Impact of various preservation methods on the antioxidant profile and stress biomarkers of tomato (Solanum Lycopersicum)

Tomatoes (Solanum lycopersicum) are vital sources of dietary antioxidants, but their post-harvest shelf-life is limited by rapid physiological degradation. Identifying preservation techniques that maintain the biochemical integrity of the fruit is essential for reducing food waste and retaining nutritional value. This study evaluated the impact of five preservation techniques; freezing, shade drying, microwave drying, hot air drying, and sun drying on the antioxidant capacity, glutathione homeostasis, and enzymatic defense systems of tomato fruit. Fresh tomatoes (control) and preserved samples were analyzed for total antioxidant capacity (TAC), lipid peroxidation markers; malondialdehyde (MDA) and 4-hydroxynonenal (4-HNN), reduced and oxidized glutathione (GSH and GSSG), levels and the activity of key antioxidant enzymes, including Catalase (CAT), Superoxide Dismutase (SOD), Glutathione Reductase (GR), and Glutathione Peroxidase (GP). Preservation led to a progressive decline in antioxidant capacity, with IC50 values increasing from 13.49 g/mL in fresh samples to 25.81 g/mL in sun-dried samples. Freezing was the most effective method, maintaining GSH levels (63.52 g/g) and oxidative stress markers MDA and 4-HNN (2.14 and 1.02 g/g) closest to fresh control values (p>0.05). Conversely, thermal dehydration methods particularly sun drying, induced significant oxidative stress (p<0.05), evidenced by a 95% increase in MDA (4.02 g/g) and a sharp rise in 4-HNN and GSSG. The GSH/GSSG ratio, a critical indicator of cellular redox status, plummeted from 8.95 in fresh samples to 2.27 in sun-dried samples. Furthermore, enzymatic activities (CAT, SOD, GR, and GP) showed significant depletion across all drying methods, with sun drying exhibiting the lowest residual activity. Our findings showed that freezing is superior for preserving the biochemical and antioxidant integrity of tomatoes. While drying methods extend shelf-life, they significantly compromise the enzymatic defense system and increase lipid peroxidation, with sun drying being the most detrimental to the fruit’s nutritional quality.