Effects of Pulsed Electric Fields and Ultrasound Processing on Proteins and Enzymes: A Review

Computational analysis of the simultaneous application of ultrasound and electric fields in a lipid bilayer

The combined application of electric fields and ultrasonic waves has shown promise in controlling cell membrane permeability, potentially resulting in synergistic effects that can be explored in the biotechnology industry. However, further clarification on how these processes interact is still needed. The objective of the present study was to investigate the atomic-scale effects of these processes on a DPPC lipid bilayer using molecular dynamics simulations. For higher electric fields, capable of independently forming pores, the application of an ultrasonic wave in the absence of cavitation yielded no additional effects on pore formation. However, for lower electric fields, the reduction in bilayer thickness induced by the shock wave catalyzed the electroporation process, effectively shortening the mean path that water molecules must traverse to form pores. When cavitation was considered, synergistic effects were evident only if the wave alone was able to generate pores through the formation of a water nanojet. In these cases, sonoporation acted as a mean to focus the electroporation effects on the initial pore formed by the nanojet. This study contributes to a better understanding of the synergy between electric fields and ultrasonic waves and to an optimal selection of processing parameters in practical applications of these processes.

Tailoring the Techno-Functional Properties of Fava Bean Protein Isolates: A Comparative Evaluation of Ultrasonication and Pulsed Electric Field Treatments

The fava bean protein isolate (FBPI) holds promise as a sustainable plant-based protein ingredient. However, native FBPIs exhibit limited functionality, including unsuitable emulsifying activities and a low solubility at a neutral pH, restricting their applications. This study is focused on the effect of ultrasonication (US) and pulsed electric fields (PEF) on modulating the techno-functional properties of FBPIs. Native FBPIs were treated with US at amplitudes of 60-90% for 30 min in 0.5 s on-and-off cycles and with PEF at an electric field intensity of 1.5 kV/cm with 1000-4000 pulses of 20 μs pulse widths. US caused a reduction in the size and charge of the FBPIs more prominently than the PEF. Protein characterization by means of SDS-PAGE illustrated that US and PEF caused severe-to-moderate changes in the molecular weight of the FBPIs. In addition, a spectroscopic analysis using Fourier-transform infrared (FTIR) and circular dichroism (CD) revealed that US and the PEF induced conformational changes through partial unfolding and secondary structure remodeling from an α-helix to a β-sheet. Crystallographic and calorimetric determinations indicated decreased crystallinity and lowered thermal transition temperatures of the US- and PEF-modified FBPIs. Overall, non-thermal processing provided an effective strategy for upgrading FBPIs' functionality, with implications for developing competitive plant-based protein alternatives.

Pulsed electric field treatment of soymilk: Impact on Kunitz trypsin inhibitor allergenicity, antinutritional factor, and aroma characteristics

Allergens, antinutritional factors, and lipoxygenase (LOX) enzyme present in soymilk limit its consumption as vegan milk. Therefore, the present study focuses on reducing these limiting factors using pulsed electric field (PEF) treatment. In this regard, 20-40 kV/cm electric field was applied to soymilk for the effective treatment periods of 450, 1350, and 2250 ms. After the treatment, a reduction in pH (6.60 ± 0.10 to 6.47 ± 0.12) and an increase in the conductivity (173.03 ± 0.40 to 177.33 ± 0.72 µS) were observed. Furthermore, FTIR (Fourier Transform Infrared Spectroscopy), UV (Ultra Violet) intrinsic spectra, and CD (Circular Dichroism) spectra (α-helix reduction and β-sheet increase) data indicated mild structural changes in the proteins of soymilk. As a result, PEF treatment reduced the soymilk allergenicity (67.33 ± 20.48%), LOX activity (69.45 ± 9.38%), and trypsin inhibitor activity (75.61 ± 4.04%). Apart from that, the color, viscosity, and volatiles of soymilk also had significant changes due to PEF treatment. The aroma changes in PEF-treated soymilk were highly influenced by two major principal component (PC1 & PC2) groups and they accounted for about 70% of the aroma variations. However, these changes were mild and did not induce any off-flavors and the treatment remained effective against the quality hazards like allergens, antinutritional factors, and LOX enzyme. PRACTICAL APPLICATION: PEF treatment of soymilk reduces the possible allergic reactions in human body at least by 30%. Further, it reduces the antinutritional factor and off-odor inducing compounds. Therefore, the PEF treatment can be used in industries as a pre-treatment to produce allergen and antinutritional compounds free protein isolates from soybeans.

Mechanism of ultrasonic combined with different fields on protein complex system and its effect on its functional characteristics and application: A review

In recent years, new food processing technologies (such as ultrasound, high-pressure homogenization, and pulsed electric fields) have gradually appeared in the public 's field of vision. These technologies have made outstanding contributions to changing the structure and function of protein complexes. As a relatively mature physical field, ultrasound has been widely used in food-related fields. However, with the gradual deepening of related research, it is found that the combination of different fields often makes some characteristics of the product better than the product under the action of a single field, which will not only lead to a broader application prospect of the product, but also make the product a better solution in some special fields. There are usually synergistic and antagonistic effects when multiple fields are combined, and these effects will also gradually enlarge the interaction between different components of the protein complex system. In this paper, while explaining the mechanism of ultrasonic combined with other fields affecting the steric hindrance and shielding site of protein complex system, we will further explain the effect of this effect on the function and application of protein complex system.

Emerging Postharvest Technologies to Enhance the Shelf-Life of Fruit and Vegetables: An Overview

Quality losses in fresh produce throughout the postharvest phase are often due to the inappropriate use of preservation technologies. In the last few decades, besides the traditional approaches, advanced postharvest physical and chemical treatments (active packaging, dipping, vacuum impregnation, conventional heating, pulsed electric field, high hydrostatic pressure, and cold plasma) and biocontrol techniques have been implemented to preserve the nutritional value and safety of fresh produce. The application of these methodologies after harvesting is useful when addressing quality loss due to the long duration when transporting products to distant markets. Among the emerging technologies and contactless and non-destructive techniques for quality monitoring (image analysis, electronic noses, and near-infrared spectroscopy) present numerous advantages over the traditional, destructive methods. The present review paper has grouped original studies within the topic of advanced postharvest technologies, to preserve quality and reduce losses and waste in fresh produce. Moreover, the effectiveness and advantages of some contactless and non-destructive methodologies for monitoring the quality of fruit and vegetables will also be discussed and compared to the traditional methods.

Impact of Non-Thermal Technologies on the Quality of Nuts: A Review

Nuts are widely consumed worldwide, mainly due to their characteristic flavor and texture, ease of consumption, and their functional properties. In addition, consumers increasingly demand natural or slightly processed foods with high quality. Consequently, non-thermal treatments are a viable alternative to thermal treatments used to guarantee safety and long shelf life, which produce undesirable changes that affect the sensory quality of nuts. Non-thermal treatments can achieve results similar to those of the traditional (thermal) ones in terms of food safety, while ensuring minimal loss of bioactive compounds and sensory properties, thus obtaining a product as similar as possible to the fresh one. This article focuses on a review of the main non-thermal treatments currently available for nuts (cold plasma, high pressure, irradiation, pulsed electric field, pulsed light, ultrasound and ultraviolet light) in relation to their effects on the quality and safety of nuts. All the treatments studied have shown promise with regard to the inhibition of the main microorganisms affecting nuts (e.g., Aspergillus, Salmonella, and E. coli). Furthermore, by optimizing the treatment, it is possible to maintain the organoleptic and functional properties of these products.

Non-Thermal Processing of a Protein Functional Beverage Using Pulsed Electric Fields: Escherichia coli Inactivation and Effect on Proteins

The application of pulsed electric fields (PEFs) for the inactivation of Escherichia coli, suspended in a protein shake beverage and diluted with sterilized distilled water was carried out. Square bipolar pulses in the range of 25–40 kV/cm electric field intensities were applied at different frequencies (400–900 Hz) to investigate the effect of different PEF conditions on the microbial population and proteins relevant to this functional beverage. The treatment temperature was kept below the lethal temperature of the microorganism under investigation. As power consumption plays an important role in the efficiency of the PEF application, the dissipated power was also estimated. Four log reductions in the E. coli population were obtained with 10 pulses at a 40 kV/cm field intensity and 25 pulses at a 25 kV/cm field intensity. PEF-treated whey-protein concentrates showed less denaturation in proteins than thermally treated concentrates, especially for lower electric field intensities (0% denaturation ± 0.007 at 25 kV/cm and 900 Hz, 4.41% denaturation ± 0.008 at 40 kV/cm and 400 Hz). Soy protein isolates manifested high sensitivity to PEF processing and resulted in denaturation and aggregation in the protein structure.

Special Issue on “Feature Review Papers in Section Food Processes”

The successive growth of the population, degradation of the natural environment, and development of civilization diseases force a continuous increase in the production of high-quality food [...]

Response to "Non-thermal microwave effects: Conceptual and methodological problems"

The objective of this response letter is to expose the reader of Food Chemistry to the most recent advances and discussions about non-thermal effects of microwaves on microorganisms and enzymes. Although these effects showed to be too subtle for any practical use in food processing, experimental and molecular dynamics studies bring evidences that electric fields at low frequencies or with high intensity can have non-thermal effects, such as activity changes in enzymes during ohmic processing or electroporation of cells in pulsed electric field processing. This brief review broadens the scope of this controversial topic to show that innovative experiments and simulations are collaborating with the advance of emerging electro technologies in food processing. .

Legumes as basic ingredients in the production of dairy-free cheese alternatives: a review

Research into dairy-free alternative products, whether plant-based or cell-based, is growing fast and the food industry is facing a new challenge of creating innovative, nutritious, accessible, and natural dairy-free cheese alternatives. The market demand for these products is continuing to increase owing to more people choosing to reduce or eliminate meat and dairy products from their diet for health, environmental sustainability, and/or ethical reasons. This review investigates the current status of dairy product alternatives. Legume proteins have good technological properties and are cheap, which gives them a strong commercial potential to be used in plant-based cheese-like products. However, few legume proteins have been explored in the formulation, development, and manufacture of a fully dairy-free cheese because of their undesirable properties: heat stable anti-nutritional factors and a beany flavor. These can be alleviated by novel or traditional and economical techniques. The improvement and diversification of the formulation of legume-based cheese alternatives is strongly suggested as a low-cost step towards more sustainable food chains. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of Microwaves, Ultrasonication, and Thermosonication on the Secondary Structure and Digestibility of Bovine Milk Protein

Cow’s milk is considered an excellent protein source. However, the digestibility of milk proteins needs to be improved. This study aimed to evaluate the relationship between the functional properties of milk proteins and their structure upon microwave, ultrasound, and thermosonication treatments. The protein content, digestibility, and secondary-structure changes of milk proteins were determined. The results demonstrated that almost 35% of the proteins in the untreated samples had a α-helix structure and approximately 29% a β-sheet and turns structure. Regarding the untreated samples, the three treatments increased the α-helices and correspondingly decreased the β-sheets and turns. Moreover, the highest milk protein digestibility was observed for the ultrasound-treated samples (90.20–94.41%), followed by the microwave-treated samples (72.56–93.4%), whereas thermosonication resulted in a lower digestibility (68.76–78.81%). The milk protein content was reduced as the microwave processing time and the temperature increased. The final milk protein available in the sample was lower when microwave processing was conducted at 75 °C and 90 °C compared to 60 °C, whereas the ultrasound treatment significantly improved the protein content, and no particular trend was observed for the thermosonicated samples. Thus, ultrasound processing shows a potential application in improving the protein quality of cow’s milk.