Abstract
The volatile compounds formed by thermal degradation of the carotenoids present in Dunaliella bardawil were investigated by microwave irradiation (MW) and water bath heating (WB) in different conditions of temperature and time using central composite design. Volatiles extraction by solid phase microextraction (SPME) was optimized and performed at 40 °C for 15 minutes, and those in greater amount were quantified by a validated method of gas chromatography coupled to a quadrupole mass spectrometer (GC-qMS). Employing WB, 10, 12 and 120 ng mL-1 of β-cyclocitral, α-ionone e β-ionone, respectively, were obtained between 60 and 87 °C for 30-75 min, while by MW, 5, 5, 50 ng mL-1 were obtained between 75-107 °C for 1.5-2.8 min. Considering the shorter time of MW, it can be concluded that if the time necessary to obtain the best yield by WB is employed in multiple MW cycles, an amount 10 times greater of those compounds would be obtained by MW than by WB. The results suggest a new biotechnology application for the carotenoids of the microalgae of the Dunaliella genus.
Highlights
Microalgae are photosynthetic microorganisms widely distributed in marine, freshwater and terrestrial ecosystems.[1,2] They produce a great diversity of compounds with high commercial value, such as polyunsaturated fatty acids, carotenoids, phycobilins, polysaccharides, vitamins and sterols.[3,4,5,6,7] The production of microalgae supplies the cosmetic and food supplement industries, and boosts the development of natural food products, an emerging and promising field for industrial application.[8]
In order to evaluate the influence of time and temperature on the degradation of the carotenoids present in D. bardawil biomass (BC2), a central composite design with two variables was used, in which five levels of temperature were employed for both water bath heating (WB) and microwave irradiation (MW) processes (Table 2)
In the solid phase microextraction (SPME) analyses of D. bardawil biomass, seven volatiles were identified: α-ionone, β-ionone, β-cyclocitral, dihydroactinidiolide, 7,8-dihydro-β-ionone, 5,6-epoxyβ-ionone and trans-geranyl acetone, among which β-cyclocitral, α-ionone and β-ionone were the major compounds in all experiments performed (Supplementary Information section, Figure S1)
Summary
Microalgae are photosynthetic microorganisms widely distributed in marine, freshwater and terrestrial ecosystems.[1,2] They produce a great diversity of compounds with high commercial value, such as polyunsaturated fatty acids, carotenoids, phycobilins, polysaccharides, vitamins and sterols.[3,4,5,6,7] The production of microalgae supplies the cosmetic and food supplement industries, and boosts the development of natural food products, an emerging and promising field for industrial application.[8]. The aim of this study was to investigate the formation of volatile compounds from the controlled degradation of carotenoids present in D. bardawil microalgae by microwave irradiation versus water bath heating. The experimental conditions of solid phase microextraction (SPME) were optimized to monitor the production of volatile compounds in the biomass (BC2) process.
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