In previous QualiTru Newsletters we discussed the difficulty of obtaining an accurate raw milk sample from tanker trucks by conventional sampling methods. QualiTru Newsletters also have pointed out how unrepresentative samples can cause economic hardship for processing plants.
QualiTru is developing an alternative method of milk truck sampling, a portable peristaltic pump. With the use of the QualiTru aseptic Single Sampler and portable pump, along with a QualiTru composite Sampling Bag, a sample can be obtained as the truck is unloaded. This sampling method is aseptic because the peristaltic pump utilizes sterile tubing, safe because the operator remains on the ground and accurate because it samples the entire tanker volume of milk.
QualiTru, in cooperation with Turkey Hill Dairy conducted a bulk milk tanker truck sampling and un- loading study. Turkey Hill is a full line dairy processor located in Lancaster County, Pennsylvania.
The study compared three quality measurements. The first compared butterfat content.
The second compared apparent bacterial measurement: preliminary incubation (PI), laboratory pas- teurization count (LP), and coliform and E. coli counts.
The third compared the remaining components of the sample: total solids, true protein, cryoscope and somatic cells. The second and third areas will be discussed in future QualiTru Newsletters.
The sampling locations were:
- Farm bulk tanks sampled by the milk hauler
- The milk tanker sampled by the milk hauler immediately after the last producer was loaded on the tanker
- The milk tanker sampled by conventional dip methods at the dairy plant
- The milk tanker sampled using the QualiTru System as the truck was unloaded at the dairy plant
There were 158 loads in the butterfat comparison study. The loads represented milk from one to seven producers. The loads were assembled over a span of one to six hours. Delivery times to the Turkey Hill plant ranged from one half hour to nineteen and a half hours after pickup. The longest delivery time was what the industry would call a hold – over load: loaded on one day but not delivered to the plant until the next day.
The overall QualiTru results on butterfat were the closest to the weighted average of the producers on the loads when compared to the bulk milk tanker driver or the milk plant receiver overall results.
Some loads showed higher receiver results, mainly due to loads being on the tanker for hours before deliv- ery. Milk will stratify when it remains on the tanker, especially during hold overs.
The producer sample test results on some of the other loads were higher than the weighted average. The receiver and the QualiTru sample test results correlated very closely. This could be an indication of too short an agitation time at the farm bulk tank.
Regarding the hold over loads, the driver and QualiTru sample compared well with the weighted average. The plant receiver sample showed considerably higher butterfat, even into the 6% range.
The drug residue tests that have been approved to screen the incoming loads are only approved for a sam- ple of 6% or below. This number is stated on most drug kits. If you are sampling hold over loads without agitating or making sure a representative sample is obtained for testing (as stated in NCIMS and PMO in- structions) you will be testing the load in an unapproved manner.