Organic acids
Tartaric, malic, citric, and fumaric acids were identified and quantified using HPLC (Bushway et al., 1984). Briefly, 1 g of freeze-dried sample was mixed with 18 mL of distilled water and stirred for 15 min. Then, 0.5 mL of Carrez I solution and 0.5 mL of Carrez II solution were added and the solution again stirred for 5 min and subsequently 6 mL of distilled water added. Samples were filtered through filter paper no. 615 ¼ Ø 150 mm (Macherey-Nagel, Dueren, Germany) and the supernatant stored at -20°C. Samples were thawed at room temperature before analysis, following which samples were filtered through injection filter 0.45 μm PTFE membrane and measured using HPLC.