Effect of guard cells electroporation on drying kinetics and aroma compounds of Genovese basil ( Ocimum basilicum L.) leaves

Electrostimulation improves plant growth and modulates the flavonoid profile in aeroponic culture of Scutellaria baicalensis Georgi

Scutellaria baicalensis Georgi is a valuable medicinal plant of the Lamiaceae family. The roots, Scutellariae baicalensis radix, are valued in the traditional medicine of East Asia and are also listed in several pharmacopeias, such as the Chinese and European versions. The roots contain a high amount of flavones, such as baicalein, wogonin and their glucuronides, baicalin and wogonoside, respectively, with rare structures of unsubstituted B-ring. These major constituents are responsible for its pharmacological activity, mainly anti-inflammatory, antiviral, and antitumor, as well as BDZ-receptor modulating. There is a fast-growing demand for both the crude drug and the individual flavonoids obtained from it. However, the variability of content and composition of flavonoids in the roots is significant and affects pharmaceutical use, and little is known about the influence of various factors on root quality. In our experiments, we use aeroponics to determine the effect of electroporation as an abiotic stressor on plant growth, development, and root mass, as well as on its metabolic profile.

RESULTS

Electroporation significantly impacted plant growth and the content of flavonoids, especially baicalein and wogonin, depending on the treatment parameters. Concentrations of aglycones were increased in at least half of the treatment conditions. The greatest amounts (a 2.5-fold increase compared to controls) were recorded after applying an electrical field characterized by the following parameters: E = 3 kV/cm, t = 100 μs, and N = 10. In conclusion, electrostimulation is an innovative and efficient way to increase plant growth and yield in an aeroponic system, as well as modulate the profile and content of bioactive flavones in the roots. However, the fine-tuning of these parameters, such as the electrical field strength (E), length (t), and number (N) of impulses delivered, is of great importance. It was also shown that cultivation of the experimental plants in aeroponics had a positive impact on their survival and development while being a sustainable and efficient horticultural practice.

Pulsed electric field-assisted drying: A review of its underlying mechanisms, applications, and role in fresh produce plant-based food preservation

Drying is a key processing step for plant-based foods. The quality of dried products, including the physical, nutritional, microbiological, and sensory attributes, is influenced by the drying method used. Conventional drying technologies have low efficiency and can negatively affect product quality. Recently, pulsed electric field (PEF)-assisted techniques are being explored as a novel pretreatment for drying. This review focuses on the application of PEF as pretreatment for drying plant-based products, the preservation effects of this pretreatment, and its underlying mechanisms. A literature search revealed that PEF-assisted drying is beneficial for maintaining the physicochemical properties of the dried products and preserving their color and constituent chemical compounds. PEF-assisted drying promotes rehydration and improves the kinetics of drying. Unlike conventional technologies, PEF-assisted drying enables selective cell disintegration while maintaining product quality. Before the drying process, PEF pretreatment inactivates microbes and enzymes and controls respiratory activity, which may further contribute to preservation. Despite numerous advantages, the efficiency and applicably of PEF-assisted drying can be improved in the future.

Reversible Electroporation and Post-Electroporation Resting of Thai Basil Leaves Prior to Convective and Vacuum Drying

Pretreatment by reversible electroporation followed by resting (storage under saturated moisture at 21 ± 2 °C) was evaluated for modification of the properties of dried and rehydrated Thai basil leaves. The treated leaves were dried by convection at 40 °C or in a vacuum at room temperature. The results showed that vacuum drying provoked more cell damage and tissue collapse than convective air drying at a moisture ratio (MR) of 0.2 and 0.1. Under this level of MR, the pulsed electric field (PEF) and resting pretreatment exerts a protective effect of the tissue for both drying methods. However, under complete dehydration (water activity, aw = 0.05) damage seems to be similar for both drying methods despite the PEF pretreatment. Remarkably, reversible electroporation followed by resting resulted in higher trichome preservation. At MR of 0.05, the area of trichomes on the surface of convective-dried, PEF-rested and fresh samples were not statistically different at 2267 ± 89 µm2 and 2218 ± 65 µm2, respectively, showing that this pretreatment still exerts a protective effect on trichomes when complete dehydration is achieved.

The effect of reversible permeabilization and post-electroporation resting on the survival of Thai basil (O. Basilicum cv. thyrsiflora) leaves during drying

Horticultural crops have a low tolerance to dehydration. In this paper, we show that the reversible electroporation (200 monopolar, rectangular pulses of 50 µs pulse duration, 760 µs between pulses and nominal field strength of 650 V/cm) of Thai basil leaves followed by 24 h resting before hot air drying at 40 °C enhanced the survivability of the tissues at certain levels of dehydration (moisture ratio = 0.2 and 0.1). However, this increased survival was rather limited. Through measurements of metabolic heat production during resting, rehydration kinetics, respiration and photosynthesis of the rehydrated leaves, we show that resting after the application of a reversible pulse-electric field (PEF) may allow a phase of hardening that has a protective effect on the cells, thus decreasing damage during the subsequent drying phase. Increased preservation of cell vitality would be associated with a more turgid and fresh-like rehydrated product, as cells would have the capacity to retain the rehydration water.

A review of drying methods for improving the quality of dried herbs

A large number of herb-drying studies have been conducted in recent decades and several herb-drying techniques have been introduced. However, the quality of commercial dried herbs is still lower than that of fresh herbs. In this paper, studies regarding the effect of drying techniques and pre-drying treatments on the aroma and color of dried herbs are reviewed with the aim of providing an overview of different technological strategies developed for improving the quality of aromatic herbs for their industrial drying.

Gene transfer to plants by electroporation: methods and applications

Developing gene transfer technologies enables the genetic manipulation of the living organisms more efficiently. The methods used for gene transfer fall into two main categories; natural and artificial transformation. The natural methods include the conjugation, transposition, bacterial transformation as well as phage and retroviral transductions, contain the physical methods whereas the artificial methods can physically alter and transfer genes from one to another organisms' cell using, for instance, biolistic transformation, micro- and macroinjection, and protoplast fusion etc. The artificial gene transformation can also be conducted through chemical methods which include calcium phosphate-mediated, polyethylene glycol-mediated, DEAE-Dextran, and liposome-mediated transfers. Electrical methods are also artificial ways to transfer genes that can be done by electroporation and electrofusion. Comparatively, among all the above-mentioned methods, electroporation is being widely used owing to its high efficiency and broader applicability. Electroporation is an electrical transformation method by which transient electropores are produced in the cell membranes. Based on the applications, process can be either reversible where electropores in membrane are resealable and cells preserve the vitality or irreversible where membrane is not able to reseal, and cell eventually dies. This problem can be minimized by developing numerical models to iteratively optimize the field homogeneity considering the cell size, shape, number, and electrode positions supplemented by real-time measurements. In modern biotechnology, numerical methods have been used in electrotransformation, electroporation-based inactivation, electroextraction, and electroporative biomass drying. Moreover, current applications of electroporation also point to some other uncovered potentials for various exploitations in future.

Novel Food Processing and Extraction Technologies of High-Added Value Compounds from Plant Materials

Some functional foods contain biologically active compounds (BAC) that can be derived from various biological sources (fruits, vegetables, medicinal plants, wastes, and by-products). Global food markets demand foods from plant materials that are “safe”, “fresh”, “natural”, and with “nutritional value” while processed in sustainable ways. Functional foods commonly incorporate some plant extract(s) rich with BACs produced by conventional extraction. This approach implies negative thermal influences on extraction yield and quality with a large expenditure of organic solvents and energy. On the other hand, sustainable extractions, such as microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), high-pressure assisted extraction (HPAE), high voltage electric discharges assisted extraction (HVED), pulsed electric fields assisted extraction (PEF), supercritical fluids extraction (SFE), and others are aligned with the “green” concepts and able to provide raw materials on industrial scale with optimal expenditure of energy and chemicals. This review provides an overview of relevant innovative food processing and extraction technologies applied to various plant matrices as raw materials for functional foods production.

Extraction of bioactive compounds and essential oils from mediterranean herbs by conventional and green innovative techniques: A review

Market interest in aromatic plants from the Mediterranean is continuously growing mainly due to their medicinal and bioactive compounds (BACs) with other valuable constituents from essential oils (EOs). From ancient times, these plants have been important condiments for traditional Mediterranean cuisine and remedies in folk medicine. Nowadays, they are considered as important factors for food quality and safety, due to prevention of various deteriorative factors like oxidations and microbial spoilage. EOs have different therapeutic benefits (e.g. antioxidant, anti-inflammatory, antimicrobial, and antifungal), while BACs mostly affect nutritive, chemical, microbiological, and sensory quality of foods. Currently, many plant extracts are used for functional (healthy) foods, which additionally fuels consumer and industrial interest in sustainable and non-toxic routes for their production. EO yields from dried plants are below 5%. Their extraction is strongly dependent on the hydrophobic or lipophilic character of target molecules, hence the common use of organic solvents. Similarly, BACs encompass a wide range of substances with varying structures as reflected by their different physical/chemical qualities. Thus, there is a need to identify optimal non-toxic extraction method(s) for isolation/separation of EO/BCs from plants. Various innovative non-thermal extractions (e.g. ultrasound-, high-pressure-, pulsed electric fields assisted extraction, etc.) have been proposed to overcome the above mentioned limitations. These techniques are "green" in concept, as they are shorter, avoid toxic chemicals, and are able to improve extract yields and quality with reduced consumption of energy and solvents. This research provides an overview of such extractions of both BAC and EOs from Mediterranean herbs, sustained by innovative and non-conventional energy sources.