Innovative physical techniques in freeze-drying

Exploring the efficacy of pulsed electric fields (PEF) in microbial inactivation during food processing: A deep dive into the microbial cellular and molecular mechanisms

Inactivating effect of pulsed electric field on lipase in brown rice

Advances in innovative processing technologies for microbial inactivation and enhancement of food safety – pulsed electric field and low-temperature plasma

Acoustic and mechanical properties of carrot tissue treated by pulsed electric field, ultrasound and combination of both

Inactivation of Staphylococcus aureus by a non-thermal argon operated plasma jet and by microsecond pulsed electric fields (PEF) was investigated. The different methods were either applied by themselves or in combination with each other. Treatments with plasma alone or pulsed electric fields alone were found to result in significant but not complete inactivation. A 2-log reduction was observed for the longest plasma exposure time of 3 min or for the application of 300 consecutive electric field pulses with 100-μs duration and 15-kV/cm amplitude. For the combined treatment with non-thermal plasma and pulsed electric fields, significant synergistic antibacterial effects were observed when samples were treated with plasma first. However, only an additive or at most a slight synergistic effect was observed when samples were first treated with pulsed electric fields instead. The acidification of the bacteria suspension after plasma treatment is likely responsible for the support of subsequent reaction mechanisms that are induced by exposures to pulsed electric fields and is hence the reason for the observed synergy.

Technologies based on pulsed electric field (PEF) are increasingly pervasive in medical and industrial applications. However, the detailed understanding of how PEF acts on biosamples including proteins at the molecular level is missing. There are indications that PEF might act on biomolecules via electrogenerated reactive oxygen species (ROS). However, it is unclear how this action is modulated by the pro- and antioxidants, which are naturally present components of biosamples. This knowledge gap is often due to insufficient sensitivity of the conventionally utilized detection assays. To overcome this limitation, here we employed an endogenous (bio)chemiluminescence sensing platform, which enables sensitive detection of PEF-generated ROS and oxidative processes in proteins, to inspect effects of pro-and antioxidants. Taking bovine serum albumin (BSA) as a model protein, we found that the chemiluminescence signal arising from its solution is greatly enhanced in the presence of H2O2 as a prooxidant, especially during PEF treatment. In contrast, the chemiluminescence signal decreases in the presence of antioxidant enzymes (catalase, superoxide dismutase), indicating the involvement of both H2O2 and electrogenerated superoxide anion in oxidation-reporting chemiluminescence signal before, during, and after PEF treatment. We also performed additional biochemical and biophysical assays, which confirmed that BSA underwent structural changes after H2O2 treatment, with PEF having only a minor effect. We proposed a scheme describing the reactions leading from interfacial charge transfer at the anode by which ROS are generated to the actual photon emission. Results of our work help to elucidate the mechanisms of action of PEF on proteins via electrogenerated reactive oxygen species and open up new avenues for the application of PEF technology. The developed chemiluminescence technique enables label-free, in-situ and non-destructive sensing of interactions between ROS and proteins. The technique may be applied to study oxidative damage of other classes of biomolecules such as lipids, nucleic acids or carbohydrates.

Moderate pulsed electric field-induced structural unfolding ameliorated the gelling properties of porcine muscle myofibrillar protein

The increasing consumer demand for 'fresh-like' foods has led to much research effort in the last 20 years to develop new mild methods for food preservation. Nonthermal methods allow micro-organisms to be inactivated at sublethal temperatures thus better preserving the sensory, nutritional and functional properties of foods. The aim of this review is to provide an overview of the microbiological aspects of the most relevant nonthermal technologies for microbial inactivation currently under study, including irradiation, high hydrostatic pressure, pulsed electric field and ultrasound under pressure. Topics covered are the mechanisms of inactivation, sensitivity of different microbial groups and factors affecting it and kinetics of inactivation.

According to the U.S. Food and Drug Administration (FDA), most people in the United States consume too much sodium. Reducing sodium may help reduce the risk of high blood pressure, a leading cause of heart disease and stroke. Most sodium comes from processed, packaged, and prepared foods, not from table salt added to food when cooking or eating. In October 2021, the FDA issued guidance for industry that finalized short-term voluntary sodium reduction targets in over 160 categories of packaged and restaurant-prepared food. On April 10, 2023, the FDA published a proposed rule to amend the standard of identity (SOI) regulations that specify salt (sodium chloride) as a required or optional ingredient to permit the use of salt substitutes in standardized foods, to reduce the sodium content. If finalized, this proposed rule may help manufacturers to meet these voluntary targets because several foods for which targets were established are covered by SOIs. The proposed rule, if finalized, would help support a healthier food supply by providing flexibility to facilitate industry innovation in the production of standardized foods lower in sodium while maintaining the basic nature and essential characteristics of the foods. The upcoming proposed rule is part of the Biden–Harris Administration's National Strategy on Hunger, Nutrition, and Health. This National Strategy was previously discussed in an Industrial Application Brief in 2022. The National Strategy provides a roadmap of actions the federal government will take to end hunger and reduce diet-related diseases by 2030—all while reducing disparities. The National Strategy was released in conjunction with the first White House Conference on Hunger, Nutrition, and Health in more than 50 years. The upcoming proposed rule also complements the goals of the FDA's voluntary sodium reduction targets for processed, packaged, and prepared foods. SOIs typically describe what ingredients a food must contain and what is optional. They may describe the amount or proportion of ingredients or components. Some SOIs also prescribe a method of production or formulation. There are more than 250 SOIs, and they include products like milk, milk chocolate, various breads, various cheeses, and ketchup. Foods with SOIs are often referred to as standardized foods. Salt substitutes are currently used in many nonstandardized foods in the United States, but most FDA SOIs do not permit the use of salt substitutes. The proposed rule would use a “horizontal” approach for SOIs, under which a single rule would apply to multiple SOIs across several categories of standardized foods. Specifically, the proposed rule would amend the 80 SOIs that specify salt as a required or an optional ingredient. Because these 80 SOIs are referenced in other SOIs, 140 of the 250 SOIs currently established for a wide variety of foods could be affected. The proposed rule does not list permitted salt substitutes but defines them as safe and suitable ingredients used to replace some or all of the added sodium chloride and that serve the functions of salt in food. The extent to which salt can be replaced depends on the ability of a salt substitute to replace the functions of salt in food without compromising food safety and the characteristics of the food. The comment due date for the proposed rule is August 8, 2023. Electronic comments can be sent to Regulations.gov. Submit written comments to Dockets Management Staff (HFA-305), Food and Drug Administration, 5630 Fishers Lane, rm. 1061, Rockville, MD 20852. For more information, see the media release, FDA Takes Additional Steps to Improve Nutrition, Reduce Disease with Expanded Use of Salt Substitutes to Help Lower Sodium Intake: https://www.fda.gov/food/cfsan-constituent-updates/fda-propose-permit-salt-substitutes-reduce-sodium-standardized-foods Highlights in this issue include how Pseudomonas can survive thermal processing in emulsified meat; sweet taste dominance and body mass index (BMI); a new Coffee Brewing Control Chart; improving salt diffusion in pork; and developing a hybrid greenhouse dryer for potato chips. As these researchers note, controlling the presence and growth of pathogenic organisms in meat and poultry products has been a public health priority for nearly 30 years, after the widespread implementation of the hazard analysis and critical control points systems. However, they add that to achieve sustainable meat and poultry production, it is important to gain a deeper understanding of both the evolving threat of biological hazards and the population dynamics of spoilage bacteria during shelf life. According to the researchers, some Pseudomonas species are common meat spoilage bacteria that are often associated with the spoilage of fresh meat. The recently reported ability of these bacteria to also spoil cooked and vacuum packaged meat products has created the need to investigate all potential routes of spoilage they may be able to utilize. The objective of this experiment was to determine if spoilage Pseudomonas spp. survive thermal processing and grow during refrigerated storage under vacuum. Pseudomonas spp. isolates collected from spoiled turkey products were inoculated into a salted and seasoned meat emulsion that was vacuum sealed and thermally treated to final temperatures of 54.4 and 71.1°C to mimic thermal processes commonly used in the meat industry. Samples were stored for a total of 294 days at 4 and 10°C and plated using Pseudomonas spp.-specific agar plates. Pseudomonas spp. concentrations were below the detection limit immediately after thermal processing and were first recovered from thermally processed samples after 14 days of storage. The final concentration was greater than 2 log10 CFU/g in the thermally processed treatment groups at the end of storage, indicating that these Pseudomonas spp. isolates were able to survive thermal processing and grow during extended vacuum storage. The researchers say that this raises concerns about the ability of spoilage bacteria to survive the thermal processing schedules commonly used in the meat industry and confirms that some Pseudomonas spp. are capable of thriving in products other than aerobically stored fresh meat. They conclude that heat resistance should be evaluated for commensal and spoilage bacteria to better understand possible ways spoilage of food products may occur. P 2162–2167 Overweight and obese individuals may experience taste perception in foods in a different way. This study investigated the dominance of sweet taste perception in a fruit beverage by adults with adequate weight and overweight. Excess adipose tissue is associated with basic taste perception change, which can negatively affect food choices. However, the effect of overweight and obesity on sensory perception is not clearly explained in the literature yielding heterogeneous results. These researchers investigated the temporal dominance of sweet taste according to BMI classification in adults during the ingestion of five passion fruit nectar samples prepared with different sucrose concentrations. The sensory analysis was performed with the participation of 90 adult consumers, divided into three groups: EG = eutrophic, WG = overweight, and OG = obesity group, according to the BMI classification. Among the groups, a difference in the perception of the attribute “sweet taste” was observed: The EG demonstrated perception of the stimulus in food samples at lower sucrose concentrations, whereas WG and OG showed a higher rate of sweet taste dominance in the food samples with higher concentration of sucrose. Overweight and obese individuals have a lower sensory perception of sweet taste and require a greater amount of sucrose to produce sensory dominance of the attribute “sweet taste” when compared to eutrophic individuals. According to the researchers, the results support the hypothesis that obese and nonobese individuals differ in the sweet taste perception, which can help to understand which factors are involved in sensory perception and food consumption, in addition to providing subsidies for the nonalcoholic beverage industry to elaborate products with new alternatives for concentration and/or replacement of sucrose. P 2191–2202 In this study, a novel chitosan-based composite, carboxymethyl chitosan (CMCHS)/oxidized carboxymethyl cellulose (OCMC), was fabricated and characterized. The composite film (CMCHS 1.5% [w/v] + OCMC 0.8% [w/v]) was more uniform and had better tensile properties, UV blocking, water vapor permeability, and antifungal properties than pure CMCHS film. Preservation experiments showed that the CMCHS/OCMC film was more efficient for retaining the quality decrease of strawberry during storage. By the end of 7 days’ storage, the hardness and contents of organic acid, soluble solids, and reducing sugar in coated strawberries were increased by 35.1%, 38.5%, 14.1%, and 3.5%, respectively, compared to the control group, and the decay rate of strawberries in CMCHS/OCMC group also dropped to 36%, about 42% decrease than that in control, suggesting the promising application of CMCHS/OCMC composite in coating preservation. P 1865–1878 The classic Coffee Brewing Control Chart (BCC) was originally developed in the 1950s. It relates coffee quality to brew strength and extraction yield, and it is still widely used today by coffee industry professionals around the world to provide guidance on the brewing of coffee. Despite its popularity, recent experimental studies have revealed that sensory attributes and consumer preferences actually follow much more complicated trends than those indicated by the classic BCC. In this study, the researchers present a methodology to synthesize the results of these recent studies on drip-brewed coffee to generate new versions of the BCC: a new Sensory BCC that displays a broad array of statistically significant sensory attributes across typical total dissolved solids and percent extraction ranges, a new Consumer BCC that highlights the existence of two preference clusters with different likes and dislikes across those ranges, a new Sensory and Consumer BCC that combines both sensory descriptive and consumer preferences on the same chart, and a more streamlined BCC that omits consumer preferences and focuses on the overarching sensory descriptive trends. The new BCCs provide more accurate insight on how best to brew coffee to achieve desired sensory profiles. P 2168–2177 Pulsed electric field (PEF) is an emerging nonthermal processing technology. In this study, PEF is used to enhance salt diffusion in pork. Pork lions were pretreated with PEF before being immersed in the brine at 4°C to investigate the effect of needle–needle PEF pretreatment on pork brine salting. Results demonstrated that after brining for 8 h with PEF pretreatment, the weight, moisture, and salt changes increased significantly. The central salt content achieved by 12 h brining after PEF treatment (4.5 kV) is equivalent to that achieved by brining for 20 h without any treatment. The effective diffusion coefficient (De) was raised to 4.0 × 10−10 (PEF) from 3.1 × 10−10 (control). Scanning electron microscopy and Fourier transform infrared spectroscopy revealed that PEF altered the microstructure of pork. The researchers say that PEF generated by needle–needle electrodes could effectively promote salt diffusion and shorten salting processing. P 2023–2035 These researchers used a combination of heat and mass transfer developed using a finite element (FE) model to explain the drying performance of a hybrid greenhouse dryer for potato chips. The hybrid greenhouse dryer is integrated with a single-pass solar air heater (SAH). To see the spatial moisture distribution within the potato sample, a three-dimensional FE model was created. Moisture removal takes place from the surface during drying of the products. Lagrange triangle FEs of extremely small size and second-order geometry shape were employed for meshing the geometry of the model. The developed model showed the maximum crop and ground temperature are 67.1 and 79.1°C, respectively. Moisture ratio on a dry basis is reduced from 1 to 0.005 in 3 h and remains constant at 0.005. The average moisture ratio on a dry basis was found to be 0.18902. Drying efficiency for the hybrid greenhouse dryer was found to be 20.52%, and thermal efficiency for SAH was found to be 54.53%. Relative humidity inside the drying chamber found to be 26.50% in the hybrid greenhouse dryer. The predicted versus the experimental results observed found that the hybrid greenhouse dryer having moderate inside temperature is suitable for crop drying as well as sustaining the environmental balance. P 1800–1815

Pulsed electric field (PEF) processing has emerged as a promising technology in the development of tailor-made processes to effectively control the enzyme activity. It has been proven as an effective technique for the preservation of food products as it can result in substantial inactivation of most undesirable enzymes. When compared to microbial inactivation, however, large specific energy inputs are required to inactivate enzymes. The existing evidence suggests that PEF can also stimulate the activity of beneficial enzymes at low intense treatments. The PEF affects enzyme activity by changing mainly the secondary (α-helix, β-sheets, etc.), tertiary (spatial conformation), and quaternary (number and arrangement of protein subunits) structures of the enzyme. There is not yet strong evidence that PEF induce chemical changes in primary structure. Both electrochemical effects and ohmic heating associated with PEF impact contribute to the change in enzyme structure and function. In addition, a number of factors including the physicochemical properties the enzyme, PEF treatment parameters, the processing condition, and the composition of the medium can significantly contribute to the enzyme activity. However, the exact mechanism of PEF action on enzymes at atomic level is not fully understood. In the past 20 years, several studies have confirmed that PEF at high intensity or in combination with mild heat causes substantial inactivation of several food quality-related enzymes such as alkaline phosphatase, peroxidase, proteases, lipase, pectin methylesterase, polyphenol oxidase, etc. Meantime, some reports show that PEF treatment has no effect on inactivation of certain enzymes at a given treatment condition. However, results obtained in different studies cannot be compared as the equipment used, treatment parameters, and medium are inconsistent in these studies. For effective treatment, PEF processing parameters must be optimized depending on the enzyme and target product.

On new possibilities of measuring electric fields in plasmas using molecule emission spectra

Quantitative description of the Stark effect on Rydberg levels of argon atoms is given. Theoretical dependences of the shift and splitting of both allowed and forbidden spectral lines of argon atoms on the magnitude of the electric field are obtained. These dependences can be used for laser‐aided measurements of weak electric fields in low temperature plasmas.

Consumers demand healthier fresh tasting foods without chemical preservatives. To address the need, food industry is exploring alternative preservation methods such as high pressure processing (HPP) and pulsed electric field processing. During HPP, the food material is subjected to elevated pressures (up to 900 MPa) with or without the addition of heat to achieve microbial inactivation with minimal damage to the food. One of the unique advantages of the technology is the ability to increase the temperature of the food samples instantaneously; this is attributed to the heat of compression, resulting from the rapid pressurization of the sample. Pulsed electric field (PEF) processing uses short bursts of electricity for microbial inactivation and causes minimal or no detrimental effect on food quality attributes. The process involves treating foods placed between electrodes by high voltage pulses in the order of 20–80 kV (usually for a couple of microseconds). PEF processing offers high quality fresh-like liquid foods with excellent flavor, nutritional value, and shelf life. Pressure in combination with other antimicrobial agents, including CO2, has been investigated for juice processing. Both HPP and PEF are quite effective in inactivating harmful pathogens and vegetative bacteria at ambient temperatures. Both HPP and PEF do not present any unique issues for food processors concerning regulatory matters or labeling. The requirements are similar to traditional thermal pasteurization such as development of a Hazard Analysis Critical Control Point (HACCP) plan for juices and beverages. Examples of high pressure, pasteurized, value added products commercially available in the United States include smoothies, fruit juices, guacamole, ready meal components, oysters, ham, poultry products, and salsa. PEF technology is not yet widely utilized for commercial processing of food products in the United States. The presentation will provide a brief overview of HPP and PEF technology fundamentals, equipment choices for food processors, process economics, and commercialization status in the food industry, with emphasis on juice processing. Paper published with permission.

Chapter 1 - Fundamentals of High-Intensity Pulsed Electric Fields (PEF)

PURPOSE: Alopecia affects more than half of the population worldwide.1 Current therapeutic options including minoxidil and finasteride are minimally effective, expensive, and require daily use to avoid recurrent alopecia. Hair transplantation is expensive, minimally effective, and leads to donor site morbidity. Pulsed Electric Fields (PEF) create transient vasoconstriction followed by vasodilation. We have evidence that PEF stimulate hair follicles and we hypothesize that this stimulation shifts the hair cycle from resting telogen to active anagen. The objective of this study is to prove that PEF stimulate hair growth in a dose-dependent manner, and to optimize treatment parameters. METHODS: Sprague Dawley rats were shaved and treated with PEF using two 1cm2-contact electrodes. Three treatment and three control sites were tattooed onto the dorsum of each rat. Following the taguchi experimental design, a range of low-dose parameters were investigated: 30, 90, 270-Volts; 100, 300, 900-pulses; and 10, 90, 270us pulse length. Animals were euthanized 1-month after treatment and tissue was harvested for histological analysis. The percent of anagen follicles per treatment site was calculated. Taguchi analysis was performed to rank parameters. RESULTS: We prove that PEF shift the hair cycle from telogen to anagen, resulting in dense patches of hair. The optimal dose tested was 270V, 300pulses, and 270us pulse length duration, which induced a 5.05-fold increase in anagen follicles at treated sites as compared to controls. Treated sites demonstrated 45.55±18.07% of follicles in anagen, contrasting 9.02±6.00% of follicles in the anagen phase at control sites (p=0.0008). A dose response was demonstrated among the tested parameters. Additionally, the taguchi analysis generated the following rank: voltage, pulse length, and number of pulses, demonstrating that voltage has the greatest effect on anagen stimulation. Digital photography correlated with histological findings, revealing defined patches of hair at treated sites distinctly contrasting untreated skin (Figure 1).Figure 1: Gross photography of control vs. PEF-treated sites with corresponding histology. Dense patches of well-demarcated hair growth at treated sites with increased anagen follicles as compared to controls.CONCLUSION: PEF shifted hair follicles from resting telogen to active anagen, and voltage was the most influential parameter. A single treatment at 270V, 300pulses, and 270us pulse length, lead to a 5.05-fold increase in anagen follicles at treated sites. Additional studies are needed to evaluate duration of results, effect of multiple treatments, and mechanism of action. In conclusion, we showed that low-dose PEF effectively stimulate hair follicles in a rat model.