Increasing solubility of red bell pepper carotenoids by complexation with 2-hydroxypropyl-ß-cyclodextrin.

Red bell pepper carotenoids were complexed with 2-hydroxypropyl-ß-cyclodextrin (2-HPßCD) in different mass ratios (1:4, 1:6, 1:8 and 1:10) through ultrasonic homogenization in order to increase carotenoid solubility and their use as natural pigment in food. Inclusion complexes, red bell pepper extract and physical mixtures were analyzed by DSC, FT-IR, (1)H NMR and DLS. Solubility assay was performed to identify the effect of complexation on the solubility of carotenoids. From characterization assays, results showed that inclusion process occurred for all tested ratios. Results for water solubility assays demonstrated clear differences between solubility index of inclusion complexes (8.06±2.59-16.55±4.40mg/mL) and physical mixtures (3.53±1.44-7.3±1.88mg/mL), while carotenoid extract was no water soluble, as expected. These results indicated that molecular inclusion of carotenoids in 2-HPßCD was efficient to enhance their solubility in water, enabling application of red bell pepper carotenoid as natural pigment and/or bioactive substances in food.

Inclusion complexes of red bell pepper pigments with ß-cyclodextrin: preparation, characterisation and application as natural colorant in yogurt.

This work aimed to prepare inclusion complexes between red bell pepper pigments and ß-cyclodextrin using two different procedures (i.e., magnetic stirring and ultrasonic homogenisation), to characterise the prepared inclusion complexes and to evaluate the colour stability of a selected complex added to yogurt. The mass ratio of extract to ß-cyclodextrin was 1:4. The formed extract: ß-cyclodextrin complexes and a physical mixture of extract and ß-cyclodextrin were evaluated by differential scanning calorimetry, Fourier transform-infrared spectroscopy, proton nuclear magnetic resonance, particle size distribution and Zeta potential. The obtained data showed that ultrasonic homogenisation resulted in better yield and inclusion efficiency compared to magnetic stirring. The yogurt with the added complex produced by ultrasonic homogenisation showed slower variations for the a(∗) (redness) and b(∗) (yellowness) indices compared to yogurt with added extract, indicating a higher protection of the colour during storage.