Application of multi-frequency power ultrasound in selected food processing using large-scale reactors: A review

Novel strategies for enhancing quality stability of edible flower during processing using efficient physical fields: A review

Edible flowers are an exotic part of the human diet due to their distinct sensorial properties and health benefits. Due to consumers demand edible flowers and their products with natural freshness and high nutritional value, there is increasing research on the application of green and efficient edible flower processing technologies. This paper reviews the application of a number of physical fields including ultrasound, microwave, infrared, ultraviolet, ionizing radiation, pulse electric field, high hydrostatic pressure, and reduced pressure aiming to improve the processing and product quality of edible flowers. The mechanism of action, influencing factors, and status on application of each physical energy field are critically evaluated. In addition, the advantages and disadvantages of each of these energy fields are evaluated, and trends on their future prospects are highlighted. Future research is expected to focus on gaining greater understanding of the mechanism action of physical field-based technologies when applied to processing of edible flowers and to provide the basis for broaden the application of physical field-based technologies in industrial realm.

Effect of ultrasound processing on rheological properties and color of green food products

Changes in rheological behavior and physical properties of avocado dressing and green juice samples processed by ultrasound (US) technology (120 µm, 24 kHz, up to 2 min, 20 °C) were investigated. The avocado dressing followed pseudoplastic flow behavior, which had good fit to the power law model, with R2 values >0.9664. The lowest K values 3.5110, 2.4426, and 2.3228 were determined for avocado dressing samples with no treatment at 5 °C, 15 °C, and 25 °C, respectively. At the shear rate of 0.1/s, viscosity of 2 min US-treated avocado dressing increased significantly from 19.1 to 55.5 Pa.s at 5 °C, 13.08 to 36.78 Pa.s at 15 °C, and 14.55 to 26.75 Pa.s at 25 °C. Flow instability occurred in green juice after reaching shear rate of 300/s due to narrow gap in concentric cylinder; however, constant viscosity between 10 and 300/s indicated that the sample was Newtonian. Increasing temperature from 5 °C to 25 °C decreased viscosity of US-treated green juice from 2.55 to 1.50 mPa.s at the shear rate of 100/s. Color of both samples did not change after US processing, but lightness increased in green juice which denoted lighter color compared to the sample without treatment. There was no difference in pH and total soluble solids of samples. Results represent that US technology may be a good alternative in producing green liquid foods with acceptable rheological properties and color.

Effect of Multi-Mode Divergent Ultrasound Pretreatment on Hardness, Microstructure and Digestion of Acid-Induced Whey Protein Gels

Whey protein was pretreated with multi-frequency ultrasound in mono-, dual-, and tri-frequency modes. The effect of multi-frequency ultrasound pretreatment on the hardness, chemical forces, and microstructure of acid-induced whey protein gel was investigated. Whey protein gels pretreated with dual- and tri-frequency ultrasound showed higher hardness (p < 0.05) and a denser network than mono-frequency ultrasound and control. Moreover, they had higher hydrophobic interaction and lower disulfide bonds than the control (p < 0.05). The effect of gel properties on digestion was evaluated using an in vitro static model. Whey protein gels pretreated with dual- and tri-frequency ultrasound had a higher proportion of large fragments in the oral boluses than in the control. Large fragments (>3.35 mm) in those samples were resistant to gastric digestion. Moreover, the tri-frequency ultrasound pretreatment of whey protein gel released the least free amino group during gastric digestion. In contrast, whey protein gel with the mono-frequency ultrasound pretreatment released the highest amount of free amino acid group during intestinal digestion. Findings from this study suggests that gel hardness and network density could modulate the digestion behaviors of protein gels.

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.

Recent advancements in the utilization of ultrasonic technology for the curing of processed meat products: A comprehensive review

Curation meat products involves multiple stages, including pre-curing processing (thawing, cleaning, and cutting), curing itself, and post-curing processing (freezing, and packaging). Ultrasound are nonthermal processing technology widely used in food industry. This technology is preferred because it reduces the damages caused by traditional processing techniques on food, while simultaneously improving the nutritional properties and processing characteristics of food. The utilization of ultrasonic-assisted curing technology has attracted significant attention within the realm of meat product curing, encouraging extensive research efforts. In terms of curing meat products, ultrasonic-assisted curing technology has been widely studied due to its advantages of accelerating the curing speed, reducing nutrient loss, and improving the tenderness of cured meats. Therefore, this article aims to comprehensively review the application and mechanism of ultrasound technology in various stages of meat product curing. Furthermore, it also elaborates the effects of ultrasonic-assisted curing on the tenderness, water retention, and flavor substances of the meat products during the curing process. Besides, the implication of the ultrasound in the processing of meat curation plays a potent role together with other technologies or methods. The use of ultrasound technology in the process of meat curation was analyzed, which might be a theoretical insight for the industrialization prospects of the meat product.

Selenium Decipher: Trapping of Native Selenomethionine-Containing Peptides in Selenium-Enriched Milk and Unveiling the Deterioration after Ultrahigh-Temperature Treatment

Selenopeptide identification relies on databases to interpret the selenopeptide spectra. A common database search strategy is to set selenium as a variable modification instead of sulfur on peptides. However, this approach generally detects only a fraction of selenopeptides. An alternative approach, termed Selenium Decipher, is proposed in the present study. It involves identifying collision-induced dissociation-cleavable selenomethionine-containing peptides by iteratively matching the masses of seleno-amino acids in selenopeptide spectra. This approach uses variable-data-independent acquisition (vDIA) for peptide detection, providing a flexible and customizable window for secondary mass spectral fragmentation. The attention mechanism was used to capture global information on peptides and determine selenomethionine-containing peptide backbones. The core structure of selenium on selenomethionine-containing peptides generates a series of fragment ions, namely, C3H7Se+, C4H10NSe+, C5H7OSe+, C5H8NOSe+, and C7H11N2O2Se+, with known mass gaps during higher-energy collisional dissociation (HCD) fragmentation. De-selenium spectra are generated by removing selenium originating from selenium replacement and then reassigning the precursors to peptides. Selenium-enriched milk is obtained by feeding selenium-rich forage fed to cattle, which leads to the formation of native selenium through biotransformation. A novel antihypertensive selenopeptide Thr-Asp-Asp-Ile-SeMet-Cys-Val-Lys TDDI(Se)MCVK was identified from selenium-enriched milk. The selenopeptide (IC50 = 60.71 μM) is bound to four active residues of the angiotensin-converting enzyme (ACE) active pocket (Ala354, Tyr523, His353, and His513) and two active residues of zinc ligand (His387 and Glu411) and exerted a competitive inhibitory effect on the spatial blocking of active sites. The integration of vDIA and the iteratively matched seleno-amino acids was applied for Selenium Decipher, which provides high validity for selenomethionine-containing peptide identification.

A comprehensive review of the application of ultrasonication in the production and processing of edible mushrooms: Drying, extraction of bioactive compounds, and post-harvest preservation

Edible mushrooms are high in nutrients, low in calories, and contain bioactive substances; thus, they are a valuable food source. However, the high moisture content of edible mushrooms not only restricts their storage and transportation after harvesting, but also leads to a shorter processable cycle, production and processing limitations, and a high risk of deterioration. In recent years, ultrasonic technology has been widely applied to various food production operations, including product cleaning, post-harvest preservation, freezing and thawing, emulsifying, and drying. This paper reviews applications of ultrasonic technology in the production and processing of edible mushrooms in recent years. The effects of ultrasonic technology on the drying, extraction of bioactive substances, post-harvest preservation, shelf life/preservation, freezing and thawing, and frying of edible mushrooms are discussed. In summary, the application of ultrasonic technology in the edible mushroom industry has a positive effect and promotes the development of this industry.

Impact of ultrasound treatment on the structural modifications and functionality of carbohydrates - A review

Carbohydrates are crucial in food as essential biomolecules, serving as natural components, ingredients, or additives. Carbohydrates have numerous applications in the food industry as stabilizers, thickeners, sweeteners, and humectants. The properties and functionality of the carbohydrates undergo alterations when exposed to various thermal or non-thermal treatments. Ultrasonication is a non-thermal method that modifies the structural arrangement of carbohydrate molecules. These structural changes lead to enhanced gelling and viscous nature of the carbohydrates, thus enhancing their scope of application. Ultrasound may improve carbohydrate functionality in an environmentally sustainable way, leaving no chemical residues. The high-energy ultrasound treatments significantly reduce the molecular size of complex carbohydrates. Sonication parameters like treatment intensity, duration of treatment, and energy applied significantly affect the molecular size, depolymerization, viscosity, structural modifications, and functionality of carbohydrate biomolecules. This review provides a comprehensive analysis of ultrasound-assisted modifications in carbohydrates and the changes in functional properties induced by sonication.

A comprehensive review of ultrasonic assisted extraction (UAE) for bioactive components: Principles, advantages, equipment, and combined technologies

The increasing focus on health and well-being has sparked a rising interest in bioactive components in the food, pharmaceutical, and nutraceutical industries. These components are gaining popularity due to their potential benefits for overall health. The growing interest has resulted in a continuous rise in demand for bioactive components, leading to the exploration of both edible and non-edible sources to obtain these valuable substances. Traditional extraction methods like solvent extraction, distillation, and pressing have certain drawbacks, including lower extraction efficiency, reduced yield, and the use of significant amounts of solvents or resources. Furthermore, certain extraction methods necessitate high temperatures, which can adversely affect certain bioactive components. Consequently, researchers are exploring non-thermal technologies to develop environmentally friendly and efficient extraction methods. Ultrasonic-assisted extraction (UAE) is recognized as an environmentally friendly and highly efficient extraction technology. The UAE has the potential to minimize or eliminate the need for organic solvents, thereby reducing its impact on the environment. Additionally, UAE has been found to significantly enhance the production of target bioactive components, making it an attractive method in the industry. The emergence of ultrasonic assisted extraction equipment (UAEE) has presented novel opportunities for research in chemistry, biology, pharmaceuticals, food, and other related fields. However, there is still a need for further investigation into the main components and working modes of UAEE, as current understanding in this area remains limited. Therefore, additional research and exploration are necessary to enhance our knowledge and optimize the application of UAEE. The core aim of this review is to gain a comprehensive understanding of the principles, benefits and impact on bioactive components of UAE, explore the different types of equipment used in this technique, examine the various working modes and control parameters employed in UAE, and provide a detailed overview of the blending of UAE with other emerging extraction technologies. In conclusion, the future development of UAEE is envisioned to focus on achieving increased efficiency, reduced costs, enhanced safety, and improved reliability. These key areas of advancement aim to optimize the performance and practicality of UAEE, making it a more efficient, cost-effective, and reliable extraction technology.

Effects of multi-frequency ultrasonic assisted sodium hypochlorite on the cleaning effect and quality of fresh-cut scallion stems

This study aimed to evaluate the feasibility of multi-frequency ultrasound-assisted sodium hypochlorite (NaClO) on fresh-cut scallion stem (FCS) cleaning. Ultrasonic cleaning parameters (frequency mode, frequency amplitude, and the sample to water ratios) were optimized against cleanliness and microbial biomass as evaluation indexes. Under the optimum conditions, the free chlorine residues and quality attributes of FCS were also investigated. The results showed that the cleanliness of FCS improved significantly (p < 0.05) and the total number of microorganisms, especially Escherichia coli, decreased dramatically under the optimized cleaning condition with the simultaneous ultrasound (US) at the sweep frequency (SF) combination of 20 + 28 kHz, the ultrasonic density of 60 W/L, pulse time of 10 s, which indicated that the shelf life of FCS would be extended. Compared to FCS after the 250 ppm NaClO cleaning, the retention of ascorbic acid (AA), color, and texture structure of FCS had no significant difference after ultrasound-assisted NaClO treatment. Meanwhile, the content of allicin increased by 52.5% under ultrasound-assisted cleaning. The integration of US into the cleaning process resulted in a notably reduction of 68% in NaClO concentration, as well as the weight loss and respiration rate (RR) of the scallion stems. Therefore, ultrasound-assisted NaClO cleaning was regarded as a promising and effective approach for cleaning fresh-cut vegetables.

Impacts of Ultrasonic Treatment for Black Soybean Okara Culture Medium Containing Choline Chloride on the β-Glucosidase Activity of Lactiplantibacillus plantarum BCRC 10357

The effects of ultrasonic treatment for the culture medium of solid black soybean okara with choline chloride (ChCl) on the survival and β-glucosidase activity of Lactiplantibacillus plantarum BCRC 10357 (Lp-BCRC10357) were investigated. A mixture of 3% dried black soybean okara in de Man-Rogosa-Sharpe (w/v) was used as the Oka medium. With ultrasonic treatment (40 kHz/300 W) of the Oka medium at 60 °C for 3 h before inoculation, the β-glucosidase activity of Lp-BCRC10357 at 12 h and 24 h of incubation amounted to 13.35 and 15.50 U/mL, respectively, which was significantly larger than that (12.58 U/mL at 12 h and 2.86 U/mL at 24 h) without ultrasonic treatment of the medium. This indicated that ultrasonic treatment could cause the microstructure of the solid black soybean okara to be broken, facilitating the transport of ingredients and Lp-BCRC10357 into the internal structure of the okara for utilization. For the effect of ChCl (1, 3, or 5%) added to the Oka medium (w/v) with ultrasonic treatment before inoculation, using 1% ChCl in the Oka medium could stimulate the best response of Lp-BCRC10357 with the highest β-glucosidase activity of 19.47 U/mL in 12 h of incubation, showing that Lp-BCRC10357 had a positive response when confronting the extra ChCl that acted as an osmoprotectant and nano-crowder in the extracellular environment. Furthermore, the Oka medium containing 1% ChCl with ultrasonic treatment led to higher β-glucosidase activity of Lp-BCRC10357 than that without ultrasonic treatment, demonstrating that the ultrasonic treatment could enhance the contact of ChCl and Lp-BCRC10357 to regulate the physiological behavior for the release of enzymes. In addition, the analysis of the isoflavone content and antioxidant activity of the fermented product revealed that the addition of 1% ChCl in the Oka medium with ultrasonic treatment before inoculation allowed a higher enhancement ratio for the biotransformation of isoflavone glycosides to their aglycones, with a slight enhancement in the antioxidant activity at 24 h of fermentation. This study developed a methodology by combining ultrasonic treatment with a limited amount of ChCl to allow the culture medium to acclimate Lp-BCRC10357 and release high levels of β-glucosidase, and this approach has the potential to be used in the fermentation of okara-related products as nutritional supplements in foods.

Comparative Analysis of Volatile Compounds from Four Radish Microgreen Cultivars Based on Ultrasonic Cell Disruption and HS-SPME/GC-MS

The ultrasonic cell disruption method was used to efficiently extract isothiocyanates and other volatile compounds from radish microgreens. A total of 51 volatiles were identified and quantified by headspace solid-phase micro-extraction and gas chromatography-mass spectrometry (HS-SPME/GC-MS) in four radish microgreen cultivars, mainly including alcohols, aldehydes, isothiocyanates, sulfides, ketones, esters, terpenes, and hydrocarbons. The correlation between cultivars and volatile compounds was determined by chemometrics analysis, including principal component analysis (PCA) and hierarchical clustering heat maps. The aroma profiles were distinguished based on the odor activity value (OAV), odor contribution rate (OCR), and radar fingerprint chart (RFC) of volatile compounds. This study not only revealed the different flavor characteristics in four cultivars but also established a theoretical basis for the genetic improvement of radish microgreen flavors.

Application progress of ultrasonication in flour product processing: A review

Flour products played a vital role in the global diet structure. With the increasing demand for dietary health and food standardization, the staple food of flour products made from coarse grains due to its unique flavor and rich nutrition has become a trend and is favored by consumers. However, the lack of gluten protein in the raw materials prevented the formation of a stable gluten network structure, leading to the deterioration of the quality of flour products. Ultrasonic treatment, as an innovative food processing technology, generated energy during the action of ultrasonic waves that had a positive impact on the texture, organizational structure, or flavor characteristics of food. That was of great significance for improving food production efficiency, improving food processing quality, and extending food shelf life. This article applied ultrasonic technology to the processing of flour products from the perspective of promoting fermentation and improving production efficiency of flour products. The cavitation effect of ultrasound promoted the formation of gluten network structure, improved the rheology properties of dough and the quality of flour products by promoting protein cross-linking, improving the foaming and emulsifying stability of gluten protein, and promoting the growth and reproduction of yeast. All reviewed studies indicate that ultrasound would be a promising technology for producing high-quality surface products under appropriate conditions.

Application of ultrasound and its real-time monitoring of the acoustic field during processing of tofu: Parameter optimization, protein modification, and potential mechanism

Tofu is nutritious, easy to make, and popular among consumers. At present, traditional tofu production has gradually become perfect, but there are still shortcomings, such as long soaking time, serious waste of water resources, and the inability to realize orders for production at any time. Moreover, tofu production standards have not yet been clearly defined, with large differences in quality between them, which is not conducive to industrialized and large-scale production. Ultrasound has become a promising green processing technology with advantages, such as high extraction rate, short processing time, and ease of operation. This review focused on the challenges associated with traditional tofu production during soaking, grinding, and boiling soybeans. Moreover, the advantages of ultrasonic processing over traditional processing like increasing nutrient content, improving gel properties, and inhibiting the activity of microorganisms were explained. Furthermore, the quantification of acoustic fields by real-time monitoring technology was introduced to construct the theoretical correlation between ultrasonic treatments and tofu processing. It was concluded that ultrasonic treatment improved the functional properties of soybean protein, such as solubility, emulsifying properties, foamability, rheological properties, gel strength, and thermal stability. Therefore, the application of ultrasonic technology to traditional tofu processing to optimize industrial parameters is promising.

Structural and functional properties of self-assembled peanut protein nanoparticles prepared by ultrasonic treatment: Effects of ultrasound intensity and protein concentration

Peanut protein isolate (PPI) nanoparticles were prepared by self-assembly under the combined action of ultrasound (US) and protein concentration. The effects of ultrasound intensity (150-500 W) and protein concentration (1-12 %, w/v) on the structural and functional properties of PPI nanoparticles were investigated. Low-intensity US significantly increased the particle size of PPI, but high-intensity US decreased it. The largest PPI nanoparticles were obtained when 10 % PPI was subjected to low-intensity US treatment (200 W for 5 min). These nanoparticles possessed unique structural characteristics, such as the lowest absolute ζ-potential and the highest contents of exposed free sulfhydryl and disulfide bond, which may be responsible for their excellent heat-set gelling properties. The 12 % PPI treated with low- and high-intensity US had the highest emulsifying activity index and emulsifying stability index, respectively. The self-assembled PPI nanoparticles induced by US treatments at high protein concentrations have great potentials for application in the food industry.

Ultrasound-assisted enzymatic synthesis of galacto-oligosaccharides using native whey with two commercial β-galactosidases: Aspergillus oryzae and Kluyveromyces var lactis

Native whey obtained during casein micelle microfiltration was used as a novel source to produce galacto-oligosaccharides (GOS). Since the presence of macromolecules and other interferers reduces biocatalyst performance, this work evaluated the effect of different ultrasound processing conditions on GOS synthesis using concentrated native whey. Ultrasonic intensities (UI) below 11 W/cm² tended to increase the activity in the enzyme from Aspergillus oryzae for several minutes but accelerated the inactivation in that from Kluyveromyces lactis. At 40 °C, 40 % w/w native whey, 70 % wave amplitude, and 0.6 s/s duty-cycle, a UI of 30 W/cm² was achieved, and the increased specific enzyme productivity was similar to the values obtained with pure lactose (∼0.136 g GOS/h/mg_E). This strategy allows for obtaining a product containing prebiotics with the healthy and functional properties of whey proteins, avoiding the required purification steps used in the production of food-grade lactose.

Ultrasound treatments improve germinability of soybean seeds: The key role of working frequency

In this paper, the effects of ultrasound with different frequency modes on the sprouting rate, sprouting vigor, metabolism-related enzyme activity and late nutrient accumulation in soybean were investigated, and the mechanism of dual-frequency ultrasound promoting bean sprout development was explored. The results showed that, compared with control, the sprouting time was shortened by 24 h after dual-frequency ultrasound treatment (20/60 kHz), and the longest shoot was 7.82 cm at 96 h. Meanwhile, ultrasonic treatment significantly enhanced the activities of protease, amylase, lipase and peroxidase (p < 0.05), particularly the phenylalanine ammonia-lyase increased by 20.50%, which not only accelerated the seed metabolism, but also led to the accumulation of phenolics (p < 0.05), as well as more potent antioxidant activity at later stages of sprouting. In addition, the seed coat exhibited remarkable cracks and holes after ultrasonication, resulting in accelerated water absorption. Moreover, the immobilized water in seeds increased significantly, which was beneficial to seed metabolism and later sprouting. These findings confirmed that dual-frequency ultrasound pretreatment has a great potential to be used for seed sprouting and promoting the accumulation of nutrients in bean sprouts by accelerating water absorption and increasing enzyme activity.

Ultrasound-assisted limited enzymatic hydrolysis of high concentrated soy protein isolate: Alterations on the functional properties and its relation with hydrophobicity and molecular weight

The effects of power ultrasound (US) pretreatment on the preparation of soy protein isolate hydrolysate (SPIH) prepared at the same degree of hydrolysis (DH) of 12 % were measured. Cylindrical power ultrasound was modified into mono-frequency (20, 28, 35, 40, 50 kHz) ultrasonic cup coupled with an agitator to make it applicable for high density SPI (soy protein isolate) solutions (14 %, w/v). A comparative study of the alterations of the hydrolysates molecular weight, hydrophobics, antioxidants and functional properties change as well as their relation were explored. The results showed that under the same DH, ultrasound pretreatment decelerated the degradation of protein molecular mass and the decrease rate of the degradation lessened with the increase of ultrasonic frequency. Meanwhile, the pretreatments improved the hydrophobics and antioxidants properties of SPIH. Both surface hydrophobicity (H0) and relative hydrophobicity (RH) of the pretreated groups increased with the decrease of ultrasonic frequency. Lowest frequency (20 kHz) ultrasound pretreatment had the most improved emulsifying properties and water holding capacities, although decrease in the viscosity and solubility were found. Most of these alterations were correspondence toward the change in hydrophobics properties and molecular mass. In conclusion, the frequency selection of ultrasound pretreatment is essential for the alteration of SPIH functional qualities prepared at the same DH.

Ultrasonic washing as an abiotic elicitor to increase the phenolic content in fruits and vegetables: A review

Ultrasonic washing has been widely applied to the postharvest storage of fruits and vegetables as a residue-free physical washing technology, which plays an important role in improving shelf-life, safety, and nutritional value. Phenolics are a large group of phytochemicals widespread in fruits and vegetables, and they have been considered potential protective factors against some diseases because of potent antioxidative properties. Previous studies have shown that ultrasonic washing can increase the phenolic content of fruits and vegetables immediately or during storage through the induction of plant stress responses, which is of great significance for improving the functional and nutritional value of fruits and vegetables. However, the mechanisms of ultrasound as an elicitor to improve the phenolic content remain controversial. Therefore, this review summarizes the applications of ultrasonic washing to increase the phenolic content in fruits and vegetables. Meanwhile, the corresponding physiological stress response mechanisms of the phenolic accumulation in terms of immediate stress responses (i.e., higher extractability of phenolics) and late stress responses (i.e., metabolism of phenolics) are expounded. Moreover, a hypothetical model is proposed to explain phenolic biosynthesis triggered by signaling molecules produced under ultrasound stress, including primary signal (i.e., extracellular adenosine triphosphate) and secondary signals (e.g., reactive oxygen species, Ca²⁺ , NO, jasmonates, and ethylene). Additionally, the techno-economic feasibility of ultrasonic washing technology is also discussed. Further, challenges and trends for further development of ultrasonic washing as an abiotic elicitor applied to the postharvest storage of fruits and vegetables are presented.

Insights into Ultrasonication Treatment on the Characteristics of Cereal Proteins: Functionality, Conformational and Physicochemical Characteristics

BACKGROUND

It would be impossible to imagine a country where cereals and their byproducts were not at the peak of foodstuff systems as a source of food, fertilizer, or for fiber and fuel production. Moreover, the production of cereal proteins (CPs) has recently attracted the scientific community's interest due to the increasing demands for physical wellbeing and animal health. However, the nutritional and technological enhancements of CPs are needed to ameliorate their functional and structural properties. Ultrasonic technology is an emerging nonthermal method to change the functionality and conformational characteristics of CPs. Scope and approach: This article briefly discusses the effects of ultrasonication on the characteristics of CPs. The effects of ultrasonication on the solubility, emulsibility, foamability, surface-hydrophobicity, particle-size, conformational-structure, microstructural, enzymatic-hydrolysis, and digestive properties are summarized.

CONCLUSIONS

The results demonstrate that ultrasonication could be used to enhance the characteristics of CPs. Proper ultrasonic treatment could improve functionalities such as solubility, emulsibility, and foamability, and is a good method for altering protein structures (including surface hydrophobicity, sulfhydryl and disulfide bonds, particle size, secondary and tertiary structures, and microstructure). In addition, ultrasonic treatment could effectively promote the enzymolytic efficiency of CPs. Furthermore, the in vitro digestibility was enhanced after suitable sonication treatment. Therefore, ultrasonication technology is a useful method to modify cereal protein functionality and structure for the food industry.

Preparation Process Optimization of Peptides from Agaricus blazei Murrill, and Comparison of Their Antioxidant and Immune-Enhancing Activities Separated by Ultrafiltration Membrane Technology

Agaricus blazei murrill (ABM), a large fungus, is reported to have extensive biological activities but the antioxidant and immune-regulatory capacities have been less studied and the components responsible for the functions are unclear. This study prepared ABM peptides (ABMP) using ultrasound-assisted enzymatic extraction (UAEE) strategy and cascade ultrafiltration (UF) membrane technology. The UAEE extraction conditions were optimized using response surface methodology (RSM) with four factors and three levels to achieve the maximum ABMP yield (34.03%); the optimal conditions were an enzyme amount of 4%, ratio of ABM to water of 1:30, ultrasonic power of 360 W, and ultrasonic time of 30 min. Four ABMP fractions were obtained after UF with different pore size and their antioxidant and immune-regulatory abilities were evaluated and compared. The results showed that they could effectively scavenge DPPH, hydroxyl, and ABTS radicals, especially for ABMP-2; the scavenging rate of the above radicals were 79.31%, 63.60%, and 96.08%, respectively. In addition, four ABMP fractions also activated macrophage activity through strengthening phagocytosis and the production of NO, IL-6, IL-1β, and TNF-α in a dose-dependent manner. Notably, the ABMP-2 fraction with a MW of 3-5 kDa and peptide purity of 82.88% was found to have the best effect, showing the maximum phagocytosis (189.37%) as well as NO (7.98 μM), IL-6 (195.05 pg/mL), IL-1β (876.15 pg/mL), and TNF-α (1620 pg/mL) secretion at a treatment concentration of 150 μg/mL. The findings indicated that the ABMP, especially for the separate ABMP-2, could be used as dietary supplements and have the potential to be exploited as immune-enhancing agents.

Improvement of structural, physicochemical, and rheological properties of porcine myofibrillar proteins by high-intensity ultrasound treatment for application as Pickering stabilizers

This study aimed to evaluate the potential of time-dependent (0, 15, 30, 60, 120 min) treatment of porcine-derived myofibrillar proteins (MPs) with high-intensity ultrasound (HIU) for utilizing them as a Pickering stabilizer and decipher the underlying mechanism by which HIU treatment increases the emulsification and dispersion stability of MPs. To accomplish this, we analyzed the structural, physicochemical, and rheological properties of the HIU-treated MPs. Myosin heavy chain and actin were observed to be denatured, and the particle size of MPs decreased from 3,342.7 nm for the control group to 153.9 nm for 120 min HIU-treated MPs. Fourier-transformed infrared spectroscopy and circular dichroism spectroscopy confirmed that as the HIU treatment time increased, α-helical content increased, and β-sheet decreased, indicating that the protein secondary/tertiary structure was modified. In addition, the turbidity, apparent viscosity, and viscoelastic properties of the HIU-treated MP solution were decreased compared to the control, while the surface hydrophobicity was significantly increased. Analyses of the emulsification properties of the Pickering emulsions prepared using time-dependent HIU-treated MPs revealed that the emulsion activity index and emulsion stability index of HIU-treated MP were improved. Confocal laser scanning microscopy images indicated that small spherical droplets adsorbed with MPs were formed by HIU treatment and that dispersion stabilities were improved because the Turbiscan stability index of the HIU-treated group was lower than that of the control group. These findings could be used as supporting data for the utilizing porcine-derived MPs, which have been treated with HIU for appropriate time periods, as Pickering stabilizers.

Effect of ultrasound assisted cleaning on pesticide removal and quality characteristics of Vitis vinifera leaves

In this study, the pesticide (acetamiprid, deltamethrin, and pyridaben) removal and physicochemical quality improvement of vine (Vitis vinifera) leaf were examined using ultrasonic and traditional cleaning for 5, 10, and 15 min. After an ultrasonic cleaning procedure at 37 kHz for 10 min, acetamiprid, deltamethrin, and pyridaben in vine leaf were reduced by 54.76, 58.22, and 54.55 %, respectively. Furthermore, the total phenolic content (TPC) in vine leaf increased to 13.45 mg GAE/g DW compared to that in control samples using traditional cleaning (10.37 mg GAE/g DW), but there were no significant differences in DPPH radical scavenging activity. After 15 min of conventional cleaning, the total chlorophyll and total carotenoid content of leaves were found to be lowest among all samples, at 6.52 mg/kg and 0.48 mg/kg, respectively. In conclusion, when compared to conventional cleaning methods, ultrasonic cleaning with no chemicals or heat treatment has proven to be a successful and environmentally friendly application in reducing commonly used pesticides and improving the physicochemical qualities of leaves.

Application and potential of multifrequency ultrasound in juice industry: Comprehensive analysis of inactivation and germination of Alicyclobacillus acidoterrestris spores

The majority of acidic fruits are perishable owing to their high-water activity, which promotes microbial activity, thus exhibiting metabolic functions that cause spoilage. Along with sanitary practices, several treatments are used during processing and/or storage to inhibit the development of undesirable bacteria. To overcome the challenges caused by mild heat treatment, juice manufacturers have recently increased their involvement in developing novel non-thermal processing procedures. Ultrasonication alone or in combination with other hurdle technologies may be used to pasteurize processed fruit juices. Multifrequency ultrasound has gained popularity due to the fact that mono-frequency ultrasound has less impact on bacterial inactivation and bioactive compound enhancement of fruit juice. Here, we present and discuss the fundamental information and technological knowledge of how spoilage bacteria, specifically Alicyclobacillus acidoterrestris, assemble resistant spores and inactivate and germinate dormant spores in response to nutrient germinants and physical treatments such as heat and ultrasound. To the authors' knowledge, no prior review of ultrasonic inactivation and germination of A. acidoterrestris in fruit juice exists. Therefore, this article aims to provide a review of previously published research on the inactivation and germination of A. acidoterrestris in fruit juice by ultrasound and heat.

Reduction of oil uptake in vacuum fried Pleurotus eryngii chips via ultrasound assisted pretreatment

The reduction of oil uptake in vacuum-fried Pleurotus eryngii chips by ultrasound assisted pretreatment was investigated regarding the pore structure changes. Pore structure of P. eryngii chips with four pretreatments, such as blanching, blanching + osmosis, blanching + ultrasound and blanching + ultrasound assisted osmosis was determined by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). In addition, the quality parameters of vacuum-fried P. eryngii chips such as hardness, rehydration ratio, reducing sugar, protein and oil content were also measured. The results showed that the oil absorption of vacuum fried P. eryngii chips was affected by the porous structure. The oil content of vacuum fried P. eryngii chips was significantly and positively correlated with the pores with diameters above 50, 5–50, and 0.5–5 μm in the samples both before and after vacuum frying, while negatively correlated with the pores with diameters below 0.5 μm. Ultrasound pretreatment changed the microporous structure of P. eryngii chips, effectively hindering the oil absorption of samples. In particular, ultrasound assisted osmosis pretreatment induced the formation of more micropores. It was concluded that blanching + ultrasound assisted osmosis pretreatment is a promising method to reduce oil absorption and improve the quality of vacuum fried foods.

Comparison between the use of polyether ether ketone and stainless steel columns for ultrasonic-assisted extraction under various ultrasonic conditions

The ultrasound-assisted extraction (UAE) was conducted using the stainless steel (SS) and polyether ether ketone (PEEK) columns and analyzed with high-performance liquid chromatography (HPLC) to understand the mechanism of ultrasound-assisted chromatography (UAC). Empty SS and PEEK columns were used to extract dyes from a fabric under identical conditions with several parameters including the initial ultrasonic bath temperatures (30 °C and 40 °C), ultrasound power intensities (0, 20, 40, 60, 80, and 100 %), ultrasound operation modes (normal and sweep), and ultrasound frequencies (25 kHz, 40 kHz, and 132 kHz) to compare their extraction capabilities. After 30 min of extraction, the amount of extract was determined by HPLC. The PEEK material was significantly affected by ultrasonic radiation compared to the SS material, especially at a higher temperature (40 °C), power intensity (100 %), and frequency (132 kHz) with sweep mode. At a maximum power density of 45 W/L, the extraction effectiveness ratio of PEEK to SS was in the range of 1.8 - 3.9 depending on the specific frequency, initial temperature, and with or without temperature control. The most optimal ultrasound frequencies, in terms of enhancing extraction effectiveness, are in the order of 132 kHz, 40 kHz, and 25 kHz. Unlike the SS material, the PEEK material was more affected by temperature and acoustic effects under identical conditions, especially at 132 kHz ultrasound frequency. In contrast, at lower frequencies of 40 kHz and 25 kHz, no significant differences in the acoustic effects were observed between the PEEK and SS materials. The findings of this study contribute to elucidating the roles of column materials in UAE and UAC.

New ultrasonic assisted technology of freezing, cooling and thawing in solid food processing: A review

Solid foods include fish, shrimp, shellfish, and other aquatic products, fruits, and vegetables. These products are commonly used for food freezing, cooling, and thawing. However, traditional freezing, cooling, and thawing of solid food technologies have limitations in quality, such as protein denaturation and water loss in food. Ultrasound-assisted technology has become a useful method in solid food processing due to improved preservation quality of solid food. This paper comprehensively reviews the mechanism and application of ultrasonic in solid food processing technology. Although the application of ultrasound-assisted ultrasound in solid food processing is relatively comprehensive, the energy saving of food cold processing is essential for practical application. This paper analyzes the optimization of ultrasonic in solid food processing, including orthogonal/multi-frequency technology and the combination of ultrasonic and other technologies, which provides new ideas for freezing, cooling, and thawing of solid food processing.

Extraction of phenolics and anthocyanins from purple eggplant peels by multi-frequency ultrasound: Effects of different extraction factors and optimization using uniform design

In this work, multi-frequency ultrasound (working modes for the single-, dual- and tri-frequency in simultaneous ways) was applied to extract bioactive compounds from purple eggplant peels. The single-factor experiments were performed by varying six independent variables. A six-level-five-factor uniform design (UD) was further employed to evaluate the interaction effects between different factors. It was found that extraction temperature and extraction time significantly affected the total phenolic content (TPC), whereas the total monomeric anthocyanins (TMA) was mainly influenced by ethanol concentration, extraction temperature and solid-liquid ratio. Based on partial least-squares (PLS) regression analysis, the optimal conditions for TPC extraction were: 53.6 % ethanol concentration, 0.336 mm particle size, 44.5 °C extraction temperature, 35.2 min extraction time, 1:43 g/mL solid-liquid ratio, and similar optimal conditions were also obtained for TMA. Furthermore, the TPC and TMA extraction were investigated by ultrasound in different frequencies and power levels. Compared with single-frequency (40 kHz) and dual-frequency ultrasound (25 + 40 kHz), the extraction yield of TPC and TMA with tri-frequency ultrasound (25 + 40 + 70 kHz) increased by 23.65 % and 18.76 % respectively, which suggested the use of multi-frequency ultrasound, especially tri-frequency ultrasound, is an efficient strategy to improve the TPC and TMA extracts in purple eggplant peels.

Effects of dual-frequency slit ultrasound on the enzymolysis of high-concentration hydrolyzed feather meal: Biological activities and structural characteristics of hydrolysates

Ultrasound-assisted enzymolysis has been applied to improve conventional enzymolysis, while there are rare reports on the application of ultrasound to high-concentration feather protein enzymolysis. Therefore, the feasibility of dual-frequency slit ultrasound (DFSU) for enzymolysis of high-concentration hydrolyzed feather meal (HFM), as well as the biological activities and structural characteristics of hydrolysates were investigated. The single-factor test was used to optimize the ultrasonic processing parameters: substrate concentration, frequency mode, intermittent ratio, power density, and time. The results showed that protein recovery rate and conversion rate increased by 6.08% and 18.63% under the optimal conditions (200 g/L, 28/80 kHz, 5:2 s/s, 600 W/L, and 3 h) compared with conventional enzymolysis, respectively. The macromolecular proteins in hydrolysates were converted into micromolecular peptides (< 500 Da) when treated by DFSU, and antioxidant activity and angiotensin-I-converting enzyme (ACE) inhibitory activity of hydrolysates were increased. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images illustrated the microstructure changes of feather protein particles in the ultrasound-assisted enzymatic hydrolysates of HFM (UEH), including more porous, smaller, and more uniform. Additionally, the conformation of protein molecules was significantly affected (P < 0.05), including the increase in free sulfhydryl (SH), the decrease in disulfide bond (SS) and surface hydrophobicity (H₀). Fourier transform infrared (FTIR) spectra analysis further showed that the secondary structure of feather proteins was modified with a reduction in α-helix, β-turn, and β-sheet, while an increase in random coil content was observed. These results indicated that DFSU could be a promising method to enhance high-concentration HFM for preparing peptide-rich hydrolysates with high antioxidant activity and ACE inhibitory activity.

Effect of Multi-Mode Thermosonication on the Microbial Inhibition and Quality Retention of Strawberry Clear Juice during Storage at Varied Temperatures

Strawberry juice, which is rich in nutrients and charming flavor, is favored by consumers. To explore whether multi-mode thermosonication (MTS) can ensure the quality stability of strawberry clear juice (SCJ) during storage, the effects of microbial inhibition, enzyme activity, and physicochemical properties of SCJ pretreated by MTS were evaluated during storage at 4, 25, and 37 °C in comparison with thermal pretreatment (TP) at 90 °C for 1 min. The MTS, including dual-frequency energy-gathered ultrasound pretreatment (DEUP) and flat sweep-frequency dispersive ultrasound pretreatment (FSDUP), were conducted at 60 °C for 5 and 15 min, respectively. Results showed that the total phenols, flavonoids, anthocyanins, ascorbic acid, and DPPH free radical scavenging ability of SCJ decreased during the storage period. The control sample of SCJ was able to sage for only 7 days at 4 °C based on the microbiological quality, while the FSDUP and DEUP group extended the storage period up to 21 and 14 days, respectively. The polyphenol oxidase in SCJ pretreated by MTS did not reactivate during the storage period. The MTS remarkably (p < 0.05) reduced the color deterioration, browning degree, and nutrient degradation during the storage period. Moreover, the FSDUP group exhibited the maximum shelf life with a minimum loss of quality, demonstrating that it was the most suitable processing method for obtaining high-quality SCJ. It can be concluded that the MTS has the potential to inhibit enzymatic browning, inactivating microorganisms, preserve original quality attributes, and prolong the shelf life of SCJ.

Multi-frequency power ultrasound as a novel approach improves intermediate-wave infrared drying process and quality attributes of pineapple slices

This study evaluated the effect of mono-frequency ultrasound (MFU, 20 kHz), dual-frequency ultrasound (DFU, 20/40 kHz), and tri-frequency ultrasound (TFU, 20/40/60 kHz) on mass transfer, drying kinetics, and quality properties of infrared-dried pineapple slices. Pretreatments were conducted in distilled water (US), 35 °Brix sucrose solution (US-OD), and 75% (v/v) ethanol solution (US-ET). Results indicated that ultrasound pretreatments modified the microstructure of slices and shortened drying times. Compared to the control group, ultrasound application reduced drying time by 19.01-28.8% for US, 15.33-24.41% for US-OD, and 38.88-42.76% for US-ET. Tri-frequency ultrasound provoked the largest reductions, which exhibited time reductions of 6.36-11.20% and better product quality compared to MFU. Pretreatments increased color changes and loss of bioactive compounds compared to the control but improved the flavor profile and enzyme inactivation. Among pretreated sample groups, US-OD slices had lower browning and rehydration abilities, higher hardness values, and better retention of nutrients and bioactive compounds. Therefore, the combination of TFU and osmotic dehydration could simultaneously improve ultrasound efficacy, reduce drying time, and produce quality products.

Is enzyme immobilization a mature discipline? Some critical considerations to capitalize on the benefits of immobilization

Enzyme immobilization has been developing since the 1960s and although many industrial biocatalytic processes use the technology to improve enzyme performance, still today we are far from full exploitation of the field. One clear reason is that many evaluate immobilization based on only a few experiments that are not always well-designed. In contrast to many other reviews on the subject, here we highlight the pitfalls of using incorrectly designed immobilization protocols and explain why in many cases sub-optimal results are obtained. We also describe solutions to overcome these challenges and come to the conclusion that recent developments in material science, bioprocess engineering and protein science continue to open new opportunities for the future. In this way, enzyme immobilization, far from being a mature discipline, remains as a subject of high interest and where intense research is still necessary to take full advantage of the possibilities.

Recent advances in modified food proteins by high intensity ultrasound for enhancing functionality: Potential mechanisms, combination with other methods, equipment innovations and future directions

High intensity ultrasound (HIU) is an efficient and green technology that has recently received enormous research attention for modification of food proteins. However, there are still several knowledge gaps in the possible mechanisms, synergistic effects of HIU with other strategies and improvement of HIU equipment that contribute to its application in the food industry. This review focuses on the recent research progress on the effects and potential mechanisms of HIU on the structure (including secondary and tertiary structure) and functionality (including solubility, emulsibility, foamability, and gelability) of proteins. Furthermore, the combination methods and innovations of HIU equipment for proteins modification in recent years are also detailed. Meanwhile, the possible future trends of food proteins modification by HIU are also considered and proposed.

Recent Advances in the Application of Enzyme Processing Assisted by Ultrasound in Agri-Foods: A Review

The intensification of processes is essential for the sustainability of the biorefinery concept. Enzyme catalysis assisted by ultrasound (US) may offer interesting opportunities in the agri-food sector because the cavitation effect provided by this technology has been shown to improve the efficiency of the biocatalysts. This review presents the recent advances in this field, focused on three main applications: ultrasound-assisted enzymatic extractions (UAEE), US hydrolysis reactions, and synthesis reactions assisted by US for the manufacturing of agri-food produce and ingredients, enabling the upgrading of agro-industrial waste. Some theoretical and experimental aspects of US that must be considered are also reviewed. Ultrasonic intensity (UI) is the main parameter affecting the catalytic activity of enzymes, but a lack of standardization for its quantification makes it unsuitable to properly compare results. Applications of enzyme catalysis assisted by US in agri-foods have been mostly concentrated in UAEE of bioactive compounds. In second place, US hydrolysis reactions have been applied for juice and beverage manufacturing, with some interesting applications for producing bioactive peptides. In last place, a few efforts have been performed regarding synthesis reactions, mainly through trans and esterification to produce structured lipids and sugar esters, while incipient applications for the synthesis of oligosaccharides show promising results. In most cases, US has improved the reaction yield, but much information is lacking on how different sonication conditions affect kinetic parameters. Future research should be performed under a multidisciplinary approach for better comprehension of a very complex phenomenon that occurs in very short time periods.