Saline extraction assisted by ultrasound: a method to obtain purified phycocyanin.

The influence of ultrasound intensity and saline solution concentration (NH4Cl and CaCl2) on phycocyanin extraction from Arthrospira platensis was evaluated. The intensity had a significant effect on phycocyanin content and purity, while the saline solution concentration only had an effect on purity. The optimum extraction condition was obtained at 41% of intensity and 8.5 g.L-1 of CaCl2 solution. In this condition, ultrasound promoted cell disruption efficiently, increasing the extraction yield. The combination of ultrasound with CaCl2 solution reduced the co-extraction of chlorophylls and other proteins, providing more purified extracts. The freezing and thawing method was compared to the best condition obtained, and it showed no significant difference for phycocyanin content but better results for purity. Overall, ultrasound treatment may be considered a promising technology to obtain phycocyanin by the food industry without additional purification techniques due to the reduced extraction time, less use of energy, and easy scale-up.

Effect of ultrasound on Pseudoneochloris marina and Chlorella zofingiensis growth.

The present work evaluated the ultrasound (US) effects on the growth of Pseudoneochloris marina and Chlorella zofingiensis. For P. marina, US treatment did not increase cell proliferation and reduced cell density when used for 60 min (exponential phase, for 5 days), indicating a possible occurrence of cell damage. For C. zofingiensis, the application of discontinuous US for 10 min resulted in an increase of 65 % in biomass concentration compared to the control. These distinct behaviors indicate that microalgae species react differently to physical stimuli. After US treatment, a reduction of carotenoid, chlorophyll, lipid and protein concentrations was observed, which may be related to changes in the metabolic pathways to produce these compounds. Overall, the results of the present study show the potential of discontinuous US to enhance microalgae cell proliferation.

Extraction of valuable compounds from Arthrospira platensis using pulsed electric field treatment.

Pulsed electric field (PEF) treatment was evaluated for phycocyanin and proteins extraction from Arthrospira platensis (Spirulina platensis). PEF extractions were performed using different specific energies (28, 56 and 122 J·ml-1 of suspension) and the results were compared to the extraction with bead milling. At highest PEF-treatment energies a damage of the cell morphology could be observed and the highest yields (up to 85.2 ±â€¯5.7 mg·g-1 and 48.4 ±â€¯4.4 g·100 g-1 of phycocyanins and proteins, respectively) could be obtained at 122 and 56 J·ml-1. The yields increased with incubation time after PEF-treatment. The antioxidant capacity of the extracts obtained after PEF-treatment was higher than of those obtained after bead milling. PEF treatment is a promising technology to obtain blue-green antioxidant extracts from A. platensis in an environmental friendly process.

Ultrasound as an alternative technology to extract carotenoids and lipids from Heterochlorella luteoviridis.

The present work evaluated the use of ultrasound as a pre-treatment to lipid and carotenoid extraction from the microalgae Heterochlorella luteoviridis. The pre-treatment was performed in the presence of ethanol (25%, v/v) with the ultrasound intensity varying from 0 to 100% (435kJkg-1). After the pre-treatment, a diffusive step was performed in order to evaluate different ethanol concentrations (50-75%, v/v). The results regarding carotenoid extraction showed that there is an optimal extraction region: 40-80% of ultrasound intensity and 60-75% of ethanol concentration. The lipid extraction was not influenced by the ultrasound pre-treatment and increased with the increase of ethanol concentration.

Evaluation of non-thermal effects of electricity on ascorbic acid and carotenoid degradation in acerola pulp during ohmic heating.

The effect of electric field on ascorbic acid and carotenoid degradation in acerola pulp during ohmic heating was evaluated. Ascorbic acid kinetic degradation was evaluated at 80, 85, 90 and 95°C during 60 min of thermal treatment by ohmic and conventional heating. Carotenoid degradation was evaluated at 90 and 95°C after 50 min of treatment. The different temperatures evaluated showed the same effect on degradation rates. To investigate the influence of oxygen concentration on the degradation process, ohmic heating was also carried out under rich and poor oxygen modified atmospheres at 90°C. Ascorbic acid and carotenoid degradation was higher under a rich oxygen atmosphere, indicating that oxygen is the limiting reagent of the degradation reaction. Ascorbic acid and carotenoid degradation was similar for both heating technologies, demonstrating that the presence of the oscillating electric field did not influence the mechanisms and rates of reactions associated with the degradation process.

Degradation kinetics of anthocyanins in acerola pulp: comparison between ohmic and conventional heat treatment.

Degradation kinetics of monomeric anthocyanins in acerola pulp during thermal treatment by ohmic and conventional heating was evaluated at different temperatures (75-90°C). Anthocyanin degradation fitted a first-order reaction model and the rate constants ranged from 5.9 to 19.7 × 10(-3)min(-1). There were no significant differences between the rate constants of the ohmic and the conventional heating processes at all evaluated temperatures. D-Values ranged from 116.7 to 374.5 for ohmic heating and from 134.9 to 390.4 for conventional heating. Values of the free energy of inactivation were within the range of 100.19 and 101.35 kJ mol(-1). The enthalpy of activation presented values between 71.79 and 71.94 kJ mol(-1) and the entropy of activation ranged from -80.15 to -82.63 J mol(-1)K(-1). Both heating technologies showed activation energy of 74.8 kJ mol(-1) and close values for all thermodynamic parameters, indicating similar mechanisms of degradation.