater treatment must include correlations between the removal kinetics and the structure and development of the biological film.

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