Konstantina Kyriakopoulou

Effects of Drying and Extraction Methods on the Quality and Antioxidant Activity of Sea Buckthorn (Hippophae rhamnoides) Berries and Leaves

Sea buckthorn is a promising source of bioactive compounds. However, there is limited information on the effect of post harvest drying and extraction of sea buckthorn on its antioxidant capacity. The effect of freeze, air, and solar dryingon the extraction yield of sea buckthorn berries and leaves was evaluated with respect to their bioactive content. Sequential extraction with solvents of different polarity and solvent-free microwave-assisted extraction were applied. Freeze-drying has better performance in the berries’ extracts, while air-drying has better performance in the leaves’ extracts. All data were analyzed by Multi Factor Analysis of Variance (ANOVA) and Duncans post-hoc tests at a level of α = .05. Although the extraction yield in the sequential extraction of sea buckthorn berries is significantly better, the leaves’ extracts exhibit superior radical scavenging ability. Accelerated solar drying appears to preserve sea buckthorn leaves without degrading their antioxidant content. The components responsible for the high antioxidant activity of leaves’ extracts were found to be several flavonoids and polyphenols. The extract obtained by the microwave extraction of fresh berries exhibits moderate antioxidant activity compared to the polar extracts of freeze-dried berries.

Environmental Assessment of Industrially Applied Drying Technologies for the Treatment of Spirulina Platensis

Spirulina platensis is a high protein content cyanobacterium with known therapeutic properties. Its main protein Phycocyanin is currently as a functional ingredient into various food products to enhance their nutritional qualities acting as food colorant, antioxidant and emulsifier, reducing the use of synthetic additives. The post-harvest treatment of the microalga affects its content of proteins and pigments (carotenois, chlorophylls, etc.), as in the long run the environmental performance of the recovery process. In this study, industrially applied drying techniques, such as Accelerated Solar Drying (ASD) and Vacuum Drying (VD), were examined. The untreated Spirulina biomass showed the highest content in pigments and antioxidant activity, while in the case of dried biomass a significant decrease of the bioactivity was observed. ASD performed better on phycocyanin recovery, while VD showed higher total carotenoids content. Finally, ASD process showed a higher impact in all environmental impact categories, while VD’s cultivation and harvesting stage prior to drying showed significantly higher energy and carbon footprint.

Recovery of Functional Pigments from four Different Species of Microalgae

In the present work, four species of microalgae: Spirulina platensis (SP), Chlorella vulgaris (CV), Haematococcus pluvialis (HP), and the diatom Phaeodactylum tricornutum (PT) were selected as raw materials for the recovery of multifunctional extracts. Ultrasonic assisted extraction (UAE) using different solvents was applied under specific optimized conditions. Organic solvents such as hexane, acetone and ethanol, as well as food grade solvents, such as limonene, MCT oil, soybean oil and phosphate buffer (pH= 7) were used. The total carotenoid, β-carotene and chlorophyll a content in the extracts was determined for all species using UV-Vis spectrometry. Moreover, in the case of SP the phycocyanin content was also measured. The extracts were evaluated regarding their antiradical activity using the DPPH method. Taking into consideration the nature of the solvent used and the total pigment content, acetone and ethanol can be replaced by limonene for the extraction of total carotenoids from HP and PT. For the extraction of phycocyanin from SP, water was considered the most efficient solvent. Ethanol extracts of CV were found rich in β-carotene. The DPPH assay revealed that HP and PT biomass exhibited the highest antiradical activity which can be recovered using suitable solvents.

Effect of drying and extraction conditions on the recovery of bioactive compounds from Chlorella vulgaris

Microalgae and especially green algae are microorganisms that are used in a wide range of industrial applications of high economic interest, such as fish farming, food, cosmetics, pharmaceuticals, and biofuel. In this study, the green microalga Chlorella vulgaris was examined as raw material for the recovery of bioactive compounds and the production of multifunctional extracts. Firstly, the drying of raw biomass, which is a crucial pre-treatment stage, was examined with freeze-drying having the best performance. Ultrasound assisted extraction (UAE) applying various solvent systems was studied under optimized conditions. For the untreated microalgal biomass, ethanol was indicated as the preferable solvent, whereas on dried samples, water was a more suitable solvent. UV-Vis spectrometry and high-performance liquid chromatography (HPLC) were used for the determination of total carotenoid, chlorophyll, and protein content in the raw materials, extracts, and extraction residues. Moreover, the suitability of drying technique and extraction solvent system was evaluated according to the obtained antiradical activity of the relevant treated biomass and extraction samples using the DPPH method.