Evaluation of solar drying techniques for preserving avocado leaves (Persea americana): physicochemical and bioactive compound analysis

A mixed-mode solar dryer (direct/50% mesh shade) was used to evaluate the impact of solar drying on the physicochemical properties and bioactive compounds of avocado leaves (Persea americana var. drymifolia). Also, oven drying at 50 °C and open sun drying were performed. Fresh avocado leaves moisture was 55.6% and water activity 0.96. Color parameters were as follows: lightness (L*) 31.12, a* −7.91, b* 11.45, chroma 5.10 and hue angle 124.63°. The flavonoid content was 5.26 mg QE/g db (quercetin equivalents/g dry basis), total phenols 27.57 mg GAE/g db (gallic acid equivalents/g dry basis), ascorbic acid 62.79 mg/100 g, and antioxidant activity of 92.32%. After drying antioxidant activity remained unchanged (89.04 to 94.27% p > 0.05). Flavonoids decreased (1.04–2.71 mg QE/g db, p < 0.05), and total phenols showed an increase with the open sun, oven, and mesh shade solar drying (28.53–30.88 mg GAE/g db p < 0.05). Ascorbic acid was better preserved with mesh shade solar drying (52.71 mg/100 g). Mesh shade drying described the least color difference (ΔE = 6.98). Page model better described the drying kinetics with an R² ≥ 0.994. The study suggests that solar drying effectively preserves bioactive compounds in avocado leaves, offering an alternative for food and pharmaceutical use.