28 September 2004 Tomatoes – Your Eyes Don't Tell You Everything

If a tomato is bright red, round and reasonably large, it should be a tasty tomato, right? Wrong!

Research undertaken in the Food Group at Lincoln University has confirmed that when people buy tomatoes they make their choice based on the colour of the tomatoes. However, choosing a highly coloured tomato does not guarantee that it will also be tasty.

Food researcher, Mrs Janette Busch, asked a group of thirty seven staff and students from the University to evaluate six different varieties of tomatoes and rank them in order of preference for a number of different qualities – firmness, juiciness, sweetness, bitterness, intensity of tomato flavour and colour of the skin and flesh.

What she found was the tomato varieties the panellists preferred when asked about the colour were completely different from the varieties they preferred when asked about the qualities that described the taste of the tomatoes.

"I was really excited by the results," said Mrs Busch, "they were just so clear cut.

"Anybody who has bought tomatoes can tell you about being disappointed by the taste of some delicious looking tomatoes but this is the first time in New Zealand that this has been studied.

"However, although we know which varieties of tomatoes the panellists liked best consumers can't just go and ask for these tomatoes by name in their local supermarket. This is because these tomatoes are sold under a number of different trade names throughout New Zealand," said Mrs Busch.

"What I would like to happen is that tomato growers name their tomatoes in much the same way as potato growers do. They need to tell which tomatoes are best for eating raw and which are best for cooking. That would be one way of ensuring customers always get the tomato that best suits the use they want it for."

Australian tomatoes were included as part of the research and did not rate highly with the panellists, except for skin colour and firmness.

"In New Zealand, tomatoes are the second most commonly eaten vegetable after potatoes so they make a valuable contribution to the 5 a day vegetables we are recommended to eat each day," said Mrs Busch.

Mrs Busch's work is part of on-going research into tomatoes being undertaken in Lincoln University's Food Group. Other research involves the analysis of different tomato cultivars for their antioxidant properties.

Antioxidants are compounds naturally present in fruits and vegetables that are said to have a role in reducing some types of cancer. Tomatoes contain significant amounts a number of different antioxidants, including: lycopene (a carotenoid), phenolic compounds (flavonoids and phenolic acids) and vitamin C (ascorbic acid). As these antioxidants are found mostly in the skin it is important to eat the skin as well as the flesh of the skin.

Further research has also shown that different varieties of tomatoes contain different levels of these protective compounds and also that these levels change, depending on the time of year.

Food research at Lincoln University involves the study of a wide range of different fruits and vegetables including: taro, nuts (walnuts, hazelnuts, etc.), marrowfat and chickpeas, wasabi, ulluco (Earth Gems), pumpkins, Māori potatoes, apples, mushrooms, yams and lentils as well as tomatoes.

Ian Collins, Journalist, Lincoln University, Canterbury, New Zealand

Janette Busch, Science Writer, Agriculture and Life Sciences Division, Lincoln University, Canterbury, New Zealand