I spiked in 4-8 log CFU/ml of Lactococcus lactis into milk, and use DNeasy Powered Food Kit to extract DNA from it. Nanodrop 2000 was used to determine the values. The yield and quality are weird: the concentration of DNA was only 0.5-1.6 ng/ul, and 260/230 is 0.11 to 0.58. Both I and the lab assistants got similar results. We followed exactly the manufacturer's protocol.