UNSPECIFIC INCREASE IN BACTOSCAN COUNTS DURING THE STORAGE OF MILK SAMPLES

The development of Bactoscan (BSC) counts during storage was investigated in preserved supplier milk samples and in single cow samples. Most of the single cow samples were milks from cows in late lactation. In all 5 different versions of BSC chemicals were tested. In milk samples preserved with Azidiol, normally, BSC counts decrease slightly during 3 days of storage. The plate count in the same period decreased by approx. 30 %. In milk from cows in late lactation BSC counts may increase drastically during such period, caused by particles. The particles also influence the protein determination in the Milkoscan. They had different appearances. Heavy mechanical strain caused an amplification of the increase in single cases. Preservatives play an important role in the increase of BSC counts. Use of Azidiol causes a rapid increase in impulses, whereas use of the boric acid-glycerin-potassium sorbate mixture (''Ly 20'') caused none or only minor increases in the counts. The use of new chemicals and improvements in signal/noise ratio caused some reduction of the increase, but not sufficiently. The particles are dissolved in a strong alkaline EDTA-solution and by Subtilisine or Alcalase with added detergent. According to these findings, the manufacturer has developed chemicals which dissolve the particles in Bactoscan 8000. An investigation of these chemicals proved that none out of 53 milk samples with an increase in BSC II showed an increase in BSC 8000.