OPTIMIZATION OF OXALATE EXTRACTION CONDITIONS APPLIED TO LEGUMINOUS AND CEREAL PRODUCTS USING HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

Extraction of oxalate has been found to be problematic due its formation from precursors as well as variability in extraction recovery. Exact determination of oxalate is highly important for the provision of dietary advice to subjects that are at a high risk of kidney stone formation. Present study was proposed to optimize oxalate extraction conditions including acid type, time and temperature. Cereal (wheat bran, barley bran and oat bran) and bean (red bean and white bean) samples were selected for analysis. Hot (80 degrees C) and cold acidic extraction (21 degrees C) was performed with 15 and 30 min incubation times. Total and soluble oxalate was analyzed by HPLC. Extraction of total and soluble oxalate increased at higher temperatures along with long incubation times i.e. ranging from 576 +/- 5 to 73 +/- 1 mg/100g for total oxalate and 255 +/- 2 to 75 +/- 2 mg/100 g for soluble oxalate respectively. This was attributed to generation of oxalate from its precursors at higher temperatures. Cold extraction with shorter incubation time gave reproducible values along with good recovery in the range 279 +/- 4 to 71 +/- 2 mg/100 g for total oxalate and 112 +/- 3 to 58 +/- 3 mg/100 g for soluble oxalate with recovery ranging from 95 to 99%.