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CONFERENCE PROCEEDING
Title: Increasing Qualities of Amaranth Microgreens Under Plant Factory System by LED light
Warada Yusoh1*, Wachiya Malaeh2 &Eaknarin Ruangrak3
1,2Islamic Sciences Demonstration School, Prince of Songkla University, Pattani Campus , 94000, Rusamilae, Meuang, Pattani, Thailand
3Division of Agricultural Technology, Department of Science and Technology, Prince of Songkla University, Pattani Campus, 94000, Meuang, Pattani, Thailand
*Corresponding author: [email protected]
ABSTRACT
Microgreens are seedlings grown from the seeds of vegetables, herbs, and grains that are regarded as functional food with high mineral contents and helpful bioactive compounds. Nowadays, the research on the effects of light factors affecting the growth and quality of microgreens is usually confined.
Therefore, this study was focused on determining the optimal light spectrum that enhanced the growth and nutritional values of Thai amaranth microgreens with growth LED artificial light. There were cultured under different light spectra for 8 days provided by illuminated continuously 16 hours for a day. The experiment was replicated three times using statistics of a randomized complete block design (RCBD). Thai amaranth microgreens gave different light spectrums: red, blue, red + blue (70:30), and white. The results revealed that the light spectrum played an important role in the production of phytochemicals in Thai amaranth microgreens. Although the monochromatic blue spectrum had the worst overall performance, it provided the highest antioxidant capacities of Thai amaranth microgreens.
For the overall performance, a red and blue ratio of (70:30) LED spectrum can increase the nutritional value of Thai amaranth microgreens, according to the findings.
Keywords: Microgreens ; Light spectrum ; Plant factory
INTRODUCTION
The covid-19 pandemic has made people around the world that has turned their attention to health and food consumption. Microgreens have become one of the options for nutritional food. Most of the scientific research has found that plants grown in the microgreen stage have the highest nutritional value, such as carotenoids, vitamins, antioxidants, and phenols. Most people are interested in growing microgreens because their nutritional value is higher than that of mature vegetables up to 40 times. This result in high market value due to higher demand. The amaranth is one of the most commonly used vegetables for microgreens. They are known for their different flavors and textures for each variety of amaranth. Amaranth can produce a good nutritional food, flavors and textures under suitable light spectrums. LED light source is one of light source that can produce specific spectrum, electrical saving and low heat.
Therefore, the LED lighting system is used as the light source for microgreens production system, recently. The lighting spectrum can be set to suit the needs of the plants. It allows plants to grow better than they get from sunlight and the yield is higher quality. Research into the effects of light factors on microgreen growth and quality is usually confined. Thus, this study was focused on identifying suitable light spectrum
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for enhancing the growth and nutrition of Thai amaranth microgreens under LED light source.
METHODOLOGY
Part 1: Growing microgreens
Put the coconut coir in the tray water the coconut dust with moisture, then sow Thai amaranth seeds into a tray after that controlled at 25 ± 2 °C and leave it for 1-2 days.
Part 2: Experiment
The experiments: The study used a randomized complete block design (RCBD) with 3 replications consisting of 4 light spectrums include: red (600−700 nm), blue (400−500 nm), red + blue ratio of (70:30), and white (430−780 nm) with the lights on for 16 hours/day to Thai amaranth microgreens all over the experiment period for 8 days.
Part 3: Preparation of yield
At harvest time, cut the stem and leaves, wash the coconut dust from the Thai amaranth microgreens and keep it at -20 ° C for biochemical determination.
Part 4: Biochemical determination
Biochemical determination is divided into 4 determinations as follows:
4.1 Determination of chlorophyll a, b, total chlorophyll, and total carotenoids content 1 g of fresh Thai amaranth microgreens were ground with 5 mL of 95% ethanol. Then sample 15 min, then filtrated using a filter paper (no.1), after that centrifuge, 3,000 rpm for15 min at 4 °C, transferred to 96 - cell and measured with a microplate reader at wavelengths of 440, 480, 495, 649 and 665 nm.
4.2 Determination of total vitamin C contents
7 g of fresh Thai amaranth microgreens were immediately macerated in 14 mL of oxalic acid (0.5% w/v). The mixture was then filtrated using filter paper (no. 1). The filtrates (1 mL) were mixed with 4 mL of 10% trichloroacetic acid, then immediately placed on ice for 5 min. Centrifuge at 8,000 rpm for 5 min, 3 mL of the supernatant was mixed with 0.2 mL of 0.2 M folin-ciocalteu reagent and left at room temperature for 1 hour and measured using a spectrophotometer at 760 nm.
4.3 Determination of total phenolic contents
0.2 mL of extracted sample, distilled water 2.5 mL, then add 0.2 mL of 10 % folin- ciocalteu reagent and 2 mL of 7.5 % Na2CO3 that keep in dark for 90 min and measure using a spectrophotometer at 765 nm.
4.4 Determination of total antioxidant capacity
Diluted filtered water in ratio 1:10, take sample 0.3 mL, then add 1.5 mL of 0.1 mM DPPH after that keep it in dark for 40 min, and measure using a spectrophotometer at 517 nm.
RESULTS AND DISCUSSION
The effects of light spectra on chlorophyll b, total chlorophyll, and total carotenoids content of Thai amaranth microgreens were affected by light spectra treatments, chlorophyll a content was not affected by light spectra, chlorophyll b and total chlorophyll contents were found under red + blue (70:30) spectrum, even if not different from the white spectrum. However, the total carotenoid content of Thai
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amaranth microgreen was found under the red + blue (70:30) spectrum did not different from white spectrum, and it was the lowest under the blue spectrum (Table 1.).
Table 1. Effect of light spectrum on chlorophyll a, b and carotenoids content (mg/g) of Thai amaranth microgreens
Light spectrum Chlorophyll a Chlorophyll b Total Chlorophyll
(a+b)
Total carotenoids
Red (660 nm) 0.100±0.00 0.073±0.01b 0.173±0.01b 0.054±0.00b
Blue (447 nm) 0.097±0.01 0.070±0.02b 0.167±0.04b 0.053±0.04b
Red: Blue (70:30) nm 0.110±0.00 0.110±0.02a 0.220±0.02a 0.056±0.00a White (430-780 nm) 0.110±0.01 0.105±0.02a 0.215±0.02a 0.058±0.03a
RCBD ns * * *
Note: * significant difference at p <0.05 level, respectively.
The effect of light spectrum on vitamin C of Thai amaranth microgreens was not affected by light spectrum, and it was the lowest under the blue spectrum. The total phenolic content of Thai amaranth microgreens was affected by light spectra treatments, the highest total phenolic contents were found under the white spectrum, while the highest antioxidant capacities were detected under the blue spectrum, although the lowest was found under white spectrum (Table 2.).
Table 2. Effect of light spectrum on vitamin c contents, total phenolic content (TPC) and antioxidants capacities by DPPH of Thai amaranth microgreens
Light spectrum Vitamin C (mg/100g)
TPC (mg GAE/g DW)
Antioxidant Capacities (%Inhibition)
Red (660 nm) 1.075±0.01 17.65±0.09b 57.55 ± 0.17b
Blue (447 nm) 1.020±0.02 7.98±0.09b 80.14 ± 0.19a
Red: Blue (70:30) nm 1.170±0.01 16.84±0.09b 61.20 ± 0.21b
White (430-780 nm) 1.050±0.01 21.05±0.09a 52.91 ± 0.22b
RCBD ns * *
Note: * significant difference at p <0.05 level, respectively.
CONCLUSION
The results of the study findings revealed that the light spectrum played an important role in the production of phytochemicals in Thai amaranth microgreens. Although The combination of red and blue (70:30) spectra increased chlorophyll, carotenoids and total vitamin C contents, white spectra could enhance total phenolic contents, while the single blue spectra could enhance total antioxidants capacity. For the overall performance, combined red and blue (70R:30B) LED spectrum was more effective.
Further studies are needed to investigate the effect of ratios of red and blue combination.
ACKNOWLEDGEMENT
This project was supported by Science Classroom in University Affiliated School (SCiUS) under Prince of Songkla University and Islamic Sciences Demonstration School. The funding of SCiUS is provided by Ministry of Higher Education, Science, Research and Innovation, which is highly appreciated. This extended abstract is not for citation.
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