Microgreen

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Technicians harvesting different types of microgreens for shelf-life studies and nutrient analyses Liping Kou observes microgreens.jpg
Technicians harvesting different types of microgreens for shelf-life studies and nutrient analyses

Microgreens are vegetable greens (not to be confused with sprouts or shoots) harvested just after the cotyledon leaves have developed with one set of true leaves. They are used as a visual, flavor and texture enhancement. Microgreens are used to add sweetness and spiciness to foods. Microgreens are smaller than "baby greens" because they are harvested soon after sprouting, rather than after the plant has matured to produce multiple leaves.

Contents

They provide garnishing for salads, soups, sandwiches, and plates. [1] [2] Some recipes use them as a garnish while others use them as a main ingredient.

Edible young greens are produced from various kinds of vegetables, herbs, or other plants. They range in size from 1 to 3 inches (2.5 to 7.6 cm), including the stem and leaves. The stem is cut just above the soil line during harvesting. Microgreens have fully developed cotyledon leaves and usually, one pair of small, partially developed true leaves.

History

Microgreens began showing up on chefs' menus as early as the 1980s in San Francisco. [1] In Southern California, microgreens have been grown since the mid1990s. Initially, a few varieties were offered; those available were: arugula, basil, beets, kale, cilantro, and a colorful mixture of those called a "Rainbow Mix". Having spread eastward from California, they are now being grown in most areas of the United States, with an increasing number of varieties. Today, the U.S. industry for microgreens consists of a variety of seed companies and growers. [1]

Form

Microgreens have three basic parts: a central stem, cotyledon leaf or leaves, and typically, the first pair of very young true leaves. They vary in size depending upon the specific variety grown, with the typical size being 1 to 1.5 in (25 to 38 mm) in total length. When the plant grows beyond this size, it is generally no longer considered a microgreen, instead being called a petite green. The average crop-time for fast-growing microgreens, such as many brassicas, is 10–14 days from seeding to harvest. [1] [3] [4] Slower growing microgreens, such as beets, chard, and many herbs, may take 16–25 days to reach harvestable size. Both baby greens and microgreens lack any legal definition. The terms "baby greens" and "microgreens" are marketing terms used to describe their respective categories. Sprouts are germinated seeds and are typically consumed as an entire plant (root, seed, and shoot), depending on the species. Sprouts from almond, pumpkin, and peanut reportedly have a better flavor when harvested prior to root developments. Sprouts are legally defined and have additional regulations concerning their production and marketing due to their relatively high risk of microbial contamination compared to other greens. Growers interested in producing sprouts for sale must be aware of the risks and precautions summarized in the FDA publication Guidance for Industry: Reducing Microbial Food Safety Hazards for Sprouted Seeds (FDA 1999). [5]

Growing

Microgreens are generally described as being an easier plant to grow but may have complication ranging from preventing and managing fungus or mold growth to providing the right nutrients and growing media to the plants in order to ensure quality produce. Many small "backyard" growers have sprung up selling their greens at farmers markets or to restaurants. [6] A shallow plastic container with drainage holes, such as a nursery flat or prepackaged-salad box, will facilitate sprouting and grow out on a small scale. [7] However, for commercial scale growing, specific trays better suited to growing and supporting microgreens are used.

Growing and marketing high-quality microgreens commercially is more intensive, but also shows potential for providing better quality produce under controlled and sterile environments and could provide local communities with better nutritional diversity at scale. [5] Artificial lighting is not necessarily needed for growing microgreens but is required for indoor commercial setups. Microgreens can grow under various lighting conditions, including indirect natural light and grow lights, but some source of light is necessary for them to have grown adequately enough for harvest. [8] Different lighting conditions can change the flavors of the microgreens being grown. For instance, corn microgreens are sweet when grown in the dark, but become bitter when exposed to light due to photosynthesis processes taking place in the sprouting plants. [8]

Light-emitting diodes, otherwise known as LEDs, now provide the ability to measure impacts of narrow-band wavelengths of light on seedling physiology. The carotenoid zeaxanthin has been hypothesized to be a blue light receptor in plant physiology. A study was carried out to measure the impact of short-duration blue light on phytochemical compounds, which impart the nutritional quality of sprouting broccoli microgreens. Broccoli microgreens were grown in a controlled environment under LEDs using growing pads. Short-duration blue light acted to increase important phytochemical compounds influencing the nutritional value of broccoli microgreens. [9]

Nightshade family plants such as potatoes, tomatoes, eggplants, and peppers should not be grown and consumed as microgreens, since nightshade plant sprouts are poisonous. [8] These sprouts contain toxic alkaloids such as solanine and tropanes, which can cause adverse symptoms in the digestive and nervous systems. [10]

Nutritional analysis

ARS scientists analyzed key nutrients in twenty-five different varieties of microgreens and found that red cabbage microgreens (shown here) had the highest concentrations of vitamin C and these nutritious microgreens are ready to harvest just ten days after sowing. Red Cabbage Microgreens.jpg
ARS scientists analyzed key nutrients in twenty-five different varieties of microgreens and found that red cabbage microgreens (shown here) had the highest concentrations of vitamin C and these nutritious microgreens are ready to harvest just ten days after sowing.

Researchers at the USDA Agricultural Research Service have published, as of early 2014, several studies that identify the nutritional make-up and the shelf life of microgreens. Twenty-five varieties were tested, with the key nutrients measured being ascorbic acid (vitamin C), tocopherols (vitamin E), phylloquinone (vitamin K), and beta-carotene (a vitamin A precursor), plus other related carotenoids in the cotyledons.

Among the 25 microgreens tested, red cabbage, cilantro, garnet amaranth, and green daikon radish had the highest concentrations of vitamin C, carotenoids, vitamin K, and vitamin E, respectively. In general, microgreens contained considerably higher levels of vitamins and carotenoids—about five times greater—than their mature plant counterparts. [1]

Comparison of microgreens to sprouts

Sprouts are germinated or partially germinated seeds. A sprout consists of the seed, root, stem, while microgreens are harvested without the roots.

Microgreens have stronger flavors compared to sprouts, and come in a wider selection of leaf shapes, textures, and colors.

Microgreens are grown in soil or soil-like materials such as peat moss. [11] Microgreens require high light levels, preferably natural sunlight with low humidity and good air circulation. Microgreens are planted with very low seed density compared to sprout processing. Crop times are generally one to two weeks for most varieties, although some can take four to six weeks. Microgreens are ready to harvest when the cotyledons are fully expanded. Harvesting is usually with scissors cutting just above the soil surface, excluding any roots. Some growers sell them while still growing, rooted in the growing trays so that they may be cut later. Once removed from their growing environment, these trays of microgreens must be used quickly, or they will rapidly begin to elongate and lose color and flavor.

Sprout seeds are soaked in water, usually for eight hours, and then drained. A high density of seed is placed inside of sprouting equipment or enclosed containers. The seed germinates rapidly due to the high moisture and humidity levels maintained in the enclosures. Seeds can also be sprouted in cloth bags that are repeatedly soaked in water. The sprouting process occurs in dark or very low light conditions. After a few days of soaking and repeated rinsing in water (several times a day to minimize spoilage), the processing is complete, and the sprouts are ready to consume.

The conditions that are ideal for properly grown microgreens do not encourage the growth of dangerous pathogens. These growing methods would not work for the production of sprouts.

However, the potential for food safety issues with microgreens may be increasing due to the number of indoor microgreen growing operations in which excessive seed density, low light intensity, low air circulation, or most commonly, a lack of GAP (good agricultural practices) and GMP (good manufacturing practices) based food safety procedures. Certain provisions of the Guidance for Industry: Reducing Microbial Food Safety Hazards For Sprouted Seeds [12] may be beneficial and prudent for growers of microgreens to follow. Also, not all plants can be grown as microgreens due to toxicity concerns. For instance, nightshade plants (eggplants, tomatoes, potatoes, peppers, etc.) should not be grown as microgreen sprouts, since nightshade sprouts are toxic. [8] [10]

Storage and commercial transport

Microgreens have a long shelf life if stored and packaged properly. Optimal methods of storing and transporting microgreens are currently being studied. [13] Commercial microgreens are most often stored in plastic clamshell containers, which do not provide the right balance of oxygen and carbon dioxide for live greens to breathe.[ citation needed ] This is why microgreens are normally sold cut and packaged in a non breathable container. When freshly cut the shelf life for microgreens can be several weeks. Some growers add a food safe moisture wicking material in the bottom of the container to extend shelf life. Moisture control and temperature are the two most important factors when considering the longevity of packaged microgreens and their transport.

The ARS researchers found that buckwheat microgreens packaged in films with an oxygen transmission rate of 225 cubic centimeters per square inch per day had a fresher appearance and better cell membrane integrity than those packaged in other films tested. Following these steps, the team maintained acceptable buckwheat microgreen quality for more than fourteen days—a significant extension, according to authors. This study was published in LWT-Food Science and Technology in 2013. [1]

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<span class="mw-page-title-main">Turnip</span> Type of root vegetable

The turnip or white turnip is a root vegetable commonly grown in temperate climates worldwide for its white, fleshy taproot. Small, tender varieties are grown for human consumption, while larger varieties are grown as feed for livestock. In Northern England, Scotland, Ireland, Cornwall, Devon, and parts of Canada, the word turnip often refers to rutabaga, also known as swede, a larger, yellow root vegetable in the same genus (Brassica).

<span class="mw-page-title-main">Cabbage</span> Leafy vegetable in the flowering plant family Brassicaceae

Cabbage, comprising several cultivars of Brassica oleracea, is a leafy green, red (purple), or white biennial plant grown as an annual vegetable crop for its dense-leaved heads. It is descended from the wild cabbage, and belongs to the "cole crops" or brassicas, meaning it is closely related to broccoli and cauliflower ; Brussels sprouts ; and Savoy cabbage.

<span class="mw-page-title-main">Alfalfa</span> Perennial flowering plant in the legume family Fabaceae

Alfalfa, also called lucerne, is a perennial flowering plant in the legume family Fabaceae. It is cultivated as an important forage crop in many countries around the world. It is used for grazing, hay, and silage, as well as a green manure and cover crop. The name alfalfa is used in North America. The name lucerne is more commonly used in the United Kingdom, South Africa, Australia, and New Zealand. The plant superficially resembles clover, especially while young, when trifoliate leaves comprising round leaflets predominate. Later in maturity, leaflets are elongated. It has clusters of small purple flowers followed by fruits spiralled in two to three turns containing 10–20 seeds. Alfalfa is native to warmer temperate climates. It has been cultivated as livestock fodder since at least the era of the ancient Greeks and Romans.

<span class="mw-page-title-main">Broccoli</span> Edible green plant in the cabbage family

Broccoli is an edible green plant in the cabbage family whose large flowering head, stalk and small associated leaves are eaten as a vegetable. Broccoli is classified in the Italica cultivar group of the species Brassica oleracea. Broccoli has large flower heads, usually dark green, arranged in a tree-like structure branching out from a thick stalk which is usually light green. The mass of flower heads is surrounded by leaves. Broccoli resembles cauliflower, which is a different but closely related cultivar group of the same Brassica species.

<span class="mw-page-title-main">Lentil</span> Species of flowering plant with edible seeds in the family Fabaceae

The lentil is an edible legume. It is an annual plant known for its lens-shaped seeds. It is about 40 cm (16 in) tall, and the seeds grow in pods, usually with two seeds in each. As a food crop, the largest producers are Canada and India, producing 29% and 27%, respectively, of the world's total lentils in 2021.

<span class="mw-page-title-main">Sprouting</span> Practice of germinating seeds to be eaten raw or cooked

Sprouting is the natural process by which seeds or spores germinate and put out shoots, and already established plants produce new leaves or buds, or other structures experience further growth.

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<span class="mw-page-title-main">Seedling</span> Young plant developing out from a seed

A seedling is a young sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle, the hypocotyl, and the cotyledons. The two classes of flowering plants (angiosperms) are distinguished by their numbers of seed leaves: monocotyledons (monocots) have one blade-shaped cotyledon, whereas dicotyledons (dicots) possess two round cotyledons. Gymnosperms are more varied. For example, pine seedlings have up to eight cotyledons. The seedlings of some flowering plants have no cotyledons at all. These are said to be acotyledons.

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References

  1. 1 2 3 4 5 6 "Specialty Greens Pack a Nutritional Punch". USDA. Retrieved 23 January 2014.
  2. Millard, E. (2014). Indoor Kitchen Gardening: Turn Your Home Into a Year-round Vegetable Garden. Cool Springs Press. p. 63. ISBN   978-1-61058-981-9 . Retrieved May 28, 2017.
  3. Vanderlinden, Colleen. "Grow Your Own Microgreens". About.com. Retrieved 30 January 2014.
  4. "What are Microgreens?". Waterfields. Archived from the original on 2015-04-02. Retrieved 2015-03-04.
  5. 1 2 Treadwell, Danielle D. "Microgreens: A New Specialty Crop". Univ. of Florida IFAS Extension. Retrieved 31 January 2014.
  6. "Selling Microgreens". Instageeked. Retrieved December 8, 2020.
  7. Galloway, Will. "Growing Microgreens Indoors". Organic Gardening. Archived from the original on April 5, 2015. Retrieved 21 October 2015.
  8. 1 2 3 4 "Growing Microgreens and Sprouts Part 3: Growing and Eating". KUED (Utah State University).
  9. Kopsell, Dean A. "Increases in Shoot Tissue Pigments, Glucosinolates, and Mineral Elements in Sprouting Broccoli after Exposure to Short-duration Blue Light from Light Emitting Diodes". Journal of the American Society for Horticultural Science. Archived from the original on February 25, 2013. Retrieved 31 January 2014.
  10. 1 2 "Solanine poisoning – how does it happen?". 7 February 2014. Retrieved 24 September 2018.
  11. "Microgreens and Sprouts Are Not the Same Thing". Urban Cultivator. 2015-06-12. Retrieved 2022-04-06.
  12. "Sprout Safety: Letter to Seed Suppliers, Distributors, and Sprouters". U.S. Food and Drug Administration. Archived from the original on 21 October 2016. Retrieved 21 October 2016.
  13. "Publication: USDA ARS". www.ars.usda.gov. Retrieved 2018-06-15.