Tasting sour flavours is genetic

Researchers have found that genes play a central role in the recognition of sour tastes but not in the recognition of saltiness. The findings could help identify the taste receptor that detects sourness in food. 

Scientists at the Monell Chemical Senses Center, Philadelphia, US, tested 74 pairs of identical twins and 35 pairs of fraternal twins to discover the lowest concentration needed for each twin to correctly identify a citric acid solution as sour. The results showed more similar responses between identical twins, who have nearly identical genes, than between fraternal twins, who only share about 50 per cent of their genes. This suggests that genes help determine sensitivity to sourness.  

Computer modelling estimated that genes play a more important role than environment in determining individual differences in sour taste sensitivity. The results for salty taste sensitivity suggested that the environment plays a larger role than genetics. 

’It was surprising to find no significant genetic influence on saltiness, as there is at least some small genetic influence on bitter, sweet and sourness,’ said Jonathan Hansen, of the Queensland Institute of Medical Research, Australia, who contributed to the study. 

’However, we do have a very small sample size here so there may be small genetic effects on the perception of saltiness but we could not detect them,’ he said. 

Future studies will look at possible sour taste receptors by determining whether individual differences in genes for these structures correlate with individual differences in sensitivity to sourness. Research has suggested a number of possible receptors, including PKD ion channels, acid-sensing ion channels, proton-sensitive K channels, hyperpolarisation-activated and cyclic nucleotide-gated ion channels and, possibly, proton-sensitive G-protein-coupled receptors. 

Other factors may also play a role in sensitivity to sourness. For example, differences in salivary flow rates change the mouth’s buffering capacity which can lead to individual differences in sourness perception. Although the genes that determine salivary flow rate are unknown, studies could determine whether salivary flow rate is heritable. 

Karen Harries-Rees 

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