Pink grapefruit lycopene encapsulated in alginate-based beads: stability towards freezing and drying

Abstract

Alginate-based beads containing lycopene extract were produced with the addition of various sugars and biopolymers. In present work, lycopene stability was studied on beads subjected to thermal treatments: continuous freezing (−18 °C, 30 days), four freezing/thawing (f/t) cycles, dehydration by vacuum- and freeze-drying. The progress of crystallisation was assessed using transversal relaxation times (T2) obtaining isothermal curves at different temperatures. Alginate beads containing trehalose with β-cyclodextrin and arabic gum retained a high lycopene content (>80%) after freezing and drying, regardless of the freezing or drying method. Instead, beads containing only alginate showed sever lycopene decrease in all cases. Continuous freezing affected both lycopene content and stability to a higher extent than f/t cycles. Isothermal studies revealed the lower amount of crystallised water in beads containing trehalose (with or w/o other excipients), reducing also the time to arrive at the 50% of crystallisation during freezing.