Effect of citric acid concentrations, storage time and temperature, and steaming on antioxidant activities of Siam tulip (Curcuma alismatifolia Gagnep) flower
Siam tulip (Curcuma alismatifolia Gagnep) flowers are commonly consumed as a vegetable in many Thai dishes especially steamed flower as a side-dish for Thai dipping sauce. They have to be cooked within few days after harvesting due to dramatically physical changes. Investigation in order to prolong the shelf-life of Siam tulip flowers using citric acid was performed and antioxidant activities were evaluated. The stem of flowers was cut and covered with wet cotton wool soaking in citric acid solution with concentrations of 200, 400, 600 and 800 ppm. The one covered with cotton wool soaking in distilled water was set as the control. They were then wrapped with aluminium foil to prevent the solution evaporation. The untreated flower was set as the reference. Flowers were stored at room temperature (30°C) and in a refrigerator (4°C) for 7 days. The samples were determined for moisture content, total phenolic content (TPC) and antioxidant activities every day for a period of 7 days. For all treatments, TPC, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant power (FRAP) of Siam tulip flowers were decreasing along the storage time. Based on the above three parameters, citric acid at 600 ppm was the best choice to maintain antioxidant activities but not different from the use of 800 ppm citric acid (P>0.05). Compared to room temperature storage, storage at 4°C could retard a decrease in antioxidant activities. After steaming for 10 min, TPC and DPPH radical scavenging activity of Siam tulip flowers stored at both conditions increased about 10% while FRAP increased about 8%.
Wongsiri, S. and Duangmal, K. (2018). Effect of citric acid concentrations, storage time and temperature, and steaming on antioxidant activities of Siam tulip (Curcuma alismatifolia Gagnep) flower. Acta Hortic. 1213, 565-572
Curcuma alismatifolia Gagnep, antioxidant activities, total phenolic content, Siam tulip