SODIUM CHLORIDE ON BIOACTIVE COMPOUNDS OF EGGPLANT (Solanum melongena L.) GROWN IN HYDROPONICS UNDER TWO PROTECTED STRUCTURES

Abstract

The consumption of fruits and vegetables of nutritional quality increases due to their high amounts of bioactive compounds with antioxidant activity, to prevent diseases and improve health. The hypothesis is that salinity, light and temperature in different protected structures influence the chemical composition and nutritional value of eggplant (Solanum melongena L.) fruits. The objective was to evaluate the effect of different doses of sodium chloride (NaCl) on the concentration of bioactive compounds in eggplant fruits grown in hydroponics under greenhouse and shade mesh. Eggplants were grown in a hydroponic system in pots with tezontle. The experimental design was completely randomized with a 4 × 2 factorial arrangement, four doses of NaCl (0, 15, 30 and 45 mM) and two protected structures (greenhouse and shade mesh). The variables evaluated were fruit weight, firmness, total soluble solids (SST), titratable acidity (AT), sodium, vitamin C, phenols, total flavonoids and antioxidant activity. Fruits obtained from plants grown in greenhouses with 45 mM NaCl decreased 35.9 % in weight compared to fruits from the 30 mM NaCl shade mesh treatment; and increased 51.9 % in firmness compared to the 15 mM NaCl treatment under shade mesh. The 15 mM NaCl dose under shade mesh increased SST by 95.8 % compared to the 30 mM NaCl treatment in the greenhouse. Under shade mesh without salinity, the highest AT in fruits was obtained; also, it was observed that the AT of fruits under shade mesh was 60.5 % higher than the AT of fruits in the greenhouse; regardless of the NaCl dose. The highest fruit concentration was found in the 45 mM NaCl treatment in the greenhouse. Under shade mesh with 15 mM NaCl dose, the lowest concentration of vitamin C in fruit was recorded, being 37 % lower than the concentration of vitamin C with the same dose in the greenhouse. No significant differences were found in phenols and total flavonoids. Fruits from plants under shade mesh with the 30 mM NaCl dose had 165.2 % more antioxidant capacity than fruits from plants under shade mesh without salinity. It is concluded that the environmental conditions of temperature and radiation in the greenhouse promoted an increase in the concentration of bioactive compounds in eggplant fruits, which provides greater nutritional value.