2009 - Volume #33, Issue #1, Page #07[ Sample Stories From This Issue | List of All Stories In This Issue | Print this story | Read this issue]
Mobile Freezer Preserves Fruit In The Field
"We wanted a flow-through rate of 600 lbs. per hour with the ability to freeze produce to û5 to -10 degrees F within 45 minutes," explains Brian Norder, project director and designer of the mobile freezer.
To be practical for small producers, the freezing unit had to be mobile and easily hooked up to standard power. It also had to be able to handle enough produce in a short enough time to be practical. The final design incorporated an insulated, double-walled, 18-ft. tow-behind trailer. The trailer was equipped with a 5 hp, single-phase compressor and a fruit drying station. Total cost was $40,000.
All washing and rinsing is done outside. The clean fruit is moved inside the air-conditioned trailer and through a blower/dryer. From there, the trays are rolled into an 8 by 4-ft. freezer. Norder says the unit draws about 17 amps during freezing, though startup draw is a lot higher.
"We found over the summer that it was most efficient if we did two turns of 300 lbs. each per hour rather than the single turn of 600 lbs.," says Norder. "If we redid it, we would install a crossover thermostat. We found that small growers wanted to blast freeze down to -25 degrees and then hold the produce overnight at -5 degrees."
In fact, he adds, a new unit would probably utilize a tunnel flash freezer for even faster freezing. Other modifications would include a longer trailer to lower the compressor and the trailer's center of gravity. Norder would also suggest adding a generator to avoid problems where power hookups were not available.
Late season trials with the trailer were largely successful this past year, reports Norder. At least one Vermont pie maker has indicated a desire to expand use of local strawberries and raspberries if they can be frozen at the growing site for higher quality. This year, the unit will be turned over to an independent contractor who will work with small growers.
"The thought is that it can be set up at a larger grower's operation and smaller area growers can bring their produce for freezing," says Norder. "That way, it will only be moved occasionally with fewer high energy draw start-ups needed."
Contact: FARM SHOW Followup, Vermont Food Venture Center, 1126 Main St., P.O. Box 138, Fairfax, Vt. 05454 (ph 802 849-2000; email@example.com; www. edcnv.org).
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