Application of membrane separation processes to purify and concentrate bioactive extracts from annatto seeds (Bixa orellana L.)

Abstract

The growing demand for natural colorants and functional compounds highlights the strategic potential of annatto (Bixa orellana L.), especially due to the presence of bixin, norbixin, and phenolic compounds. However, conventional extraction and purification methods still present limitations regarding efficiency, sustainability, and environmental impact. In this context, membrane separation processes emerge as an innovative and environmentally responsible alternative, capable of producing purer, more stable extracts with higher added value, in line with current industrial and regulatory requirements. This study aimed to investigate the application of polymeric and ceramic membranes for the purification and concentration of bioactive compounds from annatto seed extracts, with emphasis on the influence of membrane structure and material on the retention efficiency of bixin, phenolic compounds, and the associated antioxidant potential. The methodology encompassed the production of alumina-based hollow fiber ceramic membranes, subsequently characterized in terms of morphology, mechanical strength, chemical stability, and filtration performance. In parallel, experiments were conducted using polymeric membranes in a dead-end configuration, with the aim of evaluating their selectivity and retention capacity of bioactive compounds. Furthermore, the use of natural deep eutectic solvents, classified as a green alternative, was investigated for bixin extraction, with results compared to those obtained by conventional solvents, such as ethanol and water. The resulting samples were analyzed using chromatographic techniques, including high-performance liquid chromatography and mass spectrometry, enabling the precise quantification of bixin and phenolic compounds. The main results revealed that polymeric membranes with a molecular weight cut-off (MWCO) of 5 kDa were able to retain up to 90% of bixin and approximately 54.2% of phenolics compounds. The microfiltration ceramic hollow fiber membranes showed similar performance, reaching retentions close to 90% of bixin and 47,53% of phenolics compounds. The final permeate fluxes with polymeric and ceramic membranes were of 10.72 and 9,26 L h-1 m-2, respectively. Thus, both membranes were efficient for the concentration of bioactive compounds from annatto seed extracts, which reinforces the role of additional retention mechanisms in addition to the pore size exclusion. Results regarding the use of natural deep eutectic solvents confirmed not only higher extraction efficiency but also demonstrated their ability to stabilize bixin, preventing its degradation and ensuring greater preservation of bioactive properties. In these trials, the maximum yield reached 2.31% (w/w), while the ethanol:water mixture (1:1 v/v) yielded only 0.0075% (w/w) for bixin extraction. In addition to the superior performance, the extracts obtained were richer in bixin and showed greater stability compared to those produced by conventional solvents, reinforcing both the technical feasibility and the environmentally sustainable contribution of green solvents over the evaluated alternatives. It is concluded that membrane separation processes associated with natural deep eutectic solvents represent a promising route for the valorization of annatto seeds, by combining technical efficiency, sustainability, and feasibility of industrial-scale application. This study contributes to broadening the understanding of the use of clean technologies in obtaining natural colorants and bioactive compounds, providing foundations for the development of innovative processes aimed at the food, pharmaceutical, and cosmetic industries.