Line sampling has been effectively used for a number of years by dairy processors as a method of identifying sources of contamination. Samples from HTST (High-Temperature Short-Time), product storage tanks and lines prior to the fillers have been routinely analyzed. However accurate testing of HTST samples has been difficult because of small sample size, sampling timing and low oxygen levels in the milk. A composite sampling bag, incorporated into the QualiTru aseptic sampling system, has proven to be effective. This sterile bag has tubing and a needle attached which allows a sample to be taken over a 5-10 minute time period.

Contamination can occur when the HTST system goes through the clarifier desludge mode. At this time, pressure changes occur which can result in contamination. Therefore, samples should be taken a few minutes before the clarifier desludges until a few minutes after it desludges. Procedures require that two samples be taken. One to determine gram-negative bacteria using a test such as the dairy stress test. Since the growth of gram-negative bacteria is very oxygen sensitive, it is suggested to add air (headspace) to the samples. A second sample must be taken and treated the same as a 7-day keeping quality test (7-days at 7OC, followed by plating on SPC media).

The QualiTru composite sampling system also allows dairy farmers to obtain contamination-free samples, resulting in accurate bacterial counts. Precise composite sampling aids in mastitis control and accurate composite samples of cow groups.