26 Oct 16 Understanding why refrigeration is uncool for tomatoes
Most foodies warn against storing tomatoes in the fridge, saying it saps them of their flavour. New research confirms this culinary opinion.
The study, published in Proceedings of the National Academy of Sciences, shows that the practice of chilling tomatoes below 12°C inhibits their ability to generate substances that contribute to aroma and flavour.
Conducted by researchers from the University of Florida, Cornell University, and several other institutions, this work explains why commercial tomatoes — which are often preserved in low-temperature storage — tend to be bland.
The research team got their teeth into the problem by studying the expression of more than 25,000 genes in two tomato varieties. They looked at these genes before and during chilling, and after returning the tomatoes to room temperature.
Chilling, a major stress for a tropical plant such as the tomato, reduced the activity of hundreds of genes. Some of these produce enzymes responsible for synthesising the volatile chemicals that make tomatoes taste sweeter and give them a more complex, appealing aroma.
Many of the enzymes never recovered, even after the tomatoes were back at room temperature. Taste tests confirmed that chilling did, indeed, give rise to less flavourful tomatoes.
Further analysis showed that chilling led to changes in DNA methylation, affecting many genes. Since methylation is a common mechanism for turning genes on and off for long periods, this may account for the long-lasting effect of chilling on flavour, say the researchers.
With this knowledge, breeders may be able to modify the temperature-sensitive enzymes to be more robust, or else select tomato varieties with gene variants that are naturally less inhibited by cold, they add.
Elizabeth Baldwin, a plant physiologist with the USDA’s research lab in Fort Pierce, Florida, agrees. “With this knowledge, we could definitely do breeding or genetic manipulation,” she says.
The other message of this work, of course, is a simple one: “Don’t put your tomatoes in the fridge,” says Baldwin. “They lose their aroma.”