phd ana paula

Encapsulation of anthocyanic extracts obtained from residues of small fruit processing using the supercritical antisolvent technique

Author: Ana Paula Fonseca Machado

Abstract. Anthocyanins are flavonoids widely distributed in nature and are plant pigments responsible for most blue and violet colors, and almost all shades of red that appear in flowers and fruits. These pigments have attracted great interest due to their potential use as natural dyes and mainly due to their biological activities, such as antioxidant, anti-inflammatory, anticancer and antimutagenic. In addition, they exhibit great solubility in aqueous solutions. However, the introduction of anthocyanins into food and/or pharmaceuticals and cosmetics has proven to be a technological challenge, since these compounds have low stability under conditions of processing, storage and consumption. They are susceptible to degradation by factors such as light, pH, temperature, oxygen, metal ions, sulfite, ascorbic acid and enzymes. One possible way to effectively protect them would be through encapsulation/co precipitation techniques in polymer matrices. Therefore, this thesisproject had the main objective of extracting and encapsulating anthocyanins from residues generated from the processing of small red fruits using emerging and conventional techniques. For the extraction, the effect of four different techniques (ultrasonic assisted extraction (UAE), pressurized liquid extraction (PLE), combination of UAE with PLE (UAE+PLE) and Soxhlet conventional extraction) and three different solvents (hydroethanolic mixtures with 50% and 70% ethanol v/v and acidified water pH 2.0) was evaluated on the content of total monomeric anthocyanins (MA) and individual, total phenolic content (TP) and antioxidant capacity (AC) from extracts obtained from the residues of blackberry, blueberry and grumixama. For the particle formation, spray-drying (SD), freeze-drying (FD) and supercritical antisolvent (SAS) processes were applied using the polymer polyvinylpyrrolidone (PVP) as core material. A study on the effect of temperature, PVP concentration and solution flow rate under the co-precipitation of anthocyanin pigments, by SAS technique was also performed. All encapsulation assays were performed with an ethanolic extract obtained from the lyophilized and crushed blackberry residue. The produced particles were evaluated in terms of MA, AC, morphology, residual ethanol content, moisture, overall yield, anthocyanin precipitation yield, mean size and size distribution, in terms of crystalline state, thermal behavior and structural properties. It was verified that the extraction techniques PLE, UAE and, mainly, the combined method UAE+PLE using the hydroethanolic mixtures (50 and 70% ethanol v/v) are viable alternatives to the conventional Soxhlet method for the recovery of anthocyanins. Acidified water combined with the sonication process did not prove to be an interesting strategy for the recovery of polyphenols. Two, four and fourteen anthocyanins were identified by ultra-high efficiency liquid chromatography (UHPLC) in the extracts of grumixama, blackberry and blueberry, respectively. The SD, FD and SAS processes produced particles with high antioxidant capacity, without involving large degradations of these compounds, and were efficient to concentrate the anthocyanins. These processes did not influence the crystalline state, the structural properties and the thermal behavior of PVP. The presence of the polymer increases the thermal stability of the anthocyanic extract. The decrease in temperature (< 35 °C), PVP concentration (< 2%) and solution flow rate (< 2.0 mL/min), in the SAS process, contributed to the production of smaller particles, with lower content of residual ethanol, moisture, water activity and less agglomeration. The antioxidant capacity of the precipitates was strongly correlated with their anthocyanin content. The SAS process proved to be an interesting and promising option to remove the solvent from the ethanolic extract and to produce a dry material rich in anthocyanins and with greater purity.

Keywords: Pressurized liquid extraction, ultrasonic assisted extraction, anthocyanins, polyvinylpyrrolidone, supercritical antisolvent, particles.