The effect of different combinations of LED lights on the nutritional value and quality of microgreens

Nasr Esfahani, Ramin; Haghighi, Maryam; Esmaielpour, Behrooz

doi:10.22034/iuvs.2024.2022296.1353

The effect of different combinations of LED lights on the nutritional value and quality of microgreens

Document Type : Original Article

Authors

Ramin Nasr Esfahani ¹

Maryam Haghighi ²

Behrooz Esmaielpour ³

¹ Department of Horticulture, College of Agriculture, Isfahan University of Technology, Isfahan, Iran

² Department of Horticulture,College of agriculture, Isfahan University of Technology

³ Department of Horticultural Sciences, Faculty of Agriculture, University of Mohaghegh Ardabili, Ardabil, Iran

10.22034/iuvs.2024.2022296.1353

Abstract

Extended Abstract
1.      Introduction: Microgreens represent a unique category of products derived from seeds, vegetables, medicinal plants, and certain wild species. These microgreens have attracted attention for their aesthetic appeal and potential health benefits due to the presence of phytochemicals. They are primarily consumed as fresh vegetables. LED lights, particularly those emitting blue and red light, play a significant role in fostering the growth and development of plants. They enhance chlorophyll absorption, boost photosynthesis, and influence the mineral content in plants. The primary objective of this research was to examine changes in mineral nutrient compositions and flavor profiles of fennel, chia, and chicory microgreens under varying LED spectra in a controlled greenhouse environment.
2.      Materials and Methods: This study was conducted in 2021-2022 in a controlled greenhouse for seedling production in the city of Douche, Guatemalan region, with temperatures of 26.16 ±2°C and relative humidity of 65%, using a completely randomized block design with three replications. The light treatments included LED light at four levels (natural light, 100% red light, 100% blue light, and 70% red light + 30% blue light), applied to chia (Salvia hispanica L.), chicory (Cichorium intybus L.), and fennel (Foeniculum vulgare L.) microgreens. Seeds were purchased from Pagan Bar Company of Isfahan and cultivated in planting trays with dimensions of 60 cm length, 30 cm width, and 5 cm height, using a medium containing a mixture of agricultural soil and perlite in a volume ratio of 1:1. During the first three weeks, irrigation was performed daily and subsequently every other day. Microgreens at the two-leaf stage were subjected to light treatments for 12 hours daily. The wavelength of red light was 650 nm, and the wavelength of blue light was 460 nm, with a total photon flux density (TPFD) of 100 μmol.m^-2 s^-1, embedded at a distance of 80 cm from the microgreens' surface.
3.      Results and Discussion: The research findings indicated that blue light caused a reduction in internode length, while increased 100% red light exposure led to longer internodes. Hence, maintaining a balance between the blue and red light spectrums is crucial for optimal growth in certain plants. Chicory and fennel microgreens exhibited the longest internodes under 70% red light + 30% blue light, with a 23% increase in chicory and a 45% increase in fennel compared to using only 100% blue light. The highest total chlorophyll content was observed across all three microgreens under 100% blue light and 70% red light + 30% blue light. In chicory and fennel microgreens, 100% red light followed by 70% red light + 30% blue light enhanced phenol content, with 100% red light increasing phenol levels by 26% in chicory and 18% in fennel compared to the control light. The greatest antioxidant activity was noted in chia and chicory under 100% red light and in fennel under 70% red light + 30% blue light. Potassium and iron concentrations increased in chia microgreens under 70% red light + 30% blue light, while zinc concentrations improved by 42% in chia and 16% in fennel. However, magnesium concentration decreased under 70% red light + 30% blue light compared to the control. In chia and chicory microgreens, manganese levels increased by 40% and 9%, respectively, under 70% red light + 30% blue light compared to the control light. Fennel microgreens exhibited a sweet taste with a mild aroma under 100% blue light, a sweet taste with a relatively sharp aroma under 100% red light, and a sweet taste with a strong aroma under 70% red light + 30% blue light combined. Microgreen chia had a bitter taste across all light treatments, with 100% red light resulting in a relatively sharp aroma, 100% blue light producing a mild aroma, and 70% red light + 30% blue light yielding a sharp aroma. Similarly, microgreen chicory displayed a bitter taste under all light treatments, with 70% red light + 30% blue light causing a m
4.      Conclusion: In general, the use of LED lighting enhanced most of the studied parameters and increased the nutritional value of microgreens compared to natural light in the greenhouse. Specifically, 100% blue light increased total chlorophyll content and induced a mild aroma in all three microgreens: chia, chicory, and fennel. The highest phenol and flavonoid content, along with spicy aromas, were observed in chicory and fennel microgreens under 100% red light. A combination of 70% red light and 30% blue light increased internode length and sweet taste with high aroma in fennel while improving nutrients in chia, chicory, and fennel microgreens. Overall, 70% red light and 30% blue light were identified as the most effective combination for microgreens growth.

Keywords

Essential oil

Mineral elements

Phenolic compounds

Supplementary light

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