Stabilization of natural pigments in ethanolic solutions for food applications: the case study of Chlorella vulgaris

• Published in: Molecules (Basel, Switzerland) Switzerland), 2023-01, Vol.28 (1), p.1-15
• Main Authors: Ferreira, Andreia S., Pereira, Liliana, Canfora, Feliciana, Silva, Tiago H., Coimbra, Manuel A., Nunes, Cláudia
• Format: Article
• Language: English
• Subjects: Case studies; Chlorella; Chlorella vulgaris; Chlorophyll; Chloroplasts; Color; Color stability; Cryopreservation; Efficiency; Ethanol; Ethanolic extract; Food; Food ingredients; Food products; Light; Modified atmospheres; Natural & organic foods; Pigments; Science & Technology; Sodium hydroxide; Solvents
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules28010408

Chlorella vulgaris is a green microalga with a high chlorophyll content, representing a valuable source of green pigments for food applications. As the application of whole biomass can promote an unpleasant fish-like flavor, the use of chlorophyll extract can overcome this drawback. However, chlorophylls tend to easily degrade when out of the chloroplasts, decreasing their potential as a food ingredient. Thus, to study the suitable conditions for isolated chlorophylls preservation, in this work, the influence of temperature (4 to 60 °C), light (dark or 24 h photoperiod), alkaline conditions (with or without aqueous NaOH addition), and modified atmosphere (air or argon atmosphere) on the stability of the color in ethanolic solutions obtained from C. vulgaris were studied. The loss of green color with temperature followed the first-order kinetics, with an activation energy of 74 kJ/mol. Below 28 °C and dark conditions were suitable to preserve isolated chlorophylls. The addition of NaOH and an inert argon-rich atmosphere did not exhibit a statistically positive effect on color preservation. In the case study, cooked cold rice was colored to be used in sushi. The color remained stable for up to 3 days at 4 °C. Therefore, this work showed that C. vulgaris chlorophylls could be preserved in ethanolic solutions at room or lower temperatures when protected from light, allowing them to obtain a suitable natural food ingredient to color foodstuffs. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials (UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020) and LAQV-REQUIMTE (UIDB/50006/2020 and UIDP/50006/2020), financed by national funds through the FCT/MEC (PIDDAC). Authors acknowledge the European Union (FEDER funds through the Operational Competitiveness Program (COMPETE2020) POCI-01-0247-FEDER-046080–Project cLABEL+-Innovative natural, nutritious, and consumer-oriented clean label foods). Andreia S. Ferreira thanks FCT for the individual grant (SFRH/BD/102471/2014) and for her post-Doc grant ref. REQUIMTE 2021-51.