Dehydrated onions offer a wide range of possible applications in the food industry, especially as flavour additives for convenience food products, such as sauces, soups and dressings. When compared to fresh onions the use of dehydrated product has various advantages in terms of transportation, storage and handling. Due to the high demand for dried products, the enhancement of the drying process is of particular interest to the food industry in respect to potential time and energy savings as well as the preservation of product quality. Previous studies have documented the cell disruption of different food materials initiated by the pre-treatment with Pulsed Electric Fields (PEF), resulting in faster moisture release during the drying process.

At Elea we see ourselves as the link between science and industry, so we took advantage of our experience from small scale trials and scaled up the process of onion drying including a PEF pre-treatment step to generate a superior onion drying process that is more efficient, much shorter, and results in energy savings and a high quality safe product.

The aim of the project was to investigate the influence of the PEF treatment parameters on the cell disruption and on the convective drying process of fresh onions, and subsequently to ascertain the optimal treatment settings using a combination of economy, technology, and quality improvements as the basis.

The influence of PEF parameters such as electrical field strength and specific energy on the disintegration and finally on the drying of onions could be determined.

The drying trials were performed at various drying temperatures (45 – 75 °C) covering all ranges of drying from fast high temperature to longer gentle drying. Applying PEF treatment prior to further processing resulted in up to 30 % faster drying time achieving a target residual moisture of 7 %, as this is often the industrial specification. Nevertheless, additional trials indicated that drying to even lower moisture levels still resulted in 22 % shorter drying times.

Applying PEF prior to drying for strong-coloured products such as carrots allows an improvement in colour retention. As onions by nature are not coloured no significant difference could be observed. However, using PEF technology allows the use of lower drying temperatures whilst retaining the same drying time resulting in a gentler drying and therefore quality improvement in the dried end-product.

This example is a further illustration of how many different products Elea PEF technology can be applied to. With our experience throughout a wide range of applications within the food industry our world leading technologists will also add value to your business. For more information please contact us and visit our website.