The effect of different drying techniques on phytochemical content and in vitro antioxidant properties of Australian-grown prickly pears (Opuntia ficus indica)

Abstract: Prickly Pear (Opuntia ficus indica) is commonly consumed but limited by short harvesting seasons and shelf life. Drying may resolve such issues. The effects of different methods were examined to investigate the phytochemicals in Australian prickly pear (PP). White, orange and purple fruits were dried using freeze-drying, microwave, draft-oven, and dehydrator-drying (35°C, 55°C, and 75°C). Total Phenolic Content (TPC), Total Flavonol Content (TFC), Total Betalain Content (TBC), Betacyanin (BE), and Betaxanthin (IE) and antioxidant characteristics (2,2-diphenyl-1-picrylhydrazyl [DPPH], Cupric Ion Antioxidant Reducing Capacity [CUPRAC], and Ferric Reducing Antioxidant Power [FRAP]) were determined as methanolic extracts (skin/flesh). The highest content is as follows: TPC (149 ± 5.06 µg _GAE ; microwave; purple skin), TFC (76.6 ± 1.98 µg _CE ; microwave; purple-skin), TBC (4.17 ± 0.846 mg/100 g; freeze-dried; orange-skin and flesh), BE (2.29 ± 1.00 mg _BE /100 g; freeze-dried; purple-flesh), IE (3.42 ± 0.569 mg _IE /100 g; freeze-dried; purple-flesh); DPPH (224 ± 41.2 µM _TE ; freeze-dried; white-flesh), CUPRAC (2,937 ± 43.3 µM _TE ; microwave; purple-skin) and FRAP (1,377 ± 27.0 µM _TE ; microwave; purple-skin). Significant differences (p < 0.05) occurred between drying methods. When compared to freeze drying, microwaving, in some cases elicited the highest content. Practical applications: The gap between the nutrient-dense prickly pear fruit, and its consumption is prominent, particularly in Australia. This is potentially the consequences of social misconceptions, a short harvesting season and shelf life, thus potentially contributing to Australia's growing food waste challenge. Therefore, such obstacles could be reduced with the use of the most appropriate drying technique in order to extend the products shelf life. Our manuscript investigates the effect of different drying techniques on the phytochemical content of the prickly pear fruit. The investigated drying methods were considered accessible to small agricultural producers, the predominant farmers for this fruit in Australia. The findings of this paper can be potentially implemented in agricultural practice, assisting with year-round food supply and reduce on-site foods waste.