The effect of ultrasound irradiation on the convective heat transfer rate during immersion cooling of a stationary sphere

Application of ultrasound treatment in pork marination: Effects on moisture migration and microstructure

To better understanding the effects of ultrasonic marination on the porcine tissue, the moisture migration and microstructure were investigated in this study. Additionally, the acoustic field distribution was analysis using COMSOL Multiphysics. The low-filed NMR results demonstrated that ultrasonic curing induced a leftward shift in T21 and a rightward shift in T22, accompanied by a significant reduction in A22, thereby enhancing the water-holding capacity of pork. The SEM and TEM observation showed that the presence of larger interstitial gaps between muscle fibers facilitated the diffusion of NaCl. The simulation analysis revealed that the acoustic field at 26.8 kHz showed minimal standing wave effects and more pronounced cavitation, which was the main reason for the best curing effect at this frequency. The scale-up test showed the NaCl content in pork reached 1% after ultrasound curing, indicating the potential application of ultrasonic marination technology in domestic refrigerators.

Acoustic cavitation for agri-food applications: Mechanism of action, design of new systems, challenges and strategies for scale-up

Acoustic cavitation, an intriguing phenomenon resulting from the interaction of sound waves with a liquid medium, has emerged as a promising avenue in agri-food processing, offering opportunities to enhance established processes improving primary production of ingredients and further food processing. This comprehensive review provides an in-depth analysis of the mechanisms, design considerations, challenges and scale-up strategies associated with acoustic cavitation for agri-food applications. The paper starts by elucidating the fundamental principles of acoustic cavitation and its measurement, delving then into the diverse effects of different parameters associated with, the acoustic wave, mechanical design and operation of the ultrasonic system, along with those related to the food matrix. The technological advancements achieved in the design and set-up of ultrasonic reactors addressing limitations during scale up are also discussed. The design, engineering and mathematical modelling of ultrasonic equipment tailored for agri-food applications are explored, along with strategies to maximize cavitation intensity and efficiency in the application of brining, freezing, drying, emulsification, filtration and extraction. Advanced US equipment, such as multi-transducers (tubular resonator, FLOW:WAVE®) and larger processing surface areas through innovative designing (Barbell horn, CascatrodesTM), are one of the most promising strategies to ensure consistency of US operations at industrial scale. This review paper aims to provide valuable insights into harnessing acoustic cavitation's potential for up-scaling applications in food processing via critical examination of current research and advancements, while identifying future directions and opportunities for further research and innovation.

Spatiotemporal Control of Ice Crystallization in Supercooled Water via an Ultrashort Laser Impulse

Focused irradiation with ultrashort laser pulses realized the fine spatiotemporal control of ice crystallization in supercooled water. An effective multiphoton excitation at the laser focus generated shockwaves and bubbles, which acted as an impulse for inducing ice crystal nucleation. The impulse that was localized close to the laser focus and accompanied by a small temperature elevation allowed the precise position control of ice crystallization and its observation with spatiotemporal resolution of micrometers and microseconds using a microscope. To verify the versatility of this laser method, we also applied it using various aqueous systems (e.g., plant extracts). The systematic study of crystallization probability revealed that laser-induced cavitation bubbles play a crucial role in inducing ice crystal nucleation. This method can be used as a tool for studying ice crystallization dynamics in various natural and biological phenomena.

Ultrasound enhanced butyric acid-lauric acid designer lipid synthesis: Based on artificial neural network and changes in enzymatic structure

Ultrasound is a green technology for intensifying enzymatic reactions. In this study, an ultrasonic water bath with equipment parameters of 28 kHz, 1750.1 W/m², 60% duty cycle was used to assist the synthesis of butyric acid-lauric acid designer lipid (BLDL), which was catalyzed by Lipozyme 435. A convincing three-layer feed-forward artificial neural network (ANN) model was established (R² = 0.949, RMSE = 4.759, ADD = 7.329) to accurately predict the optimal parameters combination, which was described as 13.72 mL reaction volume, 15.49% enzyme loading, 0.253 substrate molar ratio (tributyrin/lauric acid), 56.58 °C reaction temperature and 120 min reaction time. The ultrasonic assistance increased actual butyric acid conversion rate by 11.38%, and also enhanced the consumption rate of tributyrin and lauric acid during the reaction. Meanwhile, the esterification activity of Lipozyme 435 was enhanced and its effectiveness up to 6 cycles. Structurally, ultrasound assistance significantly disrupted the secondary structure of the Lipozyme 435: reduced the content of α-helices, increased the content of β-sheet and β-turn. In addition, sonication caused an increase in crevice and micro-damage on the surface of the immobilized enzyme. In conclusion, low-intensity ultrasound at 28 kHz improved the synthesis efficiency of BLDL, which was scientifically predicted by ANN model, and the change of enzyme structure may be the vital reason for ultrasound enhanced reaction. However, the effect of ultrasound on immobilized enzymes' activity needs to be further explored.

Ultrasound-assisted regeneration of activated alumina/water adsorption pair for drying and dehumidification processes

Desorption processes are important part of all processes which involve utilization of solid adsorbents and are inherently energy-intensive. Here we investigate how those energy requirements can be reduced through the application of ultrasound for the activated alumina/water adsorption pair. To analyze the energy-saving characteristics of ultrasound, the ultrasonic-power-to-total power ratios of 0.2, 0.25, 0.4 and 0.5 were investigated and the results compared with those of no ultrasound at the same total input power. Duplicate experiments were performed at three nominal frequencies of 28, 40 and 80 kHz to observe the influence of frequency on regeneration dynamics. Regarding moisture removal, the highest desorption was achieved at the lowest ultrasonic-to-total power ratio corresponding to about 27% reduction in energy consumption. A nonlinear inverse proportionality was observed between the effectiveness of ultrasound and the frequency at which it is applied. Regarding regeneration temperature, application of ultrasound at higher ultrasonic-to-total power ratios of 0.4 and 0.5 reduces the regeneration temperature without taking a toll on desorption. Based on the variation of desorption dynamics with ultrasonic power and frequency, a novel ultrasound-enhanced desorption mechanism involving adsorbate surface energy is proposed and a relationship between acoustically induced strain and adsorbate surface energy is introduced. An analytical model that describes the desorption process is developed based on the experimental data. From this a novel efficiency metric is proposed, which can be employed to justify incorporating ultrasound in regeneration and drying processes.

Kinetics and bixine extraction time from achiote (Bixa Orellana L.)

The effects of the use of solvents (96% ethanol and PEG 400), solute ratios: solvent (1: 4 and 1: 6 w/w), extraction temperatures (50 and 60 °C) and leaching techniques (conventional and assisted by ultrasound) on the concentration and time of extraction of bixin from Achiote (Bixa Orellana L.) were evaluated. The extraction kinetics were constructed, and their orders were determined. The experimental values were adjusted through the mathematical models of Peleg and Azuara. ANOVA was used based on a 2³ design, blocking type of technology. The kinetics showed two stages of extraction: rapid and slow. The reaction orders were decimal numbers, which indicates the complexity of the extraction mechanism. The highest orders of reaction (2.97 and 2.075) were presented with extraction with ultrasound-assisted and ethanol as solvent, at 50 and 60 °C and solute solvent ratio 1: 4 and 1: 6, respectively. The concentration of Bixin was increased by approximately 30% by increasing the temperature. The Azuara model presented the highest adjustment with a standard error < 0.1. The conventional leaching with PEG-400 required the lowest activation energy (9.2 kJ / mol) and with this treatment in 66 min the highest concentration of bixin (2.74 mgBix / gExt) was obtained. It was concluded that ultrasound-assisted leaching facilitates the extraction of bixin pigment, and the use of PEG 400 solvent is useful to obtain higher yields.

Sequential phenolic acid co-pigmentation pretreatment and contact ultrasound-assisted air drying to intensify blackberry drying and enhance anthocyanin retention: A study on mass transfer and phenolic distribution

In this work, the spraying of ethanol solution containing phenolic acid (ferulic acid or caffeic acid) was performed before subjecting to contact ultrasound-assisted air drying of blackberry. The mass transfer modeling results revealed that sonication intensified both internal water diffusion and external water exchange during drying, and ethanol pretreatment enhanced the effective diffusivity of water. Compared with air drying alone, the drying time for sequential ferulic acid pretreatment and drying with sonication was shortened by 89.2%. Owing to the co-pigmentation between phenolic acid and anthocyanins, the retention of anthocyanins was significantly enhanced after dehydration. At the end of drying, the total anthocyanin contents in the ultrasound-dried samples pretreated with ferulic acid and caffeic acid were 25.3% and 10.5% higher than the sonicated samples without pretreatments, respectively. Furthermore, drying simultaneously with sonication promoted the preservation of non-anthocyaninic soluble phenolics including catechin, phloretic acid, rutin in blackberry compared to air drying alone. Besides, bound phenolics in blackberry were less influences by the applied dehydration treatments. This study demonstrates that the combination of phenolic acid co-pigmentation pretreatment and ultrasound drying could be a promising method to protect anthocyanin pigments during dehydration of berry fruits.

Characterization of heat transfer and friction loss of water turbulent flow in a narrow rectangular duct under 25-40 kHz ultrasonic waves

This study experimentally investigated the effect of low-frequency ultrasonic waves on the heat transfer augmentation of turbulent water flow in a narrow rectangular duct with a width of 5 mm. 25-, 33-, and 40-kHz ultrasonic transducers were set to release waves in a downward direction to disturb the flow, with Reynolds numbers (Re) of 10,000-25,000 at increments of 2500. The results indicated that the ultrasonic waves increased the friction loss by only 0.2-2% over the entire testing Re range, while an 8.1-48.6% enhancement of the heat transfer capability was obtained for the Re range of 10,000-15,000. The maximum Nusselt number occurred at a Re of 12,500 and frequency of 33 kHz. However, beyond Re values of 12,500, the thermal performance tended to decrease with an increase in Re. Consequently, the average Nusselt number ratios at ultrasonic frequencies of 25, 33, and 40 kHz over the tested Re range were 1.123, 1.039, and 1.033, respectively, while the thermal performance values were 1.108, 0.989, and 1.036, respectively. These results confirmed that ultrasound has significant potential for application in heat transfer augmentation of turbulent pipe flow. This paper also provides formulas to predict the friction factor and Nusselt number and discusses the mechanisms of heat transfer enhancement by ultrasonic waves at 25, 33, and 40 kHz.

Analysis of ultrasound-assisted convective heating/cooling process: Development and application of a Nusselt equation

In this study, the convective heating/cooling process assisted by US irradiation is analyzed with the aims of developing a new convective heat transfer correlation. Heat transfer experiments were conducted with different copper machined geometries (cube, sphere and cylinder), fluid velocities (0.93-5.00 × 10^-3 m/s), temperatures (5-60 °C), and US intensities (0-6913 W/m²) using water as heat transfer fluid. The Nusselt (Nu) equation was obtained by assuming an apparent Nu number in the US-assisted process, expressed as the sum of contributions of the forced convection and cavitation-acoustic streaming effects. The Nu equation was validated with two sets of experiments conducted with a mixture of ethylene glycol and water (1:1 V/V) or a CaCl₂ aqueous solution (30 g/L) as immersion media, achieving a satisfactory reproduction of experimental data, with mean relative deviations of 17.6 and 17.8%, respectively. In addition, a conduction model with source term and the proposed correlation were applied to the analysis of US-accelerated heating kinetics of dry-cured ham reported in literature. Results demonstrated that US improves heating of ham slices because of the increased heat transfer coefficients and the direct absorption of US power by the foodstuff.

Optimization of ultrasonic-assisted freezing of Penaeus chinensis by response surface methodology

Objectives

Optimization of ultrasonic-assisted freezing of Penaeus chinensis by response surface methodology was studied in order to (1) obtain frozen Penaeus chinensis of high quality and (2) provide practical guidance for the application of ultrasonic-assisted freezing in Penaeus chinensis.

Materials and Methods

Three independent and major variables were selected, including initial ultrasonic temperature (°C), ultrasonic power (W) and ultrasonic time (s on/2 s off). On the basis of one-factor experiments, 17 groups of experiments were established by response surface methodology according to Box–Behnken design. Using multiple regression analysis the experimental data were fitted into a second-order polynomial equation, which was tested by proper statistical methods.

Results

The optimal ultrasonic conditions were as follows: initial ultrasonic temperature 0 °C, ultrasonic power 180 W, ultrasonic time 5 s on/2 s off. Under the optimization conditions, the time of passing through maximum ice crystal generation zone was 105.500 s, which was very close to the predictive passage time of 101.541 s.

Conclusions

Initial ultrasonic temperature, ultrasonic time and ultrasonic power played an important role in the process of ultrasonic-assisted freezing of Penaeus chinensis. Response surface methodology was used to optimize the three factors in ultrasonic-assisted freezing, which could greatly shorten the time of passing through the maximum ice crystal generation zone and maintain the tissue structure of Penaeus chinensis well.

Comparison between airborne ultrasound and contact ultrasound to intensify air drying of blackberry: Heat and mass transfer simulation, energy consumption and quality evaluation

This study aimed at investigating the performances of air drying of blackberries assisted by airborne ultrasound and contact ultrasound. The drying experiments were conducted in a self-designed dryer coupled with a 20-kHz ultrasound probe. A numerical model for unsteady heat and mass transfer considering temperature dependent diffusivity, shrinkage pattern and input ultrasonic energies were applied to explore the drying mechanism, while the energy consumption and quality were analyzed experimentally. Generally, both airborne ultrasound and contact ultrasound accelerated the drying process, reduced the energy consumption and enhanced the retentions of blackberry anthocyanins and organic acids in comparison to air drying alone. At the same input ultrasound intensity level, blackberries received more ultrasound energies under contact sonication (0.299 W) than airborne sonication (0.245 W), thus avoiding the attenuation of ultrasonic energies by air. The modeling results revealed that contact ultrasound was more capable than airborne ultrasound to intensify the inner moisture diffusion and heat conduction, as well as surface exchange of heat and moisture with air. During air drying, contact ultrasound treatment eliminated the gradients of temperature and moisture inside blackberry easier than airborne ultrasound, leading to more homogenous distributions. Moreover, the total energy consumption under air drying with contact ultrasound assistance was 27.0% lower than that with airborne ultrasound assistance. Besides, blackberries dehydrated by contact ultrasound contained more anthocyanins and organic acids than those dried by airborne ultrasound, implying a higher quality. Overall, direct contact sonication can well benefit blackberry drying in both energy and quality aspects.

Effect of dielectric barrier discharge plasma, ultra-sonication, and thermal processing on the rheological and functional properties of sugarcane juice

The present work was designed to study the impact of dielectric barrier discharge (DBD) plasma, ultrasound (US), and thermal treatment on the functional, rheological, and microbial analysis of sugarcane juice. The results showed that plasma and US treatment did not significantly affect the pH and color of the juice. Total soluble solids (°Brix) value increased from 16.30 ± 0.10 for untreated to 20.50 ± 0.15 during plasma treatment at 45 V for 2 min and 16.65 ± 0.27 during US treatment (40 kHz, power 240 W, and time 40 min). The maximum increase of 25% in total phenolic contents (TPC) and 21% in total flavonoid contents (TFC) was observed in a plasma-treated sample at 40 and 45 V (for 2 min) respectively, whereas 18% in TPC and 16% TFC was observed in the US-treated sample (40 kHz, power 240 W, and time 30 min) as compared to control sample. Plasma treatment increased the antioxidant activities (Ferric reducing antioxidant power (FRAP) assay and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) activity) toward maximum at 40 V and only 6% of vitamin C was degraded than others. Similarly, plasma treatment significantly reduced particle size, which further led to decreased significantly (P < 0.05) the apparent viscosity of sugarcane juice with a rise in shear rate and drove to a speedy breakdown on initial shearing. A significant reduction was observed in the microbial load among all treatments as compared to the control. Significant reductions of 3.6 and 0.50 log CFU/mL were observed in the total aerobic mesophilic and yeast and mold counts after DBD plasma treatment at 45 V for 2 min, respectively. Thus, we can conclude that novel technology like plasma treatment can be effectively used at an industrial scale for the preservation and processing of sugarcane juice. PRACTICAL APPLICATION: Nowadays, novel processing techniques are employed to improve the nutritional quality and stability of juices. The consequences of the present research showed that DBD plasma treatment could improve the TPC, TFC, antioxidant activities, vitamin C, and rheological properties while reducing the activity of the microbial load better than the US and thermal treatment. The verdicts described that novel processing methods can enhance the quality of sugarcane juice at an industrial scale.

Ultrasound-assisted regeneration of zeolite/water adsorption pair

The use of ultrasound to enhance the regeneration of zeolite 13X for efficient utilization of thermal energy was investigated as a substitute to conventional heating methods. The effects of ultrasonic power and frequency on the desorption of water from zeolite 13X were analyzed to optimize the desorption efficiency. To determine and justify the effectiveness of incorporating ultrasound from an energy-savings point of view, an approach of constant overall input power of 20 or 25 W was adopted. To measure the extent of the effectiveness of using ultrasound, the ultrasonic-power-to-total power ratios of 0.2, 0.25, 0.4 and 0.5 were investigated and the results compared with those of no-ultrasound (heat only) at the same total power. To analyze the effect of ultrasonic frequency, identical experiments were performed at three nominal ultrasonic frequencies of ~28, 40 and 80 kHz. The experimental results showed that using ultrasound enhances the regeneration of zeolite 13X at all the aforementioned power ratios and frequencies without increasing the total input power. With regard to energy consumption, the highest energy-savings power ratio (0.25) resulted in a 24% reduction in required input energy and with an increase in ultrasonic power, i.e. an increase in acoustic-to-total power ratio, the effectiveness of applying ultrasound decreased drastically. At a power ratio of 0.2, the time required for regeneration was reduced by 23.8% compared to the heat-only process under the same experimental conditions. In terms of ultrasonic frequency, lower frequencies resulted in higher efficiency and energy savings, and it was concluded that the effect of ultrasonic radiation becomes more significant at lower ultrasonic frequencies. The observed inverse proportionality between the frequency and ultrasound-assisted desorption enhancement suggests that acoustic dissipation is not a significant mechanism to enhance mass transfer, but rather other mechanisms must be considered.

Power ultrasound and its applications: A state-of-the-art review

Ultrasonic processing has attracted increasing attention by people because ultrasonic technology may represent a flexible 'green' alternative for energy efficient processes. The major challenges for the power ultrasound application in real situations are the design and development of specific power ultrasonic systems for large-scale operations. Thus, new families of power ultrasonic transducers have been developed in recent years to meet actual needs, and this contributes to the implementation of power ultrasound of application in many fields such as chemical industry, food industry and manufacturing. This paper presents the current state of ultrasonic transducers of magnetostrictiv type and piezoelectric type as well as applications of power ultrasound in various industrial fields including chemical reactions, drying/dehydration, welding, extraction, heat transfer enhancement, de-ice, enhanced oil recovery, droplet atomization, cleaning and fine particle removal. The review paper helps to understand the current development of power ultrasonic technology and its applications in various situations, and induce extended applications of power ultrasound to more and more fields.

Effects of multi-frequency ultrasound on freezing rates and quality attributes of potatoes

The effects of multi-frequency ultrasound assisted freezing on the freezing rate, microstructure, quality properties (drip loss, firmness, total calcium content, l-ascorbic acid content and total phenol content) of potatoes were studied. The results indicated that the freezing effects of multi-frequency ultrasound was better than those of single-frequency ultrasound. Multi-frequency ultrasound could significantly increase the freezing rate and preserve the quality of frozen samples better. With increase in the number of ultrasonic frequencies, the freezing effect was more obvious. In addition, scan electron microscopy (SEM) images showed that the ice crystals formed by the multi-frequency ultrasonic treatment were fine and uniformly distributed, which caused less damage to the frozen potato samples. From the analysis of the quality attributes, the nutritional values of the samples after multi-frequency ultrasonic treatment was higher, but attention should be paid to the negative influence of the hydroxyl radical generated by the multi-frequency ultrasound.

Cold Plasma-Mediated Treatments for Shelf Life Extension of Fresh Produce: A Review of Recent Research Developments

Fresh produce, like fruits and vegetables, are important sources of nutrients and health-promoting compounds. However, incidences of foodborne outbreaks associated with fresh produce often occur; it is thus important to develop and expand decay-control technologies that can not only maintain the quality but can also control the biological hazards in postharvest, processing, and storage to extend their shelf life. It is under such a situation that plasma-mediated treatments have been developed as a novel nonthermal processing tool, offering many advantages and attracting much interest from researchers and the food industry. This review summarizes recent developments of cold plasma technology and associated activated water for shelf life extension of fresh produce. An overview of plasma generation and its physical-chemical properties as well as methods for improving plasma efficiency are first presented. Details of using the technology as a nonthermal agent in inhibiting spoilage and pathogenic microorganisms, inactivating enzymes, and modifying the barrier properties or imparting specific functionalities of packaging materials to extend shelf life of food produce are then reviewed, and the effects of cold plasma-mediated treatment on microstructure and quality attributes of fresh produce are discussed. Future prospects and research gaps of cold plasma are finally elucidated. The review shows that atmospheric plasma-mediated treatments in various gas mixtures can significantly inhibit microorganisms, inactive enzyme, and modify packaging materials, leading to shelf life extension of fresh produce. The quality attributes of treated produce are not compromised but improved. Therefore, plasma-mediated treatment has great potential and values for its application in the food industry.

Effects of ultrasound-assisted freezing at different power levels on the structure and thermal stability of common carp (Cyprinus carpio) proteins

This study investigated the effect of ultrasound-assisted immersion freezing (UIF) at different ultrasonic power levels on the myofibrillar protein primary, secondary and tertiary structures of common carp (Cyprinus carpio). Furthermore, protein thermal stability, electrophoresis pattern, and microstructure of the muscle tissue were also studied. Compared with a control, an ultrasonic power of less than 175 W had no significant negative effect on protein primary structure (P > 0.05), including total sulfhydryl, reactive sulfhydryl, carbonyl groups, free amino groups, dityrosine content, and surface hydrophobicity. UIF at 175 W (UIF-175) minimized the changes in protein secondary and tertiary structures. There were no obvious changes in the SDS-PAGE patterns of the control and frozen sample proteins. Microstructure analysis showed that an appropriate ultrasonic power (UIF-175) promoted the formation of smaller and more uniform ice crystals, reduced the damage of muscle tissue by ice crystals, and maintained the sarcomere integrity. In addition, UIF-175 samples had higher protein thermal stability. Overall, ultrasound treatment at a proper power (UIF-175) effectively minimized the changes in protein structure and protected the protein thermal stability during freezing process.

Effects of pretreatments on quality attributes of long-term deep frozen storage of vegetables: a review

As one of the essential parts in human diet, vegetables are important in health keeping and their consumption increases continuously. Due to their highly perishable nature, the shelf life of fresh vegetables is considerably short, due to cellular respiration, microorganism, enzyme reaction, oxidation and so on. Therefore, short- and long-term storages of vegetables are required and various methods and technologies are applied for different commercial goals. For long-term storage, deep frozen storage is one of the most widespread used preservation methods for vegetables, as under temperatures low enough, the rate of most deteriorative reactions and microbial activities are significantly reduced. This review provides a critical comprehensive summary of long-term storage (≥6 months) vegetables under low temperatures (≤ -18 °C), and effects of the storage methods on various quality attributes of vegetables, such as texture, colour, contents of ascorbic acid, chlorophyll and carotenoids. Besides, the impacts of common pretreatments prior to freezing on the subsequent frozen storage are also briefly discussed. The current review shows that although some important biochemical attributes are more or less deteriorated and the quality loss of them is inevitable, a substantial portion of quality attributes appear to be stable during long-term deep frozen storage especially the physical parameters. Meanwhile, pretreatments prior to freezing, such as blanching process, also show significant influence on quality preservation in subsequent storage. Therefore long-term deep frozen storage can be applied as an effective storage method under proper conditions of pretreatments and storage.

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.

Effect of low frequency ultrasound thawing method on the quality characteristics of Peru squid ( Dosidicus gigas)

The effects of different thawing methods (air thawing, water soak thawing, refrigeration thawing, low frequency ultrasound thawing at 160, 240, 320 and 400 W) on thawing time, thawing loss, cooking loss, water-holding capacity and texture of frozen squid were investigated. The results showed that thawing loss and thawing time were reduced significantly ( p < 0.05) by ultrasound thawing compared with the water soak thawing and air thawing, but the cooking loss had no significant difference ( p > 0.05). Results of the ultrasound thawing especially at 160 and 240 W on microstructure showed less destructive effect on muscle. The microstructure of the muscle was destroyed significantly after air thawing and water soak thawing compared with the ultrasound thawing, which showed that more fibre structure was broken and the gap between the muscle fibres was increased significantly. Low-field NMR results showed that the ability of immobile water shifting to free water after ultrasound thawing was lower than air thawing and water soak thawing, which was consistent with the results of thawing loss and cooking loss. Ultrasound thawing might be chosen as an alternative method to enhance the quality during thawing process.

Application of Ultrasound in Food Science and Technology: A Perspective

Ultrasound is composed of mechanical sound waves that originate from molecular movements that oscillate in a propagation medium. The waves have a very high frequency, equal to approximately 20 kHz, are divided into two categories (i.e., low-intensity and high-intensity waves) and cannot be perceived by the human ear. Nature has created the first ultrasound applications. Bats use ultrasound to navigate in the dark, and many cetaceans use echolocation to detect prey or obstacles using ultrasound produced by their vocal system. Ultrasound is commonly associated with the biomedical field. Today, ultrasound-based methods and equipment are available to detect organs, motion, tumour masses, and pre/post-natal handicaps, and for kidney stone removal, physiotherapy, and aesthetic cures. However, ultrasound has found multiple applications in many other fields as well. In particular, ultrasound has recently been used in the food industry to develop various effective and reliable food processing applications. Therefore, this review summarizes the major applications of ultrasound in the food industry. The most common applications in the food industry include cell destruction and extraction of intracellular material. Depending on its intensity, ultrasound is used for the activation or deactivation of enzymes, mixing and homogenization, emulsification, dispersion, preservation, stabilization, dissolution and crystallization, hydrogenation, tenderization of meat, ripening, ageing and oxidation, and as an adjuvant for solid-liquid extraction for maceration to accelerate and to improve the extraction of active ingredients from different matrices, as well as the degassing and atomization of food preparations.

Introducing ultrasonic falling film evaporator for moderate temperature evaporation enhancement

In the present study, Ultrasonic Falling Film (USFF), as a novel technique has been proposed to increase the evaporation rate of moderate temperature liquid film. It is a proper method for some applications which cannot be performed at high temperature, such as foodstuff industry, due to their sensitivity to high temperatures. Evaporation rate of sodium chloride solution from an USFF on an inclined flat plate compared to that for Falling Film without ultrasonic irradiation (FF) at various temperatures was investigated. The results revealed that produced cavitation bubbles have different effects on evaporation rate at different temperatures. At lower temperatures, size fluctuation and collapse of bubbles and in consequence induced physical effects of cavitation bubbles resulted in more turbulency and evaporation rate enhancement. At higher temperatures, the behavior was different. Numerous created bubbles joined together and cover the plate surface, so not only decreased the ultrasound vibrations but also reduced the evaporation rate in comparison with FF. The highest evaporation rate enhancement of 353% was obtained at 40 °C at the lowest Reynolds number of 250. In addition, the results reveal that at temperature of 40 °C, USFF has the highest efficiency compared to FF.

An assessment of the application of ultrasound in the processing of ready-to-eat whole brown crab (Cancer pagurus)

This study assesses the potential of incorporating ultrasound as a processing aid in the production of whole cooked brown crab (Cancer pagurus). The FDA recommended heat treatment to reduce Listeria monocytogenes by 6 log₁₀ cycles in this product is a F₇₀^7.5 of 2min. An equivalent F value was applied at 75°C in presence and absence of ultrasound in water alone or in water with 5% w/v NaCl added. Heat penetration, turbidity and conductivity of the cook water and also salt and moisture content of the crab meat (white and brown) were determined. Ultrasound assisted cooking allowed a reduction of the cooking time by up to 15% while still maintaining an F₇₀^7.5 of 2min. Ultrasound also enhanced the rate and total amount of compounds released from the crab, which suggests that crabs cooked in the presence of ultrasound would be expected to be cleaner. Ultrasound also proved to be effective in reducing the salt content but hardly affected the final moisture content of the crab meat.