Exquisite taste

时间:2019-03-08 08:18:15166网络整理admin

By Andy Coghlan STRAWBERRIES could soon become tastier thanks to the discovery of the genes which govern flavour formation and make strawberries red. Details of the genetic discovery were presented in Britain last month at a conference on achieving quality improvements in fruit and vegetables. Ken Manning of Horticulture Research International in Wellesbourne, Warwickshire, which hosted the conference, says that he and his colleagues have identified genes which govern the sweetness, tartness and smell of strawberries. “Taste is a balance between sweetness and astringency,” says Manning, adding that odours also have a big impact on taste. Armed with these discoveries, Manning and his colleagues hope to develop superior strawberries that taste sweeter and richer as well as smelling more appetising. And given the current furore over the genetic modification of food crops, the team wants to achieve these results through traditional methods of plant breeding, guided by molecular markers which show which varieties have the key flavour genes. Another possibility might be to transfer the flavour and odour genes into microorganisms, which would be added to processed foods as flavourings. Manning’s team has discovered a protein that delivers sugar into fruit cells from the phloem, the tissue that circulates nutrients to all parts of the plant. Called a sucrose transporter, the protein dumps sucrose sugar in vacuoles, large chambers within plant cells. The protein sits astride the cell membrane and allows more sugar in as the fruit ripens. “The whole basis of fruit ripening is to make it tasty enough to ensure seed dispersal,” says Manning. “But if the gene which makes the protein were overexpressed, we could raise the amount of sucrose coming into the fruit, which would result in a sweeter strawberry,” he says. Manning’s team has also discovered as many as six families of genes which play a part in removing the sharp taste of unripe strawberries, turning them red at the same time. The genes produce enzymes which convert polyphenolics, which taste sharp, into anthocyanins, which give ripe strawberries their red colour. Manning says that all fruits produce sharp-tasting phenolic compounds to discourage consumption before the seeds in the fruit are ready for dispersal. “It’s a keep-off signal,” he says. Another of the team’s findings is the identification of genes crucial to the manufacture of volatile substances that give strawberries their rich smell. “There are at least 280 different compounds involved in the aroma,” says Manning. These have a big impact on the overall taste. One gene manufactures an enzyme called an acyltransferase, which makes sweet-smelling ester compounds by combining alcohols with acids. Another makes O-methyltransferase, which may help to manufacture eugenol,