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UW Research Points Way To Tastier, Safer Apple Cider

Such a label would scare off many consumers, but cider makers in Wisconsin and around the nation are now required to use such a warning unless their product has been treated in a way that destroys 99.999 percent of salmonella, cryptosporidium, e-coli and other bacteria that can cause illness.

The label has been required since last fall. It was a result of several serious outbreaks of illness resulting from microbial contamination in fresh cider that caused illness and several deaths.

“The label requirement poses a dilemma for cider makers. They do not wish to make any one ill, but pasteurization equipment is very expensive and some pasteurization treatments can make cider taste like ordinary apple juice,” said Steven Ingham, a food scientist and Extension food safety specialist at UW Madison.

However, research conducted by Ingham and Ph.D. student Heidi Uljas and recently accepted for publication in the Journal of Applied and Environmental Microbiology indicates that far less expensive techniques may destroy bacteria without sacrificing the unique taste of fresh cider.

What Ingham found is that freezing and thawing kills a significant percentage of bacteria. And holding cider at a relatively warm temperature weakens the bacteria so that even more are killed during the freezing process.

“The exact treatment combination depends on the pH (tartness or sweetness) of the cider, but for all but the sweetest apples some combination of these treatments achieved the required standard,” he said. Furthermore, in taste tests at the UW-Madison, Ingham found that most people preferred the taste of cider that had been treated this way over the taste of pasteurized cider. For the very sweet ciders, Ingham found it was necessary to add an organic acid preservative to the mix, but most testers liked the flavor of these samples less than pasteurized cider.

The research is good news for the 100 or so apple growers who produce cider in Wisconsin. A pasteurizing machine can cost $15,000 to $30,000, and only the biggest producers make enough cider to make it worthwhile to take it to a dairy plant for pasteurization.

“The cost of these alternate treatments will be much lower. Small producers will need only a device to measure the pH (acidity or sweetness) of the cider, a double-walled tank and a source of heat to hold the cider at 77 to 95 degrees F, and some chest freezers.”

The research findings go against common sense about food safety procedures, ingham added. “Most people assume that you must keep things cold to keep bacteria from growing. But when you let cider stand at a higher temperature, the acid in the juice weakens the bacteria so they are more readily killed by heating or by freezing and thawing.”

Ingham and Uljas are finishing confirmatory studies and plan to develop a kind of decision tree to guide producers in selecting the right treatment for each batch of cider — depending on its pH.

The new method probably will not be approved and ready for the 1999 cider season, he added. But he expects that by autumn of the year 2000, cider producers will be able to use this option.