When a child in California died after drinking apple cider tainted by E. coli O157:H7 bacteria, it sent shock waves through the nation’s apple cider industry. Suddenly, a food-safety issue was threatening to derail the entire industry.
Virginia producers turned to Susan Sumner, faculty member in food science and technology at Virginia Tech, and graduate student Jim Wright. The challenge was to develop a method that could be used by cider producers to eliminate E. coli O157:H7 from their product, and to do it before the start of another cider season.
Although he hadn’t met this particular bacteria, the task was not on-the-job training for Wright. He has a bachelor’s degree in biology from Indiana University of Pennsylvania and worked four years as a microbiologist with the U.S. Department of Commerce’s national seafood laboratory in Mississippi, where his job was to find traces of microbes in seafood before consumers were exposed.
Apple cider is essentially the juice created when apples are crushed. The unprocessed juice is refrigerated and quickly sold. Its high acidity was thought to prevent harmful organisms from surviving in it. Apple juice, on the other hand, is pasteurized or otherwise processed to ensure there are no organisms present that could pose a health risk. Pasteurization of cider, producers feared, would eliminate the distinction between cider and juice, thereby destroying the very thing that makes cider a unique product.
“Cider producers in Virginia are generally small producers,” Sumner says. “Some of the larger companies nationally are looking at flash pasteurization (quickly heating, then cooling, the product), which involves large equipment costs and really requires a large volume of production to make it practical.”
Though Virginia apple growers produce an estimated 1 million gallons of cider yearly, there are no large, dominant cider producers in the state. The industry needed a less expensive means of ensuring there are no pathogens in the product.
Sumner is using ultraviolet light to kill the organisms in cider. Because UV light does not penetrate, the cider must be made to cascade in a thin sheet at the point where it is exposed to the light. She will also be looking at ways to use a UV light system to sanitize tanks and equipment.
Sumner and Wright adapted commercially available equipment, used to purify water, for use by the cider industry. Their research provided data that convinced federal Food and Drug Administration regulators that the system eliminates E. coli O157:H7.
Sumner, an Extension specialist with a background in food safety procedures, also incorporated other steps, such as washing the fruit, to increase the safety factor.
The Virginia Tech researchers continue to study the UV system, determining the impact on pathogens that are not currently the target of federal regulations and looking at shelf-life issues. Sumner also expects to recruit Virginia Tech’s wine specialist to assist with sensory evaluations of treated cider.
– Stewart McInnis