So it is no wonder that end users are pressing the rest of the dairy supply chain to come up with more effective quality management systems.
Just as problematic, there seems to be a shift in the types of defects that are showing up. Traditional spoilage occurred with fluid milk at less than 10 days on the shelf and could typically be traced back to Gram-negative bacteria. Now it is much more common for spoilage issues to occur at greater than 14 days on the shelf and caused by Gram-positive spore-formers.
Gram-positive spore-formers are typically bacillus- and clostridial-type organisms. While these are some of the most common types of organisms we see in the environment, we frankly don't know as much as we need to know about the ways in which they impact the milk supply chain and shelf life. But we are learning that they are causing significant problems.
The current tests that we run to determine raw milk quality do not correlate well to the actual quality levels of the finished milk product. In some cases, this is probably due to the fact that the problem originates after the milk leaves the farm.
However, there is growing evidence that the types of screening we use, including lab pasteurized counts, might not actually be measuring the types of bugs that are involved.
There is also growing concern that even low levels of these bugs present in raw milk may be more significant than we think. There are several potential reasons for this:
- First, the volumes of milk shipped from any one dairy tend to be greater now than in the past. This means the ability of bacteria to affect commingled milk at the plant is increased.
- Second, milk tends to travel farther from farm to processor. This makes the initial bacteria levels in the milk more critical and puts more pressure on the transport system to perform efficiently.
- Third, longer run times at processing as well as higher pasteurization temperatures may in fact favor these types of bugs.
I am convinced that Gram-positive spore-forming bacteria is rapidly becoming one of the most significant milk-quality issues in the industry. Those of us at the cow level will be expected to do our part to help better define the problem and then solve it.
Stay tuned for the science to evolve and solutions to emerge.
- Click on the a title below to view presentation on shelf-life research and other efforts:
- Dairy Farm Processes to Address Spores by Mark Wustenberg, DVM ,VP Quality Assurance & Member Services Tillamook County Creamery Association.
- Current research in North America by Kathryn Boor, Ph.D. Food Science Department Cornell University
- Special Considerations for Spores in Cultured and Processed Dairy Products by Kathleen Glass, Ph.D. Food Research Institute University of Wisconsin-Madison
- A Changing Industry by Ray McCoy, Dean foods.
- Follow this link to read the Journal of Dairy Science paper on " Tracking Heat-Resistant, Cold-Thriving Fluid Milk Spoilage Bacteria from Farm to Packaged Product."
- Follow this link to read the Journal of Dairy Science paper on "Tracking Spore-Forming Bacterial Contaminants in Fluid Milk-Processing Systems."