Optimum aquaculture and drying conditions for Wolffia arrhiza (L.) Wimn

This study aimed to investigate the effects of aquaculture and the optimum conditions for drying duckweed plants to maintain the highest nutritional value and bioactive substances. Protein quantification was used to screen duckweed plants subjected to the 14 treatments under aquaculture conditions. Proximate analysis of three aquaculture conditions showed the highest quantification of protein. Moreover, these samples were analyzed for total phenolics, flavonoids, and chlorophylls. The optimal drying conditions for duckweed plants with the highest protein content were determined using a factorial design with three temperature and time parameters. The results showed that the duckweed under aquaculture conditions in an outdoor cement pond with hydroponic electrical conductivity (EC) of 0.5 mS/cm contained the highest protein at 41.81 ± 3.40%. Moreover, proximate analysis of this sample showed fat, fiber, moisture, ash, and carbohydrate contents of 1.99 ± 0.08%, 4.46 ± 0.71%, 3.29 ± 0.17%, 22.06 ± 0.07% and 14.12 ± 1.63%, respectively. In addition, the optimum drying conditions for this sample were 50 °C and a drying time of 6 h. Under optimum drying conditions, this sample showed total phenolics, flavonoids, and chlorophylls contents of 55.28 ± 1.35 (μg GAE/g dry weight), 159.84 ± 6.65 (μg catechin equivalent [QE]/g dry weight) and 22.91 ± 0.15 (mg/g dry weight), respectively. In conclusion, the dried duckweed under aquaculture conditions in an outdoor cement pond with hydroponic EC 0.5 mS/cm contained the highest contents of proteins, total phenolics, total flavonoids, and total chlorophyll, which could be used as functional ingredients in health food products.