You could use existing HPLC equipments. Most labs have versatile organic acid detection columns like the Phenomenex ROA column, or the Hi-Plex H.

Or use the spectrophotometric method outlined here

www.jbc.org/content/138/2/535.full.pdf

Also, check out this method which measure

Lactic Acid Dehydrogenase Activity

Good luck

I think titration with NaOH (probably 0.1N) will do , there is standard methods in book dealing with Dairy microbiology OR Dairy chemistry ,book like"Pearson's chemical analysis of foods" cab be helpful

Thanks Dr. Carole, Its really a nice paper!

Thank you Dr. Carole. Even I was looking for a reference on the same topic.

I used HPLC

http://www.emergentresearch.org/uploads/38/3151_pdf.pdf