As well as providing the first description of the nutritional value of processed yellow tomatoes, the originality of this work published by INRA scientists in Avignon resided in its simultaneous analysis of three families of micronutrients found in tomatoes: carotenoids (by monitoring ß-carotene and lycopene levels), polyphenols and vitamin C.
The scientists studied two types of transformation: cooking, a process used by both industry and consumers, and lyophilisation.
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"Russian Lemon"
tomato ©Jean Weber/INRA
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Their results showed that red tomatoes suffered less from cooking than yellow tomatoes. More specifically, they did not observe any change to ß-carotene and lycopene levels in red varieties, while major losses were seen with yellow tomatoes. The levels of polyphenols, and vitamin C, which are known to display low resistance to heat, fell in both types of tomato.
With respect to lyophilisation, a preservation process widely used by researchers in laboratories to store samples for long periods, they observed that it exerted a negative impact on carotenoid levels in both red and yellow tomatoes, but only affected the polyphenol content of yellow tomatoes. This process had no effect on vitamin C in either case. These experimental findings therefore call into question the use of this technique, hitherto considered to be harmless.
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"Jaune côtelée de Montlouis" tomato ©Jean Weber/INRA
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Study of the mechanisms underlying the evolution of these micronutrients during the processing of tomatoes is currently under way in order to examine the onset of any protective phenomena and/or interactions between the micronutrients.
These new data will certainly be of considerable value in the field of human nutrition and could be applied by industry to ensure changes to the transformation processes used for tomatoes.
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