Effect of the multi-stage block freeze concentration process on the physicochemical and biological properties of noni tea (Morinda citrifolia L.): a case study in Brazil to obtain a promising functional food

Morinda citrifolia, widely known as “noni”, provides fruits of which it is a raw material not only for the preparation of foods, such as beverages, but is also used, for example, in the preparation of cosmetics. However, processing the fruit results in the generation of waste, in which the leaves represent the majority. Taking into account that noni leaves are proven to hold a high amount of bioactive compounds with phytotherapeutic properties, this study proposes the application of multi-stage block freeze concentration performed through the passive thaw method with the aid of the microwave-assisted technique to promote a greater speed and efficiency in the process of concentration of the bioactive components present in Morinda citrifolia L. leaves. The effect of the cryoconcentration steps on the physical, chemical and biological characteristics of the concentrated fractions and residual ice was evaluated in order to quantitatively verify presence and content of phenolics and total solids, viscosity, antioxidant activity, and bioavailability gastrointestinal in vitro. An increase in the phenolic and total solids values was observed at the end of the process, resulting in efficiency in the retention of phenolics above 90%. High-performance liquid chromatography assay detected catechin as bioactive compound of the largest amount in the final product. The use of the microwave-assisted concentration system allowed concentrated fractions with high biological, nutritional and phytotherapic value; indicating that the technique can contribute as a reference in the use of a sustainable technology in the generation of a promising product of high biological value, since the execution and elaboration of the microwave-assisted method allows for a lower energy consumption and waste production, in addition to providing less expensive and easy-to-operate tests.