Effect of mixed light emitting diode spectrum on antioxidants content and antioxidant activity of red lettuce grown in a closed soilless system.

BACKGROUND: Light spectra have been demonstrated to result in different levels of comfort or stress, which affect plant growth and the availability of health-promoting compounds in ways that sometimes contradict one another. To determine the optimal light conditions, it is necessary to weigh the vegetable's mass against the amount of nutrients it contains, as vegetables tend to grow poorly in environments where nutrient synthesis is optimal. This study investigates the effects of varying light conditions on the growth of red lettuce and its occurring nutrients in terms of productivities, which were determined by multiplying the total weight of the harvested vegetables by their nutrient content, particularly phenolics. Three different light-emitting diode (LED) spectral mixes, including blue, green, and red, which were all supplemented by white, denoted as BW, GW, and RW, respectively, as well as the standard white as the control, were equipped in grow tents with soilless cultivation systems for such purposes. RESULTS: Results demonstrated that the biomass and fiber content did not differ substantially across treatments. This could be due to the use of a modest amount of broad-spectrum white LEDs, which could help retain the lettuce's core qualities. However, the concentrations of total phenolics and antioxidant capacity in lettuce grown with the BW treatment were the highest (1.3 and 1.4-fold higher than those obtained from the control, respectively), with chlorogenic acid accumulation (8.4 ± 1.5 mg g- 1 DW) being particularly notable. Meanwhile, the study observed a high glutathione reductase (GR) activity in the plant achieved from the RW treatment, which in this study was deemed the poorest treatment in terms of phenolics accumulation. CONCLUSION: In this study, the BW treatment provided the most efficient mixed light spectrum to stimulate phenolics productivity in red lettuce without a significant detrimental effect on other key properties.

Combined effects of cations in fertilizer solution on antioxidant content in red lettuce (Lactuca sativa L.).

BACKGROUND: Red lettuce is consumed worldwide because it is a great source of natural antioxidants. To design a fertilizer formula to boost its nutritional value, this research simultaneously studied the effects of significant cations among the macronutrients for plant growth (K, Mg and Ca) and the effects of the electrical conductivity (EC) of the nutrient solution on phenolic compound production and mass productivity of hydroponically grown red lettuce. RESULTS: Red lettuce grown under the control treatment provided the highest mass productivity (under low-stress conditions). The highest antioxidant content, measured as milligrams of phenolic compounds per gram dry weight (at a high-stress condition) via both Folin-Ciocalteu and HPLC analyses, was observed in growth media containing 100 ppmK : 20 ppm Mg : 70 ppm Ca (with EC equal to 1241 µS cm-1 ). It was found that EC within the range of this examination had no significant effect on the mass productivity or on phenolic compound productivity. The phenolic compound productivity, defined as the amount of phenolic compounds produced per unit of planting area per unit of time, was optimized with the optimum formula for maximum phenolic compound productivity of 90 ppm K : 29 ppm Mg : 77 ppm Ca, or a corresponding EC of 1307 µS cm-1 . CONCLUSIONS: The study demonstrates that health-promoting nutrient production in red lettuce could be stimulated in a practical manner by adjusting the cation concentrations in fertilizer solution. © 2021 Society of Chemical Industry.

Digestibility and structural parameters of spray-dried casein clusters under simulated gastric conditions.

The digestibility of casein clusters prepared from sodium caseinate solution (plain or pH-adjusted (pH=6.0)) was studied. The prepared solutions were spray-dried at different inlet air temperatures (150°C and 180°C), and the properties (i.e. encapsulation efficiency, surface hydrophobicity, and digestibility) of the resultant powders were investigated. The specimens obtained from the pH-adjusted solution had higher encapsulation efficiencies than the specimens obtained from the plain solution. A higher spray-drying temperature resulted in lower encapsulation efficiencies and higher surface hydrophobicities. Simulated gastric digestion tests were carried out to study the digestibility of the obtained casein clusters, which was analyzed in terms of reaction kinetics and structural changes during digestion. The effects of drying temperature and pH on the amount of casein digested were not significant; that is, approximately 30% of casein was digested in 120min for all specimens. Small-angle and ultra-small-angle X-ray scattering measurements were used to analyze the structure of the obtained clusters and their changes during digestion. The results suggested that all the obtained casein clusters, with an average size of approximately 428nm, had a rough, fractal-structured surface with many dense primary clusters. These structures changed during digestion; specifically, the cluster size increased both in the overall diameter and on the primary structure scale. The fractal characteristics changed from surface to mass fractals, and simultaneously, the cluster density decreased. The drying temperature affected the cluster size during digestion, and the trends were different in the specimens obtained from the plain and pH-adjusted solutions. These results could be useful in the design of protein-based encapsulation systems with desirable digestibility and bioavailability.