19 February 2007 Seeing red – a new tomato product

 

Are you disappointed by the dark and unattractive colour of so many dried tomatoes sold in New Zealand?

Scientists from the food group at Lincoln University believe they have found a way to produce bright red semi-dried tomatoes that have an acceptable taste and keeping qualities.  

Sébastien Viellet, a food engineering exchange student from France was given the task of producing a new tomato product that retained all the essential characteristics of fresh tomatoes, with a bright red colour similar to fresh tomatoes.

The high temperatures commonly used to produce dried tomatoes damage their cells, causing them to develop a dark colour that many people find unattractive while also lowering their nutritional content. Sébastien was successful in developing a new drying method that used lower temperatures than those used to produce commercially available dried tomatoes, and this did not affect their nutritional content or shelf life.

After devising a range of different treatments he carried out two sensory evaluation trials where people were able to eat two different semi-dried tomato cultivars prepared in different ways and give their preferences.

“I was quite surprised by the sensory evaluation results. What I found was that when the panellists were asked to choose between two different times of smoking of the semi-dried tomatoes it was very clear that older people liked the longer smoked tomatoes far more than the students did,” said Sébastien.

“In the second sensory evaluation I used tomatoes smoked for a longer time and compared my product (sprayed with either white or Balsamic vinegar) with two commercial products.  In this evaluation the panellists definitely preferred the plain semi-dried tomato and the one treated with white vinegar because they said they were a much brighter red than the commercially prepared products. In fact, the redder the tomato, the more it was liked."

As the shelf life of a product depends on its moisture content, Sébastien also prepared a selection of tomatoes with a range of different levels of moisture and recorded the colour, vitamin C and antioxidant levels of the fresh tomatoes and the final products in order to find the best combination that was liked by consumers and ensured a long shelf life.

“Many people will think that a functional food is a food that is altered in some way to make it more nutritious,” said Professor Geoffrey Savage who supervised Sébastien’s Lincoln project, “but that is not necessarily so."

“Many of our familiar foods already contain compounds that are of benefit to us, like tomatoes. In addition we found that the semi-dried product actually contained higher lycopene levels than the fresh tomatoes it was made from.”

“I was delighted that Sébastien was so successful in developing a new and exciting functional food product that has the potential to be developed commercially,” he said.

Dr Savage said that in France it is common for universities to require their Food Engineering students to complete a final year project in an English speaking country, and that’s what brought Sébastien to New Zealand.

Sébastien’s work followed on from previous research projects undertaken by other students in the Lincoln University food group.