Mineral Content Differs among Microgreen, Baby Leaf, and Adult Stages in Three Cultivars of Kale

Abstract

<jats:p>Kale (<jats:italic>Brassica oleracea</jats:italic> L. and other species) is considered a rich source of important minerals. Kale at the early stage of leaf development is assumed to contain higher levels of minerals than at maturity. However, literature supporting this assumption is scarce. In this study, the concentrations of macronutrients [potassium (K), calcium (Ca), magnesium (Mg), and phosphorus (P)] and micronutrients [sodium (Na), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu)] either essential to plant growth and development, or important to human health, were determined. Three kale cultivars (green leaf ‘Dwarf Blue Curled’ and red leaf ‘Scarlet’ in <jats:italic>B. oleracea</jats:italic>, and green leaf with purple midvein ‘Red Russian’ in <jats:italic>Brassica napus</jats:italic>) were evaluated at five different leaf developmental stages; cotyledon [microgreen 1 (MG1)], two true leaf [microgreen 2 (MG2)], four true leaf [baby leaf 1 (BL1)], six true leaf [baby leaf 2 (BL2)], and adult. As kale matured, total mineral (ash) decreased from 14.6–19.1% at the microgreen stages to 3.9–6.4% at the adult stage, on a dry weight (DW) basis. Microgreen kale contained higher concentrations of most minerals than adult kale, on a DW basis, in all cultivars. On a fresh weight (FW) (as consumed) basis, the highest level of total mineral concentration was detected at baby leaf stage 1 (1.3–1.7%) and there was no difference between microgreen and adult stages. Fresh microgreens generally contained lower K, Ca, Mg, Fe, and Zn than fresh baby leaves, and lower concentrations of Ca and Mg and higher Na compared with fresh adult kale. Overall, water content deceased from 95.1% at MG1 stage to 80.0% at adult stage. The variation in water content and mineral accumulation during leaf development might contribute to the discrepancy. In addition, fresh leaves of ‘Scarlet’ contained higher concentration of total minerals than that of ‘Dwarf Blue Curled’ or ‘Red Russian’. Although ‘Dwarf Blue Curled’ and ‘Red Russian’ are different species, their mineral content profile during leaf development was similar. Together, cultivar and leaf developmental stage influenced mineral content in kale.</jats:p>

Sprouts vs. Microgreens as Novel Functional Foods: Variation of Nutritional and Phytochemical Profiles and Their In vitro Bioactive Properties

“…No significant differences between sprouts and microgreens were detected, but the content of ash was higher in microgreens, especially for amaranths and kale ( Table 1 ). According to previous studies, sprouts, microgreens or “baby” vegetables at early growth stages are better sources of nutrients than their mature counterparts [ 21 , 22 ]. The content of ash depends on the agrotechnical techniques and growing conditions, such as soil and climatic factors, exposure to light, and the type of species or varieties [ 22 ].…”

Variation in Macronutrient Content, Phytochemical Constitution and In Vitro Antioxidant Capacity of Green and Red Butterhead Lettuce Dictated by Different Developmental Stages of Harvest Maturity

“…Minerals take a crucial part in versatile biological processes during plant growth stages and development, where up to 17 key minerals take part, which are transferred to human nutrition [25]. These major minerals in human diet are of utmost importance to avert any disorders, their absence affect body homeostasis and metabolism [5].…”

“…Kyriacou et al [5] stated that potassium is the most concentrated macronutrient in microgreens followed by calcium and magnesium. In fact, potassium is abundant in plant cells and tissues, calcium partakes in coordinating plant response to internal and external stimuli and magnesium is involved in chlorophyll and protein synthesis [25]. Refering to lettuce, Weber [20] showed that hydroponically grown romaine lettuce had higher P, Mg and S and lower K, Ca and Na than mature lettuce, which is not completely in line with our results, noting that in this previous experiment mature romaine lettuce were bought from the store and the cultivar was not defined.…”

Health-Promoting Phytochemicals from 11 Mustard Cultivars at Baby Leaf and Mature Stages

“…Nonetheless, the nutritional profiles of mustard leaves have been limited in their analysis and quantification across different cultivars at different physiological stages. Immature plants such as microgreens and baby leaf plants have been getting popular, partially due to their intense flavor and tender texture compared to mature plants [ 17 , 18 ]. Considering their growing popularity, immature plants merit research on their nutritional value, which can assist growers in their determination of cultivation regime, as well as consumers in their food choices.…”