The aim of this study is to produce external standards for Z-lycopene induced by processing of tomatoes. The general goal of this thesis was to produce external standards for Z-lycopene isomers which occur in processed tomatoes. In order to reach this goal several questions needed to be answered: Are Z-lycopene isomers formed during processing of tomatoes? How can Z-lycopene isomers, formed during processing of tomatoes, be produced with high yield? Is it possible to collect the Z-lycopene isomers separately? How can the targeted isomers be obtained as a pure solid? What is the position of the Z-double bond of the Z-lycopene isomers? What is the extinction coefficient of the Z-lycopene isomers?