Title: Microgreen nutrition, food safety, and shelf life: A review
Authors: Ellen R. Turner, Yaguang Luo, and Robert L. Buchanan
Read or download the PDF: https://onlinelibrary.wiley.com/doi/epdf/10.1111/1750-3841.15049
Microgreens have gained increasing popularity as food ingredients in recent years because of their high nutritional value and diverse sensorial characteristics. Microgreens are edible seedlings including vegetables and herbs, which have been used, primarily in the restaurant industry, to embellish cuisine since 1996. The rapidly growing microgreen industry faces many challenges. Microgreens share many characteristics with sprouts, and while they have not been associated with any foodborne illness outbreaks, they have recently been the subject of seven recalls. Thus, the potential to carry foodborne pathogens is there, and steps can and should be taken during production to reduce the likelihood of such incidents. One major limitation to the growth of the microgreen industry is the rapid quality deterioration that occurs soon after harvest, which keeps prices high and restricts commerce to local sales. Once harvested, microgreens easily dehydrate, wilt, decay and rapidly lose certain nutrients. Research has explored preharvest and postharvest interventions, such as calcium treatments, modiﬁed atmopsphere packaging, temperature control, and light, to maintain quality, augment nutritional value, and extend shelf life. However, more work is needed to optimize both production and storage conditions to improve the safety, quality, and shelf life of microgreens, thereby expanding potential markets.
Microgreens are an emerging class of produce that have gained increasing popularity (Kyriacou et al., 2016; Pinto, Almeida, Aguiar, & Ferreira, 2015; Xiao, Lester, Luo, & Wang, 2012). They are the seedlings of edible plants harvested 7–14 days postplanting when the ﬁrst true leaves start to emerge. Microgreens have been used primarily in the restaurant industry to embellish cuisine and are most commonly consumed fresh in salads, soups, and sandwiches. An assortment of colors, visual textures, aromas, and ﬂavors give appeal to these tender young greens pictured in Fig. 1.
Microgreens are ideally suited for indoor production and are part of the global movement towards controlled environmental agriculture (CEA) (Riggio, Jones, & Gibson, 2019a). This movement is driven by population growth, shrinking arable land, and the need for ensuring food security (Goodman & Minner, 2019; Stoleru, Ionitᾰ, & Zamﬁrache, 2016; Wood, 2019). The short time to harvest for microgreens and high market values makes them important CEA crops (Wood, 2019).
The microgreen market is growing rapidly (Charlebois, 2019; Riggio et al., 2019a; Wood, 2019), but faces many challenges. Microgreens share many characteristics with sprouts, and have been associated with seven recalls in the United States and Canada; three due to Salmonella (Canadian Food Inspection Agency [CFIA], 2018a; Clark, 2017; Marler, 2016), and the other four due to Listeria contamination (CFIA, 2018b, CFIA, 2019; U.S. Food and Drug Administration [FDA], 2018; Whole Foods Market,
One major limitation to the growth of the microgreen industry is rapid quality deterioration postharvest. Microgreens are difﬁcult to store, due to their high surface area to volume ratio, high respiration rate, and delicate leaves that easily wilt, and rapid postharvest decay transpiration, leakage of nutrient rich exudates, tissue damage, and early senescence (Berba & Uchan-ski, 2012; Chandra, Kim, & Kim, 2012; Kou et al., 2013). Some growers sell microgreens as a “living product” so that the customer harvests and washes them as they are needed to serve the freshest quality. Hydroponic pads and soil-less substrates tend to be favored for this practice for ease of transport and perception of cleanliness in a kitchen environment (Renna, Di Gioia, Leoni, Mininni, & Santamaria, 2017). However, these microgreens still need to be used quickly to maintain peak quality. Most research on microgreens has taken place in the last 7 years by a limited but growing number of international research groups (Brazaityte et al., 2018; Craver, Gerovac, Lopez, & Kopsell, 2017; Kyriacou et al., 2016; Riggio, Wang, Kniel, & Gibson, 2019b; Xiao et al., 2012). Each group has focused on a narrow subset of microgreens and their issues. The intention of this review is to ﬁt together these pieces and bring attention to the areas that are potential impediments to commercialization.
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