•A convective dryer was developed for drying of potato, garlic and cantaloupe.•Effect of drying conditions (air temperature and air velocity) on effective moisture diffusivity and energy consumption ...of potato, garlic and cantaloupe.•Minimum effective moisture diffusivity and energy consumption for potato, garlic and cantaloupe occurred at the temperature of 40 °C and air velocity 0.5 m/s application.•ANFIS method had the higher ability to evaluate all output (moisture ratio, drying rate, Deff and SEC) as compared to ANNs method.
The main purpose of this study was to develop and apply an adaptive neuro-fuzzy inference system (ANFIS) and Artificial Neural Networks (ANNs) model for predicting the drying characteristics of potato, garlic and cantaloupe at convective hot air dryer. Drying experiments were conducted at the air temperatures of 40, 50, 60 and 70 °C and the air speeds of 0.5, 1 and l.5 m/s. Drying properties were including kinetic drying, effective moisture diffusivity (Deff) and specific energy consumption (SEC). The highest value of Deff obtained 9.76 × 10−9, 0.13 × 10−9 and 9.97 × 10−10 m2/s for potato, garlic, and cantaloupe, respectively. The lowest value of SEC for potato, garlic, and cantaloupe were calculated 1.94 × 105, 4.52 × 105 and 2.12 × 105 kJ/kg, respectively. Results revealed that the ANFIS model had the high ability to predict the Deff (R2 = 0.9900), SEC (R2 = 0.9917), moisture ratio (R2 = 0.9974) and drying rate (R2 = 0.9901) during drying. So ANFIS method had the high ability to evaluate all output as compared to ANNs method.
•Jujube slices were subjected to cold plasma pretreatment (CPP) before drying.•CPP changed the surface topography of jujube slices by etching larger cavities.•CPP significantly enhance drying rate ...and effective diffusivity.•CPP improved polyphenol contents and antioxidant capacity of dried jujube slices.•Cold plasma is a very promising pretreatment tool for drying processes.
Jujube slices were pretreated by cold plasma for 15, 30, and 60 s on each side, followed by hot air drying at 50, 60, and 70 °C. Scanning electron microscopy investigation indicated that the application of cold plasma significantly changed the surface topography of jujube slice by etching larger cavities, which can facilitate moisture transfer and consequently enhance drying rate and effective diffusivity. Modified Henderson & Pabis model and Two‐term model were the two most recommended models for describing the drying kinetics of jujube slices. Cold plasma pretreatment improved the contents of procyanidins, flavonoids, and phenolics by 53.81%, 33.89%, and 13.85% at most, respectively, and thereby enhanced antioxidant capacity by 36.85% at most. Besides, cold plasma pretreatment can reduce the production of 5-hydroxymethylfurfural by 52.19% at most. In summary, cold plasma can be used as a promising pretreatment tool for drying processes of jujube slices.
•Recent progress in the use of ultrasound (US) pretreatment for food drying is overviewed .•US pretreatment is able to preserve food quality more effectively.•US application increase the drying rate ...while decreasing the amount of energy required for drying.•This review compiles findings on how ultrasound-pretreatment and ultrasound-assisted drying technology alter food's quality attributes.
One of the earliest and most prevalent processing methods to increase the shelf-life of foods is drying. In recent years, there has been an increased demand to improve product quality while lowering processing times, expenses, and energy usage in the drying process. Pre-treatments are therefore effectively used before drying to enhance heat and mass transfer, increase drying efficiency, and lessen degradation of final product quality. When food is dried, changes are expected in its taste, color, texture, and physical, chemical, and microbial properties. This has led to the need for research and development into the creation of new and effective pre-treatment technologies including high-pressure processing, pulsed electric field, ultraviolet irradiation, and ultrasound. Sound waves that have a frequency >20 kHz, which is above the upper limit of the audible frequency range, are referred to as “ultrasound”. Ultrasonication (US) is a non-thermal technology, that has mechanical, cavitational, and sponge effects on food materials. Ultrasound pre-treatment enhances the drying characteristics by producing microchannels in the food tissue, facilitating internal moisture diffusion in the finished product, and lowering the barrier to water migration. The goal of ultrasound pre-treatment is to save processing time, conserve energy, and enhance the quality, safety, and shelf-life of food products. This study presents a comprehensive overview of the fundamentals of ultrasound, its mechanism, and how the individual effects of ultrasonic pre-treatment and the interactive effects of ultrasound-assisted technologies affect the drying kinetics, bioactive components, color, textural, and sensory qualities of food. The difficulties that can arise when using ultrasound technology as a drying pretreatment approach, such as inadequate management of heat, the employment of ultrasound at a limited frequency, and the generation of free radicals, have also been explained.
The present study aims at developing a low-temperature energy-efficient sequential drying approach, using radiofrequency (RF) waves and low humidity air (LHA) for heat-sensitive foods like apple. ...Efficacy of employing RF at primary (RF + LHA) and secondary (LHA + RF) drying stage with LHA was studied in comparison with LHA and HA (hot air) and RF (2 A) drying, individually at 40 °C. LHA + RF reduced the drying time by 37% and energy consumption by 52% compared to LHA. Apple slices dried with sequential LHA + RF approach well preserved the polyphenols (98%), flavonoids (87%), and ascorbic acid (77%) compared to FD. Sequential drying did not affect the color (ΔE = 7.4 ± 0.7) and also improved the rehydration ratio (3.9 ± 0.1). The principal component analysis demonstrated that LHA + RF had higher retention of volatile compounds (aldehydes, esters, acids, alcohols) than other studied methods. The study suggests that the application of RF at the secondary drying stage with LHA accelerates the drying process and reduces energy requirement with better retention of product quality attributes.
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•Sequential drying using low humidity air (LHA) and radiofrequency (RF) is explored.•Using RF at secondary drying stage with LHA was more efficient than at primary drying.•Secondary drying with RF accelerated the drying rate and reduced drying time by 55%.•Sequential approach decreased the energy requirement by 52% compared to LHA drying.•LHA + RF drying well retained the physicochemical quality & flavour of dried apple.
The present study investigated the effect of drying temperature (50, 60, 70, and 80 °C) on the drying kinetics and water properties of burdock slices. The changes in water mobility and water ...distribution were characterized using 1H low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) techniques. The Page model satisfactorily described the hot-air drying curves of burdock. The drying kinetic curves showed that the second stage of drying corresponded exactly with when the relaxation times of free and immobile water decreased to the equilibrium points. MRI showed that water diffused from the center to the surface during drying. Overall, the LF-NMR, color and HPLC data showed that, at 60 °C, free water in burdock dissipated slowly, its color stability was higher, and its chlorogenic acid content was higher than at 70 and 80 °C. Significant correlations were found between moisture content, color and NMR parameters.
•The rule of water variation of burdock during the drying process was obtained.•Drying kinetics and LF-NMR revealed the turning points where the drying rate drops.•LF-NMR parameters predict changes in water and color of burdock.•The quality of burdock is closely related to the change of water.
•Configurations of throat-pore and throat-node models for drying are simulated.•Drying kinetics and liquid structure obtained from both models are compared.•Volume-averaged data is exploited to ...determine the moisture transport coefficient.•The continuum model of drying is revisited by pore network simulations.
In this work, the volume-averaged transport parameters of one-dimensional macroscopic continuum model for drying is determined from three-dimensional microscopic discrete pore network models. The discrete models are called throat-node model (TNM) and throat-pore model (TPM) and the respective drying simulations are carried out under identical initial and boundary conditions. In the first place, the predictive capabilities of these two discrete models are compared. The void space is overestimated by the TNM when the mean radius of throats and pores is larger than 100 µm. The drying time of TPM is found to be less than half of the simulated drying time from TNM. Next, the continuum model parameters are computed based on the simulation results obtained from these two different pore network models. Two functions between the spatially-averaged local partial vapor pressure and the saturation vapor pressure as well as the moisture transport coefficient are determined. Profiles of moisture transport coefficient can be divided into three regions by two critical saturation values – the saturation of maximum interfacial area and turning point saturation. The partial vapor pressure in the two-phase region deviates from the saturation vapor pressure, considered as a non-local equilibrium effect. Such an effect is observed for both network configurations but is less pronounced for TPM. Finally, feeding these parameters to the continuum model can predict the characteristics of the drying process, bridging the gap to the macroscale.
The feasibility of using non-conventional osmotic agents such as coconut sugar, and jaggery in coconut chips production was evaluated, and compared with sucrose treated chips in terms of quality and ...sensory attributes. Samples were processed at the identical condition of 0.60 mm slice thickness, 45 oBrix solution concentration, and 65 °C drying temperature. Osmotic dehydration ability of different osmotic agents on coconut slices was found to be comparable in terms of water loss and solute gain. Pretreatment significantly enhances mass transfer rate of water during convective drying. However, sucrose treated samples shown slightly higher effective diffusivity values during both osmotic dehydration and hot air drying due to the inherent nature of solution. Introduction of new osmotic agents was positively reflected in the sensory attributes. Other important quality indices like rehydration ratio, solute gain, textural parameters and hygroscopicity also came under an acceptable range for all samples. Thin-layer drying behavior of slices was analyzed with six widely used drying models. According to the model fittings, the drying behavior of sucrose and jaggery-treated slices can be well described by the modified Henderson and Pabis equation, and the logarithmic equation was best suited to coconut sugar-based chip samples.
•Jaggery and coconut sugar based coconut chips exhibited higher sensory score.•Coconut chips with new osmotic agents shown higher antioxidant activity.•Osmotic dehydration ability of novel osmotic agents is comparable with conventional ones.
•This study examines the drying kinetics of food waste and its impact on biogas production.•Temperature and airflow play a crucial role in the drying kinetics of food waste.•Drying reduces biogas ...production, minimizing methane emissions and environmental impact.•For sustainability reasons, solar drying can be easily integrated into existing food waste management systems.
The present work analyzes the drying kinetics of food waste, focusing on the effects of temperature, airflow and drying on biogas production. The work involves the experimental determination of food waste drying kinetics under controlled environmental conditions, including modeling the curves using a mathematical model. Indirect solar drying experiments of food waste have been performed at different air flow rates (300 m3.h-1 and 150 m3.h-1) and temperature values (40, 50, 60, and 70 °C). The temperature in the drying room was adjusted to the desired level using an auxiliary electric heating system. Energetic and environmental performance metrics of different air flow rate and temperature configurations have also been investigated and presented within the scope of this work. Additionally, an experimental investigation to measure the biogas generated by the fermentation of dried food waste was conducted. It was established that a logarithmic model best captures the drying kinetics, and the temperature and airflow are crucial variables. Increasing the drying temperature from 40 °C to 70 °C for the tests that performed in lower and higher flow rates improved the specific moisture extraction rate as 45.02 % and 130.65 %, respectively. It can also be observed that only phase 2 is present in the drying curve, phases 0 and 1 are absent. Furthermore, drying decreases the generation of biogas, which is primarily composed of methane, a potent greenhouse gas, according to experimental studies.
•An innovative drying method of jackfruit slices was established.•Low power ultrasound intensified the infrared drying of jackfruit slices.•The drying rate and effective moisture diffusivity were ...increased.•Quality properties of dried jackfruit slices were protected by ultrasound.•A more porous microstructure was observed after ultrasound treatment.
This study investigates the enhancing effect of power ultrasound (US, 80 W) on the drying characteristics, quality properties and microstructure of jackfruit slices treated with infrared (IR) treatments of 900 W, 1200 W and 1500 W in the meantime. Results showed that when ultrasound was applied, the drying time was reduced by 31%, 35% and 25% compared to pure IR 900 W, 1200 W and 1500 W, respectively. Meanwhile, Deff values of dried samples were improved. The application of ultrasound significantly increased vitamin C retention and total phenolic content at IR 900 W. The micrographs indicate that ultrasound provided a more porous microstructure of dried jackfruit slices thus accelerating the drying process. The color characteristics of IR-US samples showed no significant change compared to IR drying slices. This study shows that infrared assisted with ultrasound can be a potential method for industrial production of dried jackfruit slices.
This paper reports a study of the physicochemical quality and the drying behavior of regal seedless grapes (RSG), pretreated with a novel solution (Olive oil: 2%, calcium carbonate: 2% and distilled ...water: 96%), then open sun-dried and dried in an indirect solar dryer. To show the effect of soaking time and temperature of the solution, two soaking times are carried out (120 and 240 s) at two temperatures (333.15 and 353.15 K). Quality indicat or such as shrinkage, color, rehydration capacity, titratable acidity, power of hydrogen (pH) and polyphenol content are evaluated. The results show that the time required to dry treated RSG varies from 220 to 328h during indirect solar drying (ISD) (during 428 h for untreated samples), and from 164 to 180 h during open sun drying (OSD) (during 290 h for untreated samples). The effective moisture diffusivity of solar-dried RSG ranges from 0.316 to 3.030 mm2s−1and that of open sun-dried regal seedless grape ranges from 0.706 to 5.700 mm2 s−1. Pretreatment affects the pH values significantly, whereas the rehydration capacity showes a large difference between the treated and untreated RSG. The solar-dried RSG has more stable color and ISD retains more of their polyphenol content.
•A novel pretreatment solution considerably reduces moisture and drying duration.•The pretreatment improves color, pH and rehydration capacity of dried grapes.•The solution temperature and soaking time influence the grapes quality factors.•Indirect solar drying preserves the polyphenol content of dried grapes.•Solar drying increases the rehydration capacity of pretreated grapes.
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