Journal of Plant Biochemistry & Physiology
Open Access
ISSN: 2329-9029
+44 1478 350008
ISSN: 2329-9029
+44 1478 350008
Research Article - (2024)Volume 12, Issue 3
Barley, a key ingredient in beer, has recently garnered attention for its potential health benefits. Specifically, barley grain has been found to promote the growth of beneficial intestinal microorganisms, positioning it as a functional food. To enhance the functional biomolecules in barley seeds, barley was germinating under Light-Emitting Diode (LED) lighting. After 4 days of germination, the barley exposed to red LED lighting displayed longer shoot elongation, higher α-amylase activity, and lower starch content compared to those germinated in the dark. On the other hand, blue LED lighting resulted in similar root and shoot elongation as the dark condition but significantly increased vitamin C content and DPPH radical scavenging activity in the germinated barley. Interestingly, red LED lighting did not show any significant effects on these antioxidant components. These findings suggest that blue LED lighting could be a potential method to produce functional germinated barley with enhanced antioxidant potential while maintaining the quality standards of malt.
Antioxidant; Barley; Germination; LED
Light plays an important role in regulating various morphological and physiological changes in mature plants [1,2]. Blue and red wavelengths are the primary spectral wavelengths that significantly influence the primary and secondary metabolism of plants [3]. Light-Emitting Diodes (LEDs) have been increasingly used as artificial light sources for plant growth in controlled environments. Research has shown that antioxidant activity increases in lettuce and Gynura when exposed to blue LED light [4,5]. Additionally, rose, Chrysanthemum, and Campanula exhibited higher flavonoid and phenolic contents when exposed to mix red and blue LED light with a higher proportion of blue [6]. Tomato seedlings cultivated under blue LED light displayed the highest antioxidant activity [7], whereas pea seedlings grown under red LED light showed the highest antioxidant potential [8]. These findings suggest that LED lighting can be strategically used to produce 'functional food'-food that contains enhanced levels of health-promoting or disease risk-reducing compounds such as antioxidants, minerals, and vitamins. However, it is important to note that the effects of LED lighting vary depending on the plant cultivar.
Barley is a versatile crop with multiple applications, serving as a source of food, livestock feed, and an essential ingredient for malt brewing. Recently, there has been growing interest in barley as a potential functional food. Young green barley leaves are particularly rich in antioxidants, flavones C-glycoside, saponarin, lutonarin, minerals, and vitamins, which are associated with various physiological benefits [9-12]. Additionally, barley grain contains β-glucan, a type of soluble dietary fiber [13,14] that has been linked to positive effects on obesity, cardiovascular diseases, diabetes, and cholesterol levels [15-17]. It also promotes the growth of beneficial intestinal microorganisms, such as lactobacilli and bifidobacteria [18-20]. Previous studies on the influence of LED light on young green barley leaves found that red LED light promoted plant height and weight gain [21], while blue LED light increased the contents of saponarin and polyphenol compared to red or far-red LED lighting [22]. However, the effects of LED lighting on the quality of germinated barley seeds remain unclear.
In the present study, barley seeds were germinated under LED lighting to enhance their quality. The results showed that the seeds germinated under blue LED light for 4 days exhibited increased levels of vitamin C and DPPH radical scavenging activity. On the other hand, seeds germinated under red LED light displayed higher α-amylase activity, lower starch content, and longer shoot length compared to seeds germinated in dark.
Germination and light treatment conditions
Seeds of malting barley, Hordeum vulgare L., Haruna Nijo, were soaked in water at 15°C for 5 h. The seeds were then arranged in a single layer on a water-filled sponge. They were incubated at 20°C for 4 days under constant lighting conditions: Red LED light (660 nm, 140 μmol/m2/sec), blue LED light (470 nm, 140 μmol/m2/sec), or kept in darkness. After germination, the shoots and roots were removed, and the seeds were stored at -80°C for further analysis.
Preparation of extracts
Five germinated seeds were ground into a fine powder using a mortar and pestle, and this powder was considered one sample. The weight of the powder was recorded, and it was then transferred to a glass centrifuge tube. The powder was suspended in 3 ml of 80% methanol for total polyphenol content and DPPH radical scavenging activity assays. For the vitamin C assay, the powder was suspended in 3 ml of 5% metaphosphoric acid. The suspensions were incubated with shaking at room temperature for 10 minutes, and then the supernatants were collected by centrifugation to be used as extracts for subsequent assays.
α-Amylase activity
α-Amylase activity was measured were performed using amylase assay kit (Abcam, Cambridge, UK) according to the manufacturer’s protocol. The rate of p-nitrophenol formation was determined by measuring at 405 nm.
Starch assay
The starch content in the germinated seeds was assayed using Starch Assay Kit (Cell Biolabs, INC., San Diego, USA) according to the manufacturer’s protocol. Twenty mg of germinated seeds was grinded to prepare the starch extract. The extract diluted 100 times was used to the assay.
Total polyphenol assay
The total polyphenol content in the extracts was analyzed using the Folin-Ciocalteu reagent method [23]. The extract was diluted ten times with water, and 0.2 ml of this diluted extract was mixed with 5 ml of Folin and Ciocalteu reagent (1:1 diluted with water). After a 3 minute incubation, 5 ml of 0.4 M Na2CO3 was added to the mixture. The solution was incubated at 50°C for 5 minutes and then cooled on ice. The absorbance was measured at 765 nm, and the results were compared to a standard curve prepared using tannic acid.
DPPH radical scavenging activity
The antioxidant activity of the extract was assessed using the DPPH method [24]. One ml of the extract was combined with 9 ml of 0.5 mM DPPH dissolved in 50% methanol and incubated in the dark at room temperature for 10 minutes. The decrease in absorbance was measured at 517 nm, and the results were compared to a standard curve prepared using Trolox.
Vitamin C assay
The vitamin C content was determined following the method described by Bradley et al., [25]. The extract (200 μl) was mixed with 12 μl of 3% bromine and incubated at room temperature for 5 minutes. Then, 70 μl of 5% metaphosphoric acid/2% SnCl2 solution was added, followed by 20 μl of 2% DNPH dissolved in 44% H2SO4). The mixture was incubated at 37°C for 3 h. Finally, 100 μl of 85% H2SO4 was added, and the solution was allowed to stand at room temperature. After 30 min, the absorbance was measured at 530 nm, and the results were compared to a standard curve prepared using L-ascorbic acid.
Effect of red and blue LEDs on root and shoot elongation
Red LED lighting significantly promoted the elongation of both roots and shoots in barley seeds, while blue LED lighting had no significant effect compared to the dark condition (Figure 1).
Figure 1: Barley seeds germinated for 4 days under constant lighting of red LED, blue LED, or dark conditions. Seeds were incubated at 20°C for 4 days under constant lighting conditions: red LED light (660 nm, 140 μmol/m2/sec), blue LED light (470 nm, 140 μmol/m2/ sec), or in the dark after soaking in water at 15°C for 5 h.
The shoot length of seeds germinated for 4 days under red LED, blue LED, and dark conditions were 22.1 ± 2.9*, 10.4 ± 2.7, and 10.0 ± 2.2 mm, respectively (n=30, *p<0.001). Similarly, the root lengths were 21.1 ± 3.9, 16.1 ± 2.3, and 19.0 ± 4.3 mm, respectively (n=30). Red LED lighting increased shoot length significantly by approximately 2.2-fold compared to the dark condition, while blue LED lighting had no significant impact. These results align with the findings reported by Kochetova et al., [26] where red LED lighting increased shoot length by 13% in 9-day-old seedlings.
In addition to the morphological changes, we also observed differences in α-amylase activities and starch content (Table 1).
| Seeds | Red LED | Blue LED | Dark |
|---|---|---|---|
| α-amylase (mU/g seed | 11.1 ± 0.8** | 8.75 ± 0.9 | 8.55 ± 1.1 |
| Starch (g/g seed) | 412 ± 45* | 441 ± 41 | 469 ± 41 |
| DPPH radical scavenging activity (mM/g seed) | 3.30 ± 0.15 | 3.72 ± 0.04* | 3.30 ± 0.16 |
| Total polyphenol (g/g seed) | 14.1 ± 0.30 | 14.6 ± 1.0 | 14.1 ± 0.32 |
| Vitamin C (g/g seed) | 46.5 ± 1.6 | 78.1 ± 1.2* | 55.0 ± 2.9 |
Note: n=3; *p<0.001 and **p<0.05
Table 1: Properties of barley seeds germinated for 4 days under constant lighting of red LED, blue LED or dark conditions.
Red LED lighting increased α-amylase activity by 1.3-fold and decreased starch content significantly compared to the dark condition. As explained by Beck et al., Fincher [27,28], α- amylase plays an important role during cereal germination, converting starch in the endosperm into nutrients that support seedling growth. The increased α-amylase activity and decreased starch content under red LED lighting suggests enhanced metabolism, which may contribute to the accelerated shoot growth observed in our study.
Effect of red and blue LEDs on antioxidant properties
Previous studies have reported conflicting results regarding the effect of LED lighting on the antioxidant properties of barley. Lee et al., found that young barley leaves grown under blue LED lighting showed an increasing tendency in antioxidant activity compared to those grown in the dark [29]. On the other hand, Paulickova et al., observed that barley sprouted for 20 days had the highest vitamin C level, while Koga et al., reported decreased vitamin C and E contents in 15-day-old barley leaves under red LED lighting compared to natural light [30,21]. These discrepancies suggest that the impact of LED lighting on antioxidant production depends on the harvest period and environmental factors.
In this study, the effect of LED lighting on DPPH scavenging activity, total polyphenol content, and vitamin C content in 4- day-old germinated barley were investigated (Table 1). The results indicate that blue LED lighting increased the levels of DPPH radical scavenging activity and vitamin C significantly. Notably, vitamin C content increased by 1.4-fold under blue LED lighting compared to the dark condition. However, red LED lighting had no significant effect on these antioxidant properties in 4-day-old germinated barley.
The malting process for brewing beer involves steeping, germinating, and kilning. Germination initiates the degradation and modification of cell wall, protein, and starch compounds, producing bioactive molecules that influence beer quality. Therefore, maintaining the quantity and quality of these molecules during germination is crucial in the malting and brewing industries. Additionally, antioxidants in germinated barley contribute to the oxidative stability and flavor of beer and offer potential health benefits for consumers by neutralizing Reactive Oxygen Species (ROS) associated with various diseases [31]. The finding that blue LED lighting, when applied for 4 days, does not affect root and shoot elongation supposes the same biomolecule content such as starch and protein, which ensures the quality of malt, and that increases the antioxidant content of germinated barley suppose the enhancing function of the germinated barley. This presents an opportunity to develop a low-cost process for producing functional germinated barley, not only as a raw material for brewing but also as an ingredient in functional foods, providing high levels of bioactive compounds with potential health-promoting properties.
The result of this study demonstrated that germination of barley seeds under constant blue LED lighting for 4 days enhances the bioactive compounds with the same quality as the germinated barley under dark condition. Blue LED lighting did not affect starch content, and α-amylase activity but enhanced DPPH radical scavenging activity and vitamin C content in the germinated barley. Thus, barley germinated barley under constant blue LED lighting for 4 days can be a valuable raw material and functional food.
This research was supported by the Ohara Foundation, Kurashiki, Japan.
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Citation: Sugimoto M (2024). Blue Light-Emitting Diode Lighting Improves Antioxidant Potential in Barley Germinated Seeds. J Plant Biochem Physiol. 12:345
Received: 05-Aug-2024, Manuscript No. JPBP-24-33359; Editor assigned: 07-Aug-2024, Pre QC No. JPBP-24-33359 (PQ); Reviewed: 21-Sep-2024, QC No. JPBP-24-33359; Revised: 28-Aug-2024, Manuscript No. JPBP-24-33359 (R); Published: 04-Sep-2024 , DOI: 10.35248/2329-9029.24.12.295
Copyright: © 2024 Sugimoto M. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.