Drying Method Shapes Phenolic Retention in Cactus Cladodes

The research team collected wild cactus cladodes from a single field in Antalya, Turkey, in May, choosing medium-mature pads measuring 18 to 22 centimeters. After washing, cleaning, and removing spines, the cladodes were sliced to a uniform 5-millimeter thickness.

Convectional drying was carried out in a tray-type oven with forced-air circulation at an average airflow velocity of 0.83 meters per second, using temperatures of 50, 60, 70, and 80 degrees Celsius.

Color analysis using the CIE L*, a*, b* system revealed that total color difference from the fresh sample was highest in the ultrasound-pretreated vacuum-dried sample at 80 degrees, reaching a ΔE of 23.62. The lowest color changes appeared in microwave drying at 720 watts and convectional drying at 70 degrees.

Total phenolic content, measured by the Folin–Ciocalteu assay and expressed as milligrams of gallic acid equivalents per gram of dry matter, fell significantly after all drying processes. Fresh cladodes contained 8.85 mg GAE/g DM, while dried samples ranged from 2.16 to 5.30 mg GAE/g DM. Notably, ultrasound-pretreated vacuum drying at 60 and 70 degrees preserved more phenolics than convectional drying at the same temperatures, yielding 4.97 and 5.30 mg GAE/g DM respectively, compared with 2.75 and 3.11 mg GAE/g DM for convectional drying.

Microwave drying also outperformed convectional drying in phenolic retention, with samples dried at 720 watts reaching 4.41 mg GAE/g DM.

High-performance liquid chromatography identified nine phenolic components across the samples: eight phenolic acids—gallic, protocatechuic, syringic, ellagic, m-coumaric, caffeic, p-coumaric, and ferulic acids—and one flavonoid, chrysin. Ellagic acid dominated the fresh sample at 3.988 mg/g DM but dropped dramatically after drying, ranging from 0.150 to 0.595 mg/g DM, indicating its susceptibility to thermal and oxidative degradation.

Antioxidant capacity, measured by both DPPH and TEAC assays, decreased with drying regardless of technique, with fresh samples showing 17.42 and 54.26 μmol TE/g DM respectively. Dried samples ranged from 5.27 to 7.51 μmol TE/g DM by DPPH and 8.74 to 18.51 μmol TE/g DM by TEAC, but no significant differences emerged between drying methods or conditions.

Subject of Research: Effects of different drying methods on antioxidant compounds and physicochemical characteristics of cactus cladodes

Article Title: Valorization of Cactus Cladodes (Opuntia ficus indica): The Effects of Different Drying Methods on Antioxidant Compounds and Physicochemical Characteristics

Article References: Bağirsakci, Ş. G., Karacabey, E., & Karasu, S. (2026). Valorization of Cactus Cladodes ( Opuntia ficus indica ): The Effects of Different Drying Methods on Antioxidant Compounds and Physicochemical Characteristics. Food Science & Nutrition, 14(11), Article e72461. https://doi.org/10.1002/fsn3.72461

Image Credits: AI Generated

DOI: 10.1002/fsn3.72461

Keywords: cactus cladodes, Opuntia ficus indica, drying methods, antioxidant capacity, total phenolic content, ultrasound pretreatment, microwave drying, convectional drying, ascorbic acid, phenolic profile, food preservation, scanning electron microscopy