Energy efficient drying strategies to retain nutritional components in broccoli (Brassica oleracea var. italica)

• Controlled drying trajectories enhance retention of nutritional components.
• State diagrams explain the strategies for optimal drying trajectories.
• The most heat sensitive components in vegetables dominate the drying trajectories.

This work concerns the combined optimization of the retention of bioactive components and energy efficiency during drying of broccoli. Kinetics for the degradation of glucosinolates, vitamin C and drying of broccoli are used to calculate optimal drying trajectories for the control variables air flow rate and temperature. It is shown from plots of the optimal drying trajectories in moisture–temperature state diagrams with degradation and drying rates, that areas with high degradation rates are circumvented. The optimized drying strategies result in significant improvement of energy efficiency (65%) and vitamin C retention of 55%.