Microgreens and novel non-thermal seed germination techniques for sustainable food systems: a review

Abstract

There are a number of cutting-edge techniques implemented in the germination process, including high pressure processing, ultrasonic, ultraviolet, light, non-thermal plasma, magnetic field, microwave radiation, electrolyzed oxidizing water, and plasma activated water. The influence of these technological advances on seed germination procedure is addressed in this review. The use of these technologies has several benefits, including the enhancement of plant growth rate and the modulation of bioactive chemicals like ABA, protein, and peroxidase concentrations, as well as the suppression of microbial development. Microgreens’ positive health effects, such as their antioxidant, anticancer, antiproliferative/pro-oxidant, anti-obesity, and anti-inflammatory properties are extensively reviewed. The phytochemical and bioactive components of microgreens were investigated, including the concentrations of vitamin K, vitamin C, vitamin E, micro and macro nutrients, pro-vitamin A, polyphenols, and glucosinolates. Furthermore, the potential commercial uses of microgreens, as well as the current market transformation and prospects for the future are explored.

Introduction

The majority of higher plants begin their lives as seeds, and the decision to germinate those seeds is regarded as the first adaptive action that higher plants take (Bewley et al., 2013). Successful plant establishment in the field is essential for crop output and efficient resource use. In contrast, seed vigor refers to the capacity of germination of seeds and the establishment of seedlings quickly, consistently, and vigorously under a variety of climatic conditions (Savage & Bassel, 2016). The Testa/seed coat shows radicle protrusion during germination, which marks the end of phase II and the start of phase III, or the post-germination stage. In Phase III, store reserves deposited in storage organs, such as the endosperm in cereals, are mobilized, which promotes greater water uptake and seedling growth. The third step of water intake also involves the division of cells, gene control, and the development of radicle cells (Tuan et al., 2018). Germination begins with seed imbibition and completes with radicle emerging via the seed covering layers. In general, water retention by dry seeds occurs in the following three stages. During phase I, the initial water uptake is followed by swelling and a change in seed shape. The fast rehydration breaks down the membrane morphology, allowing low molecular mass metabolites and cellular solutes to drain out of the seed, and the rebounding of membrane morphology happens after a very squat period of hydration (Tuan et al., 2018). During water uptake, the synthesis of protein with mRNA and the resumption of respiratory activities like glycolytic and oxidative pentose phosphate respiratory pathways are characterized by a significant increase in oxygen consumption and carbon dioxide release within minutes of imbibition. Hence, germination stimulation is the major crop yield and growth rate factor. To meet the need for a fresh, nutrient-dense, and phytochemical rich diet for healthy body development, the vegetable industry has introduced a new product called microgreens.

Microgreens are seen as a concept or best innovation in vegetable growing in general, with the potential to change the whole idea of vegetables. Microgreens are plant foods, also known as “vegetable confetti” or “micro grasses” for aromatic herbs. Microgreens vegetable confetti, or micro herbs are grown for their immature tender greens that are being raised from herb, vegetable, or grain seeds (Othman et al., 2021). Microgreens, however, may be a good short-term solution to guarantee adequate human nutrition at the household level in situations of emergency. Besides being appealing for their nutritional profile, microgreens are gaining popularity for the opportunity they offer to produce high-quality fresh and healthy greens year-round, in a relatively short time, using small spaces, under all conditions. In fact, microgreens may be produced at the commercial level in the open field, in high tunnels, specialized greenhouses, and indoor production facilities, including vertical farm facilities in urban and peri-urban settings or in non-conventional growing spaces.

Microgreens are dynamic, highly exotic, and tending bio-products that are currently popular in most culinary practices. These are young and tender cotyledon green leaves harvested at the first true stage, which is the true leaf emergence stage. They are harvested after 7–21 days of germination when they grow to 1–3 inches from the shoot with completely developed cotyledon leaves (Senevirathne et al., 2019). Microgreens can be grown with fast-growing crops that are easy to germinate. Growing, harvesting and postharvest handling can notably affect crop plants’ accumulation and degradation of phytonutrients. These are diverse products when it comes to growing circumstances. They can be cultivated in a greenhouse or inside, with natural or artificial light, in soil or in soilless systems, with natural or artificial light sources. The composition of phytonutrients is higher than that of mature and fully developed plant leaves. Microgreens are “functional foods” where the only drawback is that are highly perishable, i.e., one to two days when stored at ambient storage conditions (Xiao et al., 2012).

Based on this, the review studied the bioactive and phytochemical composition of microgreens, such as the presence of Vitamin K -Phylloquinone, Vitamin C-Ascorbic acid, Vitamin E- Tocopherol, Micro and Macroelements, Pro Vitamin A-Carotene, Polyphenols, and Glucosinolates. High pressure processing (HPP), pulsed electric field (PEF), ultrasonic (US), UV light, non-thermal plasma (NTP), magnetic field, microwave radiation, electrolyzed oxidizing water (EOW), and plasma activated water (PAW) are among the innovative approaches used in the germination process. The review discusses the impact of these emerging technologies on the germination process. The health-promoting characteristics of microgreens are thoroughly explained, including antioxidant effects, anticancer benefits, anti-proliferative/pro-oxidant effects, anti-inflammatory effects, and anti-obesity effects. This review additionally addresses prospective industrial uses of microgreens, emerging market trends, and future perspectives.

Bioactive & phytochemical composition of microgreens

Recently, a lot of herbs and vegetables have been grown as microgreens. Numerous additional taxonomic groups, including Apiaceae (carrot, parsley, celery), Asteraceae, Amaranthaceae, and Fabaceae (fenugreek, sweet pea, alfalfa), are also frequently cultivated (Liu et al., 2021). The different varieties of commonly grown microgreens are presented in Table 1. Although a variety of microgreens are already being grown, there is a dearth of scientific data regarding their capacity to affect human physiological systems directly. The morphology of microgreens is presented in Fig. 1. Microgreens are comprised of three major parts, a central shoot or stem, true cotyledon leaves, and a pair of young leaves. Sprouts are grown earlier than microgreens, which are smaller than baby greens. Research in both in vitro and in vivo studies has demonstrated that microgreens are a novel functional food advantageous to human health and possess anti-inflammatory, anti-cancerous, antibacterial, and anti-hyperglycemia benefits (Zhang et al., 2021). Germination of microgreens can occur using various conventional and innovative techniques. However, novel non-thermal play an essential role in reducing germination time and increasing germination yield. The novel non-thermal processes are impactful in minimizing the microbial layers on seeds and changing their water absorption properties (Randeniya & De Groot, 2015). Sprouts and microgreens differ from one another. Sprouts are majorly produced in dark, moist, soaked environments, which helps to promote the growth of microbes that might cause food-borne epidemics (Ebert, 2022). The comparison of sprouts, microgreens, and baby greens is presented in Table 2.

Table 1.

Different varieties of microgreens

Families	Commonly grown microgreens	References
Alliaceae	Chives, shallots, onions, garlic	Xiao et al., (2012)
Amaranthaceae	Spinach, amaranth, fennel, parsley, carrot, beets, swiss chard apiaceae celery, cilantro, chervil and dill	Liu et al. (2021)
Asteraceae	Lettuce, sunflower, garland chrysanthemum, endive, tagetes (marigold)	Othman et al. (2021)
Brassicaceae	Mustards, kale, pakchoi, collard, nasturtium, broccoli, cauliflower, radish, arugula, cress, kohlrabi, turnip, savoy, cabbages, kale, pakchoi, collard, nasturtium, brussel sprouts, rutabaga	Tomas et al. (2021)
Cucurbitaceae	Cucumber, melon, squash	Othman et al. (2021)
Fabaceae	Sweet pea, alfalfa, fenugreek, fava	Kyriacou et al. (2016)
Lamiaceae	Mint, basil, chia	Othman et al. (2021)
Poaceae	Corn, lemongrass	Kyriacou et al. (2016)
Polygonaceae	Buckwheat	Othman et al. (2021)
Portulacaceae	Claytonia	Xiao et al., (2012)

Fig. 1.

Morphology of microgreens having tender, delicate stems supporting the cotyledons and true leaves

Table 2.

Comparison of sprouts, microgreen and baby greens

Characteristics	Microgreens	Sprouts	Baby greens	References
Indoor cultivation	Yes	Yes	Both indoor and outdoor	Di Bella et al. (2020)
Growth period	7–21	4–10	20–40	Dhakshayani and Priya (2022)
Edible portion	Shoots (cotyledons and true leaves)	Sprouts	True leaves (no roots)	Dhakshayani and Priya (2022)
Growing method	Require a growing medium	Zerosoill (only water)	Both soils, soilless and growing media	Choe et al. (2018)
Light requirement	Yes	No	Yes	Ebert (2022)
Nutrient requirement	Yes	No	Yes	Ebert (2022)
Agrochemical requirements	No	No	Yes	Ebert (2022)
Harvesting (stage)	Done between cotyledonary leaf and 1st true leaves stage	After germination but before full cotyledonary leaves stage	Between 1st to 8th–10th true leaves	Di Bella et al. (2020)
Harvesting (cutting)	Yes	No	Yes	Dhakshayani and Priya (2022)
Sensory acceptability	Mostly acceptable	Acceptable	Mostly acceptable	Di Bella et al. (2020)

Microgreens are drastically different from mature plants in terms of their chemical makeup. Substantial evidence supports the existence of numerous beneficial substances in considerable quantities, including carotenoids, vitamins and minerals, glycosylates, and polyphenols. Consuming plant-based meals rich in bioactive compounds, commonly known as phytochemicals, has been linked to a variety of positive effects on human health (Malfa et al., 2020). Many factors, including crop and farmer selection, genotype breeding status, and growth & development stage, influence the nutrient and phytochemical composition of microscale vegetables. Their nutrient composition may be affected by the environment in which microscale vegetables are produced, the illumination that is chosen, the substrates that are applied, nutrient modification or biofortification, and soil pH. Besides, packaging techniques and storage temperature aid the retention of nutrients and phytochemicals (Ebert, 2013). These are considered unique products rich in various phytochemicals, including vitamins, antioxidants, and minerals, for food diversification. Both farmers and consumers are fascinated by microgreens due to rising culinary demand and their ease of cultivation. (Weber, 2017).

Vitamin K -phylloquinone

Phylloquinone, vitamin K1, is essential for bone remodeling and blood coagulation. In studies, phylloquinone concentrations in mature amaranth, basil, and red cabbage were reported to be 1.14, 0.41, and 0.04 g/g fresh weight, respectively. Phylloquinone values are relatively high compared to mature vegetables (Choe et al., 2018). Blood synthesis requires vitamin K1. Dark-green vegetables such as spinach (Spinacia oleracea L.), kale (Brassica oleracea L. var. acephala), and broccoli contain significant quantities of the substance that promotes coagulation (Brassica oleracea var. italica) (Bolton-Smith et al., 2000). The phylloquinone content in the Amaranthaceae, Brassicaceae, and Lamiaceae plant families is high, also known as vitamin K1. Phylloquinone has been found at lower concentrations in mature amaranth and cabbage (0.41 to 1.14 g/g fresh weight, respectively). Compared to their adult form, microgreens grown commercially have more phylloquinone (Xiao et al., 2012). In addition to its function in blood coagulation and preservation of healthy bone tissue by avoiding vascular calcification, it is recognized that phylloquinone also possesses immunosuppressive and anticancer actions (Halder et al., 2019).

Vitamin C -ascorbic acid

Total ascorbic acid, also known as vitamin C, is made up of free ascorbic acid and dehydroascorbic acid, both of which have strong chemical bonds to members of the Malvaceae, Brassicaceae, or Cucurbitaceae families. All the microgreens examined (such as fenugreek, radish, roselle, etc.) contained the most ascorbic acid (Ghoora et al., 2020). The Malvaceae family member roselle microgreens rank first in ascorbic acid content, ahead of radish and basil. Microgreens of broccoli and cauliflower contain total ascorbic acid (Xiao et al., 2015). Microgreens of red cabbage, broccoli, and amaranth have a total ascorbic acid content six times higher than their mature counterparts. Strong antioxidant ascorbic acid is essential for numerous biological processes in humans. Additionally, it substantially impacts the immune system’s control and collagen formation (Haytowitz et al., 2018). Scurvy and higher chances of several non-communicable diseases, including cancer, arthritis, and Alzheimer’s disease, can be brought on by severe vitamin C deficiency (Abeysuriya et al., 2020). An antioxidant, vitamin C is a necessary nutrient for human agility. Ascorbic acid is abundant in microgreens, which are also higher in TAA (Total Antioxidant Activity) than in mature plants (Huang et al., 2021).

Vitamin E -α tocopherol

Tocopherols are crucial for preserving human wellness because of their special antioxidant characteristics. They can protect a variety of tissues from oxidative damage and are essential for the immune system or muscles to function properly. Furthermore, using tocopherol supplements may assist in shielding against a number of age-related diseases like Alzheimer’s and cardiovascular disease (Thompson & Cooney, 2020). As fat-soluble antioxidants are known as “vitamin E,” (tocopherols and tocotrienols are combined). Microgreens of pepper cress, opal radish, and cilantro are all great sources of—and -tocopherol, with the -tocopherol concentrations. More ascorbic acid was present on young spinach plants than in elder harvested leaves. Vitamin E’s most active form is -tocopherol. (Ma & Lin, 2010). It is a member of the vitamin E family along with the other tocotrienols (β, γ, and δ) (Bergquis et al., 2007). On the other hand, the most prevalent form in plants is tocopherol. Microgreens from the Brassicaceae and Apiaceae families, particularly, are regarded as a rich source of nutrients (Sadiq et al., 2019). Radish or sunflower had the highest- tocopherol levels (Ghoora et al., 2020).

Micro and macroelements

In a balanced human diet, Brassicaceae microgreens are a great source of both macro elements (such as K and Ca) and microelements (such as Fe and Zn). Consuming microgreens may be a health-promoting way to meet the requirements of element dietary reference intakes, particularly for children (Rauniyar & Karki, 2023). These are regarded as vital nutrients and great sources of minerals. In comparison to mature plants, microgreen cultivars typically have higher amounts of macro-elements (such as K, Mg, Ca, and P) and trace minerals (such as Ma, Zn, Na, and Cu). Fennel microgreen may be a valuable source with the highest Ca, K, and Na levels. While roselle had the highest concentration of P, Zn, and Se, spinach microgreens had a substantially higher concentration of Mg (Ghoora et al., 2020). Compared to adult plants, microgreens have a greater composition of most minerals, such as Ca, Fe, Zn, Mg, or Mn (Pinto et al., 2014). Mustard microgreens have higher Ca and Mg concentrations (Weber, 2017).

Pro Vitamin A—β-Carotene

Provitamin A (β-carotene) is a crucial fat-soluble antioxidant that can shield cellular membranes by removing free radicals. (Singh et al., 2006). The xanthophyll carotenoids lutein and zeaxanthin accumulate in the macula of human eyes and are essential for preventing age-related macular degeneration and cataracts (Ma & Lin, 2010). Pro-vitamin A carotenoids like α-carotene, β-carotene, and cryptoxanthin are free radical scavengers, immune system boosters, cancer suppressors, and ocular tissue protectors largely linked to a decrease in cardiovascular disease. The macular pigment in the eye is made up of lutein and zeaxanthin, which shield the macula from harm caused by light (Ma & Lin, 2010). Prostate cancer and cardiovascular disease are both prevented by lycopene. Because they contain significant concentrations of cancer-fighting glycosylates and carotenoids, particularly lutein, zeaxanthin, and alpha-carotene, Brassicaceae microgreens species are indeed very healthy (Liao et al., 2007). Thus, Brassica microgreens are a supplement that can be used to support health or avoid disease as a result (Kamal et al., 2020). Microgreens like garnet amaranth, green basil, pea tendrils, and wasabi are also highly concentrated in β-carotene. These microgreens’ alpha-carotene content is comparable to that of the well-known β-carotene-rich vegetable carrot (Daucus carota L.) and sweet potato (Ipomoea batatas Lam). (Singh et al., 2006).

Polyphenols in microgreens

Microgreens’ significant vitamin, mineral, carbohydrate, and carotenoid content is a major contributor to their nutritional and practical advantages. The primary molecules required for human health are phytochemicals, which are phenolics divided into classes like tannins, stilbenes, quinones, or lignans (Jambor et al., 2022). Because microgreens are generally largely unexplored plant components with little scientific knowledge, their overall phenolic content, antioxidant capability, and nutritional profile have not yet undergone substantial research (Di Bella et al., 2020). The most potent phytoconstituents known to be present in mature brassicaceous vegetables include isorhamnetin, kaempferol, quercetin, and hydroxy-cinnamic acids and their derivatives. According to experimental evidence, adult pakchoi has isorhamnetin and quercetin-3-O-glucoside, which are 80 and 3 times lower than their microgreen counterparts (Isic, 2017). Mature plants had substantially lower values for both caffeic and ferulic acid. Compared to ferulic acid, which was anticipated to be at a similar level, quercetin glucoside concentrations in cress were found to be more than 100 times higher (Kyriacou et al., 2016).

Glucosinolates in microgreens

The last class of phytochemicals, which is particularly common in microgreens, are glucosinolates. Glucosinolates are necessary for the synthesis of nitrogen-sulfur derivatives (-D-thioglucoside-n-hydroxy sulfates), which are secondary metabolites found in plants. The bulk of glucosinolates are formed from valine, isoleucine, and other aliphatic bases, followed by indole (originated from tryptophan) and aromatic (originated from phenylalanine) derivatives (Le et al., 2020). In vitro digestion liberated the largest concentrations of glucosinolates and total phenolics from turnip cabbage and kale microgreens. After digestion, these bioactive chemicals’ high bioaccessibility can produce anti-inflammatory, anticancer, antimicrobial, and antidiabetic effects (Liu et al., 2021). Glucosinolates are one of the more useful compounds found in microgreens (Jambor et al., 2022). Glucosinolates are now recognized to have bactericidal, nematocidal, and fungicidal properties. Moreover, anti-inflammatory, antidiabetic, and antioxidant benefits are commonly stated, and researchers have explored their capacity to control lung, cancer, and cardiovascular diseases (Maina et al., 2020).

Novel techniques involved in the germination process

The development of the economy is greatly aided by novel technology. These technologies are rarely integrated into a single innovation and frequently reach their full potential through a development process that results in a series of following inventions that represent improvements or alternate uses of the technology (Pezzoni et al., 2022). High pressure processing, ultrasound, ozone processing, ultraviolet, pulsed electric field, magnetic field, microwave radiation, non-thermal plasma, electrolyzed oxidizing water, and plasma activated water are novel technologies that help improve seed germination, growth, and yield (Rifna et al., 2019).

High pressure processing (HPP) effects on germination

High hydrostatic pressure is a non-thermal food processing technology that has been shown to increase germination percentage, decrease germination time, and improve seed microbial quality (Işlek et al., 2013). High pressure processing is a method of food processing that enhances both the solid and liquid food quality and safety. Using a transmission fluid, it is carried out for three to five minutes at ambient temperature and extremely high pressures between 300 and 800 MPa. Regarding HPP in culinary applications, there are two pertinent scientific laws. The first is Le Chatelier’s principle, which says that when an equilibrium system’s pressure is altered, it tends to revert to its stable state by shrinking in volume. The second concept called the isostatic principle, states that pressure is instantly and equally distributed throughout the product. During HPP treatment, the food samples are all exposed to equal pressure, and once the pressure is released, they restore their distinctive true geometry (Rifna et al., 2019). When seedlings are treated with HPP, a rise in chlorophyll content and microbiological quality is seen. This increase can also be read as an increase in photosynthesis, which may encourage the early maturity of seedlings (Oosten et al., 2017). Early seedling maturity would lead to early harvesting, which is crucial for lowering investments (Işlek et al., 2013). HPP can disrupt bacterial cell membranes, interfere with homeostasis, inactivate and denature proteins, including replication enzymes, and change the shape of cells. While high-pressure processing may not consistently achieve total inactivation of microorganisms it may adversely impact a substantial fraction of the bacterial population. Microbial cells that survive pressurization may sustain sublethal damage, but they may not undergo complete death (Schottroff et al., 2018). A study was conducted to investigate the impact of High Pressure Processing (HPP) treatment on alfalfa seeds. The seeds were subjected to HPP treatment for two minutes at a pressure of 475 MPa. The results showed that the sprouting rate of the treated seeds was only 28%, whereas the untreated control seeds had a sprout rate of 95%. The lower germination can be attributed to the occurrence of cracks in the seeds, leading to shattering in both the seeds and their coats due to applied pressure (Ariefdjohan et al., 2004). The impact of various innovative methods on the germination of different seeds is extensively presented in Table 3.

Table 3.

Effect of novel techniques on germination of different seeds

Type of seed	Technique used	Potential effect on germination rate	References
Alfalfa seeds	HPP (High Pressure Processing)	Treated seeds showed germination only upto 28% whereas untreated seeds showed 95% germination rate	Ariefdjohan et al. (2004)
Brown rice		HPP treatment (30–90 MPa/5 min) delayed embryo growth, decreased resistant and total digestible starch	Xia and Li (2018)
Chinese tallow seed		UV treatment reduced total biomass and leaf area	Deng et al. (2019)
Onion seeds	PEF (Pulsed Electric Field)	Highest germination percentage and seedling height was observed at 9 kV/cm treatment	Molamofrad et al. (2013)
Flaxseeds		Germination rate was observed to be increased from 2 to 13%	Pozeliene (2001)
Barley seeds		The metabolic activity was not affected	Dymek et al. (2012)
Sunflower seeds	US (Ultrasound)	Treated seeds showed 95% germination rate as compared to control with 68% germination rate	Machikowa et al. (2013)
Barley seeds		After treatment, germination duration reduced by 30–45%	Yaldagard et al. (2008)
Wheat		After treatment, germination rate was increased from 90 to 94%	Aladjadjiyan (2011)
Groundnut	UV light (ultraviolet light)	Germination rate increased by 83.3% as compared to control samples	Neelamegam and Sutha (2015)
Mung beans		Germination reached 100% after UV exposure	Hamid and Jawaid (2011)
Soybean		The exposed seeds showed reduced plant height, cotyledon cell number and yield	Liu et al. (2013)
Soybean	NTP (Non-Thermal Plasma)	After treatment, germination was increased from 68 to 100%	Ling et al. (2014)
Rapeseed		Exposed seed showed increased germination rate by 7.7% as compared to control	Puligundla et al. (2017)
Rice seeds		Treated seeds showed germination percentage of 98% as compared to non-treated seeds with 90% germination rate	Khamsen et al. (2016)
Radish seeds	MF (Magnetic Field)	magnetic field of 0.02 T for a period of 720 s enhanced germination properties	Konefał-Janocha et al. (2019)
Sunflower seeds		After treatment, germination rate was increased by 5–11%	Vashisth and Nagarajan (2010)
Soybean		treatment at 0.2 T for 3600 s improved plant growth attributes, biomass & photosynthetic property	Baghel et al. (2018)
Lentil seeds	MR (Microwave Radiation)	Microwave radiation at 485 W decreased microbial infected seed rate from 17 to 9%	Taheri et al. (2019)
Garden cress		Microwave frequency at 2.4 GHz for 5–15 s showed potential modifying effect on germination properties	Tomasz (2018)
Stone pine seedling		Exposure of 280 W for 60 s reduced the live plants and improved seedling rate	Kuzugudenli (2018)

Pulsed electric field (PEF) effects on germination

PEF treatment includes subjecting food components sandwiched between two electrodes to brief pulses (s) of extremely high voltages (kV/cm). The treatment chamber, fluid management system, pulse generator, and monitoring system comprise most of the PEF treatment systems (Huang et al., 2021). The basic cell structure is altered, and the cell membrane is destroyed when the electric field is used briefly. This procedure, known as electroporation, is a crucial component of the PEF process theory (Rifna et al., 2019). The rate of chemical reactions inside the cell will alter due to the induced current and dipole motion, which changes the way molecules are chemically bound together. Modifications to the structure of proteins can have significant impacts on the biosystem, influencing a wide range of cellular functions. Electroporation is a process where biological cells become permeable, either temporarily or permanently, due to the application of pulsed electric fields. The permeability is affected by the strength and duration of the electric field, as well as the polarization of the cells. Electro-magnetic field pulsed electric field (ELE-PEF) application causes reversible electroporation of the cell membrane, which changes the permeability of cells (Novickij et al., 2016). During reversible electroporation, the plasma membrane becomes more permeable for a short period of time, typically lasting a few minutes. After this, the membrane returns to its original impermeable state. In contrast, irreversible electroporation involves the use of electric pulses that last around 100 microseconds and have an electric field amplitude of approximately 1000 V/cm (μsPEF). These pulses can disrupt the integrity of the cell membrane and lead to cell death (Al-Sakere et al., 2007). Electrical potential coupling resonance happens when the wavelengths of a pulsed electric field and the potential variability of a cell membrane are identical (Liu et al., 2021). Key plant physiological processes like respiration, metabolism, photosynthesis, water absorption, and variation in stomatal conductance all depend on such variability (Fromm et al., 2007). ELF-PEF, a low frequency pulsed electric field, was used to examine the impact on root cells. It was discovered that effective relief from the effects of drought on plant roots demonstrated the possibility of using an electromagnetic field pulsed electric field (ELF-PEF) to improve plant drought resistance (Kataria et al., 2017). A study analyzed the impact of PEF (pulsed electric field) with a field strength of 1300 V for 15 min on the germination properties of chickpea seeds. It was observed that the seeds developed a significant number of electric dipoles inside them, which aligned themselves in the presence of the electric field. This alignment improved the germination process (Mahajan and Pandey, 2014).

Ultrasound (US) effects on germination

Mechanical waves with a frequency greater than 20 kHz are considered ultrasounds. It has been proven that ultrasonic therapy can alter the status of the chemicals and even speed up reactions. Ultrasound has a wide range of chemical effects, some of which significantly enhance chemical processes (Aladjadjiyan, 2011). The pressure waves with frequencies over 20 kHz are referred to as “ultrasound.” Power ultrasound waves with frequencies between 20 and 100 kHz and sound intensities between 10 and 1000 W/cm² are used to treat food (Islam et al., 2014). The stressor ultrasound has on plant growth and development is significant. Some plant organs’ growth can be influenced by ultrasonic treatment. The use of ultrasound increases seed germination rates, root and hypocotyl growth, and microgreen yields overall. Numerous studies have demonstrated that ultrasound can accumulate beneficial chemicals, including phenolic compounds and GABA, and can stimulate the breakdown of carbohydrates, protein, and lipids in microgreens (Liu et al., 2021). Ultrasound has the ability to boost antioxidant capacity, drive cell division, and restrain it with a medium dose. However, cell death may result when processing seeds with a high dose of ultrasound. Additionally, it was shown that ultrasonic processing enhanced the germination rate of spinach and cabbage seeds (Huang et al., 2021). Mild ultrasound can boost the ability of the plant to grow and stimulate the establishment of roots, which might raise the respiration intensity of plants for two years while decreasing the respiration intensity of annual plants (Ran et al., 2015). On the ultrasonic generator, the sonication experiment can be run at 20, 30, and 40 kHz. All three treatment tests are conducted on samples (50 seeds per treatment) that have been directly sonicated for 0, 10, 20, and 30 min. Sesame seed germination percentage (GP) increased as treatment time was extended, peaking at 80% after 20 min (Shekari et al., 2015). The effect of ultrasonic treatment of seed germination depends on the frequency of the ultrasonic wave and exposure time, as well as on plant species (Aladjadjiyan, 2011). The effect of ultrasonic seed treatment on morpho-physiological and yield traits is shown in Fig. 2. A research investigation found that subjecting barley seeds to ultrasonic energy at a power level of 460 W resulted in a 30–45% decrease in the time it took for the seeds to germinate, compared to untreated seeds (Yaldagard et al., 2008). A separate investigation found that sesame seeds subjected to ultrasonic treatments at a frequency of 20 kHz for 10 and 20 min exhibited enhanced germination capabilities (Shekari et al., 2015). This phenomenon may be attributed to the formation of cracks in the protective layer around the pericarp and seed following the treatment, resulting in increased moisture levels in the seedling.

Fig. 2.

Physiological and yield characteristics of the seeds after being treated with ultrasonic waves

UV light effects on germination

Proteins can be energetically disrupted by ultraviolet radiation. The three bands of ultraviolet radiation—UV-A (320–390 nm), UV-B (280–320 nm), and UV-C (254–280 nm)—show that increased UV-B radiation might adversely influence some plant species’ physiological activities and general growth. The standard range for seeds cultivated in an incubator for eight days at 25 °C while receiving UV radiation of 220 to 400 nm (Peykarestan et al., 2012). Results revealed that sprout growth rates and seed germination percentages are inversely related to irradiation doses (Peykarestan et al., 2012). Plasma irradiation speeds up the growth rate of plant seeds. On the third day of seed germination, peroxidase activity reduced and gradually increased (Waskow et al., 2021). The enzyme’s peak activity was seen in the endosperm on days 5 and 6 and in the roots and green sprouts on days 3 and 5 of germination (Sharlaeva & Chirkova, 2021). It was determined that the compensatory mechanisms of suppression of free radicals produced by UV irradiation of seeds involved antioxidants and peroxidase (Rogozhin et al., 2000). Seed germination is accelerated by UV exposure. This is most likely because UV-B photons (280–320 nm) have a higher impact on the surface of plant cells since they are more energetic than visible light photons (400 nm) (Kovacs & Keresztes, 2002). Reactive oxygen species in low pressure plasma are effective for promoting the growth of sprouts because they react with chemical indicators to produce significant amounts of reactive oxygen species close to seeds while nitric oxide peaks have not been confirmed on the light emission spectrum of low pressure plasma (Hayashi et al., 2015). An investigation was conducted to examine the impact of UV radiation, with a dose rate of 3.42 kJ/m², on lettuce seedlings prior to sowing. According to Ouhibi et al. (2014), treated seeds were found to effectively overcome the issue of severe salinity due to the enhanced ability to remove harmful free radicals in the leaves.

Non-thermal plasma (NTP) effects on germination

Non-thermal plasma therapy is a quick, economical, and eco-friendly technology. A partially or totally ionized gas is called plasma, which is also known as the fourth state of matter. Thermal (high temperature, equilibrium) and non-thermal (cold, low temperature, non-equilibrium) plasma are distinguished from one another. The thermal plasma is inapplicable for biological applications because it does not in the Sun, lightning, electric sparks, tokamak, etc., and reaches temperatures of thousands of Kelvin. The high kinetic energy is held in electrons in the non-thermal plasma (NTP), also known as low-temperature or cold plasma, which occurs at temperatures close to ambient (Šerá et al., 2021). As a result of the pathogen incidence being reduced in seeds treated with cold plasma, plants cultivated from infected seeds did not cause oxidative stress. Plants grown from treated seeds exhibited a similar pattern of vegetative growth to that seen in the healthy control. In contrast, the infected control had obvious evidence of damage. Additionally, plasma therapy itself boosted plant growth, encouraged normal, healthy physiological function, and raised plant yield. Utilizing this method to treat seeds before sowing could reduce the need for agrochemicals throughout the crop cycle (Pérez-Pizá et al., 2019). Seed surface modification in plasma treated seeds could enhance the transmission of oxygen or water through the seed coat (Bormashenko et al., 2012). A physical agent called non-thermal plasma (NTP) can cause oxidative stress or even the death of cells or other living things when it comes into contact with them. There is a variety of charged, neutral, and radical particles in it (mostly reactive oxygen and nitrogen species). The term “non-thermal plasma” refers to a condition in which the temperature of heavy particles, such as ions, neutral molecules, and radicals, is significantly lower than that of light particles, such as electrons. This state is also referred to as low-temperature plasma or cold plasma. Since there is thermodynamic disequilibrium between electrons and heavier particles, NTP is also known as non-equilibrium plasma (Holubová et al., 2020). Plasma had minimal impact on the germination rate, but it impacted growth factors. Compared to untreated samples, the distribution of roots in plasma-treated seeds was changed toward longer lengths. Seeds treated with plasma had heavier sprouts and roots than control samples (Dobrin et al., 2015).

Magnetic field effects on germination

The quality of the seeds is improved, and their germination rate is increased when they are subjected to magnetic field treatment. The ability of molecules to attract, and transform magnetic field energy into other types of energy and then convey this energy to additional structures in plant cells, activating them, is determined by their magnetic characteristics (Aladjadjiyan, 2011). The greatest percentage of seeds germinated (52%) when a 100 mT magnetic field was applied for an hour. Without the use of a magnetic field, the rate of seed germination was only 28%. (control). A 50 mT magnetic field exposure for one hour resulted in a superior germination rate (36%) than the control, which is commensurate with the application of a 100 mT magnetic field. With 240 h of exposure to both magnetic fields, the lowest seed germination was found (27% for 100 mT and 16% for 50 mT) (Ulgen et al., 2017). An inhibitory effect on germination was seen when the electric field was more than 12 kV/cm and the exposure length was greater than 60 s (Moon & Chung, 2000). The strength of the electrical field and the electrical characteristics of the seed determine the amount of energy delivered to the seed. When seeds were continuously exposed to magnetic fields of 3 mT, and 25 mT for 5 min, the length of the roots increased by 29 and 25%, respectively, over control. The strongest magnetic fields of 3 mT per minute and 25 mT for 5 min produced the longest shoots, seedlings, and vigor indices (Feizi et al., 2012).

Additionally, the effectiveness of ultrasonic waves in enhancing germination (Yaldagard et al., 2008). Because the hydrogen bond in liquid water is greatly influenced by electrical and magnetic fields, the application of magnetic fields to water produced stimulatory effects with respect to an increase in seed germination. Water that has been magnetized, as opposed to regular water, has different chemical and physical characteristics. It has been demonstrated that pre-sowing magnetic treatment of seeds can boost germination rates by 30 to 50% (Ijaz et al., 2012). There was an improvement in germination, germination rate, shoot length, root dry weight, total embryo length, fresh seedling weight, and seedlings dry matter compared to untreated control seeds. Indicators of vigor also increased. In germination seeds, there is an appreciable increase in the activity of the enzyme’s amylase, dehydrogenase, and protease, with a maximum value of 50 mT for exposures lasting 60 min. The increased enzyme activity in cumin seeds exposed to a magnetic field may lead to quick germination and vigor in the early seedling stage (Samani et al., 2013). Anand et al. (2012) conducted a study to examine the impact of a magnetic field on maize seeds. They exposed the grains to magnetic fields of 200 and 100 millitesla for durations of 1 and 2 h. The researchers found that the treated seeds exhibited enhanced growth characteristics compared to the control group.

Microwave radiation effects on germination

The term “radiation” refers to a broad range of energy, including both ionizing and non-ionizing radiations. Diverse wavelengths of radiation have different effects, some of which may be harmful or advantageous. The heating of damp materials by dielectric occurs when radiofrequency energy (RF), which includes microwaves, is applied. Ozone depletion-related increases in the ultraviolet (UV) radiation impact plant growth, productivity, and genome stability (Kunz et al., 2006). According to studies, some plants appear to be unaffected by UV radiations, but in reality, they may be protected by secondary compounds like flavonoids that work as solar screens, absorbing UV and preventing it from penetrating the epidermis of leaves, which contains delicate tissue layers. Additionally, it has been documented that anthocyanin and flavonoid levels rise in response to UV-B (Shaukat et al., 2011). When microwave diapason electromagnetic radiation is absorbed at the molecular level, it results in changes to the vibrational energy of molecules or heat (Aladjadjiyan, 2011). To increase the dietary intake of oil in any seed disinfestation operation, microwave radiation may offer an efficient and environmentally responsible treatment method (Motallebi, 2016). Controlling the pathogen at high moisture levels is challenging due to a decrease in seed germination percentage with rising moisture content (Taheri et al., 2019). Sahin (2014) investigated the effect of microwave treatment on weed seeds and discovered that exposure to a power level of 2.8 kW completely stopped germination due to the thermal effects of microwave energy.

Electrolyzed oxidising water (EOW) effects on germination

Electrolyzed oxidizing water (EOW) has been regarded as a potential environmentally friendly broad-spectrum microbial decontaminant. By running a diluted salt solution through an electrolytic cell with anode and cathode electrodes, electrolyzed oxidized water (EOW) is created. A bipolar membrane separates the anode and cathode. Chloride and hydroxide, two negatively charged ions in a dilute salt solution, migrate to the anode, where they lose electrons to form gas (O2, Cl2) and hypochlorous acid, which has a redox potential of + 700 to + 800 mV and a pH of 4.0. It can oxidize and sterilize because of its high oxidation potential and lack of electrons. Oxidized water damages cell membranes, disrupts metabolic activities and effectively kills the cell during the process of microbial inactivation (Peykarestan et al., 2012). When the electrolyzed oxidizing water of oxidative reduction potential over 1100 mV was sprayed on cucumber planting, the disease severity of powdery mildew of a standard control was lesser than plants without electrolyzed oxidizing water (Le et al., 2020). Findings suggest that SAEW(slightly acidic electrolyzed water) could be used to decontaminate natural Enterobacteriaceae in the production of alfalfa sprouts, with no negative side effects on the alfalfa seeds (Zhang et al., 2021). Less harmful environmental effects and the absence of the challenges of carrying and storing potentially dangerous chemicals are the main benefits of employing EOW for the inactivation of microorganisms. Salmonella species, Escherichia coli O157:H7, Listeria monocytogenes, and Bacillus cereus are some harmful bacteria that electrolyzed oxidizing water (EOW) has been shown to have substantial bactericidal effects. Additionally, it might kill human immunodeficiency virus and hepatitis B virus as well as lessen the germination of numerous fungus species (Liao et al., 2007). EOW significantly increased GABA accumulation, which is crucial for producing functional meals high in GABA (Lu et al., 2010). The effect of electrolyzed oxidizing water for germination is shown in Fig. 3.

Fig. 3.

Electrolyzed oxidizing water for improved germination rates and seedling health

Plasma activated water (PAW) effects on germination

When water is treated with plasma, the outcome is plasma activated water (PAW), which produces reactive oxygen and nitrogen species as well as changes to the redox potential and conductivity of the water (RNS). PAW can be used as an alternative approach for microbial disinfection because it has a distinct chemical makeup from water. PAW can both stimulate seedling development and appear to exert a synergistic effect on food sanitation. The increase in plant growth may be mostly due to the rise in nitrate and nitrite ions in the PAW. In addition to acting as an antibacterial, soaking seeds in PAW promotes seed germination and plant growth. PAW may be used to boost agricultural production and combat drought-stressed environmental conditions (Thirumdas et al., 2018). The vigor index, soybean plant development, and germination rate were all enhanced by plasma-activated water (PAW). The plants underwent beneficial physical and chemical changes when seedlings were irrigated with PAW. These plants produce a vibrant green hue in their leaves in response to nitrogen availability, which is consistent with the rise in chlorophyll concentration (Guragain et al., 2021). The chapping of the seed coat may be caused by the high concentration of RONS generated in PAW, which may also make it easier for the seed to receive more water and other nutrients (Ding et al., 2018). When the plasma discharge time extended from 30 to 90 s, PAW had a negative impact on the germination of mung bean seeds. The total flavonoid and phenolic content and growth parameters showed similar shifting tendencies, which may be related to the active PAW ingredients NO₂⁻, NO₃⁻, and H₂O₂ (Fan et al., 2020). Plants grown from seeds treated with PAW had increased protein and sugar levels compared to control plants. As a result of PAW treatment, hydrogen peroxide, electrolysis, and phenolic leakage did not significantly differ from the control (Rathore et al., 2022).

Health-promoting properties of microgreens

Microgreens have become recognized as potential curative functional foods that can be used as dietary supplements to enhance general health. Microgreens outperform their mature counterparts in terms of nutraceutical benefits due to their delicate texture, distinctive tastes, and large volume of different nutrients. Microgreens’ rising popularity is due to their interesting organoleptic features and nutritional worth (Choe et al., 2018). The microgreens showed a far stronger link with free radical reduction power than radical scavenging activity. Additionally, the microgreens demonstrated stronger anticarcinogenic effects on colon cancer cell lines and a higher ability to block the enzyme -amylase. As a result, Capsicum sativum microgreens were found to be more effective than mature leaves at acting as antioxidants, antidiabetic, and anticarcinogenic agents (Dhakshayani & Priya, 2022). Numerous causes include the quick depletion of land resources, dietary changes, healthy eating patterns, the necessity of food for survival, etc. Microgreens have higher concentrations of vital phytonutrients and minerals than their mature counterparts, including ascorbic acid, beta-carotene, phylloquinone, magnesium, calcium, iron, and manganese selenium, and potassium (Xiao et al., 2012).

Antioxidant effects of microgreens

The health of humans depends on micronutrients, vitamin C, and antioxidants. Unfortunately, humans are unable to produce vitamin C. Therefore, we must get it from our diets because severe deficits can cause scurvy. However, consumption is typically irregular, and food sources’ vitamin C amount varies. The nutritive benefits of crops can be improved, and nutritional levels of these nutrients can be kept more consistent with enhanced antioxidant or mineral concentrations or biofortification. It is generally known that eating vegetables reduces the risk of developing chronic diseases and their mortality and that antioxidants have a substantial positive impact on health (Choe et al., 2018). Vegetable microgreens include antioxidants from numerous classes. Young seedlings in lettuce demonstrated the highest polyphenol concentration and antioxidant capability compared to older leaves after seven days of germination (Oh et al., 2010). When selenium was added to the hydroponic nutritional solution for basil microgreens, the leaves were more selenium-rich, and their antioxidant capacity rose (Puccinelli et al., 2019).

Anticancer effect of microgreens

The enzyme myrosinase can digest the glucosinolates into a range of beneficial compounds, such as isothiocyanates, oxazolidines, or epithionitriles (Le et al., 2020). Moreover, isothiocyanates have considerable anticarcinogenic potential been proven. In broccoli microgreens, sulforaphane, iberin, and erucin are created by their enzymatic conversion (Liao et al., 2007). Each of these has significantly reduced the risk of bladder and colon cancer (Dhakshayani & Priya, 2022). Because they include a variety of polyphenols, vitamins, carotenoids, and minerals as well as the regulated ability to affect certain metabolic processes and mechanisms within cancer cells, microgreens are viewed as promising in the fight against cancer (Jambor et al., 2022). Microgreens are a significant source of plant-derived phytochemicals such as indoles and flavonoids, which are crucial for prostate and breast protection in the early stages. Trefoil factor 1 and cathepsin-D are suppressed, the expression of the estrogen-responsive genes is controlled, and the tumor suppressor gene is turned on (Tomas et al., 2021). Activation of phase I and phase II xenobiotic-metabolizing enzymes is the initial step in their activity and may be helpful in cancer prevention. Cells can start defending themselves against potential carcinogens when they activate specific enzymes involved in the metabolism of cancer (Singh et al., 2006).

Anti-proliferative/pro-oxidant affect of microgreens

The “functional food” capability of microgreens—defined by their ability to enhance or control a particular metabolic technique or mechanism with the aim of either preventing or controlling a disease—has just lately been revealed, despite its reputation as promising in the fight against cancer (Truzzi et al., 2021). Increased consumption of reactive plant-derived phytochemicals will help prevent cancer in a cost-effective manner (Ding et al., 2018). These cells are inhibited from proliferating by the microgreens, which causes an increase in reactive oxygen species (ROS), a general arrest of the G2/M cell cycle, and the induction of apoptosis. As part of a healthy diet, regular use of microgreens has been recommended as a preventative (preclinical) dietary strategy to reduce the incidence of colon cancer (De la Fuente et al., 2020). Numerous phytochemical components are believed to be excellent cancer adjuvants in clinical treatment that slow tumor progression as well as effective cancer preventative agents in this preclinical stage (Truzzi et al., 2021). In addition to a complementary and/or symbiotic action with chemotherapeutics in clinical settings, the ability of plant-derived bioactive phytochemicals to treat cancer would necessitate a pro-oxidant strategy to encourage apoptosis, cell cycle arrest, and the suppression of various signaling pathways associated with cancer pathogenesis (Truzzi et al., 2021).

Anti-inflammatory effect of microgreens

In general, inflammation has a significant role in the onset of numerous diseases, including cancer, obesity, and cardiovascular disease (Choe et al., 2018). Microgreens include higher levels of phytochemicals, which are thought to regulate the immune system and shield against illnesses and health issues. For patients with an impaired renal function who must adhere to a low potassium diet, the nutritional solution can be produced with little or no potassium (Kyriacou et al., 2016). The anticancer properties of glucosinolates and isothiocyanates, especially glucoraphanin-glucoerucin/sulforaphane, act against chronic inflammation and are protective against carcinogenic effects of environmental toxins. These anticancer activities are entirely due to the hydrolytic metabolites of glucosinolates, isothiocyanates (ITCs), and indoles, which induce the death of cancer cells, and modulate (Hayes et al., 2008). Broccoli microgreens had almost four times as many total aliphatic glucosinolates as mature leaves and florets did (Lu et al., 2010).

Anti-obesity effects of microgreens

A proposed mechanism to explain how dietary-derived bioactive can work is the reduction of inflammatory disease, one of the common risk factors for the onset and progression of various chronic diseases (Choe et al., 2018). The obese model mice fed a high-fat diet to promote obesity received broccoli microgreen juice by gavage. Melbin was administered as a positive control at a dose of 300 mg/kg-bw/d, which markedly reduced body weight, adipocyte size, and the mass of white adipose tissues while dramatically increasing water consumption. Additionally, it improved glucose tolerance, decreased insulin levels, and reduced insulin resistance. These results imply that the short-chain fatty acid–lipopolysaccharide–inflammatory axis in the gut microbiota may contribute to the protective benefits of broccoli microgreens juice against diet-induced obesity. By enhancing the liver’s antioxidant capacity, broccoli microgreen juice can decrease the buildup of fat there. Based on the negative effects of microgreen juice on obesity caused by a high-fat diet in rats, it is being developed as a functional meal for people who are overweight (Li et al., 2021). Bioactive chemicals that are abundant in microgreens can affect a number of pathways associated with inflammation. Microgreens from red cabbage appeared to stop weight gain brought on by a high-fat diet (Huang et al., 2016) Microgreens’ ability to control inflammation may help in the prevention of diabetes, CVD, and obesity. Microgreens supplementation prevented body weight growth, decreased levels of LDL cholesterol, HDL cholesterol ester, and triglyceride levels, and reduced levels of inflammatory cytokines (Xiao et al., 2015). Mature red cabbage added to a high-fat diet also produced positive effects, although it did not lower triglyceride levels. Interestingly, adding red cabbage microgreens to a low-fat diet increased both the levels of low-density lipoprotein and high-density lipoprotein triglycerides (Turner et al., 2020).

Antidiabetic effects of microgreens

Diabetes is a long-term metabolic syndrome that is defined by the development of insulin resistance in the cells or by the pancreas’ inability to generate enough insulin. High blood glucose levels are a defining feature of diabetes, typically managed or treated by reducing blood glucose levels with strict dietary restrictions, insulin injections, more insulin secretion, and improved insulin sensitivity (Magkos et al., 2020). However, extended pharmaceutical use may have adverse side effects; as a result, it is typically advised to consume fruits and vegetables with minimal or no sugar content. Rapidly gaining in popularity, microgreens are very nutrient-dense, are thought to be more effective, and have a great potential to lower diabetes. In HepG2 cells, the fenugreek microgreen extract (2 mg/mL) reduced -amylase by 70%, while in L6 cells, glucose absorption was increased by 44% in the presence of insulin (Bhaswant et al., 2023). The fenugreek microgreens’ high amounts of phenolic content, antioxidants, and polyphenols likely regulate antidiabetic effects in vitro. Additionally, the non-enzymatic glycation of protein was prevented by this extract (Ma et al., 2022).

Potential industrial applications of microgreens

As people’s enthusiasm for living a healthy life and looking well has increased, so has their interest in fresh and nutraceutical foods. The cosmetic industry, where microgreens are converted into oils and ingredients for shampoo and skin care products, and chefs’ need for more colorful dishes are two factors causing the microgreens market to grow. Thus, it is projected that the market for microgreens will expand over the coming years, particularly as indoor farming techniques become more prevalent. (Paraschivu et al., 2021). These micro-scale vegetable microgreens pose the promising potential to be served as functional foods in regular diets (Du et al., 2022). It is feasible to grow nutrient-dense microgreens in space. Microgreens can be produced in space due to their quick cultivation time and high nutritional content, according to extensive research and observation of astronauts into the adaptability of human life in space (Kyriacou et al., 2016). Additionally, hydroponic, indoor, and vertical farming techniques seem to help cultivators boost the number of microgreens they can produce. Due to rising demand from chefs and the cosmetics sector, the microgreens market topped out in 2020 in the United States, Canada, Asia, and Australia. This market is becoming increasingly competitive globally (Paraschivu et al., 2021). Growing microgreens in these areas help address the scarcity of fresh vegetables for residents at higher altitudes and distant localities, where transportation may seriously affect the nutritional benefits (Bhaswant et al., 2023). Urban circular food systems can benefit from indoor vertical farms (IVF), decreasing food waste and improving resource utilization. This technology combines unused space with IVF, product processing, and the Internet of Things (Paraschivu et al., 2021). There are alternatives to removing transport for delivery and reducing waste creation of organic materials and single-use plastics where access to onsite compost treatment and retail food services is possible. Access to green infrastructure and renewable energy may also be advantageous for building integration (Parkes et al., 2022).

Emerging market trends and future perspective

The microgreen market is divided into various categories, such as dominant vegetable types (such as broccoli, lettuce and chicory, arugula, basil, fennel, carrots, sunflower, daikon, and peas), farming methods (such as greenhouse production, commercial hydroponics, vertical farming), growth mediums (such as land, wrapping paper, coconut coir, and peat), end-uses (such as foods and beverages, cosmetic products, skincare, and others), distribution networks (such as restaurants (North America, India, Japan, Korea, Europe, Asia-Pacific, South America, and Middle-East and Africa) (Paraschivu et al., 2021). The studies resulted in the finding that microgreens may be grown for astronauts under unique circumstances and satisfy their nutritional needs. Furthermore, as microgreens are a strong source of micronutrients, they can be utilized to enhance cognitive performance, which is correlated with metabolic illnesses, particularly in the elderly population (Kyriacou et al., 2016). Due to its numerous healthy and nutritive features, broccoli seems to significantly impact the growth of the microgreens market. According to the Food and Agriculture Organization, with over 10.4 million metric tons and 8.6 million metric tons, respectively, China and India produced 73% of the world’s broccoli in 2017. In 2017, the USA, Spain, Mexico, and Italy each held no more than one million metric tons (Food and Agriculture Organization, 2020). Urban agriculture this new strategy, especially in towns and cities, is driven by urban agriculture (UA). The production of microgreens appears to restore nature to the city, enhance the urban food production system, revitalize urban growth, increase food security, change people’s purchasing and consumption patterns, and promote independence in the home (Paraschivu et al., 2021).

According to the currently available study, microgreens are believed to be great low-calorie suppliers of nutrients and bioactive components. Scientists imply that these nutrient-rich plants have health-promoting characteristics connected to capacities to stop the emergence of a wide range of inflammatory-associated autoimmune disorders based on chemical compositions. In essence, microgreens could serve as a potential new food source to stimulate consumers’ interest in following a balanced diet. On the other hand, the attack of numerous pathogenic bacteria that have become resistant to medicines and other therapies and continuing environmental changes like excessive temperatures have a significant negative influence on microgreens. To map its activity, the concept of the metabolic profiles of the various microgreen kinds needs to be researched considerably more. Additionally, there is more focus on microgreen production technology. However, there is still work to be done on pre- and post-harvest procedures, packing, and shelf-life maintenance. On the other hand, there isn’t much research that backs up the use of microgreens for managing and preventing the several chronic metabolic diseases this study examines. More research is required to identify how to use microgreens to their full potential for their potential health-promoting features with proof of mechanisms of action. Microgreens must adapt to their ever-changing environment by adjusting their physiology, metabolism, and gene expression, all of which have an effect on the growth and the plant’s development. Novel non-thermal techniques such as plasma, ultrasound, and pulsed electric field showed an impactful change in germination rate and phytochemical composition. The replacement of chemical fertilizers and physical scarification with environmentally friendly techniques is a major focus of non-thermal technology. Non-thermal treatment of seeds can be used for germination stimulation, bioactive compounds such as alpha amino butyric acid enrichment, decontamination, increased hydrophilicity, and stimulating gene modification processing embryonic development, plant growth, and pathogen resistance. These approaches have been put through their paces on a range of plant seed types, and the results indicate that they have the potential to produce plants that are more resilient to abiotic stress and have faster growth.

Funding

No funding was received for conducting this study. The authors have no relevant financial or non-financial interests to disclose.

Data availability

The datasets generated and analyzed during this study are available from the corresponding author on reasonable request.

Declarations

Competing interest

The authors have no competing interests to declare that are relevant to the content of this article.

Ethical approval

Not applicable.

Consent to participate

Informed consent was obtained from all individual participants included in the study.

Consent to publish

Not applicable.