Juice processors can safely reduce energy inputs for secondary pasteurization of frozen and refrigerated juices and other acidic beverages with a pH of 4.2 or lower, researchers at Tetra Pak International S.A. say.
Based on a process engineering study validated at Valio Oy in Helsinki, Finland, last summer, the researchers concluded a 19 percent reduction in energy inputs is realistic. Processors also may be able to increase the temperature difference (dT) between the juice and water sides in a heat exchanger, raising the possibility of greater production flexibility by allowing products of different viscosities and product capacities to use the same heat exchanger, with adjustments.
“A lot of fruit juices are over-pasteurized,” says Birgitta Svensson, a technical specialist and microbiologist at Tetra Laval Group. Researchers set out to determine if the second pasteurization of juice, nectar and still drinks could be safely performed at a lower temperature. “We hoped there would be better taste and less color change” as well, Svensson adds, but that did not prove to be the case.
Juice concentrate sent to Europe undergoes primary pasteurization before shipping, then a second pasteurization when reconstituted. To deliver a shelf-stable product, the second pasteurization usually is done at 95° C, dT of 3° and a 15-second hold. Yeast is the main concern, explains Svensson, and researchers wanted to achieve a 9 log reduction of yeast ascospores. Testing validated this could be accomplished at 80° for 15 seconds and a dT of 25°.
Tetra Pak is seeking two international patents on the lower heat process.