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High pressure, pulsed electric fields produce tomatoes with increased yields, quality.

The textural properties of tomato products are highly correlated to the way they are processed and to their final total soluble sugar content--degrees Brix ([degrees]Bx).

The aim of tomato processors is to produce products that have certain desired textural and sensorial characteristics, while at the same time increasing product yield by decreasing the amount of evaporated water.

This objective can be achieved either by applying the cold break process or by applying novel technologies, such as high-pressure (HP) processing or pulsed electric fields (PEFs) that affect the extractability of water. These technologies also could selectively regulate the remaining activity of the endogenous pectinolytic enzymes, pectin methylesterase (PME) and polygalacturonase (PG), which are responsible for the final texture.

Scientists at the National Technical University of Athens applied HP or PEFs to raw tomatoes to produce tomato products that had similar viscoelastic characteristics at different Brix concentration levels, depending on the process technology used and the yield desired. The results of their work support the potential use of HP and PEFs to increase the yield of tomato products, while producing products of similar or superior quality to conventionally processed products.

In their research, the scientists measured the quality characteristics of the final products, such as texture, sensory scoring, color and lycopene content, for every sample. They then selected HP and PEF process conditions based on preliminary experiments for no PME inactivation and partial PG inactivation.

Tomatoes that were HP-treated at 500 MPa at 55 C for 10 minutes, and tomatoes that were PEF-treated at 1.8 kilovolt per centimeter (kV per cm) at 300 Hz or at 16.33 kV for 250 pulses were cold-broken and concentrated at 60 C and 0.2 bar to a final viscosity of 2,000 centipoise. Control samples were also studied.

The final [degrees]Bx for each sample was 9.1, 5.9 and 7.2 for the control, HP- and PEF-treated tomatoes, respectively. A yield increase of 26% and 11% was obtained for the HP- and PEF-treated tomatoes, respectively. The quality characteristics of the HP- and PEF-treated final products were similar to the control sample, offering a more fresh-like taste.

Further information. Petros S. Taoukis, Department of Chemical Engineering, National Technical University of Athens, Iroon Polytechniou, 9, GR15780 Athens, Greece; phone: +30 2107723171; email:

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Publication:Emerging Food R&D Report
Date:Jun 1, 2016
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