This report adds to the ongoing vivid dispute on the fate of carotenes in tomato upon thermal processing.
Although many papers dealing with changes in the raw tomatoes during industrial treatment have
already appeared, data on the fate of finished, processed tomato products when they are additionally
heated (e.g., when used in the household) is scarce. In this study, effects of heating and storage on a
commercial, double concentrated tomato puree were examined spectrophotometrically. Our results
indicate that upon exposing unopened cans with double concentrated tomato puree to thermal treat-
ments between 100 and 135 C during specific time intervals spectral profile of lycopene remained
preserved. Likewise, a slight hypsochromic shift of lycopene peak III did not occur up to 135 C. However,
significant (20%) initial loss of lycopene content was induced by thermal treatment for 20 min at 100 C.
During the more intensive treatments that followed the lycopene content was first leveling off and then
slightly increased. After storage of thermally treated samples at 18 C the content of lycopene was
found to increase. All these results suggest simultaneous working of several mechanisms: possible autooxidation
and isomerization processes of carotenes taking place, in addition to the Maillard reaction and
enhanced extractability of carotenes at increased temperatures. Results acquired from hexane solutions
of samples treated at temperatures of 120 and 135 C obtained at different time points, confirmed severe
isomerization in organic solvent and/or photo-oxidative degradation of lycopene.
This report adds to the ongoing vivid dispute on the fate of carotenes in tomato upon thermal processing.Although many papers dealing with changes in the raw tomatoes during industrial treatment havealready appeared, data on the fate of finished, processed tomato products when they are additionallyheated (e.g., when used in the household) is scarce. In this study, effects of heating and storage on acommercial, double concentrated tomato puree were examined spectrophotometrically. Our results indicate that upon exposing unopened cans with double concentrated tomato puree to thermal treat- ments between 100 and 135 C during specific time intervals spectral profile of lycopene remainedpreserved. Likewise, a slight hypsochromic shift of lycopene peak III did not occur up to 135 C. However,significant (20%) initial loss of lycopene content was induced by thermal treatment for 20 min at 100 C.During the more intensive treatments that followed the lycopene content was first leveling off and thenslightly increased. After storage of thermally treated samples at 18 C the content of lycopene wasfound to increase. All these results suggest simultaneous working of several mechanisms: possible autooxidationand isomerization processes of carotenes taking place, in addition to the Maillard reaction andenhanced extractability of carotenes at increased temperatures. Results acquired from hexane solutionsof samples treated at temperatures of 120 and 135 C obtained at different time points, confirmed severeisomerization in organic solvent and/or photo-oxidative degradation of lycopene.
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