Genetically modified tomato puree in tins. Genetic modification involves adding or deleting sections of DNA (deoxyribonucleic acid) to create desirable changes in an organism. Several GM tomatoes and related products, with improved shelf-life, are on the market. Tomato puree is concentrated paste prepared from tomatoes, and used in cooking for flavouring food. This brand of tomato puree is marketed by Sainsbury's, a British supermarket chain.