Improving value of tomato waste by development of new food ingredients

Industrial processing of tomato generates a considerable amount of waste (skins and seeds), which contain valuable nutritional compounds, especially lycopene. Improving value of tomato waste could be possible through the development of processes that convert it into new food ingredients. In this study in order to simulate both conventional and innovative technologies, heat-stabilized tomatoes and raw tomatoes were processed into two purees in a pilot-plant. From the resulting waste four powders were obtained, namely: raw skin powder, heated skin powder and raw or heated skin powders fortified with green tea (GT). As oxidation and browning could occur fast in dehydrated products depending on water availability, the aim of this study was to investigate the stability of the four tomato powders during storage in different water activity environments (aw = 0.11 - 0.75), in the dark for four months at 30°C. Changes in lycopene, beta-carotene, rutin, flavan 3-ol and chlorogenic acid contents were modelled by pseudo-first-order kinetics. Changes in the inhibition efficacy of oxidative and glyco-oxidative reactions were analyzed by polynomial regressions. Variations in Hunter’s colorimetric parameters were studied by applying pseudo-zero-order kinetics. The observed aw range for maximum stability of the powder obtained from raw tomato skins was 0.22 ≤ aw ≤ 0.56. Below the stability interval, the main degradation was lycopene oxidation, whereas above it degradation involved polyphenol oxidation. GT addition enlarged the stability interval at low aw values whereas thermal treatment extended the stability interval at high aw values. By modulating tomato skin processing it was therefore possible to obtain high-lycopene or high-lycopene and high-flavan 3-ol powders which were stable over a wide interval of aw values. The most promising uses for these powders are as food coloring, antioxidant and anti glyco-oxidative agents.