Improving Apple Cider’s Quality

Have you ever wondered if apple cider could taste better than it already does? Well, two UVM professors are investigating a way to improve the quality of cider. Currently in the United States, milk and cider are routinely pasteurized by exposing them to high temperatures, killing most microbes in them. However, pasteurizing using heat is not without its side effects, especially in cider – some of the pleasant taste may actually be lost after heat pasteurization.

Several non-thermal approaches have already been developed, including high pressure processing (HPH), which inactivates microbes through the application of high amounts of pressure, and pulsed electric field (PEF), which uses powerful electrical pulses to destroy microbes. Both of these techniques preserve the original qualities of the products which they modify, but both are expensive and difficult for small farmers to access.

Doctors Silk and Guo, from the Nutrition and Food Sciences Department at UVM, are investigating a new non-thermal pasteurization technique: ultrasound treatment. Ultrasound is a term used to describe high frequency sound waves, which can be used to outline parts of the body (a technique similar to sonar,) and is frequently employed by physicians to view unborn babies. The efficacy of using ultrasound to destroy microbes depends mainly on the type of microorganism (different types of bacteria have different structures,) and the liquid the waves must penetrate.

At the Institute for Food Technology’s (IFT) annual meeting in 2003, Silk and Guo presented their research as an attempt to eliminate the side effects of pasteurization, which include “loss of nutrients, and unacceptable changes in color and flavor.” As of the 2003 annual conference, the duo’s research was still being perfected, as they concluded that “microbial reduction need[ed] to be achieved more thoroughly and rapidly.”

Similar projects are being undertaken at universities around the country. The most successful researchers have used a combination of heat and ultrasound to eliminate microbes – a Washington State research team recently used the technique to measure the inactivation of the bacterium E. Coli in apple cider, and achieved some success, concluding that “this technology may be a useful alternative to maintain quality and safety aspects related to processing of liquid foods such as juices usually processed by conventional treatments.”

A completed study at the University of Illinois at Urbana-Champlain designed to benefit Illinois’ juice industry concluded that ultrasound treatment of cider preserves more of its original quality, and is a feasible method of pasteurization. The laboratory is currently seeking two more grants from the USDA to continue research.

If perfected, this technique may provide apple farmers a cost-effective way to sell higher quality cider. This is especially applicable to Vermont, since it has nearly four thousand acres of commercial apple farms, and the legislature has even declared the apple to be the official state fruit.