Impact of different cooking methods on food quality: Retention of lipophilic vitamins in fresh and frozen vegetables

The bioavailability of all-trans-β-carotene from vegetables depends among other things on the molecular linkage and the food matrix in which it is incorporated. It is assumed that cooking can increase the bioavailability by disruption of the plant cell wall and releasing from protein complexes. But it can also lead to isomerization and degradation of all-trans-β-carotene. In this investigation the influence of different domestic cooking methods on the all-trans- and cis-β-carotene as well as the α-tocopherol content in fresh and frozen broccoli and red sweet pepper is examined. While in fresh broccoli all cooking methods lead to a significant release of all-trans-β-carotene and α-tocopherol in the frozen broccoli no change or a decrement occurs. In the fresh and frozen peppers no change or a significant loss of α-tocopherol and all-trans-β-carotene is observed. A slight increase in the cis-isomers of β-carotene can only be found by cooking fresh broccoli.