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Mango puree was foamed using hydroxypropyl methylcellulose to achieve foam densities ranging from 0.3 to 0.8 g/cm3. Subsequently, these mango foams were dried at temperatures ranging from 60 to 80 °C. The experimental results showed that mango foam drying was in the falling rate period. The effective moisture diffusivity (Deff) was well described by the Arrhenius equation, with the pre-exponential factor (D0) and activation energy (Ea) closely related to the void area fraction in mango foam. This relationship led to higher Deff and shorter drying times at higher void area fractions. The minimum loss of total phenolics content (TPC) was observed in mango foams with an initial foam density of 0.3 g/cm3 dried at 60ºC, with only a 7% loss. Increasing drying temperatures to reduce drying time did not mitigate TPC loss. Similarly, the minimum reductions in antioxidant activities, as measured by both the 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid and ferric reducing antioxidant power assays, were observed in mango foams with an initial foam density of 0.3 g/cm3 dried at 60 °C, with values of 14% and 18%, respectively. Dried mango foams with lower densities exhibited more pronounced color changes due to the presence of more sponge-like voids. However, the drying temperature did not significantly affect the product color. In addition, dried mango foams with lower initial foam densities displayed a more brittle and spongy texture. [ABSTRACT FROM AUTHOR]

Using ultrasound (US) at microwave-assisted vacuum Frying (MVF) program was investigated to acquire better process efficacy and bodily high-quality attributes of fried edamame. Different power degrees of US (0, 150, 300, 600 W) and temperature (80, 90, and 100 °C) were utilized in a constant microwave power and frequency of 1000 W and 28 kHz during ultrasound and microwave-assisted vacuum frying (USMVF) process. Ten different mathematical models were employed to describe dehydration kinetics of the fried edamame, and nonlinear regression analysis was used to determine model parameters. Concerning fitting performance, the most suitable model was the two-term model. Drying kinetics, effective moisture diffusivity (De), activation energy (Ea), and physical properties of fried samples were evaluated in this newly designed USMVF equipment using different ultrasound power to the studied temperature range. By increasing the US power level, the calculated De increased from 1.947 × 10−9 to 4.742 × 10−9 m2/s. The results have revealed that the Ea of this fried edamame decreased significantly with increasing the US power level. The USMVF process at every frying temperature increased the drying kinetics and De when compared to the non-USMVF process. The USMVF samples always gave lower oil content and water activity in contrast to the non-USMVF samples. The color and texture properties of fried edamame were significantly improved and higher the US power level in the USMVF produced a better progress. Vitamin C and chlorophyll retention of fried edamame was highest in US600MVF process. [ABSTRACT FROM AUTHOR]

The present study was undertaken to develop a pre-drying process of an accelerated water absorption and partial gelatinization of starch in paddy using pulsed microwave-water applications. The experiments on microwave-assisted water absorption by paddy (var. Sworn Masuri) at five power density levels in the range 0.2–1 kW kg−1 were conducted in a semi-pilot-scale microwave dryer. The paddy was exposed to pre-calculated intermittent water spray and pulsed microwaves up to 100 min. The water absorption kinetics were modeled using modified Azuara's equation of mass transfer and the process was compared with traditional hot water soaking of the paddy at 60 °C for 3.33 h. The moisture content gained by paddy during microwave-assisted water absorption was faster (30% in 1.67 h) compared to hot water soaking (30% in 3.33 h). The consumption of water, specific energy, and water absorption time during microwave processing were reduced by 70%, 39.51%, and 50%, respectively. The method of slopes was used to estimate moisture diffusivity during microwave-assisted water absorption by paddy. X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) of treated paddy were done to understand the changes in the crystallinity and the microstructure of starch molecules. The microwave-assisted water absorption process was found to accelerate the moisture gain with the effect of partial gelatinization of starch in the paddy. Further, the experiment can be continued in the same microwave dryer to fully gelatinize the paddy at 30% moisture content and dry the gelatinized paddy. [ABSTRACT FROM AUTHOR]

The microwave drying performance of lignite thin layer in a bench-scale setup was highlighted in terms of three additives with 10% dosage. The dielectric loss for dried lignite, raw lignite, lignite/coal fly ash, lignite/Na2SO4, and lignite/Na2CO3at 2,450 MHz were 0.06, 0.13, 0.14, 0.15, and 0.18. In comparison with raw lignite, the average temperature rising of the thin layer at 385 W for lignite blending with sodium carbonate, sodium sulfate, and coal fly ash was about 10, 7, and 2°C. The apparent activation energies of both falling rate periods for lignite blending with three additives were less than that of raw lignite. Sodium carbonate among three additives could be preferable one, followed by sodium sulfate and coal fly ash. The energy efficiency increased with the addition of sodium carbonate, sodium sulfate, and coal fly ash. The required electricity energy for lignite/Na2CO3blend at 385 W was reduced by about one half compared with the raw lignite. [ABSTRACT FROM PUBLISHER]

The effects of osmotic dehydration (OD) with or without pulsed vacuum (PV) on hot-air drying kinetics and quality attributes of cherry tomatoes were investigated. Both OD and PVOD pre-treatments were performed for 3 h at 50°C in 50 and 70oBrix sucrose solutions with a solution-to-fruit mass ratio of 4:1, and PVOD was applied for 15 min before OD at atmospheric pressure. Samples were further dried at air temperature of 70°C. Effective moisture diffusivity (Deff) of osmotically dehydrated samples increased gradually while the Deffcurve of fresh samples had a plateau stage during hot air drying. Lower glass transition temperature, Tg, values of osmotically dehydrated samples indicated that they needed a lower storage temperature. Both OD and PVOD pre-treatments had advantages in shortening drying cycles and improving quality of products. Compared with air drying, osmo-air drying decreased the total drying time, color change, and hardness of dried samples by 32.26%, 18.11%, and 88.21%, respectively, and increased volume ratio and vitamin C retention rate by 72.31% and 125.82%. As compared with OD, PVOD decreased color change and hardness by 28.48% and 45.17%, increased volume ratio and vitamin C retention rate by 27.41% and 17.77%, but there was no significant difference shown in drying time. Therefore, osmotic pre-treatment can shorten the total dehydration time, and improve the general quality of dried cherry tomatoes. [ABSTRACT FROM PUBLISHER]

The 'loco' is a mollusk somewhat similar to abalone that exists exclusively in Chile and Peru. Given the high commercial value of loco, preservation through freeze-drying seems economically viable. In this work, the freeze-drying process of loco meat was analyzed theoretically and experimentally. The effects of particle size, freeze-drying pressure, and intermittent use or not of microwave in the secondary drying stage, on the extent of the freeze-drying period, rehydration properties, shrinkage and texture were investigated by using a 23 factorial design. Drying and rehydration kinetics were adjusted to phenomenological models in order to determine mass transfer parameters. Freeze-drying pressure significantly affects the extent of the drying process. Freeze-drying pressure results in shrinkage, while microwave produces a volume increase. The effective moisture diffusivity (Deff) estimated form drying curves fluctuated between 10-10 and 10-11 (m2/s), agreeing with values reported for other meat products. The adjustment of the rehydration kinetics to the Constant Diffusivity Model gave the best fit, resulting in Deff in the order of 10-10 (m2/s). Particle size and freeze-drying pressure significantly affected rehydration capacity. [ABSTRACT FROM AUTHOR]

U.S. sales of organic products continue to climb due to consumer perception of both environmental and health benefits of organic produce. The objectives of this study were to evaluate the effects of air and freeze drying and blanching treatment prior to air drying on phytochemical content of conventional and organic red raspberries and blueberries. Total anthocyanins and phenolics contents and total antioxidant activity were determined in two cultivars of blueberry (‘Duke’ and ‘Reka’) and in ‘Meeker’ red raspberry harvested under two different techniques (hand and machine). The phytochemical content was determined after subjecting the berries to air and freeze drying with or without blanching pretreatment. In general, no consistent differences were noted between the phytochemical concentrations in fresh conventional and organic berries. The effect of drying on the retention of phytochemicals depended on drying technique, cultivar, and production system (conventional or organic). Blanching prior to air drying significantly increased the effective moisture diffusivity in both berries, thus reducing the drying time. In general, air drying caused significant reductions in anthocyanins, phenolics, and antioxidant activity in both blueberries and raspberries. Compared to air drying, freeze drying improved retention of phytochemicals during processing and in some cases it even increased the concentration of phytochemicals. The application of blanching resulted in enhanced moisture transport, thus reducing the drying time. The blanching treatment prior to air drying increased the retention of phytochemicals in dried berries. [ABSTRACT FROM AUTHOR]

We report the synergistic and competitive interactions between multiple plasticizers in plasticized low-amylose starch that result in either enhanced or reduced water migration fluxes and effective moisture diffusivities. The starch was plasticized using glycerol and xylitol either individually or in 1:1 combination. The water migration fluxes and moisture diffusivities were higher in xylitol plasticized films compared to the glycerol plasticized ones. For low plasticizer concentrations, the presence of both the plasticizers competitively reduced the effective moisture diffusivities and moisture migration fluxes due to antiplasticization. However, at higher plasticizer contents (at and above 15 wt%), the presence of multiple plasticizers enhanced the moisture migration fluxes and effective moisture diffusivities due to synergistic plasticization. The moisture migration fluxes and effective moisture diffusivities exhibited both moisture and plasticizer concentration dependence and the former was found to be stronger than the latter. These findings can be used for designing and controlling the vapor barrier properties of starch-based bioplastics during drying and formulation phase. [ABSTRACT FROM AUTHOR]

The drying mechanism of fermented sausages (sucuks) that were cylindrical rod shaped, 40 cm long and 4 cm diameter, during ripening under natural convection conditions at different temperatures (15 to 30°C) was examined. To simulate the experimental drying curves, three empirical models and a diffusional model assuming negligible external mass transfer resistance were evaluated. The drying rate curves of sucuk samples were also simulated taking into account the influence of the external mass transfer resistance. The equation was solved using the trial-and-error solution algorithm developed in this study and the mass transfer coefficient, kc, and effective moisture diffusivity, Deff, were simultaneously determined (1.44 × 10-8 to 1.93 × 10-8 m/s and 4.30 × 10-10 to 6.85 × 10-10 m2/s, respectively). The proposed model considering the effect of external resistance allowed the accurate simulation of the experimental drying data of sucuks at different temperatures. [ABSTRACT FROM AUTHOR]

The drying of organic pigments is a challenging assignment due to the complex relationship between heat and mass transfer and the quality attributes such as color, shade, and strength. There is an urgent need to address the drying technology-related issues of this industrially important class of specialty chemicals. The widely used tray dryers and band dryers need further attention due to abysmally low energy efficiency. One of the ways to overcome the longer drying time is to make use of infrared source in addition to convective air drying. The present article discusses the effect of combinatorial IR-convective drying on the quality aspect of organic pigments. The heat and mass transfer rates were analyzed in terms of Biot number to ascertain the role of infrared in bringing down the drying time without compromising the pigment qualities. The mathematical analysis of drying of preformed pellet of pigments was carried out in terms of effective diffusivity, which was obtained in the range of 10-9 to 10-10 m2/s. [ABSTRACT FROM AUTHOR]

The effect of microwave drying technique on moisture content, moisture ratio, drying rate, drying time, effective moisture diffusivity, and porosity of spinach (Spinacia oleracea L.) were investigated. By increasing the microwave output powers (180-900 W) and the sample amounts (25-100 g), the drying time decreased from 18 to 3.5 min and increased from 7.7 to 25 min, respectively. To determine the kinetic parameters, the drying data were fitted to various models based on the ratios of the differences between the initial and final moisture contents and equilibrium moisture content versus drying time. Among of the models proposed, Page's model gave a better fit for all drying conditions applied. The activation energy was calculated using an exponential expression based on Arrhenius equation. The relationship between the drying rate constant and effective moisture diffusivity was also estimated and gave a linear relationship. [ABSTRACT FROM AUTHOR]

The effect of microwave output power and sample amount on effective moisture diffusivity were investigated using microwave drying technique on round okra (Hibiscus esculentus L.). The various microwave output powers ranging from 180 to 900 W were used for the determination of effective moisture diffusivity for constant sample amount of 100 g okra. To examine the effect of sample amount on effective moisture diffusivity, the samples in the range of 25-100 g were dried at constant microwave output power of 360 W. By increasing the microwave output powers and decreasing the sample amounts, the effective moisture diffusivity values ranged from 20.52 × 10-10 to 86.17 × 10-10 and 34.87 × 10-10 to 11.91 × 10-9 m2/s-1, respectively. The modeling studies were performed to illustrate the relationship between the ratio of the microwave output power to sample amount and effective moisture diffusivity. The relationship between drying constant and effective moisture diffusivity was also estimated. [ABSTRACT FROM AUTHOR]

The spatial distributions of water content and temperature inside moist food or biological materials (native or manufactured) during drying are important in interpretation and prediction of quality changes. The dynamics of drying in modern devices is not simple - for instance, the process of intermittent drying - thus, a liquid diffusion model is expected to be the simplest and hopefully the very effective. In this article, some controversial aspects of the concept of the effective Fickian liquid moisture diffusivity are described and discussed. These discussions are intended to stimulate more interest in working toward a better rationalization of the liquid diffusion concept. It is suggested that such a parameter may even be called a "liquid depletion coefficient" instead to avoid confusion at the fundamental level. An improved alternative model from the effective liquid diffusion model is possible and some new ideas have been explored. [ABSTRACT FROM AUTHOR]

Solutions of fructose, maltodextrin (DE 5), and their mixtures at the ratios of 20:80, 40:60, 50:50, 60:40, and 80:20 were gelled with 1% agar-agar and dried under convective-conductive drying conditions. The thin slabs were maintained at isothermal drying condition of 30 and 50°C. Yamamoto's simplified method based on regular regime approach was used to calculate the (effective) moisture diffusivity. Both the drying rates and the moisture diffusivity exhibited strong concentration dependence. The concentration dependence was stronger in the case of fructose and fructose rich solutions. Both the moisture diffusivity and drying rates of the mixture solutions were enhanced due to plasticization of fructose on maltodextrin, which is explained through free volume theory. [ABSTRACT FROM AUTHOR]

A simulation model for convective drying of wet porous materials was developed. For the simulation, we measured the moisture diffusivities within them and applied a modified Dubinin-Astakhov equation to the moisture sorption data for a membrane filter. The simulation results not accounting for internal mass transfer resistance were quite different from the experimental ones. The drying characteristics calculated by a shrinking core model with effective moisture diffusivity represented a much lower drying rate and much higher temperatures, respectively, than the experimental ones. This meant that we must consider the plural moisture transport mechanisms within the samples. Therefore, we calculated the drying rate and temperatures with an apparent overall mass transfer coefficient damping with a decrease in the moisture content. The results accounting for the hygroscopic effects broadly agreed with the experimental ones by the evaluation. [ABSTRACT FROM AUTHOR]

Vacuum drying of mango pulp at varying conditions of pulp thickness (2, 3, and 4 mm) and vacuum chamber plate temperature (65, 70, and 75 °C) was carried out under 30-50 mm of mercury absolute pressure. A model based on moisture di6usivity was found to give close prediction to moisture content of the pulp at di6erent times of drying with correlation coe7cient varying between 0.98-0.99 for pure mango pulp and pulp with ingredients. Color change of reconstituted pulp made from mango powder was found to depend more on pulp thickness than plate temperature. For getting low color change vacuum drying should be carried at maximum pulp thickness of 2.6 mm and vacuum chamber plate temperature of 72.3 °C. [ABSTRACT FROM AUTHOR]