There is a number of ways to enhance sell by and use by dates These include better education of consumers on how to use, transport , and store fresh food products , by enhancing the use by and sell by dates by adding to the package smart indicators such as TTIs Time Temperature Indicators These show through a visible color change whether the product is still fresh. TTIs are already in use by retailers and food producers in France Monoprix and Carrefour Switzerland Kneuss , and other countries in western Europe.