Jenifer Palma

Bitter orange peel (Citrus aurantium L.) is an abundant agro-industrial by-product and a promising source of natural bioactive compounds for high-value applications. This study comprehensively characterized freeze-dried bitter orange peel (BOP) and evaluated microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) for the recovery of antioxidant compounds. The freeze-dried powder exhibited low moisture content and suitable physicochemical, technological, and functional properties, supporting its use as a stable raw material for further valorization. Its chemical characterization revealed the presence of vitamin C, phenolic compounds, and carotenoids, including 0.40 mg/g DW of vitamin C and 4.31 mg/g DW of total carotenoids. Randomized full factorial designs were used to evaluate the effects of solvent type, extraction time, and microwave power or acoustic intensity on extraction yield, vitamin C recovery, total phenolic compounds (TPC), and antioxidant activity (TEAC). Solvent type was the most influential factor in both extraction processes, whereas extraction time and energy input exerted response-dependent effects. Among the experimentally evaluated MAE conditions, ethanol at 100 W for 30 s produced the highest TPC (514.38 ± 15.85 mg GAE/g extract) and the second-highest TEAC value (597.75 ± 2.40 µmol TE/g extract). For UAE, ethanol at 92 W/cm² for 5 min provided the highest TPC (760.05 ± 81.06 mg GAE/g extract) and TEAC (513.11 ± 9.18 µmol TE/g extract), although aqueous extraction resulted in higher extraction yields. Confocal laser scanning microscopy (CLSM) revealed a greater reduction in residual green autofluorescence after UAE than after MAE, providing complementary qualitative evidence of a more extensive removal of naturally fluorescent constituents from the plant matrix. In summary, freeze-dried BOP represents a promising raw material for bioactive compound recovery, while MAE and UAE provide rapid extraction approaches whose environmental performance should be further assessed using quantitative sustainability metrics. The resulting extracts warrant further investigation for potential food, nutraceutical, cosmetic, and pharmaceutical applications.

Cauliflower by-products represent a valuable source of bioactive compounds that can be valorized as functional ingredients within circular food systems; however, their stability is strongly influenced by processing conditions. This study evaluated the combined effects of plant section (leaves and stems) and drying method (freeze-drying, hot-air drying at 40 °C and solar drying at approximately 30–45 °C) on the nutritional composition, pigment content, antioxidant activity and colour of cauliflower by-product flours. Proximate composition, chlorophylls, carotenoids, total polyphenols, total flavonoids, glucosinolates, sulforaphane and antioxidant activity (ABTS and DPPH assays) were determined, and colour was assessed using CIELAB parameters (L*, a*, b*, chroma, hue angle and browning index). Freeze-drying showed the highest preservation of pigments, phenolic compounds, sulforaphane and antioxidant activity, followed by hot-air drying, while solar drying resulted in the lowest retention. Leaf-derived flours consistently presented higher pigment and phenolic contents and more favorable colour attributes than stem-derived flours. Antioxidant activity was strongly associated with matrices richer in pigments and phenolics. Although leaves exhibited higher glucosinolate contents, sulforaphane levels showed only minor differences between plant sections, suggesting that stem-derived fractions may also represent a valuable raw material considering their greater biomass availability and industrial scalability. Overall, these findings demonstrate that both plant section and drying method significantly influence the techno-functional quality of cauliflower by-product flours and should be jointly considered to optimize the development of stable, functional and sustainable food ingredients.

Parastrephia quadrangularis (tola) is a native plant of the Chilean Andean Altiplano that is traditionally used for its anti-inflammatory properties. In this study, the aerial parts of the plant were analysed to determine their fatty acid (FA) profile and to identify bioactive compounds using gas chromatography–mass spectrometry (GC–MS). Both conventional extraction methods and Supercritical Fluid Extraction (SFE) were employed, using a 2³ factorial design with centre-point replicates. The variables included temperature (30–60 °C), pressure (15–45 MPa), and ethanol as a cosolvent (0–30% v/v). Extraction kinetics were evaluated using a linear spline model under central conditions (45 °C, 30 MPa, 15% ethanol). Response variables included extraction yield, Total Phenolic Content (TPC), antioxidant activity measured by Trolox Equivalent Antioxidant Capacity (TEAC), and FA composition. A factorial design identified pressure and ethanol concentration as key drivers of phenolic content and antioxidant activity, as supported by confocal autofluorescence microscopy. Multi-response optimisation based on the desirability function was applied to simultaneously maximise all response variables, yielding predicted optimal extraction conditions at 60 °C, 45 MPa, and 30% v/v ethanol for P. quadrangularis. The FA profile highlighted polyunsaturated FAs such as oleic, linoleic, and linolenic acids, as well as saturated FAs including palmitic and lignoceric acids, and short-chain non-volatile FAs. GC–MS analysis revealed metabolites potentially responsible for the plant’s traditionally reported therapeutic effects. Overall, these results highlight ethanol-based SFE as a sustainable strategy for recovering phenolic compounds and antioxidant-related fractions from ancestral medicinal plants.

Haematococcus pluvialis is the largest producer of natural astaxanthin in the world. Astaxanthin is a bioactive compound used in food, feed, nutraceutics, and cosmetics. In this study, astaxanthin extraction from H. pluvialis by supercritical fluid extraction was evaluated. The effects of temperature (40 and 50 °C), pressure (40 and 50 MPa), and CO₂ flow rate (2 and 4 L/min) were investigated. The results showed that the highest astaxanthin recovery was obtained at 50 °C/50 MPa and the CO₂ flow rates evaluated had no significant effect. It was possible to achieve astaxanthin recoveries of 95% after 175 min for a CO₂ flow rate of 2 L/min, and 95 min for CO₂ flow rate of 4 L/min. The ω-6/ω-3 ratios obtained were similar in all conditions, reaching 0.87, demonstrating that the extracts from H. pluvialis by SFE are rich in unsaturated fatty acids (UFA) which increases their positive effects when used as a functional ingredient in food.

Astaxanthin is a powerful antioxidant, because it neutralizes free radicals and plays a vital role in the prevention of human diseases. The objective of this work was to develop an isotonic beverage (IB) of orange-red color, using an astaxanthin oleoresin emulsion (AOE) that is dispersible in water. This was carried out in order to simulate the color of commercial isotonic beverages (CIB) prepared from artificial pigments. The size of the AOE micelles ranged from 0.15 to 7.60 µm². The color difference (ΔE) was similar for the samples exposed to dark as well as light conditions. The samples subjected to light stress showed pigment degradation after seven days, followed by a decrease in the concentration of astaxanthin; whereas, the samples exposed to dark conditions remained stable for seven days and then showed a decrease in the concentration of astaxanthin (this decrease ranged from 65% to 76% when compared to the initial content) after a period of 91 days. For the astaxanthin oleoresin (AO) and AOE, the oxygen radical absorbance capacity (ORAC) values reached 5224 and 1968 µmol of trolox equivalents (TE)/100 g, respectively. When exposed to light conditions, the addition of AOE in the IB led to its rapid degradation, while it remained stable in the samples exposed to the dark conditions.

Haematococcus pluvialis is known to be a natural source of antioxidants for numerous applications. In this study, an oleoresin rich in carotenoids extracted by supercritical CO₂ treatment of H. pluvialis was extensively characterized for its antioxidant capacity. Carotenoid content, fatty acid profile, total phenol content, antioxidant capacity, and viscosity of the oleoresin were determined with the aim of ascertaining the potential of the oleoresin in terms of its antioxidant content for food applications. The oleoresin contained 96.22 mg/g of total astaxanthin (which includes free astaxanthin and astaxanthin esters) and mostly included unsaturated fatty acids (~78% of total fatty acids). High total phenol content and ferric reducing antioxidant potential indicated high antioxidant capacity, but oxygen radical absorbance capacity was lower compared to the oleoresin samples obtained from other species. The oleoresin was a non-Newtonian fluid since it had shear-thinning (pseudoplastic) and shear-thickening (dilatant) flow. Therefore, the H. pluvialis oleoresin is a potential alternative in developing functional ingredients for designing healthy food products. To the best of our knowledge, this is the first study that has reported an extensive characterization of the antioxidant properties of a microalgal oleoresin obtained by means of supercritical CO₂ fluid extraction.