The colour of tomatoes may affect their flavour

The pigments that colour tomatoes may also affect their flavour, according to a joint study by the University of Tsukuba and the University of Florida. The new method created by the scientists will increase the analysis of tomato samples and shed insight on the relationship between pigmentation and fruit and vegetables. The study was published in Metabolites.

The researchers developed a new method to rapidly measure the pigment profiles of tomatoes and used the technique to explore how pigments affect the taste and aroma of different tomato varieties.

The colour of tomatoes is produced by combinations of different types of pigments, including carotenoids and chlorophylls. These pigments can also affect the accumulation of flavour-related compounds such as sugars, which affect the taste of tomatoes, and volatile organic compounds (VOCs), which determine the aroma. As tomato fruits ripen from green to red, the amounts of pigments and flavour-related compounds change but until now the relationship between colour and flavour has been unclear.

“Pigments like carotenoids have no taste,” said lead author Professor Miyako Kusano. “But they are precursors for compounds called apocarotenoid-VOCs (AC-VOCs) which produce the fruity, floral smell of tomatoes and increase the perception of sweetness — characteristics that appeal to consumers.”

Traditional methods for identifying and measuring pigments can be slow, so the researchers developed a simple method to rapidly analyse large numbers of samples. Using the new technique, the team measured the amounts of carotenoids and chlorophylls in 157 different varieties of tomato and then analysed the flavours of each variety to find the links between pigments and flavour.

The results showed that tomato varieties with an abundance of chlorophyll also had a high sugar content, contributing to a sweet taste. They also found that the carotenoid profiles of the fruit reflected the appearance of the fruit, as well as AC-VOC levels.

“The pigment profile of one of the orange-coloured varieties called ‘Dixie Golden Giant’ was particularly interesting,” explained Professor Kusano. "It had very high levels of AC-VOCs, but the carotenoid content wasn’t that high. We discovered that the pigment prolycopene was abundant in this variety, which explained the high AC-VOC levels.”

The carotenoid content of fruit is influenced by growing conditions, like temperature and amount of light. By looking at the pigment profiles and AC-VOC content of fruits in different environments, it may be possible to find ways of improving AC-VOC production, which is good for both consumers and producers.

Given its speed, the new method developed by the team is a powerful tool for analysing pigment concentrations in large numbers of samples and could also be used for other fruits and vegetables.

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