Phenolic Constitution, Phytochemical and Macronutrient Content in Three Species of Microgreens as Modulated by Natural Fiber and Synthetic Substrates

Abstract

The present study examined the modulatory effects of natural fiber substrates (agave fiber, coconut fiber and peat moss) and synthetic alternatives (capillary mat and cellulose sponge) on the nutritive and phytochemical composition of select microgreens species (coriander, kohlrabi and pak choi) grown in a controlled environment. Polyphenols were analyzed by UHPLC-Q-Orbitrap-HRMS, major carotenoids by HPLC-DAD, and macro-minerals by ion chromatography. Microgreens grown on peat moss had outstanding fresh and dry yield but low dry matter content. Natural fiber substrates increased nitrate and overall macro-mineral concentrations in microgreens compared to synthetic substrates. The concentrations of chlorophylls, carotenoids and ascorbate were influenced primarily by species. On the contrary, variability in polyphenols content was wider between substrates than species. Out of twenty phenolic compounds identified, chlorogenic acid and quercetin-3-O-rutinoside were most abundant. Hydroxycinnamic acids and their derivatives accounted for 49.8% of mean phenolic content across species, flavonol glycosides for 48.4% and flavone glycosides for 1.8%. Peat moss provided optimal physicochemical conditions that enhanced microgreens growth rate and biomass production at the expense of phenolic content. In this respect, the application of controlled stress (eustress) on microgreens growing on peat moss warrants investigation as a means of enhancing phytochemical composition without substantial compromise in crop performance and production turnover. Finally, nitrate deprivation practices should be considered for microgreens grown on natural fiber substrates in order to minimize consumer exposure to nitrate.

Amber, red and blue LEDs modulate phenolic contents and antioxidant activities in eight Cruciferous microgreens

“…Under amber lighting one half of the microgreens (MO, MR, MS, RR) showed moderate correlation (r = 0.48-0.58) while the other half (PC, MB, MG, RO) showed weak correlation (r = −0.3-0.28) ( Table 2). It is generally reported that blue light positively enhances phenolic content in vegetables and herbs like lettuce, tomato and basil (Johkan et al, 2010;Kim et al, 2013;Kyriacou et al, 2020). In our study, TPC was more strongly correlated to blue light than amber light as seen in MO, MR, MS, RR (r = 0.61-0.73), moderately in MG (r = 0.53) and generally the same in other microgreens (Table 2).…”

Sensory Attributes and Consumer Acceptability of 12 Microgreens Species

“…Day/night temperatures and relative humidity were set at 24/18 ± 1 • C and 60%/70%, respectively. Microgreens species were grown in trays (56 × 37 × 5.5 cm: W × L × D) filled with peat moss substrate (pH 6.3 and electrical conductivity 0.2 dS m −1 ; Special Mixture, Floragard Vertriebs-GmbH, Oldenburg, Germany) and fertigated daily with a quarter-strength modified Hoagland solution described in detail in Kyriacou et al [15].…”

“…Indeed, microgreens enclose a greater load of essential phytonutrients compared to their mature counterparts [3,4,6,10,13]. Suchlike dense phytochemical composition has garnered the attention of nutrition researchers [6,15] and gained them prevalence among food technologists, urban farmers, and consumers [15]. As public concern about environmental and nutritional aspects of food production has recently arisen [16,17], consumers are orienting their purchasing behavior toward healthier and environmentally friendlier food products [18][19][20].…”

The Use of a Nutrient Quality Score is Effective to Assess the Overall Nutritional Value of Three Brassica Microgreens

“…Microgreens can be considered as a functional food due to their high content in several healthy compounds for humans [8][9][10][11][12][13][14][15]. This emerging category of vegetable products can be defined as immature greens, which are harvested when the cotyledon leaves have fully developed and the first true leaves have emerged, although the term 'microgreens' lacks any legal definition [16].…”

“…Although several studies have been carried out regarding the nutritional evaluation of microgreens [8,9,11,13,15,[22][23][24], only one reports the nutritional ranking of some microgreens on the basis of an index that is able to summarize the overall nutritional quality [14]. At the same time, the literature lacks research into the adoption of this evaluation method to be used not only to compare different genotypes but also to assess the effects of growing conditions on the microgreens' nutritional quality.…”