Evidence from epidemiological and clinical studies suggests that dietary carotenoid intake may be associated to a decrease risk of developing certain types of cancer, age-related macular degeneration, and oxidative stress mediated conditions. Tomato, the major source of dietary carotenoids in North America with several well-characterized genes affecting carotenoid metabolism, is an excellent candidate for delivering these potential health benefits to consumers. Tomato thermal processing and storage, however, may affect the extent of the health benefits by modifying content, isomeric distribution, and bioavailability of carotenoids. There is conflicting evidence on the type and degree of these chemical changes and further research is needed to understand the mechanisms and consequences of these modifications. There is a corresponding need to provide the industry with rapid and efficient analytical tools to facilitate the production of food with optimal levels of these functional components.
The overall objective of this research was to develop new methods based on Fourier-transform infrared spectroscopy (FTIR) that permit the high throughput and cost-effective analysis of tomato carotenoids and the study of their chemical changes during thermal processing and storage.
A comprehensive literature review of vibrational spectroscopic methods for the evaluation of heat-induced chemical changes in food components, and three independent experimental studies are presented in this dissertation. The first experimental study was focused on the development of a new protocol for the construction of external calibration models for measuring carotenoids by FTIR. In this method, tomato juice standards with predetermined carotenoid concentrations were prepared by spiking lycopene or beta-carotene in a low-carotenoid tomato juice. These tomato juice standards were then used for the construction of external calibration curves by correlating carotenoid concentration to their infrared spectra. The method was successfully validated by determining lycopene in genetically-diverse tomatoes.
In the second study, FTIR was used to profile carotenoids in twenty-four tomato varieties that included eight distinct combinations of genes affecting carotenoid concentration and content. FTIR combined with multivariate analysis was able to reveal differences in the chemical structure of the eight tomato groups. This information was used to classify each tomato variety by the type and quantity of carotenoids.
In the third study, carotenoid chemical changes during production and storage of canned tomato juice from ten different tomato varieties were analyzed by FTIR. Results depicted a dynamic system with lipid isomerization and oxidation reactions taking place during production and storage of tomato juice. Data proved that individual carotenoids and their isomeric forms behave differently during thermal treatment and storage.
The conclusions of this research confirm the value of FTIR for the study of bioactive carotenoids and provide new tools for the efficient analysis of tomato carotenoids that could save time and operational costs to the industry. The information collected by FTIR complemented that of standard chromatographic techniques helping to understand the chemical changes of carotenoids during thermal processing and storage.