Percorrer por autor "Nunes, Rafaela"
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- Influence of different processing techniques on microalgal protein extractionPublication . Moreira, Catarina; Ferreira-Santos, Pedro; Nunes, Rafaela; Carvalho, Bernardo; Pereira, Hugo; Teixeira, José A.; Rocha, Cristina M.R.The nutrient-rich composition of microalgae biomass positions it as a highly promising natural food ingredient. This holds the potential to not only enhance the nutritional value of various food products but also simultaneously alter their structural attributes.This work investigated the effect of five protein extraction techniques such as freeze-thawing, enzymatic-assisted extraction, high-pressure homogenization, ultrasounds-assisted extraction, and pH adjustment (pH 7, pH 10, and pH 13) in protein yield, and subsequente cell and protein structure of three microalgal suspensions, namely, Chlorella vulgaris, Nannochloropsis oceanica, and Tetraselmis chui. In Chlorella vulgaris, freeze- thawing and high-pressure homogenization exhibited a higher effect in terms of protein yield (similar to 26.60 g (protein) /100 g (protein microalgae)). The same occurred for Nannochloropsis oceanica with also ultrasounds-assisted extractions and pH 7 and 10 having a protein yield above 30 %. Tetraselmis chui was similar to Chlorella vulgaris (>20.00 g (protein) /100 g (protein microalgae)) for freeze-thawing, high-pressure homogenization and ultrasound-assisted extraction. Enzymatic-assisted had a the lower protein yield for all the three microalgae (<10.00 g (protein) /100 g (protein microalgae)). The majority of proteins extracted from Chlorella vulgaris samples had molecular weights exceeding 337 kDa, whereas proteins extracted from Nannochloropsis and Tetraselmis had molecular weights ranging from 5 to 50 kDa. alpha-helices occurred in proteins extracted from Chlorella vulgaris through freeze-thawing and enzymatic-assisted extraction, while Nannochloropsis and Tetraselmis only had beta-sheet. In conclusion, for optimal protein yield recovery, methodologies such as freeze-thawing and high-pressure homogenization are the most efficient across all studied microalgae. The method selected for extraction had a greater impact on both the protein yield and structure for spray-dried cells.
- Microalgae protein: a comparison between spray-dryed and frozen paste cellsPublication . Moreira, Catarina; Nunes, Rafaela; Kholany, Mariam; Pereira, Hugo; Teixeira, José A.; Ferreira-Santos, Pedro; Rocha, Cristina M.R.The need for sustainable protein substitutes is being driven by the growing global population. Because of their high protein content and environmental sustainability, microalgae are a viable source. In this study, proteins extracted from frozen paste and spray-dried biomass from Nannochloropsis oceanica and Tetraselmis chui were studied. High-pressure homogenization, followed by ultrafiltration (non-purified, NPS) and ammonium sulfate precipitation (purified, PS), was used to process the protein extracts. PS extracts showed higher protein concentrations, reaching approximately three-fold higher levels than NPS in spray-dried N. oceanica and about 2.7-fold higher in frozen paste samples, while frozen paste T. chui exhibited a 2.6-fold increase. Spectroscopic and chromatographic analyses revealed that frozen paste extracts preserved a greater proportion of native protein structures and displayed higher hydrophobic site exposure, whereas spraydrying and purification reduced α-helix content and promoted protein aggregation. Despite their lower protein concentration, frozen paste NPS extracts exhibited more favorable structural characteristics that may support improved techno-functional performance. These results highlight the importance of selecting processing conditions based on intended applications. Future food formulations could benefit greatly from the use of microalgal proteins, especially those derived from frozen biomass, as adaptable and sustainable ingredients.