Somatic cell count (SCC), bacteria count and antibiotic or chemical residues are some factors that determine milk quality. Generally speaking, high quality raw milk is free of all antibiotic or chemical residues and low in SCC (less than 200,000) and bacteria counts (less than 5,000). These should be the goal of every dairy producer.

But we still have a long way to go. Most other milk-producing countries in Europe, as well as Australia and New Zealand, already have national BTSCC averages near 200,000 or less. The 2005 U.S. average DHI SCC was 296,000.

Why does raw milk quality matter?
Milk quality is different than milk safety. All milk for human consumption must meet the minimum safety standards of 750,000 SCC and under 100,000 bacteria counts with no antibiotic or chemical residues. Public demand for improvement in milk quality beyond current milk safety standards is on the upswing. Why? For 25 years dairy processors have recognized that high SCC significantly reduced cheese yields. Therefore, to encourage production of low SCC, raw milk Midwestern dairy processors have been paying quality premiums since 1979. The current spread between deducts for BTSCC over 300,000 and the highest quality incentives for milk less than 100,000 can be up to $3 per hundredweight of milk. This is a strong monetary incentive for producers to work on milk quality.

More recently, it has been recognized that raw milk quality has a dramatic effect on fluid milk taste and shelf life. The presence of high levels of SCC, bacteria or both will result in activating lipolytic and proteolytic enzymes that breakdown milk fat and protein resulting in off flavors and shorter shelf life. Since these enzymes are heat stable and not completely inactivated by pasteurization, milk protein and fat degradation continues even in refrigerated pasteurized products. Today, pasteurized and properly refrigerated fluid milk has a dependable shelf life of approximately three weeks, beyond which undesirable off flavors may be detected.

Dr. Dave Barbano and a team of Cornell researchers recently reported it is possible to extend pasteurized fluid milk shelf life significantly by lowering SCC in milk. These researchers compared the difference in shelf life between very low (25,000) and high SCC milk (340,000). In their study, the 2 percent pasteurized low SCC milk was free of rancid (fat degradation) off flavor for 48 days longer than the high SCC milk. There was also a 25-day shelf life advantage in the appearance of bitter and astringent (protein degradation) off flavors in the low SCC milk.

In addition, they tested the effect of storage temperature. Detection of off flavors in the high SCC milk (340,000) stored at 43°F occurred at 28 days but was delayed until 55 days when stored at 33°F. The very low SCC (25,000) milk showed no signs of flavor deterioration at either storage temperature.

Why is longer shelf life necessary today?
Trends in the current consolidation of the grocery and dairy processing business are resulting in longer food distribution chains. Food is being produced and processed longer distances from consumers. This means in order for future dairy products to remain “fresh” and acceptable to consumers, products with a longer shelf life will be required.

What will it take for us to reach future shelf life goals?
Researchers currently speculate that with introduction of ultra filtration technology and improved refrigeration, as well as a reduction of average SCC at the farm to 100,000, it will be possible to achieve pasteurized fluid milk with a shelf life of 60 to 90 days in the future. Some of you may wonder, “is consistent production of raw milk with SCC of 100,000 possible?” Many dairies are already achieving this level of performance.

What’s the bottom line?
If we are serious about increasing milk sales against competing beverages or about opening new marketing opportunities, we must increase the shelf life of fluid milk. That’s a fact.

How do we do it?
You’ve heard all this before. Make sure teat surfaces are thoroughly and consistently cleaned before each milking. Keep teat surfaces clean between milkings. Be sure that milking equipment is consistently clean, sanitized and operating correctly. Then consistently store milk at less than 40°F.

Notice that I have emphasized the word consistency. Many of you do follow these practices most of the time, but quality milk depends on applying good management practices every day. If other dairy producing countries can produce milk with less than 200,000 SCC, we in the United States can do it too.  PD

References omitted due to space but are available upon request.

—From University of Minnesota Dairy Connections website

Jeffrey K. Reneau, Professor of Dairy Management, University of Minnesota