Effect of Exogenous Melatonin on the Quality of Soybean and Natto Products under Drought Stress

Abstract

Melatonin can directly or indirectly eliminate reactive oxygen species, regulate hormone levels, and improve drought-stressed soybean crop resistance, yield, and quality. The nutrient contents of soybeans grown under normal conditions (WW), drought stress (D), and drought stress with exogenous melatonin (D + M) ( p < 0.05 ) were compared. The differences in the quality of natto from the three groups of soybeans were also analyzed. The results showed that compared with soybeans under normal conditions, those grown under drought stress had reduced yield and carbohydrate, protein, essential amino acid, soybean isoflavone, and other nutrient contents. Besides, natto presented low nattokinase levels (674 U/mL), natto drawing ability was weak, the surface was dull, the taste was poor, and the sensory score was 12 points. Exogenous melatonin increased the carbohydrate content (starch, sucrose, glucose, and fructose) and improved the yield and quality of soybeans under drought. The natto produced by soybeans under drought stress with exogenous melatonin had high nattokinase content (756 U/mL) and long wire drawing. The surface of the product was rich in mucus and had a natto aroma. Its comprehensive sensory score was 20 points. Natto from soybeans under drought stress that were treated with exogenous melatonin showed significantly higher yield, nutrient content, and quality, than those under drought stress without treatment. This study provides theoretical data that can facilitate the development of new methods to improve the quality of soybeans grown under drought conditions.

Melatonin Application Alleviates Stress-Induced Photosynthetic Inhibition and Oxidative Damage by Regulating Antioxidant Defense System of Maize: A Meta-Analysis

“…[56,76]. Melatonin is also an antioxidant that protects plants from biotic and abiotic stresses [38,77], such as salt [41,78], drought [79][80][81], cold [59,82], and heavy metal stress [7]. Melatonin application reduced stress-induced photosynthetic inhibition (Table 2), suggesting that the overall lnRR ++ of total chlorophyll, chlorophyll a and b, and carotenoid were 18, 38, 24, and 18% higher than control, respectively.…”

Application of Exogenous Melatonin Improves Tomato Fruit Quality by Promoting the Accumulation of Primary and Secondary Metabolites

“…The sugars in tomato fruit are mainly fructose, glucose, and a small amount of sucrose [ 42 ]. Previous studies have shown that exogenous melatonin improves the yield and quality of soybean by promoting the accumulation of photosynthetic products, such as sucrose, starch, glucose, and fructose [ 15 ]. In our study, the content of fructose in tomato fruit at 48 d after anthesis was increased by melatonin treatment ( Figure 1 A) and glucose content at 34 d ( Figure 1 B), but melatonin treatment increased sucrose content in tomato fruit as early as 27 d ( Figure 1 C).…”

“…In addition, several studies have reported that melatonin can also regulate the appearance, quality, and nutrition of the fruit. For instance, the contents of starch, sucrose, fructose, glucose, and protein in soybean treated with melatonin significantly increased [ 15 ]. After irrigating the exogenous melatonin solution [ 16 ], the contents of ascorbic acid, lycopene, soluble solids, and phosphorus in tomato fruit were found to be enhanced compared to the control [ 17 ].…”

Correlation analysis between soluble sugars of soybean and mucus drawing length of fermented natto

“…The most distinctive feature of natto is that its surface is covered with white viscous material, which can form mucus after stirring. High-quality natto mucus is white, with a light or slightly sour smell, light yellow color, and soft and sticky texture, which has become an important criterion for judging high-quality natto (Yoshikawa et al, 2014;Cao et al, 2021;Wei & Chang, 2004). The stickiness and drawing properties of natto mucus are due to the strong viscous poly-γ-glutamic acid (γ-PGA) and levan, which have a stabilizing effect (Yoshioka et al, 2007).…”

“…Because food evaluations are based on psychological rather than field or laboratory factors, sensory evaluation is necessary (Yoshikawa et al, 2014). In the sensory experiments of natto, the drawing performance of mucus is mostly used as the measurement standard (Cao et al, 2021;Yoshikawa et al, 2014;Yang et al, 2021). In a sensory test aimed at the elderly in Tokyo, participants rated soft, sticky natto as better than what they generally believed to be natto, and a newly developed soft, sticky natto proved to be useful as food for the elderly (Mitsuboshi et al, 2006).…”