Enhancing phycocyanin solubility via complexation with fucoidan or κ-carrageenan and improving phycocyanin color stability by encapsulation in alginate-pregelatinized corn starch composite gel beads.

Phycocyanin (PC), as a pigment-protein complex, aggregates and precipitates in acidic environments. In this context, complex formation with anionic polysaccharides is a strategy to enhance protein solubility. Besides, acidic conditions negatively affect the inherent blue color of PC, which can be prevented by encapsulation. Thereupon, in the present study, two different biopolymer-based systems, namely complexes and hydrogel beads, were prepared to increase PC solubility and its color stability under acidic conditions, respectively. Fucoidan and κ-carrageenan (KC) were separately utilized to make a complex with PC. Calcium alginate-pregelatinized corn starch (PCS) composite gel beads were used to encapsulate PC. The prepared samples were added into model systems simulating acidic conditions and then characterized during storage at 4 and 25 °C under dark conditions. Appropriate colloidal stabilities were observed for fucoidan/PC and KC/PC model systems. The color of the samples remained stable at 4 °C. As well, the bead carriers (i.e. alginate-PCS) properly protected PC against low pH conditions over time at 4 °C. Thereupon, the blue color of the beads satisfactorily remained stable at this temperature. The findings showed that complexation with fucoidan or KC and encapsulation in mixed hydrogel beads are promising routes for improving PC solubility and its color stability, respectively.

Fabrication and characterization of phycocyanin-alginate-pregelatinized corn starch composite gel beads: Effects of carriers on kinetic stability of phycocyanin.

Composite gel beads using calcium alginate and different concentrations of pregelatinized corn starch (PCS) were produced to encapsulate phycocyanin (PC). Rheological properties of different sodium alginate/PCS/PC mixtures, structural and morphological properties of beads, and kinetic stability of encapsulated PC (upon heating at various time-temperature combinations) were then assessed. Rheological properties of the mixtures exhibited shear thinning behaviors. Aquagram revealed that the PC-containing beads had more water structure with weak­hydrogen bonds. Morphological images represented less subsidence in the structures of composite gel beads, unlike PCS-free beads. Kinetic study showed that degradation rate constant values of PC encapsulated in composite gel beads (1.08-3.45 × 10-4, 3.38-4.43 × 10-4, and 5.57-15.32 × 10-4 s-1) were lower than those in PCS-free alginate gel beads (4.45 × 10-4, 9.20 × 10-4, and 18.04 × 10-4 s-1) at 40, 50, and 60 °C, respectively. This study suggests that the composite gel beads can improve PC stability.

Improving oxidative stability of virgin olive oil by addition of microalga Chlorella vulgaris biomass.

Antioxidant activity of Chlorella (Chlorella vulgaris) was evaluated in virgin olive oil (VOO) at different concentrations of 0.5, 1.0, and 1.5% (w/w) under accelerated storage conditions. Antioxidant activity of Chlorella was compared with those of BHT and ß-carotene. Chlorella samples significantly retarded the formation of primary, secondary, and total oxidation products in comparison with those of the control. The stability increased as concentrations of Chlorella increased. Samples containing 0.5, 1.0, and 1.5% Chlorella significantly improved VOO stability by 19.99, 28.83, and 33.14%, respectively. Observed effects can be related to the release in the assortment of bioactive compounds from Chlorella algae to the VOO. Among the different antioxidants evaluatedy, BHT exhibited the highest antioxidant activity. On the contrary, ß-carotene had no preventive effect against the oxidation of VOO. It also proved incapable of limiting the progress of VOO oxidation and played role as pro-oxidant. In conclusion, Chlorella enhanced VOO oxidative stability. Thus it can be considered as a promising source of natural antioxidants.

Evaluation of synergistic effect of Chlorella vulgaris and citric acid on oxidative stability of virgin olive oil.

Green microalga Chlorella (Chlorella vulgaris) powder was employed as a natural antioxidant in virgin olive oil and its antioxidant activity was compared with those of ß-carotene and α-tocopherol during 16 days of accelerated storage. Furthermore, the synergistic effects of Chlorella and citric acid were investigated. The primary, secondary, and total oxidation products of Chlorella samples (with and without citric acid) were lower than those of the control samples. Induction period of Chlorella samples were significantly higher than those of the control, ß-carotene, and α-tocopherol samples. Furthermore, carotenoid and chlorophyll contents of Chlorella samples were significantly higher than those of the control samples. These pigments can delay the oxidation process. Using Chlorella and citric acid in combination with each other showed no synergistic effect against the oxidation of virgin olive oil. In conclusion, Chlorella can be affirmed as a natural antioxidant, which extends the shelf life of virgin olive oil.