Effect of drying treatments on content and stability of grapefruit lycopene encapsulated in alginate beads containing sugars and biopolymers

AGUIRRE CALVO, TATIANA; SANTAGAPITA, PATRICIO R.

Cordoba

Congreso; V Congreso Internacional de Ciencia y Tecnología de los Alimentos Córdoba, 2014; 2014

Subsecretaria de Innovación y Vinculación Tecnológica. Secretaría de Ciencia y Tecnología.

Lycopene is one of the main carotenoids presents in tomato, grapefruit, watermelon and papaya, and is responsible for their red/reddish color. Lycopene has a highly unsaturated acyclic structure and is lipid-soluble. In the Food Industry it is used as a source of antioxidants and as a food colorant. Labile compounds (including carotenoids) are often encapsulated in order to preserve them from degradation (by light, O2 or thermal treatments), besides of giving controlled release and adequate dosage. The purpose of this work was to study the stability of a lycopene extract encapsulated in alginate beads subjected to freeze-drying (FD) or vacuum drying (VD). Lycopene was extracted from grapefruit (Citrus paradisi, red variety) as an unconventional and local source, since Argentina is one of the main producers in South America. Lycopene was extracted by mixing freeze-dried grapefruit pulp with extra-virgin olive oil (1:2) in a hand blender. Then, emulsions were prepared by Ultraturrax using different hydrocolloids as alginate, pectin, chitosan, or commercial and natural gums, as well as sugars (trehalose and β-cyclodextrin) (2:1 lycopene extract:excipients solution). Subsequently, alginate-Ca(II) beads were prepared by dropping the emulsions in CaCl2 (2.5%w/v). The effect of drying was evaluated on both concentration and stability of lycopene. Transverse relaxation times (T2) were determined by low field-NMR. Beads were successfully dried to water contents between 2.3 and 3.9 (±0.1) %w/wdb, showing similar values for both methods. Beads containing only alginate showed a great reduction of lycopene content of 75 and 85% after FD and VD, respectively. The addition of a second biopolymer or sugar increased lycopene retention during dehydration. Alginate beads containing trehalose with β-cyclodextrin, guar or arabic gums retained a high lycopene content (>80%) after drying, regardless of the drying method. Even though lycopene content after drying showed similar trends as a function of composition for both methods, a higher loss on the spectral fine structure (an index of isomerization) was observed in VD beads than in FD ones. Alginate beads containing trehalose and guar gum showed both higher content and stability of lycopene for both drying treatments. Two T2 were obtained corresponding both to oil relaxations of 53-55 and 155-160 ms, being both times lower than the obtained for wet beads. Besides, a change on the amplitudes associated to these T2 was observed, showing a higher reduction in those samples with higher lycopene conservation, indicating that the reduction of the mobility could be one of the possible mechanisms explaining present results. The authors acknowledge the financial support of ANPCYT (PICT 0928), CONICET (PIP 100846) and UBA (Project UBACyT 20020100100397).