Quantifying lycopene synthesis and chlorophyll breakdown in tomato fruit using remittance VIS spectroscopy

The aim of this study was to increase the understanding of chlorophyll breakdown and lycopene synthe-sis at a quantitative level in Solanum lycopersicum fruit. To accomplish this, a kinetic model is proposeddescribing the transition from chloro- to chromoplast. Remittance VIS spectroscopy was used to assesschlorophyll and lycopene levels non-destructively in cocktail and round type tomatoes. Tomatoes werestored at constant temperatures between 4 and 24◦C, or at a stepwise changing temperature between4 and 16◦C. Chlorophyll and lycopene levels were measured repeatedly over time and used to cali-brate a kinetic model that describes how an autocatalytic enzyme system links chlorophyll breakdownto lycopene synthesis, including breakdown of lycopene precursor and lycopene itself. Increasing stor-age temperatures increased the reaction constant for lycopene synthesis more than that of chlorophyllbreakdown for both tomato types. The reaction constants describing chlorophyll breakdown and lycopenesynthesis were considerably larger, and the estimated enzyme levels lower for the round type. This allowsround tomatoes to quickly resume lycopene synthesis after a cold storage period when enzyme levels arelow. Lycopene breakdown was established for the round type while the cocktail type showed lycopeneprecursor breakdown. Chlorophyll breakdown and lycopene synthesis, as affected by storage temper-ature and tomato type, is covered well by the model for both tomato types. We hypothesise that thepostulated enzyme system, responsible for the direct link between chlorophyll breakdown and lycopenesynthesis, is due to STAY-GREEN proteins. Remittance VIS spectroscopy is, in combination with a param-eter estimation tool, suited to screen tomato genotypes for intended colour transformation performance,or as tool in chloroplast to chromoplast transition studies.