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Optimization of pea seed intermittent drying assisted with ultrasound technology

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Abstract

In recent years, hot air-drying coupled with ultrasonic technique or intermittent method is widely applied in food drying owing to significantly improving drying properties. The objective of this paper was to study the effect of drying temperature, ultrasonic power and intermittent method on drying kinetics, seed vitality and energy consumption of pea seed. The single factor tests were performed with air temperature of 28, 32, 36, and 40 °C, using ultrasound at four power levels of 60, 100, 150, and 200 W, and intermittent drying with intermittent ratios of 1, 1/2, 1/3 and middle intermittence. The orthogonal experiments of three factors with three levels were conducted based on the results of single factor test. Results indicated that drying temperature, ultrasonic power and drying method all had significant effects on drying kinetics, germination percentage (GP), mean germination time (MGT) and germination index (GI) ( P < 0.05), and application of intermittent drying method can greatly reduce energy consumption. Further, from the orthogonal experiment, the greatest impact on the comprehensive evaluation index of seed drying was intermittent method, followed by drying temperature and the least was ultrasonic power. The optimum drying parameters of pea seed were drying temperature of 36°C, ultrasonic power of 200 W, and drying method of intermittent ratio 1/2, which were obtained by range analysis in the scope of this experiment.

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Intermittent drying experiments for wheat (cv. Tohoku206), long- (cv. L201) and short-grain (cv. Akitakomachi) rough rice were performed and analyzed by a sphere drying model. The sphere drying model consists of three parameters: surface mass transfer coefficient H, dynamic equilibrium moisture content Me, and drying constant K. The first parameter of the model is novel, allowing simulation of every type of drying including intermittent drying simply and precisely. With this model, drying computation was performed using a similar method for both drying and tempering periods, setting H = 0 for the tempering period. The wheat and rough rice samples were dried at 40 °C, 60% relative humidity and tempered at 30, 40, and 50 °C, respectively. There was good agreement between the calculated and experimental values with a standard error of less than 0.47% db for the different initial moisture contents and tempering temperatures. The tempering temperature had a significant effect on rate of internal moisture equilibration.
Article
The main aim of this work was to evaluate the effect of high-intensity ultrasound (US) on the drying kinetics of orange peel as well as its influence on the microstructural changes induced during drying. Convective drying kinetics of orange peel slabs were carried out at a relative humidity of 26.5 ± 0.9%, 40°C and 1m/s with (AIR+US) and without (AIR) ultrasound application. In order to identify the US effect on water transport, drying kinetics were analyzed by taking the diffusion theory into account. Fresh, AIR and AIR+US dried samples were analyzed using Cryo-Scanning Electron Microscopy. Results showed that the drying kinetics of orange peel were significantly improved by US application, which involved a significant (p < 0.05) improvement of mass transfer coefficient and effective moisture diffusivity. The effects on mass transfer properties were confirmed with microstructural observations. In the cuticle surface of flavedo, the pores were obstructed by the spread of the waxy components, this fact evidencing US effects on the air–solid interfaces. Furthermore, the cells of the albedo were disrupted by US, as it created large intercellular air spaces facilitating water transfer through the tissue. KeywordsDehydration–Microstructure–Modeling–Ultrasound
Article
This review is a comprehensive survey on the latest and more recent applications of ultrasound (US) on technological properties and bioactivity of food. Apart from a brief discussion on the fundamentals of ultrasound technology, examples have been set out on the physical effects of US on the improvement of food technological properties such as emulsification ability, solubility and texture, as well as on applications such as homogenization, viscosity alteration, extraction, drying, crystallization and defoaming. Among them, special emphasis has been placed on ultrasound assisted extraction (UAE). Nowadays, developments in ultrasonic equipment are such that it is feasible to consider commercial opportunities based on industrial-scale ultrasonic-aided extraction of bioactives, with worthwhile economics gains. Additionally, the initial restrictions associated to ultrasonically generated radicals in UAE have now been explored to enhance the functionality of some types of food. Finally, and despite the improved equipment design and the higher efficiencies of US systems currently used for other applications, a better understanding of the complex physicochemical mechanism of the action of high-intensity ultrasound and its effect on technological and functional properties of food would also contribute to reinforce the future presence of ultrasonic technologies in the food industry.
Article
Potato slices were dried in a tunnel dryer, a conventional fluidised bed dryer and a fluidised bed dryer with the application of microwaves. A multifactorial experimental design (3×22) was applied to analyse the effects of type of dryer, temperature, and air speed in studies of drying kinetics, until a final moisture content of 12±1.5% (wet basis) was reached. Some quality parameters of the dried potato slices for combinations of the process variables are also compared.The type of dryer and the drying temperature had a strong effect on drying rate and on the colour and porosity of the dried potato slices, while rehydration capacity and maximum penetration force were not affected.The statistical analysis showed a marked lowering of drying time when microwaves were applied to a fluidised bed, in agreement with observations reported in the literature. Around a 70% decrease in drying time was observed when the tunnel dryer was replaced by the fluidised bed dryer. Drying time was further reduced to half of that time when microwaves were applied to the fluidised bed, resulting in an 85% drying time reduction in total.The variable diffusivity model, the modified quasi-stationary model and Page's equation were used to fit the experimental drying kinetics, and Page's equation gave the best fit with a root-mean-square error in the range of 1.6–9.1%. Additionally, the effective diffusivity values determined in this work were similar to those reported in the literature.
Article
The aim of this work was to use ultrasound as a pre-treatment method prior drying of mushrooms, Brussels sprouts and cauliflower in order to achieve reduction in drying time and to understand the effect of the ultrasound in mass transfer process, where diffusivity is the limiting step in the process. Pre-treatment with 20 kHz probe and 40 kHz bath for 3 and 10 min have been compared with blanched (80 °C/3 min) and untreated samples. The procedures used were either freeze drying or conventional drying at a temperature of 60 °C and air velocity (v = 0.3 m/s) for sonicated, blanched and untreated samples. The effect of ultrasound and blanching pre-treatments on weight and moisture loss/gain, upon drying and rehydration were investigated.The drying time after ultrasound treatment was shortened for all samples, as compared to untreated. The rehydration properties (weight gain, %) were found to be the best for freeze-dried samples which showed weight gains for mushrooms (45.3%), Brussels sprouts (21.4%) and cauliflower (51%). The rehydration properties for ultrasound treated samples were higher than those for untreated samples.
Article
In this study, apple, guava and potato were dried in a heat pump dryer under inert environmental (nitrogen or carbon dioxide) conditions and the impact on colour, surface porosity and rehydration abilities were investigated. Lemon juice and peel were used as natural inhibitors to prevent browning in air drying of apples. Comparisons were made between heat pump dried samples and those dried by freeze and vacuum drying. Results showed that MAHPD low temperature drying at about 45 °C and relative humidity around 10% led to better physical properties, such as reduced shrinkage, decreased firmness and more porous structure of the materials, which resulted in quicker rehydration. When using inert gas, the colour of heat pump dried food was similar to vacuum or freeze drying.
Drying characteristics of pear slices during ultrasound-assisted hot air drying
  • Y Liu
  • Y Sun
  • L Wang
  • S Miao
  • D Luo
  • L Luo
Characterization of seeds with different moisture content by photoacoustic microscopy
  • A Pacheco
  • A Dominguez
  • C Hernandez
  • Cruz-Orea
  • A Ortiz
  • E Martinez
Thin layer drying of tomato slices