Milk processors, cheesemakers find ways to improve shelf-life, quality

MADISON, Wis. — Extending the shelf-life of dairy products — particularly milk — has long been of interest to the dairy industry. Although the lion's share of the advancements benefit milk, new thinking also may help cheesemakers ensure higher-quality, longer-lasting products.

Most of the usage of one process which aims to extend dairy products' shelf-life — microfiltration — is happening outside the United States, mainly in Canada and Western Europe, says Mark Johnson, senior scientist, University of Wisconsin-Madison's Center for Dairy Research (CDR). Microfiltration removes upwards of 99 percent of bacteria through a filtration process driven by pressure (similar to ultrafiltration and reverse osmosis). Microfiltration not only helps in separating bacteria, it also separates out DNA, viruses and blood cells.

In addition, microfiltration is a technology that many in the dairy industry are familiar with because it can be used to clarify whey or produce whey protein isolate, says John Lucey, assistant professor in the food science department of the University of Wisconsin-Madison.

Still, U.S. fluid milk processors tend not to use microfiltration because it has not been approved by FDA as a replacement for pasteurization. Microfiltration can be used in addition to pasteurization, but it is a fairly costly process, says Tetra Pak Product Manager Brad Crooks. In addition, when it comes to using microfiltration for cheese, the butterfat must first be separated from the milk and then the skim microfiltered because butterfat is retained in the microfiltration process, Lucey points out.

That's not to say, though, that the dairy industry isn't finding uses for microfiltration of milk.

Tetra Pak offers a combination microfiltration plant and super high-temperature pasteurizer called the Bactocatch which is used by a U.S. specialty cheesemaker. Tetra Pak also offers the Tetra Therm milk microfiltration plant which it sells in Europe and Canada.

GEA Filtration, formerly known as Niro Filtration, also is working on a ceramic microfiltration system for milk which extends the shelf-life up to about 32 days, says R.J. Twiford, sales engineer, GEA Filtration.

"The fact that our microfiltered milk has almost twice the shelf-life of our regular product is a bonus for our retail customers," says Gabe Tonin of the marketing department of the Dairyland Fluid Division of Saputo Inc., which markets the microfiltered and pasteurized "Pure 'N Fresh" brand milk. "This provides for extensive retail distribution and efficient manufacturing."

A centrifugation process also is used by some to improve milk quality.

Westfalia Separator has developed a way to remove bacteria and extend shelf-life with such a process. The process can be used both to improve shelf-life of fluid milk products and to improve quality of cheese, says Markus Huellmann, market manager, dairy technology, Westfalia Separator. The primary objective of the treatment is to remove heat-resistant spores that survive the pasteurization process. This would include Clostridium tyrobutyricum which may germinate during the ripening of semi-hard and hard cheeses and cause late-blowing which creates large gas holes in cheese.

According to Huellmann, Westfalia's bacterial centrifugation process removes most microorganisms without changing the functionality of the product. The equipment consists of a centrifugal disc separator which functions much like a cream separator except that the centrifugal force removes smaller parts — including spores and somatic cells — which are heavier than milk. The loss of milk, due to Westfalia's patented recirculation system, is about 0.2 percent of the total volume, he says.

Still, both microfiltration and centrifugation to remove bacteria receive more interest in Europe and Canada than in the United States.

Huellmann, for example, notes that centrifugation is much more common in Europe than in the United States because the microbiological condition of milk is better in the United States and the refrigeration temperature is lower, helping maintain U.S. milk quality compared to that of milk in Europe.

In addition, many countries outside the United States feed their cattle more grass silage than is done in the United States and grass silage contributes to higher spore counts — another reason why microfiltration of milk is used in countries outside the United States, Lucey says.

Meanwhile, though consumers in the United States aren't really familiar with microfiltered milk, consumers in neighboring Canada are becoming much more familiar with it. It's a notable market there, if not a big one. Tonin says the market for microfiltered milk in Canada represents 7 percent of all milk (liter) purchases within retail outlets, with it being much more popular in some areas of Eastern Canada.

For example, Clement Aubin, market manager, dairy and beverages, Eastern Canada, GEA Process Technology Canada Inc., estimates microfiltered and centrifuged milk combine for a total of about 18 percent of the fluid milk market in Quebec.

"Marketing communication efforts for microfiltered milk products attempt to reach well-educated women, who are concerned with nutrition," Tonin adds. "Our experience shows that microfiltered milk sales are more highly developed in affluent urban markets."

However, just because these technologies are not commonly used in the United States doesn't mean the U.S. industry is devoid of all interest in them.

"We're always looking for longer code dates for milk," says George Muck, vice president, research and development, Dean Foods Co. "We're not developing anything specific right now, but we're always interested."

Aseptic milk — milk which is treated with an ultra-high temperature process, resulting in a shelf-stability of roughly six months — is gaining in popularity in the United States, says Kelly Luthi, aseptic plant manager, Gossner Foods.

"We're seeing more acceptance for (aseptic milk). People usually are introduced to it through emergencies, like hurricanes, or camping, and once they try it they see the benefit and use it more," Luthi says.

While there is progress being made in these areas for cheese applications, much of it still hasn't really caught on yet in the United States, according to those who use make the equipment or use it.

As it is for fluid milk, centrifugation is more commonly used in Europe for cheesemaking than it is in the United States, although there are U.S. companies that use the equipment, Huellmann says. Part of the reason is that the United States more heavily salts cheese which inhibits microbiological growth, he says.

With a relatively small amount of U.S. cheesemakers using the equipment — and considering that they generally are working with high-quality milk — one also might wonder if perhaps some of the reluctance is an issue of cost.

That, Huellmann says, is a bit of a philosophical question. If a cheese company doesn't have any problems with late-blowing, it's not cost-effective, he says. However, if it turns out that 6 million pounds of milk resulted in little usable cheese, then the equipment paid for itself in a matter of a few hours, he says.

Twiford further notes that in Canada there is some interest in using microfiltration to make raw milk cheeses.

A possible future use of microfiltration in cheesemaking would be to use it to remove all the non-starter bacteria and raw milk flora and then add back high numbers of the right adjunct bacteria with the starter culture to the "sterile milk," Lucey says, noting this could be difficult to do in an industrial setting but may provide greater control of cheese flavor development and may maintain more of the natural raw milk flavor.

However, considerations still include the necessary separation of skim and butterfat prior to the process as well as the fact that raw milk cheesemakers tend to be smaller and not as able to make large equipment investments, some industry members note.

Some believe using various technologies to extend shelf-life is one more step in the cheesemaking process that can complicate things.

"The process is much more complicated for cheese than it is for milk," says Paul Bensabat, president and CEO, Lactalis USA. Although he says he gets customer requests for extended shelf-life or aseptic cheese, "it's not such a simple thing to do."

For one thing, industry members say, the whole point of making hard cheeses is to add bacteria to milk to make different cheese flavors, so pre-treating cheesemilk is defeating. Even in soft cheeses like cottage cheese, aseptic packaging and the addition of carbon dioxide do more to extend the product's shelf-life than additional milk processing could do.

Still, oftentimes once customers have tried other extended shelf-life dairy products, they wonder if a similar product exists for cheese.

"We have a lot of customers ask, ‘The milk is great — do you do cheese as well?'" says Luthi. Gossner, which produces mostly hard cheeses, does not use aseptic processing for its cheese, although he notes that many cheese sauces are aseptically-treated.

Because hard cheeses already are a cultured product, the issue of shelf-life is not as urgent to cheesemakers as it is to fluid milk processors, says Bill Haines, vice president of business to business marketing, Dairy Management Inc. While hard cheeses are being sold, they continue to age, and Haines says "that's part of the plan."

"In hard cheese, I would think the shelf-life is OK," adds Muck.

CDR's Johnson says cheese's shelf-life can be extended by lowering the product's moisture content and controlling its pH, or by storing the cheese at near-freezing temperatures.
"Once (cheese) gets to the retailer and consumer, that's when the real problems can start," he says, adding that proper handling of cheese once it leaves the processor is the best way to protect the shelf-life of a cheese. CMN

Other top stories in this week's issue of Cheese Market News:

• U.S., New Zealand prevail in trade dispute with Canada
• Production of American-type cheese down from a year ago
• Senators introduce dairy compact bill

For more information: Cheese Market News, P.O. Box 620244, Middleton, WI 53562; Phone: 608-288-9090; FAX 608-288-9093; website: www.cheesemarketnews.com; e-mail: ksander@cheesemarketnews.com