Abstract
This work aimed to evaluate the thermal and photo stability of the antioxidant potential (AP) of the Spirulina platensis biomass. Thermal stability was established at 25ºC, 40ºC and 50ºC for 60 days, in the dark, protected from light. Photo stability was evaluated using UV (15 W, λ = 265 nm) and fluorescent (20 W, 0.16 A, power factor FP > 0.5, 50/60 Hz, 60 lm/w, 1200 lm) light for 90 days in capsules, glass and Petri dishes, at room temperature. The AP of the biomass in these conditions was determined at intervals (every 7 and 30 days in the studies of thermal and photo stability, respectively) using the induction of the oxidation of a lipid system by heat and aeration. In this lipid system, the biomass submitted to degradation was used as an antioxidant. The kinetics of the reaction was determined by the Arrhenius method. Thermal degradation was found to follow zero order kinetics, whereas photo degradation followed first order kinetics. The AP decreased 50% after 50 days at 25°C. At 40°C and 50°C, the AP decreased more than 50% after 35 and 21 days of exposition, respectively. The decrease of the AP of Spirulina was more sensible to UV and fluorescence light. After 30 days of exposition, the AP decreased more than 50% in all storage conditions tested. The antioxidant potential of Spirulina platensis is easily degraded when the biomass is exposed to heat and light, indicating the need for care to be taken in its storage.
Highlights
Spirulina platensis is a filamentous photoautotrophic cyanobacterium that inhabits various environments, such as soils and marshes, alkaline lakes, brackish, marine and candy water, forming a green scum on the water surface (Richmond, 1990; Vonshak, 1997)
A higher value of IP in the oxidation of soybean oil without S. platensis powder was observed after 10 h of oxidation (64.7±0.61 meq/kg)
Comparing the results of the IP of soybean oil oxidized for 10 hours with or without the S. platensis powder as an antioxidant, it can be observed that the maximum antioxidant potential (AP) obtained was 93.1% when powder with no exposure to thermal or photo degradation was used
Summary
Spirulina platensis is a filamentous photoautotrophic cyanobacterium that inhabits various environments, such as soils and marshes, alkaline lakes, brackish, marine and candy water, forming a green scum on the water surface (Richmond, 1990; Vonshak, 1997). The nutraceutical properties of these microalgae have been attributed to their chemical composition, which is rich in proteins (60-70%) (Henrikson, 1995), polyunsaturated fatty acids (Colla et al, 2004), phenolic compounds (Colla et al, 2007) and phycocyanin (Silva, 2008) Other properties, such as the antimicrobial action (Parisi et al, 2009; Kaushik and Chauhan, 2008; Mala et al, 2009; Kumar et al, 2011; Sarada et al, 2011; Souza et al, 2011; El-Sheekh et al, 2014) and its influence on the survival of lactic acid bacteria (Perez et al, 2007), have been reported. Among the properties of microalgae, the antioxidant action by phenolic compounds and phycocyanin has been extensively studied in vitro (Jaime et al, 2005; Souza et al, 2006; Shalaby and Shanab, 2013) and in vivo systems (Guarienti et al, 2010; Bertolin et al, 2011)
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