Effect of Roasting Temperature on Phenolic Compounds and the Antioxidant Potential of Mesquite (Prosopis juliflora) Flour

The valorization of underutilized plant-based raw materials represents a promising strategy for broadening the use of food resources and developing value-added ingredients. In this context, mesquite (Prosopis juliflora), a species adapted to semiarid regions, has potential for food applications due to its availability and the possibility of obtaining ingredients with desirable functional properties. Roasting is a thermal processing technique that can modify the chemical composition and antioxidant properties of plant materials through the release or transformation of naturally occurring compounds and the formation of products derived from thermal reactions. Therefore, this study aimed to evaluate the effects of different roasting conditions on the total phenolic and flavonoid contents and antioxidant capacity of mesquite pod flour. Mesquite pods were collected in Sumé, Paraíba, Brazil, sanitized, fragmented, and dried at 45 °C for 24 h. The dried material was used as the control or roasted in a rotating drum under 11 conditions combining temperatures from 130 to 230 °C and roasting times from 7 to 17 min. After processing, the samples were ground and homogenized. Extracts were prepared using 70% ethanol and analyzed for total phenolic content by the Folin–Ciocalteu method, flavonoids by AlCl₃ complexation, and antioxidant capacity using the oxygen radical absorbance capacity (ORAC), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. Three independent extractions were performed for each homogenized sample. Data were subjected to analysis of variance (ANOVA) and Tukey’s test at a significance level of 5% (p < 0.05). Total phenolic content ranged from 16.12 to 24.05 mg gallic acid equivalents (GAE)/g in the control and samples roasted at 130–200 °C, with no significant differences reported among these conditions. At 210, 220, and 230 °C, the values increased to 30.80, 36.92, and 41.90 mg GAE/g, respectively. In the ABTS assay, antioxidant capacity at temperatures from 200 to 230 °C ranged from 56.99 to 120.75 µmol Trolox equivalents (TE)/g. In the DPPH assay, values at 210, 220, and 230 °C were 110.36, 125.11, and 240.18 µmol TE/g, respectively. ORAC values ranged from 177 µmol TE/g in the control to 965 µmol TE/g at 230 °C. Flavonoids were not detected under the analytical conditions employed. Overall, higher-severity roasting conditions were associated with increased total phenolic content and antioxidant capacity. These changes may be related to the transformation of native compounds, the release of matrix-bound constituents, or the formation of products from thermal reactions, although these mechanisms were not directly investigated. Further research should characterize the compounds responsible for the observed responses, assess the safety of heat-derived products, and evaluate the technological performance of mesquite pod flour in food matrices. Such investigations may support its potential use as a value-added ingredient in food product development. 

Acknowledgments: CAPES - Finance Code 001