The extracting stage is one of the biggest origin of mistakes in determining vitamins, once those are frequently sensitive compounds and are found in small concentrations in a complex organic matrix, or in other words, foods. The extraction step developed by Catharino & Godoy to folic analysis in enriched milk consists of a very simple and quick technique, which is why it was chosen in this study to be evaluated. Response surface analysis was applied to investigation modification in concentration of folic acid in enriched milks with some changes, specially, in extraction step. Four parameters have been evaluated: sample quantity, time for extraction, volume of tricloroacetic acid (TCA) and waiting time for injection in the equipment. The pre-establish conditions for analysis of 1, 0g sample, 10 minutes in ultrasound, 350muL of tricloroacetic acid and immediate injection are parameters in a theoretical optimum average, according to the results obtained by response surface analysis, although inferior quantities of sample and larger volume of TCA (425muL) give a slightly superior quantity of folic acid.
folic acid; enriched milks; surface analysis
