Hygroscopic behavior of noni leaf powder (Morinda citrifolia L.) obtained by drying in foam layer

Abstract

Studies on the ethnicbotanical aspect and properties of noni (Morinda citrifolia L.) reveal that noni leaves contain chemical compounds that are related to antibacterial, antioxidant, antiviral, antifungal, antitumor, anthelmintic, analgesic, inflammatory, hypotensive and immunostimulating, among these compounds are, for example, flavanoid glycosides. The drying process is, in turn, used as a way of preserving perishable products, such as plants, due to the removal of water available for microbial deterioration, keeping the properties of the material preserved. For proper storage and increasing the shelf life of the powder obtained after the drying process, it is important to know the adsorption isotherms. This study aims to survey the adsorption isotherms of powders obtained from noni leaves. The powders to be analyzed were obtained through the foam layer drying process in the maximum, minimum and central factorials of the complete experimental planning of previously carried out studies. For the mathematical adjustment of the obtained isotherms, three different mathematical models from the literature were tested, based on experimental moisture adsorption data, for non-linear regression analysis, using the Gauss-Newton and Levenberg-Marquardt methods. The isosteric heat of the powders was also calculated to understand the behavior of the adsorbed phase with temperature variation, in addition to the affinity between adsorbate and adsorbent. The noni leaf powder showed high hygroscopicity, ranging from 0.098 to 0.969 and the Oswin model was the one that best represented empirical adjustments describing the process. The isotherms were classified as Brunauer Type III. It was also possible to infer that the energy required to remove water present in the noni leaf powder decreases with increasing equilibrium humidity.