For an apple a day to keep the doctor away, it can't harbor any bacteria. So Cornell University experts are looking at new ways of preventing E. coli from contaminating apple cider, an increasingly common public health concern.

The bacteria Escherichia coli O157:H7 has been implicated in several outbreaks, most recently in the Pacific Northwest, where 65 people have so far become sick after drinking cider made from apples contaminated with the potentially deadly bacteria.

Mark R. McLellan, Cornell associate professor of food science and director of the Cornell Institute of Food Science, and Don F. Splittstoesser, professor emeritus of food science, will be exploring alternative processing methods of apple cider to provide a good-tasting and safe product.

Apples become contaminated with E. coli when they fall to the ground where farm or wild animals roam. The fecal matter from the animals may contain the bacteria, which then may be carried by the apples into the food stream.

"It comes down to harvest and orchard management," McLellan said. "If an apple falls on the ground where there is animal fecal matter, and it is harvested from the ground, then you're inviting problems. It's best for producers not to use fruit fallen on the orchard floor."

Splittstoesser and McLellan have a two-year U.S. Department of Agriculture grant, which they believe is the only federal grant that studies this particular problem. The scientists are based at Cornell's Agricultural Experiment Station in Geneva, N.Y.

New York is home to 71 cider mills that, as recently as 1992, turned about 250 million pounds of apples per year into juice and cider.

To make cider, apples are often collected from the orchard floor, given a wash and then ground in a mill to a consistency of apple sauce, McLellan said. The mash then is pressed in a rack and frame press. Sometimes sorbic or benzoic acid may be added as preservatives, although storage at a low temperature is the principal means of retarding spoilage.

Since E. coli may be introduced by ground contact involving animal feces, McLellan suggests it is best to use apples right off the trees for apple cider.

Pasteurization is a sure-fire way to avoid the threat of E. coli. But most cider processors believe that heat treatment adversely changes the traditional flavor of their product, McLellan said, and are reluctant to pasteurize. Some studies, however, have suggested that cider flavor can be enhanced with minimal heat treatment.

"The objective of this research is to develop pasteurization processes for apple cider that will destroy the food-borne pathogen E. coli O157:H7 without adversely affecting quality of the beverage -- and that includes color, flavor and aroma," he said.

The researchers expect that a minimal heating process can be achieved with natural-style cider, preserving those characteristics. Previous research by Splittstoesser, done with Empire apple cider, shows that E. coli O157:H7 strain is heat sensitive, especially when the preservative benzoic acid is present. Researchers do not know if the type of apple has an effect during the pasteurization process.

The food scientists say that after determining the minimal process needed to eliminate E. coli, this process will be applied to ciders prepared in the experiment station's Geneva pilot plant, testing various pasteurization processes.

"Ideally these processes will duplicate the range of potential processes used by cider mills whether they are very small and use a simple heating kettle to large scale operations having tube and shell heat exchangers," McLellan said. "Sufficient quantities of cider from different apple varieties will also be prepared so that treatment effects can be assessed by taste panels.

McLellan said there is no E. coli problem with pasteurized apple juice or pasteurized apple cider. The concerns are only with fresh, unpasteurized apple cider.

"The bottom line for consumers to remember is that apple cider made from sound fresh apples harvested from the tree will make a safe, high quality apple cider," he said. "Our hope is that this research will help ensure safe ciders by giving processors methods of preparing ciders that will destroy E. coli O157:H7 without adversely affecting cider quality."