End-use technology review

Electric Perspectives, Nov/Dec 1999 by McLoughlin, Gerard

A IS FOR APPLE, 0 IS FOR OZONE

"Our pledge is to bring you freshness, good nutrition, and honest value with products as tasty as real homemade." That's part of the Tastee Apple guarantee to its caramel-apple customers.

With freshness as their goal, however, Tastee (and apple processors in general) face increasing needs to reduce the risk of spoilage from bacteria, molds, and fungi. At the same time, they need to conserve water and reduce wastewater disposal costs, particularly those associated with high biological oxygen demand-microorganisms-and suspended solids. Tastee Apple recently replaced its chlorinated water system with an ozone treatment system-and by so doing, improved the shelf-life of their apple products, reduced waste disposal costs, and conserved more than 12,000 gallons of water a week.

The Situation

Tastee Apple is a privately owned processor of fresh apples, and its Ohio plant is one of the major packers of caramel apples in the United States. This snack line accounts for a large portion of sales for Tastee Apple, though the plant also produces apple juice and apple chips,

The food processor starts with Jonathan or Empire apples, which arrive from the field in bins. To reduce bruising, speed processing, and wash the apples, the plant used a recirculating chlorinatedwater channel, or flume, to float the 950 pounds of apples out of each bin and move them toward a conveyor for further processing. The 2,000-gallon flume at Tastee Apple can handle about 40,000 apples per hour.

After washing, the apples are coated with sweet brown or red caramel, and then perhaps dipped in either peanuts or coconut.

To control microorganisms, the recirculating flume water was chlorinated and had to be dumped daily because it accumulated high levels of soil and organics. And even with the chlorination, trace bacteria, yeast, and molds remained that shortened the apples' shelf life.

The New Way

The plant wanted to improve its product and extend the use of the flume water. To do this, Tastee turned to American Electric Power (AEP) and EPRI. They gave Tastee advice about replacing the chlorine system with an ozone treatment system for the flume water. They also helped offset the equipment's purchase cost, as well as evaluate the equipment's effectiveness.

Here's how the system works. Water is circu- I lated through the flume at about 600 gallons per minute (GPM). At the beginning of the ozonation process, a side stream of about 60 GPM goes through a filter Then, gaseous ozone-which is generated at a rate of five pounds per day in a corona discharge unit-is injected into the filtered water side stream. After about 10 minutes of exposure to the ozonated water, the apples are conveyed to the sorting, caramel application, and packaging area.

The ozone concentration in the water is maintained at about 0.05 to 0.15 parts per million (Ppm). An ozone detection unit continuously monitors the amount of ozone in the environment adjacent to the flume to ensure that the maximum amount of ozone in the air does not exceed state regulations or the Occupational Safety and Health Administration's release limit of 0.08 to 0.1 Ppm. To control the loss of ozone to the environment, the generator generally is adjusted to about 85-percent capacity.

The Results

To get a general idea of the performance of the equipment, tests were performed with apples that had been dipped in a yeast suspension and then washed with water that was ozonated (to approximately 0.1 Ppm). The apples were then rinsed in sterile water. For Jonathan apples, the yeast count per gram ot apple in 100 milliliters of rinse water went from 70,000 to 1,200. For Empires, the number went from one million to 21,000.

While the 0.1 Ppm ozonated wash kept the yeast and mold count in the flume water under control, a further reduction of the count could be achievable with a final spraying of the apples wim ozonated water. In the test, the final spraying reduced the yeast count an additional 470 for Jonathans (to 730) and 19,500 (to 1,500) for Empires.

"The ozone treatment reduced the yeast and mold count in the water, resulting in cleaner apples and a longer shelf life for the caramel apples," said Greg Hackenbracht of Tastee Apple. "As a result, fewer consumer complaints of moldy apples have been received."

Because the water remains cleaner, no longer is the flume water replaced daily. Now the company can reuse the same water for seven days, saving more than 12,000 gallons a week. Since the ozonation system is running 24-hours-aday, it is able to reduce the amount of waste in the flume water-particularly during the night when apples are not being washed.

"Less waste means fewer disposal costs, particularly the costs associated with high biological oxygen demand and suspended solids," said Hackenbracht.

"Some produce companies have decided to install an additional ozone generation system in a spray bar for a final cleaning of the apples, as well as a system in juice lines," said Carl Byrd Of AEP. "These systems will help our customer improve products and production efficiency, which makes him more profitable."