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In this article, the effect of four drying techniques namely hot air drying (AD), infrared drying (IRD), hot air-assisted radio frequency drying (RFD), and microwave-assisted hot air drying (MWD) on quality attributes of dried peach (Prunus persica) leather (PL) was investigated. Drying tests were conducted at 70°C, air velocity of 1.0 m/s and at fixed power level of 4 W/g for RFD, IRD, and MWD. Moisture distribution, texture, rehydration ratio, color, and microstructure of PL were investigated. The results showed that the samples dried by MWD had the shortest drying time (180 min) followed by IRD (210 min), RFD (210 min) and AD (300 min). Study on microstructure and flavor analysis reveals that IRD gave the best results. Sensory tests using electronic tongue and electronic nose that evaluate the odor and taste profiles of dried PL indicates that IRD produced the best quality among the four drying techniques. [ABSTRACT FROM AUTHOR]

Kedondong (Spondias dulcis) contains polyphenols, vitamin C and carotenoids which are beneficial to human health. Fresh kedondong has short shelf life and drying is an option to preserve the fruit in dried form to avoid spoilage. In this research, kedondong slices were dried at three temperatures (60 °C, 70 °C and 80 °C) using convective air and RH was fixed at 30 %. High drying temperature facilitated faster drying rate but resulted in poor product quality when compared to freeze dried samples. Drying rates were observed only occurred within falling rates period. Effective diffusivities were estimated in the order of magnitude 10–7 - 10–9 m2/s based on Fick's second law. Quality assessment showed that samples dried at 60 °C had the lowest hardness and the highest total polyphenols content was observed from samples dried at 80 °C. In addition, kedondong flavour note was found favourable from samples dried at 70 °C and 80 °C based on penalty analyses. [ABSTRACT FROM AUTHOR]

The effect of drying temperature (60, 65, 70, and 75 °C) on drying characteristics, shrinkage, rehydration kinetics, microstructure and color profiles of lemon slices were investigated using a far-infrared radiation heating assisted pulsed vacuum dryer. Results showed that the drying time of lemon slices was reduced from 10.5 to 5.5 h when the drying temperature was increased from 60 to 75 °C. Weibull model could precisely describe the drying of samples under different drying temperatures ( R 2  > 0.99). Moisture effective diffusivity ( D eff ), which was determined by taking shrinkage effect into consideration, varied with moisture content. At the initial drying stages, the volume shrinkage of samples followed a linear relationship with decreasing moisture content as the volume shrinkage is approximately equal to the volume of evaporated water. Microstructure observation illustrated that the “skeleton” was fixed when moisture content decreased to approximate 60% w.b. Page model could well model the rehydration kinetics ( R 2  > 0.98). In terms of color evaluation, temperature of 75 °C significantly caused color deterioration and it recorded the highest color change ( ΔE ) of 14.23, Browning Index ( BI ) of 27.14 and lowest Hue Angle ( H 0 ) of 79.46. The findings indicate that FIR-pulsed vacuum drying is a promising alternative method for lemon slices as it can enhance drying process as well as preserve the quality attributes of lemon slices. [ABSTRACT FROM AUTHOR]

Drying is one of the essential processing steps for dried edible bird’s nest; however, sialic acid and antioxidant can be highly thermosensitive and unstable. Therefore, aim of this study was to determine the degradation kinetics of sialic acid and antioxidants during low-temperature drying at 25–40°C as compared to conventional hot air-drying at 70°C. These compounds’ degradation exhibited first-order kinetics. Sialic acid and antioxidant retentions were 83.9 and 96.6%, respectively, at 25°C, and 78.7 and 91.5% at 40°C, respectively, by low-temperature drying; while, 42.5 and 38.7%, respectively, at 70°C by conventional hot air-drying. Finally, empirical models were significantly fitted to predict sialic acid and antioxidant retention as edible bird’s nest reached a certain level of drying, which may be useful from the processing standpoint and validate the usage of low-temperature drying as a process tool for retention of sialic acid and antioxidant in edible bird’s nest. [ABSTRACT FROM PUBLISHER]

The color change kinetics of American ginseng (Panax quinquefolium) slices were investigated in an air impingement dryer under different drying temperatures (35, 45, 55, and 65°C) using the CIE Lab color parameters (L*, a*, b*) as the assessment indicators. Results illustrated that all three color parameters (L*, a*, b*) increased with drying time. The L* value decreased with increasing drying temperature. However, a* and b* values increased with the increase in drying temperature. Furthermore, at the initial drying stage the change rate of L* increased significantly, while towards the end of drying it reduced significantly. As regards a*, it slowly changed at the initial and final drying stages rather than in the intermediate drying stage. In the case of b*, it increased with increasing drying time and drying temperature during the whole process. The zero-order, first-order, and fractional conversion models were fitted to the experimental data, and the model's parameters were determined using linear regression analysis. By comparing the fitting of kinetic models to the experimental data, the most suitable model was selected to describe the color change kinetics. An Arrhenius equation was used to calculate the activation energy for color change kinetics and it was found that the values were 33.87–38.55, 56.48, and 74.03 kJ/mol for L*, a*, and b*, respectively. The findings of this work contribute to a better understanding of ginseng color changes kinetics during drying, and the established change kinetics models are a good tool for predicting, evaluating, and controlling of color change of American ginseng during its drying process. [ABSTRACT FROM AUTHOR]

Sun drying of chempedak (Artocarpus integer) was carried out on different sample sizes to investigate the effects on product quality. Fick's second law model was used to determine the effective diffusivities of sun-dried chempedak slabs based on the drying rate versus moisture content plots. In addition, texture degradation and total color changes were investigated. The texture and color changes of dried chempedak were relatively significant (p < 0.05) compared to fresh chempedak. There was an increase in dried fruit hardness and chewiness but a decrease in springiness and cohesiveness during drying. [ABSTRACT FROM AUTHOR]

The objectives of this article is to propose a new drying model for the second falling rate period known as the variable diffusion controlled period that follows after the first falling rate period and to propose a new method to determine the second critical moisture content that separates these two periods. Experimental work on paddy drying at minimum fluidization velocity was carried out in a rapid bin dryer. The effects of operating temperatures (60-120°C) and bed depths (2-6 cm) on the paddy drying characteristics were investigated. It was found that the normalized drying rate of paddy was proportional to the normalized moisture content in the first falling rate period but in the second falling rate period, the normalized drying rate of the material varies exponentially with the normalized moisture content. The different relationship between the normalized drying rate and the normalized moisture content in the first and second falling rate periods indicate that two different mechanism of moisture transport are at work. The new exponential model of the second falling rate period and the linear model of the first falling rate period were found to fit the experimental data very well. Derivation from variable diffusion equation shows that the linear model is the result of constant diffusion coefficient whereas the new exponential model is the result of linear diffusion coefficient. This also implies that the first falling rate period is a constant diffusion controlled period and the second falling rate period is a variable diffusion controlled period. In addition, drying kinetics data of a drying process that fits the exponential model over a very slow drying period will show that the drying process is under the effect of a linear diffusion coefficient. It was also found that the proposed new method to determine the second critical moisture content that distinguishes between the first and second falling rate periods by using a sudden change in the value of the drying rate gradient to a much lower value at that point is more rigorous and yet simpler than the method of determining the specific location of the receding drying boundary since it is based on the behavior of the actual drying kinetic data. [ABSTRACT FROM AUTHOR]

The article announces that Professor Min Zhang has received the Arun S. Mujumdar (ASM) Medal for Outstanding Mentorship and Excellence in Drying Research.

In this study, black chokeberries were dehydrated by sequential calcium pretreatment and ultrasonic/microwave drying. The investigation focused on exploring the mechanisms of water transport and metabolic pathways of polyphenols. A diffusional model was modified by considering the factors such as shrinkage, porosity and temperature-dependent water diffusivity to simulate the moisture transport. Accordingly, the Spatio-temporal evolutions of cytoplasm water, extracellular water and total water content in black chokeberry throughout drying were successfully revealed. On the other hand, the quality attributes involved in the metabolic pathways of polyphenols, i.e., free/bound phenolics, cell wall pectin, polyphenol oxidase (PPO) or peroxidase (POD), and viscoelastic properties under these drying treatments were intensively analysed. Through correlation analysis, it was found that CaCl 2 pretreatment strengthened the oxidation of free procyanidin B 2 by PPO. In contrast, both ultrasound and microwave drying weakened the negative influence of PPO on the stability of free rutin. Besides, temperature rise promoted the loss of free polyphenols and the degradation of cell wall pectin, weakening the attachment of bounded-caffeic acid on the cell wall. This investigation provides new physical and chemical understandings about fruit drying and reveals the potential benefits of hybrid drying technologies. • CaCl 2 immersion was combined with ultrasound/microwave drying to dry black chokeberry. • A mass transfer model with temperature rising, shrinkage and porosity was built. • Decline of free procyanidin B 2 was caused by both enzymatic and thermal degradations. • Ultrasound and microwave treatments alleviated enzymatic degradation of free rutin. • Transformation of cell wall ASP to WSP contributed to the loss of bound caffeic acid. [ABSTRACT FROM AUTHOR]

Abstract: The plasticity of hot air-dried guluronate-rich (MG) and mannuronate-rich (MC) alginate films prepared from 2% and 4% (w/w) alginate solutions, which contained the same amount of polymer, through hot-air drying at 40–80°C were investigated. These films were subjected to thermomechanical, differential scanning calorimetry, fourier-transform infrared, X-ray diffractometry, dimension, morphology, moisture content, viscosity and polymer molecular weight analysis. Film plasticity increased when dilute alginate solution and MC were employed in film preparation. This was due to decrease in polymer–polymer interaction at high-strength domains of matrix involving C–H, O–H, C–O and/or Cof alginate, attributing to plasticization effect of water and ease of molecular rearrangement of alginate. The plasticity of film decreased with an increase in drying temperature from 40 to 60°C following heat-induced polymer–polymer interaction. A further increase in drying temperature to 80°C nonetheless greatly promoted film plasticity through air bubble formation and reduced alginate molecular weight in film. [Copyright &y& Elsevier]