Method for removing antinutrient from turmeric spice
The present invention provides a method for removing antinutrients from turmeric spice. The antinutrient such as oxalic acid is removed by using the method of present invention and thus the toxicity associated with it is also eliminated. The method includes preparing the turmeric powder and repetitively extracting the turmeric powder with inorganic acid. The turmeric powder is stirred in a pre-defined volume and pre-determined concentration of the inorganic acid for pre-defined time with constant agitation at pre-determined temperature to obtain a turmeric paste. The turmeric paste is then washed with water and dried to obtain the purified turmeric powder.
1 . A method for removing oxalic acid from turmeric spice, the method comprising:
(a) preparing a turmeric powder from a turmeric rhizome;
(b) extracting the turmeric powder with an inorganic acid of 1 Normal (N) concentration, wherein the extraction comprises stirring the turmeric powder in 8 liters of the inorganic acid for 3 hours with constant agitation at 40° C. to 50° C. to obtain a first stirred solution;
(c) filtering the first stirred solution to obtain a first turmeric paste;
(d) extracting the first turmeric paste with the inorganic acid of 1 Normal (N) concentration, wherein the extraction comprises stirring the turmeric paste in 4 liters of the inorganic acid for 3 hours with constant agitation at 40° C. to 50° C. to obtain a second stirred solution;
(e) filtering the second stirred solution to obtain a second turmeric paste;
(f) washing the second turmeric paste with a distilled water to obtain a washed turmeric paste, whereby residual chloride content is removed;
(g) drying the washed turmeric paste at room temperature and measuring a moisture content of the dried turmeric powder to obtain a dried turmeric powder with a moisture content below 2%; and
(h) analyzing a content of the oxalic acid content of the dried turmeric powder;
wherein the content of the oxalic acid is gradually reduced after each of steps (b) and (d);
wherein a total content of the oxalic acid is below 100 ppm; and
wherein the curcuminoids in the dried turmeric powder are not degraded.
2 . The method according to claim 1 , wherein in step (a) the turmeric powder is obtained by grinding the rhizome to make a powder and passed 100% through #100 mesh.
3 . The method according to claim 1 , wherein the temperature of the distilled water is between room temperature and 50° C.
4 . The method according to claim 1 , wherein the inorganic acid is selected from a group consisting of hydrochloric acid (HCl) and sulfuric acid (H 2 SO 4 ).
5 . The method according to claim 1 , wherein the inorganic acid is hydrochloric acid (HCl).
6 . The method according to claim 1 , wherein a ratio of the turmeric powder to the inorganic acid is between 1:8 and 1:4.
7 . The method according to claim 1 , wherein in step (h) analyzing the content of the oxalic acid is carried out using a chromatography technique.
8 . The method according to claim 1 , wherein in step (f) washing the second turmeric paste with the distilled water for removing the residual chloride content is repeated until a clear filtrate is obtained.