Effects of Cooking and Drying on the Nutritional, Bioactive, Antioxidant, and Technological Properties of Purslane (Portulaca oleracea) Flour

In Brazil, Portulaca oleracea (purslane) is considered an unconventional food plant. It is rich in bioactive compounds, α-linolenic acid (ALA), and oxalate. Producing flour from purslane may reduce perishability, concentrate nutritional and bioactive constituents, and expand its use as a functional ingredient. However, it may also concentrate antinutritional factors such as oxalate. This study characterized purslane flours obtained with and without a preliminary cooking step, evaluating nutritional composition, fatty acid (FA) profile, bioactive compounds, antioxidant capacity, oxalic acid content, and technological properties. Aerial parts were used to obtain flour without cooking (FBN) and flour after cooking at 100 °C for 15 min (FBC), both followed by drying at 60 °C for 24 h. Fresh purslane (BN) served as the reference. Proximate composition was determined, and the FA profile was analyzed by gas chromatography–mass spectrometry (GC-MS). Total phenolic content (TPC), total flavonoid content (TFC), FRAP, ABTS, DPPH, β-carotene, oxalic acid, water activity (Aw), and instrumental color were evaluated. Data were analyzed using one-way ANOVA and an unpaired Student’s t-test at a 95% confidence level (p < 0.05). Drying reduced moisture content from 92.45 ± 1.42% in BN to 6.77 ± 1.55% in FBN and 6.38 ± 2.82% in FBC, thereby concentrating dry matter components. ALA content increased from 29.20 ± 4.03% in BN to 42.81 ± 1.91% in FBN and 47.70 ± 1.02% in FBC. On a dry matter basis, BN exhibited the highest TPC, TFC, and ABTS activity, whereas FBN showed the highest FRAP and β-carotene content. FBC generally displayed the lowest values, except for TFC, which did not differ significantly from FBN. In contrast, on a fresh-weight basis, both flours showed higher TPC, TFC, FRAP, DPPH, and ABTS values than BN, particularly FBN, indicating that water removal concentrated the retained bioactive compounds. Oxalic acid content decreased from 8.86 ± 2.30% in BN to 4.49 ± 0.24% in FBC. FBN did not differ significantly from either group, whereas FBC showed the greatest reduction relative to BN, indicating greater effectiveness of cooking, possibly due to leaching. Both flours exhibited Aw < 0.60, indicating low water availability and conditions limiting microbial growth. Cooking also caused a perceptible color change (ΔE* = 7.26), with a shift toward reddish tones. Overall, drying concentrated nutritional components and ALA, while cooking was more effective in reducing oxalic acid but resulted in greater losses of certain bioactive compounds. These results indicate that purslane flour has potential as a functional ingredient, although processing conditions should be optimized to balance oxalate reduction with the retention of bioactive compounds. Acknowledgments: FAPES – PROFIX 2024 (N^o. 12/2024) and FAPES Universal (N^o. 13/2025), Project N^o. 1512/2025; and the Multi-user Chromatography Laboratory/LabPetro (LCG/LabPetro-UFES, Brazil) (Technical Cooperation Agreements 0050.0022844.06.4, UFES/PETROBRAS and PRPPG-UFES).