What was it all about?

This project, which ran from 2013 to 2015, investigated the use of ultrasound technology to enhance the process of drying plums. The current process is energy-intensive and slow, taking around 35 hours, due to the skin of plums having a waxy layer that prevents drying.

Two ultrasonic setups were developed and tested on fresh plums under a range of drying conditions with varied levels of temperature, relative humidity and airflow. Dried fruit was assessed on a number of characteristics including colour and nutritional content.

Results showed that ultrasound pre-treatment is effective in enhancing the drying process of plums and produces a better-quality product. Specifically, the team found that…

• A combination of ultrasound and oil emulsion pre-treatment worked best
• The ultrasonic oil emulsion pre-treatment reduced the overall drying time by about half, compared to samples dried without pre-treatment, although this varied with drying conditions and ultrasonic parameters
• Levels of antioxidants and vitamin C in dried samples were higher and they had a lighter colour.

Further development of the technique will offer a superior alternative to current plum drying practices.

It is anticipated that the pre-treatment approach could also be applied to other fruits and vegetables with a waxy skin layer including grapes, berries, peas, and tomatoes.

ACT NOW 

You can still read an article about the project on p21 of the January-March 2015 edition of The Vine.