Impact of Drying Methods on Physicochemical Properties, Bioactive content, and Antioxidant Activity of Opuntia ficus-indica Fruits

Background: Opuntia ficus-indica (prickly pear), is a highly nutritious fruit known for its antioxidant and medicinal properties. However, its seasonal availability and high moisture content make it perishable, necessitating preservation methods like drying. This study aimed to assess the impact of conventional drying methods on the drying kinetics and quality characteristics of both pulp and peels of prickly pear fruit. Methods: Fruits harvested in August and September 2022 were subjected two drying methods: Shade drying and Convective drying (CD) at 40 and 60 °C using a hot air oven. Physicochemical and bioactive properties were analyzed., including Total Phenolic Content (TPC) quantified via the Folin-Ciocalteu assay, and antioxidant activity measured using radical scavenging assay. Data were analyzed using XLSTAT (version 14.5.03). One-way Analysis of Variance (ANOVA) followed by Duncan test (p<0.05), and Pearson’s correlation and Principal Component Analysis for data visualization. Results: Higher drying temperatures resulted in shorter drying times and lower moisture content. Drying also significantly increased the pH, while inducing changes in Total Soluble Solids and Titratable Acidity in both pulp and peels, along with a notable color change. Peels subjected to CD at 60 °C showed the highest Total Phenolic Content and Total Betalains content, at 35.54 mg Gallic Acid Equivalents (GAE)/g dry weight and 0.991 mg/g dry weight, respectively. Flavonoid and tannin content were highest in shade-dried pulp and at 40 °C, indicating the heat sensitivity of these compounds. Minor effects on antioxidant activity (IC50) were observed in pulp during drying, compared to the peels, where the lowest IC50 with values around 2.10 mg/ml, was recorded for convective dried peels at 60°C. Conclusion: Convective drying at 60 °C proved to be the most effective methods for drying and preserving the bioactive properties of prickly pear fruit, offering a balance between drying efficiency and retention of key nutrients and antioxidants.