Hydroponic cultivation improves the nutritional quality of soybean and its products

Hydroponic cultivation allows to control environmental conditions, save irrigation water, increase 16 productivity and prevent plant infections. The use of this technique for large commodities such as 17 soybean is not a relevant issue on fertile soils, but hydroponic soybean cultivation could provide 18 proteins and oil in adverse environmental conditions. In this paper the composition of four cultivars 19 of soybean seeds and their derivates, soymilk and okara, grown in hydroponics was compared to 20 that of the same cultivar obtained from soil cultivation in open field. Beside proximal composition, 21 the concentration of phytic acid and of isoflavones was monitored in the seeds, soymilk and okara. 22 Results demonstrated that, independently from the cultivar, hydroponic compared to the soil 23 cultivations promoted the accumulation of fats (from 17.37 to 21.94 g/100 g dry matter) and total 24 dietary fiber (from 21.67 to 28.46 g/100 g dry matter); reduced isoflavones concentration (from 25 17.04 to 7.66 mg/Kg dry matter), while protein concentration was unaffected. The differences found 26 in seed composition were confirmed in the respective okara products, while the effect of cultivation 27 system was not significant looking at the soymilk composition. 28 Data showed that hydroponic cultivation improved the nutritional quality of soybean seeds as 29 regard fats and dietary fibre. They also suggests that specific cultivar should be selected to obtain 30 the desired nutritional features of the soybean raw material depending on its final destination.