Validation of a pulsed electric field process to pasteurize strawberry purée

An inexpensive data acquisition method was developed to validate the exact number and shape of the pulses applied during pulsed electric field (PEF) processing. The novel validation method was evaluated in conjunction with developing a PEF process for pasteurizing strawberry purée. Both buffered peptone water (BPW) and fresh strawberry purée (pH 2.4) were inoculated with Escherichia coli (ATCC 35218) and processed using a pilot plant PEF system at field strengths of 24.0-33.6 kV/cm, outlet temperatures of 45.0-57.5 °C and a flow rate of 100 l/hr. An accelerated aging storage study was performed on the quality of a strawberry beverage made from the strawberry purée. The populations of E. coli were reduced by 6.5 log in BPW at 30 kV/cm and 57.5 °C and 7.3 log in strawberry purée at 24 kV/cm and 52.5 °C. The taste and color of strawberry beverage initially made from PEF processed purée was fresh and bright red, respectively. The color remained good for the first 3 months-equivalent of storage and there was only a very slight drop in flavor. The data acquisition system captured the details of every pulse applied at a rate of 400 Hz for 1 h for a total of over 1.4 million pulses. Strawberry purée was pasteurized in a pilot-scale PEF unit. In addition, a data acquisition system was developed to validate the process which should aid in obtaining FDA approval of the PEF process.