Microencapsulation of lipophilic bioactive compounds using prebiotic carbohydrates: Effect of the degree of inulin polymerization

• The effect of the degree of inulin polymerization (DP) on annatto seed oil microparticles was evaluated.
• Geranylgeraniol retention was 77%.
• The use of DP ≥ 23 increased glass transition temperature (Tg) of pure inulin samples.
• DP did not influence Tg of microparticles containing annatto seed oil.
• Samples with DP ≥ 23 showed lower water adsorption than that seen for samples with DP ≥ 10.

This paper presents novel outcomes about the effect of degree of inulin polymerization (DP) on the technological properties of annatto seed oil powder obtained by freeze-drying. Inulins with two DP's were evaluated: GR-inulin (DP ≥ 10) and HP-inulin (DP ≥ 23). Micrographs obtained by confocal microscopy were analyzed to confirm the encapsulation of bioactive compounds using both inulins, especially the encapsulation of the natural fluorescent substance δ-tocotrienol. Microparticles formed with both inulins presented the same capacity for geranylgeraniol retention (77%). Glass transitions of microparticles formed with GR-inulin and HP-inulin succeeded at 144 °C and 169 °C, respectively. Regarding water adsorption isotherms, microparticles formed with HP-inulin and GR-inulin presented behaviors of Types II (sigmoidal) and III (non-sigmoidal), respectively. Reduction of water adsorption capacity in the matrix at high relative moistures ( > 70%) was presented when HP-inulin was used. At low relative moistures ( < 30%), the opposite behavior was observed.

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