In this work, alginate-chitosan microgel particles were formed at different pH levels with the aim of using them as viscoelastic interfacial layers, which confer emulsion stability to food systems. The particles’ size and structural characteristics were determined using laser diffraction, confocal laser microscopy (CLSM), and time-domain nuclear magnetic resonance (TD-NMR). The pH affected the microgel characteristics, with larger particles formed at lower pH levels. T₂ relaxation measurements with TD-NMR did not reveal differences in the mobility within the particles for the different pH levels, which could have been related to the more or less swollen structure. The rate of adsorption of the particles at the sunflower oil–water interface differed between particles formed at different pH levels, but the equilibrium interfacial tension of all systems was similar. Higher interfacial dilatational viscoelasticity was obtained for the systems at lower pH (3, 4, 5), with G’ reaching 13.6 mN/m (0.1 Hz) at pH 3. The interfacial rheological regime transitioned from a linear elastic regime at lower pH to a linear but more viscoelastic one at higher pH. The thicker, highly elastic interfacial layer at low pH, in combination with the higher charges expected at lower pH, was related to its performance during emulsification and the performance of the emulsion during storage. As revealed by laser diffraction and CLSM, the droplet sizes of emulsions formed at pH 6 and 7 were significantly larger and increased in size during 1 week of storage. CLSM examination of the emulsions revealed bridging flocculation with the higher pH. Nevertheless, all emulsions formed with microgel systems presented macroscopic volumetric stability for periods exceeding 1 week at 25 °C. A potential application of the present systems could be in the formation of stable, low-fat dressings without the addition of any emulsifier, allowing, at the same time, the release of the bioactive compounds for which such particles are known.

Chlorella sorokiniana is a well-studied microalga with significant nutritional potential due to its health-promoting nutrients. C. sorokiniana is rich in proteins (~50%), lipids (~14%), vitamins, and other bioactive compounds, making it an attractive ingredient for the food industry. Other properties of C. sorokiniana, such as its foaming properties, have not been extensively investigated. The present work examines the foaming properties of C. sorokiniana biomass and of its fractions, namely the foaming properties of the whole-cell biomass, the disrupted-cell biomass, the water-soluble protein-rich extract, and the disrupted-cell biomass residue after oil extraction. The water/air interfacial tension, zeta potential, foaming capacity, foam stability, and foam morphology of C. sorokiniana biomass and its fractions were determined. Furthermore, the effect of the pH on the foaming properties of the water-soluble protein-rich extract was also investigated. The results show that the examined fractions decrease the water-air interfacial tension and form foams. The type of biomass fraction affects strongly the foam characteristics and foam stability. Furthermore, the stability and characteristics of the foam are significantly affected by pH. Overall, the water-soluble protein-rich extract at pH 7 presented the best foam stability, as the foam remained stable for more than 24 h and had a narrow bubble size distribution. The obtained results suggest that fractionated microalgae biomass could be used as an effective foaming agent in different commercial applications.

Microalgae are a promising alternative source of PUFAs, with Chlorella being one of the few microalgae widely available in the nutraceuticals market authorized for human consumption. This study explores the fatty acid (FA) profiles of nine C. sorokiniana biomass feedstocks produced under different combinations of light intensity and nitrogen and inorganic carbon loadings, derived via a Taguchi L9 (3³⁻¹) orthogonal array design. Additionally, the nutritional and medical value of Chlorella lipids using several nutritional indices is assessed. PUFAs were maximized under low light intensity and high nitrogen loading; however, these conditions favored the overaccumulation of omega-6 FAs. For omega-3 FA maximization, high light intensity must be applied, suggesting that high illumination induces the desaturation of linoleic acid to alpha-linolenic acid (ALA) in C. sorokiniana cells. Additionally, nitrogen-depleted conditions significantly downgraded its quality due to the overaccumulation of saturated FAs. Despite lacking EPA and DHA, C. sorokiniana lipids are an excellent source of ALA, surpassing concentrations met in plant-based oils. Thus, Chlorella lipids can be included in humans’ diet, satisfying daily ALA requirements; however, accurately labeling the FA profile of Chlorella products, prior to any nutritional claims, is indispensable, considering the sizeable variations in their profile under the impact of cultivation conditions.

Background: The valorization of byproducts to obtain high nutritional value foods is of utmost importance for our planet where the population is booming. Among these products are oils rich in ω-3 fatty acids produced from fishery byproducts. Recently, mullet roe oil from roe byproducts was produced that was rich in the ω-3 fatty acids eicosatetraenoic acid (EPA) and docosahexaenoic acid (DHA). Oils are customarily characterized for their composition and degree of oxidation but little is known of their biological effects, especially the effect of the extraction method. Methods: The purpose of this study was to evaluate the effects of freshly extracted mullet roe oil from mullet roe byproducts and the effect of the extraction method on human red blood cells (hRBCs) and platelets. To this end, the hemocompatibility (cytotoxicity), oxidative effects, and erythrocyte membrane changes were examined after 1 and 24 h of incubation. Antiplatelet effects were also assessed in vitro. Results: The expeller press oil extraction method and alcalase-assisted extraction produced the most biocompatible oils, as shown by hemocompatibility measurements and the absence of erythrocyte membrane alterations. Solvent extracts and protease-assisted extraction oils resulted in the rupture of red blood cells at different examined dilutions, creating hemolysis. Conclusions: It seems that the proper functioning of oil–erythrocyte interactions cannot be explained solely by ROS. Further investigations combining chemical analysis with oil–cell interactions could be used as an input to design high nutritional value oils using green extraction technologies. All samples exhibited promising antiplatelet and antiblood clotting effects in vitro.

Open-pond cultivation of autotrophic microalgae promises sustainable biomass production but is frequently limited by low productivity and biological contamination, restricting its application in food and nutraceutical sectors. This study systematically evaluated the improvement achieved by transitioning from batch to semi-continuous and continuous cultivation of Chlorella sorokiniana while implementing a practical contamination-management strategy. Five 21-day experiments were conducted in a 100-L indoor open-pond using a pH-based contamination control protocol. In addition to cultivation mode, the effect of the transition timing from batch to dynamic feeding was investigated as a critical process-design parameter. Semi-continuous cultivation initiated at early culture-growth phase (day 4) achieved the highest biomass production, yielding approximately 130 g of net biomass, 49% higher than batch cultivation. Under the same nominal dilution rate (10% v/v), continuous cultivation increased net biomass production by 31% relative to batch, whereas delaying the transition to semi-continuous operation until day 11, reduced the improvement to 21%. Splitting the daily removed/added volume into two dosages provided no additional benefit. Biomass composition remained largely unaffected by cultivation mode, averaging 50% proteins, 18% lipids, and 23% carbohydrates, while polyunsaturated fatty acids exceeded 50% of total fatty acids. Microscopic observations indicated effective suppression of protozoan contamination following short pH disturbances, whereas fungal contamination persisted; no rotifers were observed, possibly associated with early protozoan suppression. The results demonstrate that cultivation strategy and transition timing are key determinants of productivity improvement. Combining optimized dynamic cultivation and contamination management provides practical pathways for enhanced C. sorokiniana cultivation for food and nutraceutical applications.