Methods

ISI 12-1e Determination of Acidity 1. Scope The method is applicable to starch milk and hydrolysates   LT 12. Dec. 1966 Rev. LT 16. Dec. 1997 2. Principle Titration with NaOH to pH 8.3.   3. Apparatus 3.1 Burette 3.2 pH meter 3.3 Volumetric flask 50 ml   4. Reagents 4.1 Sodium hydroxide 0.1 N 4.2 Phenolphtalein: 1 g in 1 l ethanol 90%   5. Procedure Fill volumetric flask (3.3) with liquid sample. Transfer to 300 ml conical flask. Titration  Add 1 ml (4.2) and titrate with (4.1) to faint persistent pink  or use pH meter to 8.3 V = ml (4.2). N = normality of (4.2)   6. Calculation Calculate acidity as normality N of sample by averaging results of two samples with one decimal. N = N V / 50   7. Notes J. Assoc. Off. Anal. Chem. 66 (1983) no. 6, 1395-1399 recommend pH 6.0 as end point, but AOAC limits this method to HFCS. Ph. EUR 4ed acidity test for starch.  Add 10 g sample to 100 ml of alcohol (70 per cent V/V) R previously neutralised to 0.5 ml of phenolphthalein solution R and shake fo