Vacuum drying of apples (cv. Golden Delicious): drying characteristics, thermodynamic properties, and mass transfer parameters

Nadi, Fatemeh; Tzempelikos, Dimitrios

doi:10.1007/s00231-018-2279-5

Cited by 49 publications

(48 citation statements)

References 64 publications

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“…The determined values of D eff in the present drying conditions range from 7.352 × 10 −11 to 4.604 × 10 −10 m 2 s −1 . The calculated D eff values were in agreement with the general range reported to be between 10 −12 and 10 −6 m 2 s −1 for food materials …”

Section: Resultssupporting

confidence: 88%

Effects of sodium alginate‐based coating pretreatment on drying characteristics and quality of heat pump dried scallop adductors

et al. 2019

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Background Drying efficiency and quality maintenance are the major concerns of both manufactures and consumers. Heat pump drying (HPD) is suitable for heat sensitive foodstuffs due to its ability to independently control the drying operation parameters. However, lower drying rate and energy efficiency in the later period of HPD are the bottlenecks that restrain its application. A novel approach using hydrocolloids as pretreatment coatings prior to drying was designed to solve these problems. The effects of sodium alginate (SA) coating, drying temperatures and air velocities on the drying characteristics and quality attributes of scallop adductors were evaluated. Results Drying took place in the falling rate period. Drying time decreased with increasing temperature, air velocity and SA coating. The Two Term model and the Wang and Singh model gained the best fit for thin‐layer drying of scallop adductors and SA film, respectively. Effective moisture diffusivity increased with temperature, velocity and SA coating and were in the range 7.352–14.620 × 10−11, 9.890–17.100 × 10−11 and 2.348–4.604 × 10−10 m2 s−1 for uncoated scallop adductors, SA coated scallop adductors and SA films, respectively. The activation energies for SA films, coated and uncoated scallop adductors were 17.07, 20.78 and 26.17 kJ mol−1, respectively. Dried scallop adductors with SA coating pretreatment exhibited a significant lower value of shrinkage rate and hardness, and higher value of toughness than uncoated ones at 30 °C and 2.0 m s−1 (P < 0.05). Conclusion Hydrocolloid coating is a promising pretreatment in improving HPD efficiency and enhancing quality attributes of dried scallop adductors. © 2019 Society of Chemical Industry

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Section: Resultssupporting

confidence: 88%

Effects of sodium alginate‐based coating pretreatment on drying characteristics and quality of heat pump dried scallop adductors

et al. 2019

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“…During the drying process, a pressure gradient is developed within the dried material due to the evaporation process. In FD, the absence of evaporation and reduction in air pressure significantly decreased the pressure gradient responsible for the collapse of the unconsolidated porous structure of the dried product (Nadi & Tzempelikos, ). In contrast, rapid evaporation rate caused by microwave heating sharply increased the pressure gradient, resulting in the formation of porous structure.…”

Section: Resultsmentioning

confidence: 99%

“…For effective modeling of the drying characteristics of CCB, the experimental drying data of CCB at different conditions were fitted using six widely used thin layer drying models (Equations 3–8) given in Table . These empirical models are derived directly from the general solution of Fick's law by simplifications and are exhaustively used for designing new or improving existing drying systems or even for the control of the drying process (Fan, Chen, He, & Yan, ; Nadi & Tzempelikos, ).The parameters of the models were (1) dimensionless drying constant, k ‐drying constant (1/min), and n ‐dimensionless drying constant and (2) constant (1/min). The best fitting model was determined by comparing the sum of square error:

{SS}_{error} = \sum {(y_{i} - \overset{false^}{y})}^{2}

…”

Section: Methodsmentioning

confidence: 99%

Effect of microwave power on drying kinetics, structure, color, and antioxidant activities of corncob

Saha

Dey

Chakraborty

2019

J Food Process Engineering

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In this study, the effect of microwave drying (MWD) at four power levels (180, 300, 600, and 900 W) on kinetics, structure, color parameters, and antioxidant activity of corncob (CCB) was evaluated. Hot air‐dried (HAD) and freeze‐dried (FD) CCBs were used as controls. Drying conditions significantly affected the physicochemical characteristics as well as bioactivities of CCB. For MWD products, direct absorption of electromagnetic energy by water molecules greatly accelerated the evaporation process, leading to a faster dehydration with a very high moisture diffusivity value. Additionally, the application of microwave markedly enhanced disintegration of cellular components manifested in lowered values of structural and color attributes for MWD CCBs, which facilitated the liberation of bound polyphenols into fractions of free phenolic compounds and intensified the ultrasound‐assisted extraction of antioxidants. The presence of rutin, protocatechuic acid, gallic acid, caffeic acid, chlorogenic acid, and quercetin was responsible for high bioactivity of MWD CCB. However, thermal‐ and oxidation‐induced degradation of thermolabile polyphenols was responsible for the loss of antioxidant activity at higher (600 and 900 W) and lower (180 W) microwave powers. CCB dried using 300 W microwave power was the best drying process with the highest content of bioavailable antioxidants and antioxidant activity. Practical applications Using lignocellulosic plant part as a source of functional food or nutritional compounds requires intensive studies on the nutritional quality of products as well as bioavailabilities of such compounds. As most of the antioxidant compounds remain bound to cellulose and hemicellulose in seed, cob, and peel, techniques that promote the disintegration of bound polymeric complexes improve the bioactivity of these products. The present research highlights the potential benefits of microwave drying for the improvement in the bioactivity of corncob (CCB). The presence of several key phenolic compounds suggests a potential application of CCB in medicinal, cosmetic, and food industries.

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“…Comparing the drying times, during vacuum drying at 70°C, the onion slices were able to reach the equilibrium state within the 8,500 s in this study; however, that value was reported as 15,300 s at 70°C for convective drying of intact 3 mm onion slices by Süfer et al (). It is well known that the application of drying under vacuum conditions leads to a decrease in the water boiling point and thereby more rapid removal of water from the product becomes possible (Nadi & Tzempelikos, ).…”

Section: Resultsmentioning

confidence: 99%

“…To obtain a good quality dried product and to save energy, it is essential to know the transfer processes during drying which also play a critical role in the design, optimization, and control of the drying equipment (Nadi & Tzempelikos, 2018). Simulation and prediction of temperature and moisture distribution with mathematical modeling can be a useful tool for the design and control of the drying process and for prevention of undesirable changes during drying as well (Pasban, Sadrnia, Mohebbi, & Shahidi, 2017).…”

Section: Introductionmentioning

confidence: 99%

3D simulation of transport phenomena of onion drying with moving boundary in a vacuum oven

Demir

Cihan

2020

J Food Process Engineering

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This study aimed to perform numerical simulation of the onion drying process considering its deformed geometry. For this purpose, transport phenomena such as heat and mass transfer in the onion structure and water vapor transfer in its porous structure were simulated in 3D form with Darcy's law during the vacuum drying process for onions. The simulated results were validated by experimental data. Heat and mass transfer rates were determined using kinetic data. Simulation of onion drying revealed that deformed geometry should be included in the model to represent the faster removal of water from the onion due to the increase in mass transfer surface area. The influence of drying temperature (313, 323, 333, and 343 K) on drying time and water concentration of onion was insignificant. The mass transfer Biot number revealed that the water vapor removal from onion was controlled by intraparticle mass transfer resistance. Practical applications The main purpose of the vegetable drying industry is to obtain good‐quality dried products accompanied by savings in terms of energy and time. Recently, heat and mass transfer models constructed for drying of vegetables have focused on vegetables such as potato or carrot that provide limited information due to their uniform structure. An onion slice has a porous structure and increasing spaces between its rings; therefore in this study, heat and mass transfer occurring during vacuum drying of an onion was simulated considering the deformed geometry. The analysis of transport phenomenon mechanisms involves valuable information for researchers studying drying of food and large‐scale vacuum dryer designers in which 3D simulation of onion drying revealed that the deformed geometry fitted better to experimental results than undeformed geometry. The results of 3D simulation can be used to predict drying time and energy requirements of the process better than regular numerical modeling and may serve dried onion manufacturers.

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Vacuum drying of apples (cv. Golden Delicious): drying characteristics, thermodynamic properties, and mass transfer parameters

Cited by 49 publications

References 64 publications

Effects of sodium alginate‐based coating pretreatment on drying characteristics and quality of heat pump dried scallop adductors

Effects of sodium alginate‐based coating pretreatment on drying characteristics and quality of heat pump dried scallop adductors

Effect of microwave power on drying kinetics, structure, color, and antioxidant activities of corncob

3D simulation of transport phenomena of onion drying with moving boundary in a vacuum oven

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