Drying characteristics of ultrasound assisted hot air drying of Flos Lonicerae

Novel sequential and simultaneous infrared-accelerated drying technologies for the food industry: Principles, applications and challenges

Infrared drying (IRD) is considered an innovative drying solution for the food industry with advantages of energy-saving potentials, reduced drying time and production cost-effectiveness. However, IRD also suffers from drawbacks such as weak penetrative ability, and product overheating and burning. Therefore, over the years, significant progress has been made to overcome these shortcomings by developing infrared-accelerated drying (IRAD) technology based on the combination of IRD with other drying technologies. Although several reviews have been published on IRD, no review focusing on IRAD is yet available. The current review presents up-to-date knowledge and findings on the applications of IRAD technologies for enhancing the quality and safety of food. The fundamental principles and characteristics of IRAD, energy-saving potentials, simulation and optimization approaches for enhancing efficiency, and developments in various acceleration approaches by combining with other drying techniques for achieving better end-products are discussed, and challenges and future work for developing the novel accelerated drying technology are also presented. Due to the synergistic effects of sequential or simultaneous combined drying methods, the total drying time and energy required are drastically lowered with most IRAD technologies, and consequently there are significant improvements in the sensory, nutritional, and safety attributes of dried food products with better appearance and quality. The development of multi-wavelength IRAD systems based on infrared absorption bands, and the incorporation of novel sensing techniques for real-time monitoring during drying will further enhance process efficiency and food quality and safety.

Nostoc sphaeroides Cyanobacteria: a review of its nutritional characteristics and processing technologies

Nostoc sphaeroides is an edible Cyanobacterium which has high nutritional value and is widely used in dietary supplements and therapeutic products. N. sphaeroides contains protein, fatty acid, minerals and vitamins. Its polysaccharides, phycobilin, phycobiliproteins and some lipids are highly bioactive. Thus, N. sphaeroides possesses anti-oxidation, anti-inflammation and cholesterol reducing functions. This paper reviews and evaluates the literature on nutritionally and functionally important compounds of N. sphaeroides. It also reviews and evaluates the processing of technologies used to process N. sphaeroides from fresh harvest to dry particulates including pretreatment, sterilization and drying, including their impact on sensorial and nutritional values. This review shows that a suitable combination of ultrasound, radio frequency and pulse spouted microwave with traditional sterilization and drying technologies greatly improves the sensorial and nutritive quality of processed N. sphaeroides and improves their shelf life; however, further research is needed to evaluate these hybrid technologies. Once suitably processed, N. sphaeroides can be used in food, cosmetics and pharmaceutical drugs as an ingredient.

Optimization of pea seed intermittent drying assisted with ultrasound technology

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.

Thermal Diffusivity, Moisture Diffusivity, and Color Change of Codonopsis javanica with the Support of the Ultrasound for Drying

In this study, drying kinetics, including thermal and moisture, of Codonopsis javanica with the support of ultrasonic technology in the drying process were investigated. Experimental processes were carried out at drying air temperatures of 40°C, 45°C, and 50°C with and without ultrasound at a frequency of 20 kHz and three levels of intensity: 1.3 kW/m2, 1.8 kW/m2, and 2.2 kW/m2. Based on theoretical calculations, experimental data, and the particle swarm optimization (PSO) algorithm, the coefficient of thermal diffusion was determined in the range of 1.01–1.36 × 10−7 m2/s, and the coefficient of moisture diffusion is in the range of 3.2–6.7 × 10−10 m2/s. In addition, the color parameters (L∗, a∗, and b∗) of the drying materials were also considered. Results showed the overall color differences (∆E) of dried products change in the range of 8.0–12.9 compared with the fresh ones. In this work, the multiple boundary conditions were considered to determine the moisture and thermal diffusion coefficients; the results obtained prove that the quality of dried products in terms of color change is also improved.

Effect of ultrasonic power on drying process and quality properties of far-infrared radiation drying on potato slices

The experiments of contact ultrasound-assisted far-infrared radiation (FIR) drying on potato slices were conducted to investigate the effects of ultrasonic power on drying characteristics and quality properties. The results showed that contact ultrasound was helpful for accelerating mass transfer of the samples, and the improvement of ultrasonic power could significantly shorten drying time. The ultrasonic reinforcement effect on drying rate declined along with the decrease in moisture content. D _eff values were within 1.15 × 10^-10 and 1.96 × 10^-10 m²/s, and improved with an increase in ultrasound power. Compared with FIR dried ones, more and larger pore size of microcapillaries in the samples' tissue structure could be observed with contact ultrasound application, and higher ultrasonic power produced more microtunnels. Contact ultrasound in FIR drying could reduce the color difference of dried potato slices, and decrease the hardness and brittleness values. Higher TPC and TFC could be achieved as ultrasonic power increased.

Ultrasound-assisted intensification of a hybrid intermittent microwave - hot air drying process of potato: Quality aspects and energy consumption

The objective of this study was to intensify combined intermittent microwave - low temperature (40 °C) hot air drying with ultrasound. The process variables were ultrasound time (40 kHz for 0, 10, 20 and 30 min), microwave power (360, 600 and 900 W), and microwave pulse ratio (1, 2, 3 and 4). Results showed that the highest reduction in moisture content was observed in the samples pretreated with ultrasound for 10 min and then dried at 900 W microwave with the pulse ratio of 4. As ultrasound time, microwave power and pulse ratio increased, significant increases were noticed in D_eff by 4.89, 16.44 and 20.7%, respectively. Moreover, shrinkage was lower in the samples pretreated with lower ultrasound time and microwave pulse ratio. Besides, bulk density reduced when the microwave power was increased due to lower volume reduction. In addition, the highest increase in rehydration (32.23%) was observed in the samples dried using the high-power intermittent microwave. Finally, the highest significant reduction in specific energy consumption as a result of increased microwave power was 23.32%. In general, results of this study demonstrated that the ultrasound-intensified combined intermittent microwave - low temperature hot air drying may be a suitable alternative for industrial applications.

Deep bed rough rice air-drying assisted with airborne ultrasound set at 21 kHz frequency: A physicochemical investigation and optimization

This study investigates the feasibility of achieving a modified rough rice air-drying with ultrasound intervention (US) set at 21 kHz frequency. The process was carried out using an ultrasound assisted convective dryer and analyzed in terms of drying time, energy consumption (EC), evaporation rate (ER), broken kernel (BK), water activity (a_w), vitamin B₃ (niacin), and total phenolic content (TPC). The lab-scale dryer was set to transmit energy at power levels of 30, 60, 90, 120, and 150 W in the air temperatures of 35, 40, 45, 50, and 55 °C and velocities of 0.2, 0.5, 0.8, 1.1, and 1.4 m/s for a thickness of 20 cm. The results showed that in-range drying parameters played a major role in response analysis, suggesting that ultrasound efficiency during convective drying heavily depends on the power, air temperature, and velocity levels. Ultrasound assistance significantly increased bed evaporation rate up to 38.93%. Subsequently, it caused a reasonable reduction in total drying time, EC, and BK percentage up to 27.92%, 25.98%, and 34.22%, respectively in the case of 35 °C, v = 0.8 m/s, and P = 90 W. Remarkable advances were attained in the ultrasound assisted drying domain in grain quality via acceptable decrease in niacin and TPC losses within shorter drying time. There was a significant linear trend in BK, niacin, and TPC values across the bed thickness, which all was increased by the ultrasound application. The highest nutrient retention and physical quality preservation belonged to the top layer, which was influenced by the ultrasound radiation by the highest degree.

Effect of Ultrasound on Heat Pump Drying Characteristics of Pea Seeds

For the purpose to study the effect of ultrasound treatment on heat pump drying, the experiments were conducted on pea seeds at drying temperature of 30, 35 and 40 °C , ultrasound power of 0, 60 and 100 W and frequency of 0, 28 and 40 kHz. The influence of ultrasound and temperature on the drying process was studied by analyzing the drying characteristics of pea seeds. The results demonstrated that increasing the ultrasound power, frequency and drying temperature can improve the drying rate and the Midilli model can describe the drying kinetics of pea seeds well. The effective moisture diffusion coefficient increased with the increase of ultrasound power, frequency and drying temperature, while there was no obvious trend for the change of seed activation energy under different conditions. The seed viability was promoted with the raise of ultrasound power and fell when increasing drying temperature.

Variation in properties of tender jackfruit during different stages of maturity

This research was conducted on two varieties of tender jackfruit [hard (HV) and soft variety (SV)]. The tender jackfruit was divided into four stages (i.e. Stage 1, 2, 3 and 4) and their physical, mechanical, chemical and textural properties were determined for both the varieties. Physical properties like weight, length, diameter, geometric mean and arithmetic mean diameter were increases with increase in size for both the varieties. There was a significant increase in TSS in both the varieties (HV: 1.5 ± 0.02 to 5.1 ± 0.03; SV: 2.7 ± 0.05 to 7.1 ± 0.05 ^oBrix) from stage 1 to 4 because of ripening of fruit. The hardness, fracturability and springiness increases with maturity but on the counterpart, there is a decrease in adhesiveness, cohesiveness, chewiness and gumminess. The nutritional properties and the energy (kj) values were inevitable increases whereas vitamins content was decreases from stage 1 to 4 in both the varieties. The measured properties will be helpful in planning, design and fabrication of post-harvest processing equipment for tender jackfruits.

Application of airborne ultrasound in the convective drying of fruits and vegetables: A review

The application of airborne ultrasound is a promising technology in the drying of foods, particularly to fruits and vegetables. In this paper, designs of dryers using ultrasound to combine the convective drying process are described. The main factors affecting the drying kinetics with the ultrasound application are discussed. The results show that the ultrasound application accelerated the drying kinetics. Ultrasound application during the convective drying of fruits and vegetables shorten the drying time. Ultrasound application can produce an increase of the effective moisture diffusivity and the mass transfer coefficient. The influence of ultrasound on physical and chemical parameters evaluating the product quality is reviewed. Ultrasound application can decrease the total color change, reveal a low water activity and reduce the loss of some nutrient elements. Meanwhile, ultrasound application can also better preserve the microstructure of fruits and vegetables in comparison to convective drying.

Evaluation on the air-borne ultrasound-assisted hot air convection thin-layer drying performance of municipal sewage sludge

The thin-layer drying behavior of the municipal sewage sludge in a laboratory-scale hot air forced convective dryer assisted with air-borne ultrasound was investigated in between 70 and 130°C hot air temperatures. The drying kinetics in the convective process alone were compared to that for ultrasound-assist process at three ultrasound powers (30, 90, 150W). The average drying rates within whole drying temperature range at ultrasound powers of 30, 90 and 150W increased by about 22.6%, 27.8% and 32.2% compared with the convective drying alone (without ultrasound). As the temperature increasing from 70°C to 130°C, there were maximum increasing ratios for the effective moisture diffusivities of the sewage sludge in both falling rate periods at ultrasonic power of 30W in comparison with other two high powers. In between the ultrasound powers of 0 and 30W, the effect of the power on the drying rate was significant, while its effect was not obvious over 30W. Therefore, the low ultrasonic power can be just set in the drying process. The values of the apparent activation energy in the first falling rate period were down from 13.52 to 12.78kJmol^-1, and from 17.21 to 15.10kJmol^-1 for the second falling rate period with increasing the ultrasonic power from 30 to 150W. The values of the apparent activation energy in two falling rate periods with the ultrasound-assist were less than that for the hot air convective drying alone.