Processing of Apple Juice
Simpson and others (1995) reported that apple juice from concentrate treated with PEF at 50 kV/cm, 10 pulses, pulse width of 2 ps and maximum processing temperature of 45°C had a shelf-life of 28 days compared to a shelf-life of 21 days of fresh-squeezed apple juice.
There were no physical or chemical changes in ascorbic acid or sugars in the PEF-treated apple juice and a sensory panel found no significant differences between untreated and electric field treated juices. Vega-Mercado and others (1997) reported that PEF extended the shelf-life at 22° to 25°C of fresh apple juice and apple juice from concentrate to more than 56 days or 32 days, respectively. There was no apparent change in its physicochemical and sensory properties (US FDA, 2015).
Processing of Orange Juice
Sitzmann (1995) reported on the effectiveness of the ELSTERIL continuous process developed by the food engineers at Krupp Maachinentechnik GmbH in Hamburg, in association with the University of Hamburg, Germany. They reported the reduction of the native microbial flora of freshly squeezed orange juice by 3-log cycles with an applied electric field of 15 kV/cm without significantly affecting its quality.
Zhang and others (1997) evaluated the shelf life of reconstituted orange juice treated with an integrated PEF pilot plant system. The PEF system consisted of a series of cofield chambers. Temperatures were maintained near ambient with cooling devices between chambers. Three waveshape pulses were used to compare the effectiveness of the processing conditions. Their results confirmed that the square wave is the most effective pulse shape. In addition, the authors reported that total aerobic counts were reduced by 3- to 4-log cycles under 32 kV/cm. When stored at 4°C, both heat- and PEF-treated juices had a shelf life of more than 5 months. Vitamin C losses were lower and color was generally better preserved in PEF-treated juices compared to the heat- treated ones up to 90 days (storage temperature of 4°C or 22°C) or 15 days (storage temperature of 37°C) after processing.