Processors are looking to extended shelf life products to meet the needs of on-the-go consumers. See how this could affect milk quality standards on your dairy.

When milk bottles were delivered each week to the consumer's back door, the distribution system was pretty simple and long-term freshness was not a major concern.

However, in 2001, things are a bit more complicated. Milk leaving the farm often travels more than 100 miles to the plant. After processing, the milk generally goes to a warehouse where an independent distributor takes the milk and stocks grocery stores, convenience stores, super centers, mass-merchandising stores, club stores, and vending machines.

As the time and distance from farm to table has increased, processors have started using extended shelf life (ESL) technology to preserve milk quality. "Extended shelf life products just give us more time to reach consumers," says Penny Baker, a marketing associate with Smith Dairy in Ohio, which produces extended shelf life products.

Just as changes in the distribution system have altered how processors do business, the use of ESL will likely change how dairy producers operate. Since it's the milk with low somatic cell counts and bacteria levels that extends product shelf life, the need for high-quality milk will increase as the use of ESL grows. While processors have yet to impose higher quality standards on producers selling to plants producing extended-shelf life products, it could be another opportunity for producers to add value to their product.

Here's what you need to know about this technology - and how raw milk quality affects it.

How do you extend shelf life?
Changes in the shelf life of dairy products are occurring in two ways, notes Kathryn Boor, microbiologist and associate professor in food science at Cornell University.

First, some processors are trying to extend the shelf life of milk, while retaining conventional pasteurization techniques. Typically, processors use the high-temperature short-term (HTST) pasteurization technique, where milk is heated to 161.6 F for 15 seconds. This provides a shelf life ranging from 14 to 28 days, depending on the quality of the raw milk prior to pasteurization, post-processing contamination and storage temperatures. Processors can extend the shelf life of HTST-pasteurized milk to four to six weeks by using high-quality raw milk, certain packaging materials and systems, or a combination of the two.

Second, some processors are switching to an ultra-pasteurization (UP) technique, where milk is heated to 280 F for at least two seconds. In most cases, the product is placed in sterile packaging designed for use with extended shelf life products. These products retain their quality for 40 to 75 days. Processors also can select (UHT) ultra-high temperature pasteurization that provides a shelf life of several months.

The switch to a UP or UHT processing system requires costly investments. Processors invest at least $1 million to purchase just one UP or UHT processing system, and the packaging materials are more expensive than conventional materials. The innovation is often applied to product lines, such as whipping creams and half-and-half, which experience low turnover at the grocery store. However, ELS fluid products are being manufactured, also.

While the definitions of these two approaches for making products last longer may seem to split hairs - one is extending the shelf life of current products and the other is specifically processed as an extended shelf life product - both need high-quality milk to aid the manufacturing process.

It begins on the farm
To extend the shelf life of products, while maintaining the HTST pasteurization technique, processors and their producers must focus on lowering the bacterial count of raw milk. High bacteria levels in raw milk degrade the milk - specifically the fat and protein - and cause spoilage.

Producers measure bacterial levels with the standard plate count (SPC), with the current law requiring on-farm SPC levels to be less than 100,000 colony-forming units (cfu) per milliliter. A random survey of 855 New York dairy farms in 1998 found the average SPC was 11,400 cfu per milliliter, although 5 percent of the farms had an SPC near the legal limit.

"The quality of milk is very important in how long it keeps," says Arthur Hansen, food scientist at North Carolina State University. In fact, Hansen's research has found that raw milk with a standard plate count (SPC) of less than 5,000 cfu per milliliter has a shelf life of 28 days, while milk with a SPC of more than 100,000 cfu per milliliter lasts just 17 days.

High bacteria levels result from not cleaning the milking system adequately, not cleaning the teats and udders of cows prior to milking, not keeping cow housing clean, and failing to cool and store milk at or below 40 F immediately after harvest.

On-farm improvement in managing bacteria levels can make a difference, says John Bruhn, director of the dairy research and information center at the University of California. For example, when California regulators began to require recording thermometers for on-farm milk storage equipment to ensure that milk was being cooled and held below 40 F, the average shelf life of fluid products improved.

Bottom line: On farm, producers must watch their standard plate counts closely. Boor says producers should set a goal for SPC levels below 10,000 cfu per milliliter.

ESL requires low SCC
When processors switch to the ultra-pasteurization technique to extend shelf life to 45 to 75 days, lowering the somatic cell count of milk becomes critical. That's because the enzymes generated by high somatic cells affect milk quality of the product after pasteurization. These enzymes break down the protein and fat in the milk, causing sour taste, rancidity and bitterness.

All types of mastitis pathogens can increase the level of these enzymes, according to research by David Barbano, food scientist at Cornell University.

In a trial reported in the February 2000 Journal of Dairy Science, Barbano infected cows with Streptococcus agalactiae, elevating their somatic cell count levels to 849,000 cells per milliliter. Their milk was processed, then compared to products made from raw milk with a SCC of 45,000. After 21 days of storage, milk with the higher SCC level had off-flavors due to the degradation of protein and fat.

Research has not yet determined the exact SCC threshold that predisposes milk to early degradation. But, the message is clear: Lower SCC levels make better-tasting milk.

More milk, more places
With consumers wanting to consume dairy products in more places, industry experts expect growth in ESL products.

As the dairy industry moves toward increased production of products with extended shelf life, the quality of raw milk becomes increasingly important to final product quality, concludes Boor. Trends influencing the move to extended shelf life products

"Processors are looking at extended shelf life products as a way to grow the business by expanding the distribution channel," says Bill Haines, vice president of business-to-business marketing at Dairy Management Inc.

In other words, dairy manufacturers are trying to sell more products in more places. And, some of these outlets will sell products less quickly than the grocery store - thereby requiring a product with a longer life span.

While dairy market watchers say the interest in extended shelf life products among processors is growing, no numbers are available to quantify it. However, changes in the distribution channels can be seen.


  • Overall sales (all products, not just dairy) in convenience stores were up 25.8 percent in 1999 when compared to 1998. In 1999, nearly $26,000 was spent on fluid milk products per store, or nearly $3 billion nationally. That's an increase of 14 percent from 1998.
  • In 1998, 85,000 vending machines dispensed $474 million worth of milk sales. While price increases caused sales to rise by 11 percent from 1988, the number of machines and the amount of milk sold has declined. However, check-off-driven research may boost the number of machines in the next few years.
  • According to AC Nielsen data, super centers, mass merchandisers and wholesale clubs saw their share of milk sales increase in 1999, as compared to 1998.