Griet Knockaert

Lycopene degradation, isomerization and in vitro bioaccessibility in high pressure homogenized tomato puree containing oil: Effect of additional thermal and high pressure processing

In the present study, the effect of equivalent thermal and high pressure processes at pasteurization and sterilization intensities on some health related properties of high pressure homogenized tomato puree containing oil were investigated. Total lycopene concentration, cis-lycopene content and in vitro lycopene bioaccessibility were examined as health related properties. Results showed that pasteurization hardly affected the health related properties of tomato puree. Only the formation of cis-lycopene during intense thermal pasteurization was observed. Sterilization processes on the other hand had a significant effect on the health related properties. A significant decrease in total lycopene concentration was found after the sterilization processes. Next to degradation, significant isomerization was also observed: all-trans-lycopene was mainly converted to 9-cis- and 13-cis-lycopene. High pressure sterilization limited the overall lycopene isomerization, when compared to the equivalent thermal sterilization processes. The formation of 5-cis-lycopene on the other hand seemed to be favoured by high pressure. The in vitro lycopene bioaccessibility of high pressure homogenized tomato puree containing oil was decreased during subsequent thermal or high pressure processing, whereby significant changes were observed for all the sterilization processes.

Carrot β-Carotene Degradation and Isomerization Kinetics during Thermal Processing in the Presence of Oil

The effect of thermal processing (85-130 °C) on the stability and isomerization of β-carotene in both an olive oil/carrot emulsion and an olive oil phase enriched with carrot β-carotene was studied. During processing, degradation of total β-carotene took place. Initially, total β-carotene concentration decreased quickly, after which a plateau value was reached, which was dependent on the applied temperature. In the oil/carrot emulsion, the total β-carotene concentration could be modeled by a fractional conversion model. The temperature dependence of the degradation rate constants was described by the activation energy and was estimated to be 45.0 kJ/mol. In the enriched oil phase, less degradation took place and the results could not be modeled. Besides degradation, β-carotene isomerization was studied. In both matrices, a fractional conversion model could be used to model total isomerization and formation of 13-Z- and 15-Z-β-carotene. β-Carotene isomerization was similar in both the oil/carrot emulsion and enriched oil phase as the simultaneously estimated kinetic parameters (isomerization reaction rate constant and activation energy) of both matrices did not differ significantly. The activation energies of isomerization were estimated to be 70.5 and 75.0 kJ/mol in the oil/carrot emulsion and enriched oil phase, respectively.

Isomerisation of carrot β-carotene in presence of oil during thermal and combined thermal/high pressure processing

The effect of thermal processing (85-130°C) and combined thermal/high pressure processing (100°C combined with 0.1 to 700 MPa and 700 MPa combined with 85-115°C) on β-carotene isomerisation in an olive oil/carrot emulsion and pure olive oil phase enriched with carrot β-carotene was investigated. Thermal processing always resulted in an increase in the contribution of the cis-isomers, with the increase being more pronounced at higher temperatures. In the oil/carrot emulsion, less β-carotene isomerisation was observed during combined thermal/high pressure processing compared to thermal processing. This effect was attributed to strengthening of the carrot cell walls under high pressure, thereby hindering the transfer of β-carotene to the oil phase and lowering its susceptibility to isomerisation. In an oil phase enriched with β-carotene, β-carotene isomerisation was not influenced by the applied pressure at 100°C and became almost temperature insensitive at 700 MPa.

Carotene Degradation and Isomerization during Thermal Processing: A Review on the Kinetic Aspects

Kinetic models are important tools for process design and optimization to balance desired and undesired reactions taking place in complex food systems during food processing and preservation. This review covers the state of the art on kinetic models available to describe heat-induced conversion of carotenoids, in particular lycopene and β-carotene. First, relevant properties of these carotenoids are discussed. Second, some general aspects of kinetic modeling are introduced, including both empirical single-response modeling and mechanism-based multi-response modeling. The merits of multi-response modeling to simultaneously describe carotene degradation and isomerization are demonstrated. The future challenge in this research field lies in the extension of the current multi-response models to better approach the real reaction pathway and in the integration of kinetic models with mass transfer models in case of reaction in multi-phase food systems.

Changes in β-Carotene During Processing of Carrots

Abstract β-Carotene, which is largely present in carrots, is an important micronutrient as a result of its health-related properties. Processing might have a double effect on β-carotene. On the one hand, processing might negatively affect β-carotene stability as a result of isomerization and degradation. On the other hand, processing might alter β-carotene bioaccessibility, i.e., the amount of β-carotene that can be released from the carrot matrix during digestion and is made accessible for absorption into mucosa. Whereas thermal processing mostly results in an increase in β-carotene bioaccessibility, high-pressure processing can not in most cases improve β-carotene bioaccessibility. For thermal processing, even when processing results in β-carotene loss by isomerization and/or degradation, the increase in β-carotene bioaccessibility is probably high enough to transcend this negative effect. It can be concluded that high-pressure processing does not have a clear advantage over thermal processing concerning the nutritional quality (in terms of carotenoids) of carrot products.