The effect of Mao varieties on oxalic acid content

Abstract

Mao, as a local fruit to Northeast of Thailand, is astringent in taste, but high in nutritional value. Nowadays, Mao is a raw material in local beverage industry. The objective of this research was to study the oxalic acid content in 14 varieties of Mao-Luang fruit. For only 1 variety of Mao fruit that has the highest amount of oxalic acid was selected to study the effect of ripening stage (pink, red and black) and 3 parts of Mao fruit (pulp, seed and juice) on oxalic acid content. More over the effect of heat on oxalic acid content was studied. Oxalic acid content was analyzed by High Performance Liquid Chromatography (HPLC). The result showed that Phuphanthong variety has the highest content of oxalic acid (67.73 mg/100 g (dry weight)). The result of further analysis in seeds, pulp and juice of Phuphanthong variety showed that their seeds had the highest content of oxalic acid followed by pulp and juice. In seeds of red Mao fruit had the highest oxalic acid (335.47 mg/100 g). For the effect of mature stage of Mao fruit found that red Mao fruit had the highest content of oxalic acid followed by pink and black Mao fruit, respectively. Considering in juice, red Mao juice had the highest oxalic acid (38.86 mg/100 g) followed by pink and black Mao juice had 30.87 and 28.28 mg/100 g of oxalic acid, respectively. After heat exposure at 90oC for 15 min, oxalic acid content was decreased. Oxalic acid content of black Mao juice was decreased by 14.82% after heat exposure.