Try to imagine 21-day-old orange juice that is just as healthy and tasty as on the day it was squeezed. This is just one example of a project where Wageningen Food & Biobased Research applied the mild preservation technique Pulse Electric Field.
Pulsed Electric Field (PEF) processing is making its way from the lab to market implementation. This novel preservation method opens new perspectives for the food industry. It can be used to preserve liquid bulk products such as fruit juice, milk, yoghurt and soup. The electric impulses can be applied homogeneously through the product and the technology is readily applicable for the pasteurisation of liquid foods at low temperature.
Wageningen Food & Biobased Research has more than 15 years of experience in Pulsed Electric Field processing, including microbiology, product research, process impact, technology development and consumer acceptance. Our main applications are:
- Preservation of liquid media: PEF treatment, at sufficient high intensity, inactivates vegetative micro-organisms including yeasts, spoilage micro-organisms and pathogens. PEF can, therefore, be used to pasteurise pumpable fluids such as juices and soups without using additives. However, the products have to be kept cool as PEF has a limited effect on enzymes. As temperatures are lower than conventional heat pasteurisation quality and heat-sensitive vitamins are retained. PEF can be used as continuous process; after processing, products need to be packed aseptically.
- Permeabilisation of plant and animal tissue: at sufficient electric field strength, pulse repetition rate and energy input, PEF results in the formation of large, permanent pores in cellular tissues. This can be used for enhancing mass transfer coefficients by disintegration of biological materials. Examples include enhanced juice yield, increased concentrations of functional components in extracts, improved sugar beet processing and enhanced drying processes.
Shelf life improvement
Wageningen Food & Biobased Research works with several companies to apply Pulsed Electric Field processing for enhancing the shelf life of fresh fruit juice. We investigated the effect of this technology on shelf life and quality of a range of fruit juices. This research showed that adequate selection of process conditions is necessary to obtain a safe product with high quality. We used our lab scale facilities for detailed microbiology research, including pathogens. Our pilot scale facilities were applied for product quality research and shelf life studies. We also integrated consumer tests to determine the effect on product quality. Together with companies, the results are being transferred to industrial production lines for Pulsed Electric Field treatment of fresh fruit juices.
For Pulsed Electric Field processing it is important to evaluate the microbial safety of the product after treatment. Not only spoilage micro-organisms are important, but also the inactivation of pathogens that could potentially be present in the process. Wageningen Food & Biobased Research has the facilities to evaluate the effect of PEF on inactivation of vegetative cells, including pathogens. We determined the inactivation kinetics of spoilage micro-organisms and pathogens that can be potentially present in fruit juices and showed that it is essential to select the right process conditions to make sure that not only the shelf life is improved, but also the food safety.
In Europe 37 partners worked together on the development of novel preservation technologies. Wageningen Food & Biobased Research coordinated this project that also included an Industrial Advisory Platform to stimulate the cooperation with industry and to disseminate the project results to potential users of the technologies. In NovelQ research was done on the influence of pulsed electric fields on microorganisms, enzymes and food components. Also other mild preservation techniques are investigated such as high pressure treatments, cold plasma and advanced heating. The results are described in the final report of the project and over 150 scientific publications.