Pulsed electric field processing is a method for processing cells by means of brief pulses of a strong electric field. PEF holds potential as a type of low temperature alternative pasteurization process for sterilizing food products.
The food is placed between two electrodes, then the pulsed electric field is applied. The electric field enlarges the pores of the cell membranes which kills the cells and releases their contents. It is a developing technology still being researched, mainly for the pasteurization of fruit juices and other beverages.
Martín-Belloso et al. 2011 studied the effect of High Intensity Pulsed Electric Fields (HIPEF) on vitamin C degradation and bioactive compounds in fruit juice added to milk beverages. The authors report that the degradation rate of this vitamin was was faster in HIPEF-treated and untreated beverages than in those thermally treated, probably due to a lower peroxidase inactivation and faster microbial spoilage during storages in HIPEF treated beverages. Thermal processing was more effective than HIPEF on enzyme activity on peroxidase and lipoxygenase inactivation.
High-intensity pulsed electric field of tomato juice
Martín-Bellosos et al.2010 looked at volatile compounds and flavour-related enzymes in tomato juice submitted to high-intensity pulsed electric field (HIPEF) processing compared with those of thermal processing (90 degrees C for 30 or 60 s). Tomato juice treated by HIPEF showed lower residual lipoxygenase (LOX) activity than heated juice. Almost 50% of the hydroperoxide lyase remained active after HIPEF and heat treatment for 30 seconds, but was almost completely inactivated by 90 degrees C for 60 seconds.HIPEF treatment was found by the authors to improve organoleptic properties of tomato juice.
Enzymes related to tomato flavour
There are at least five lipoxygenases (TomloxA, TomloxB, TomloxC, TomloxD, and TomloxE) present in tomato fruit. TomloxC is a key lipoxygenase specifically involved in the generation of fatty acid-derived C6 short-chain flavor compounds and is important in generation of fruit flavour.
Hydroperoxide lyases (HPLs) catalyze the cleavage of fatty acid hydroperoxides to aldehydes and oxoacids. These volatile aldehydes play a major role in forming the aroma of many plant fruits and flowers.
Polyphenoloxidase in strawberry
High-intensity pulsed electric fields (HIPEF) were applied to strawberry juice to study the feasibility of inactivating polyphenoloxidase (PPO). HIPEF treatments were more effective in bipolar than in monopolar mode in inactivating PPO.The authors report that the PPO activity could be brought down to 2.5% using bipolar treatments at frequencies higher than 229 Hz and pulse widths between 3.23 and 4.23 μs and 2000 μseconds.
Polyphenol oxidase and peroxidase were extracted from two different varieties of strawberry fruit were found by Chisar, Barbagallo and Spagna 2007 and found responsible for the browning of the fruit.
High-intensity pulsed electric fields treatment of liquid whole egg
Liquid whole egg (LWE) is currently pasteurized at 66°C for 4.5 minutes with negative effects, such as increase of viscosity, increased opacity, reduced foaming capacity, impact on the water-soluble content and mechanical properties of the egg gels. High-intensity pulsed electric fields (HIPEF) processing (field strength: 19, 32, and 37 kV/cm) was found by Marco-Molés et al 2011 to present better technological properties as liquid whole egg obtained with heat treatment.