Introduction:
Chronic illnesses constitute a serious health issue faced by a majority of the population all over the world. According to accumulated evidence, eating veggies can greatly lower the risk of chronic illnesses. Functional foods are becoming increasingly popular, which is driven by consumer demand for diets that promote health and longevity (Granato et al., 2020). USDA dietary guidelines had recommended that an adult should have an average intake of 1-4 cups of vegetables daily. However, the average vegetable intake is below the recommended limits. Microgreens are relatively immature vegetables that are harvested 10-14 days after sowing. They range in size from 1 to 3 inches. It possesses three main components: a central stalk, cotyledon leaf or leaves and a pair of juvenile true leaves. It is considered as a new type of edible vegetable that is picked before the real leaves develop, while the initial leaves have fully grown. Microgreens have a higher concentration of nutrients and health-promoting micronutrients than mature plants. (Choe et al.,2018). Some of the microgreens include Amaranth, Basil, Broccoli, Mustard, Beet, Pea, Cabbage, Alfalfa, Buckwheat, Celery, Cilantro, Mung bean, Lettuce, Spinach and so on.
Microgreens are a smaller version of baby greens and they are collected later than sprouts. Harvest time is the most significant distinction between sprouts, baby greens and microgreens. Microgreens are collected shortly after their smallest leaves appear, while Baby greens are harvested at 2 to 4 inches for 15 to 40 days. Harvest time for sprouts is comparatively sooner in the case of microgreens. Sprouts can also be distinguished from microgreens by their composition. A sprout is made up of three parts: seed, root and stem. Microgreens, on the other hand, are collected without the roots. Microgreens feature delicate textures and unique tastes, owing to their longer development time than sprouts or baby greens. The hues of microgreens are very well-known. As a result, microgreens are frequently used to decorate salads, soups, dishes and sandwiches (Xiao et al., 2012). According to a research, there are 25 commercially available microgreens with the potential to add value to new food items.
Composition of Microgreens
A Microgreen’s chemical composition differs significantly from that of the mature variety.
Vitamins
Vitamin K1, commonly known as phylloquinone, is required for blood coagulation and bone remodelling. Dark-green vegetables with high phylloquinone content, such as spinach, kale and broccoli are common examples. Various microgreen cultivars exhibited phylloquinone concentrations ranging from 0.6 to 4.1 g/g fresh weight (FW). Vitamin C, commonly known as ascorbic acid is a necessary nutrient for humans. Total ascorbic acid (TAA), free ascorbic acid (FAA) and dehydroascorbic acid (DAA) were analyzed and reported in different microgreens. TAA concentrations in the microgreens ranged from 20.4 to 147.0 mg/100 g FW. The greatest TAA content was found in red cabbage, while the lowest was found in sorrel. Red cabbage microgreens contain 6 times greater vitamin C content than mature red cabbage, according to the USDA National Nutrient Database. In addition, as compared to its mature counterpart, garnet amaranth (131.6 mg/100 g FW) exhibited a substantially greater TAA content.
Tocopherols and tocotrienols are members of the vitamin E family and each tocopherol and tocotrienol has four isomer forms. Identified isomer forms include α, β, γ and δ. The most active form of vitamin E is -tocopherol, which is also the most prevalent form found in plants among the four isomers of tocopherols. Both α (87.4 mg/100 g FW) and γ (39.4 mg/100 g FW) forms of tocopherols are high in green daikon radish. Microgreens of cilantro, opal radish and peppercress also had significant levels of α and γ tocopherols (Xiao et al., 2012). Carotene is a pigment present in fruits and vegetables that is reddish-orange in hue.
β-carotene is best recognized as a precursor to Vitamin A and it plays an important function in eyesight and development of the body. β-Carotene can also act as an antioxidant due to its structure. The highest content of β-carotene was found in red sorrel (12.1 mg/100 g FW), while the lowest concentration was found in golden pea tendrils and popcorn shoots (0.6 mg/100 g FW). Cilantro (11.7 mg/100 g FW), the microgreen with the second highest β-carotene content has three times the amount of β-carotene as the mature one. The content of β-carotene in red cabbage microgreens (11.5 mg/100 g FW) was about 260 times higher than in mature red cabbage (0.044 mg/100 g FW). Most microgreens were high in β-carotene, with the exception of golden pea tendrils and popcorn shoots. As a result, microgreens can be regarded as a good source of β-carotene. Lutein and zeaxanthin are two prominent carotenoids present in blood among the seven carotenoids found in the human body. They’re also the only carotenoids found in the eye’s retina and lens. They act as antioxidants and protect the eyes from UV rays. Cilantro had the greatest content of lutein/zeaxanthin and violaxanthin with 10.1 mg/100 g FW and 7.7mg/100g FW respectively.
Total sugar content, Polyphenols, Glucosinolates and minerals
China rose radish, opal basil and red amaranthus, peppercress, Dijon mustard microgreens also shows total sugar content of 10.3g/kg, 2g/kg, 1.7g/kg, 8.8g/kg, 7.7g/kg respectively. Various researches reported that microgreens are excellent sources of minerals such as Sodium, Potassium, Magnesium, Copper, Manganese, Iron, Zinc, Calcium and Phosphorus (Weber, 2017). The presence of various bioactive components such as polyphenols and glucosinolates have found in microgreens which prevents different chronic diseases, such as obesity, cancer and cardio vascular diseases.
Based on their fresh weight, microgreens appeared to have higher nutritional benefits than their mature counterparts. However, there are a number of factors that might influence the chemical contents of microgreens, including cultivars and growth circumstances. As a result, more research is needed to completely describe the nutrient content of microgreens and how to improve their nutritional worth.
Growing conditions
Microgreens are environmentally friendly and provide good supplies of many nutrients, in addition to being simple to grow. Growing microgreens, for example, takes only 10 to 14 days. In addition, a study found that a broccoli microgreen needed 93-95 % less time and 158-236 times less water to produce the same amount of nutrients as mature broccolis. Microgreens also don’t require fertilizers, herbicides or energy-intensive transportation from farm to table. Growing conditions are crucial, because they have a direct impact on plant development and phytonutrient levels.
Seed Rate
The rate at which seeds are sown is critical for plant growth, since it creates competition for scarce resources like water and nutrients. Commercial seeding rate was noted as 201 g/m2. A linear connection was observed between the sowing rate and number of shoots and shoot fresh weight. Individual fresh weight/shoot, on the other hand, dropped linearly when seeding rate rose. This represents resource rivalry among microgreens.
Fertilizers
Fertilizers have long been used to provide plants with vital nutrients for development. Calcium, nitrate, ammonium nitrate and urea all have had an effect on fresh weight per plant or m2. Reports shows that nitrogen sources resulted in higher shoot fresh weight/m2 than ammonium sulphate. Calcium-treated broccoli microgreens exhibited higher glucosinolate concentrations than untreated broccoli microgreens, suggesting that growth circumstances may be modulated to improve nutritional value of microgreens.
Dosage of Light
Light has a considerable impact on the formation of secondary metabolites in plants. Recent research suggests that increasing the amount of carotenoids, tocopherols, glucosinolates and minerals in microgreens can be done by adjusting the intensity of light. Photosynthesis is a vital technique for plants to keep their energy levels up. Photosynthesis is aided by carotenoids. Carotenoids are pigments found in chloroplasts that act as free radical scavengers and thermal energy dissipators. The xanthophyll cycle is important for surplus energy dissipation and three carotenoids are involved in this cycle: zeaxanthin, antheraxanthin and violaxanthin. Plants employ the xanthophyll cycle to convert violaxanthin to zeaxanthin when they have an excess of absorbed light.
Health benefits
Microgreens have been proven to have anti-inflammatory, anti-cancer, anti-bacterial and anti-hyperglycemia effects in both in vitro and in vivo tests, making them a novel functional food beneficial to human health (Zhang et al., 2021). Microgreens have 4 to 40 times more vitamins, enzymes, minerals, antioxidants and beneficial characteristics than their mature counterparts, according to studies. Microgreens provide nutrients that are beneficial to the eyes, skin, bones and digestion, as well as lowering inflammation, avoiding cardiovascular disease, combating cancer and boosting the immune system. Sunflower greens are the most nutrient-dense of all sprouts and one of the most complete foods on the planet. Pea shoots are in second place in terms of total nutrients. It is a rich source of vitamins and minerals. Polyphenols, a kind of antioxidant related to a decreased risk of heart disease, are abundant in microgreens. Antioxidant-rich diets such as those strong in polyphenols, have been related to a reduced risk of Alzheimer’s disease.
Conclusion
Microgreens looked to be high-nutrient, low-calorie sources of bioactive compounds. They are nutrient-rich plants having health-promoting properties related to their ability to prevent the development of a wide range of inflammatory-associated chronic illnesses based on their chemical compositions. Indeed, microgreens might be a potential new food source for customers who want to follow healthier diets. Eat microgreens as soon as possible after harvesting to receive plenty of health benefits. Microgreens, like most other super foods ingested fresh, quickly lose their nutritious value once harvested. Consider growing your own microgreens at home, since you’ll be able to control when your crop is harvested. Using extra virgin olive oil or another healthy oil to increase the nutritional content of microgreens-based meals is another option. The presence of oil in microgreens aids in the absorption of fat-soluble elements (carotenoids, vitamin E and vitamin K). Understanding market integrity is crucial for growing microgreens as an important gardening crop, more fully integrating them into the global food chain and analyzing and sharing their health outcomes.
References:
1. Choe, U., Yu, L. L., & Wang, T. T. (2018). The science behind microgreens as an exciting new food for the 21st century. Journal of Agricultural and Food Chemistry, 66(44), 11519-11530.
2. Granato, D., Barba, F. J., Bursać Kovačević, D., Lorenzo, J. M., Cruz, A. G., & Putnik, P. (2020). Functional foods: Product development, technological trends, efficacy testing, and safety. Annual review of food science and technology, 11, 93-118.
3. Weber, C. F. (2017). Broccoli microgreens: A mineral-rich crop that can diversify food systems. Frontiers in nutrition, 4, 7.
4. Xiao, Z., Lester, G. E., Luo, Y., & Wang, Q. (2012). Assessment of vitamin and carotenoid concentrations of emerging food products: edible microgreens. Journal of agricultural and Food Chemistry, 60(31), 7644-7651.
5. Zhang, Y., Xiao, Z., Ager, E., Kong, L. and Tan, L., 2021. Nutritional quality and health benefits of microgreens, a crop of modern agriculture. Journal of Future Foods, 1(1), pp.58-66.
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