Effects of Various Drying Methods on Physicochemical Characteristics, Flavonoids and Polyphenol Content, and Antioxidant Activities of Different Extracts from Morinda citrifolia Fruit

Introduction: M. citrifolia is known as a medical plant in Vietnam, named Noni, which contains numerous bioactive ingredients and applying good in functional food and pharmaceuticals. The notices on the change of physicochemical characteristics (color, pH, total solids, and titration acid), the content of flavonoids and polyphenol, and antioxidant activities (total, reducing power, and 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) free radical scavenging) of different extracts from Morinda citrifolia fruit at various drying methods (solar energy, microwave, and heat pump), microwave power, and temperature have not been found. Therefore, the paper focused on these things.

Methods: Morinda citrifolia fruit were harvested in July 2020, dried by using different methods (solar energy, microwave, and heat pump), and soaked in 96% solvent (ethanol and aqueous) for evaluating physicochemical characteristics, flavonoids and polyphenol content, and antioxidant activities. Drying M. citrifolia was at the temperature (50, 60, and 70°C) and the microwave power (100, 200, 400, 600, and 800 W), corresponding to the heat pump method and the microwave method, respectively and evaluating the drying speed curve basing on the moisture of M. citrifolia according to the drying time.

Results: Physicochemical characteristics, flavonoids content, polyphenol content, and antioxidant activities (total, reducing power, and DPPH free radical scavenging) were affected by various drying methods, different extracting solvents (p<0.05) and changed the drying time, microwave power, and temperature according to the non-linear model of level 2. The stabilization of physicochemical characteristics, flavonoids content, polyphenol content, and antioxidant activities of M. citrifolia in the drying method of microwave power was the highest, followed by the heat pump and solar energy. Ethanol solvent was more effective than aqueous solvent as extracting bioactive substances (flavonoids content and polyphenol content).

Conclusion: The results will be useful for preparing the dried M. citrifolia to serve for the storage and the produce of M. citrifolia in functional food and pharmaceuticals.