Use of the Direct Epifluorescent Filter Technique for predicting the keeping quality of pasteurized milk within 24 hours.

The keeping quality (KQ) of pasteurized milk stored at 5 degrees C and 11 degrees C was predicted within 24 h by pre-incubating samples and counting bacteria by the Direct Epifluorescent Filter Technique (DEFT). For samples from 5 degrees C storage, 0.03% (w/v) benzalkonium chloride and 0.002% (w/v) crystal violet (final concentration) were added to inhibit the growth of Gram positive bacteria during pre-incubation. The samples from milk stored at 11 degrees C were pre-incubated without the addition of inhibitors. After pre-incubation there was a satisfactory relationship between the DEFT count and the KQ of milks at both 5 degrees C and 11 degrees C. The DEFT count following pre-incubation correctly classified greater than 80% of pasteurized milks on the basis of KQ.