The Utilization of Salt water on Reducing Oxalic Acid in Konjac (Amorphophallus muelleri Blume) Flour as a Hydrocolloid Source

Abstract

Konjac flour is a product from konjac tubers which glucomannan as the main composition. Konjac glucomannan has high potential to applied in food, pharmaceutical and chemical industry. Glucomannan is a water-soluble dietary fibers that is strong hydrocolloid and low in calories. In China and Japan konjac glucomannan used as food ingredients which acts as gelling agent, thickener, emulsifier and stabilizer. However, konjac flour as glucomannan source has special challenges related to food safety due to the presence of oxalic acid. In this study, we discover a method to reduce the oxalic acid regarding to produce a safer konjac flour. There were four samples to be analyzed. There were two different methods of immersed processed of konjac chips followed by two kinds of drying method which direct and indirect sun drying method. The konjac chips were immersed in 6% salt water for three days with no change and change the water in each 24 h. The result showed that the different immersed processed and different drying method have significant effect on oxalic acid content of konjac flour. Konjac chips with no immersed treatment has 0.31 ± 0.02^a % oxalic acid. Konjac chips immersed in 6% salt water with changed water in each 24h during three days followed by indirect sun drying method has the lowest oxalic acid of 0.20 ± 0.01^c % with the highest reducing oxalic acid of 35.5%. Therefore, the immersed processed combined with indirect sun drying method are suggest to reduce the oxalic acid content in konjac flour.

 Keywords:   Glucomannan, immersed, konjac flour, salt water, sun drying method, oxalic acid.