A SIMPLIFIED METHOD FOR MEASUREMENT OF LACTIC-ACID AND SULFUR-DIOXIDEIN CORN WET-MILLING STEEP WATER

A rapid HPLC method for measurement of lactic acid in corn wet milling steep water was developed. This technique is also suitable for simult aneous analysis of sulfur dioxide (sulfurous acid). Lactic acid and su lfur dioxide were analyzed using a Shodex Ionpak KC-811 HPLC column wi th a Waters 410 refractive index detector within 11 min. In preparing steep water for laboratory batch steeps, lactic acid from 85% syrup mu st be diluted to 10% (w/w) and heated at 95-degrees-C for 24h to obtai n free lactic acid. Steep water solubles, developed as steep time incr eases, did not interfere with the analysis. Duplicated injections (64) of steep water gave an average coefficient of variation of less than 4% between duplicates for both lactic acid and sulfur dioxide. Coeffic ients of variation for pure sulfur dioxide,and lactic acid solutions w ere less (2.2% and 0.2%, respectively). This HPLC method is rapid, pre cise, and suitable for automation.