Enhancing the water solubility and stability of zinc modulated chlorophyll by alginate-whey protein isolate complexes at different pH values

Chlorophyll (Chl), a natural pigment, is widely used in the food, pharmaceutical, and cosmetic industries for its vibrant green color. However, its application is limited by its poor solubility and stability in aqueous solutions, especially under acidic conditions. This study investigates a novel approach to enhance the solubility and stability of zinc modulated chlorophyll (Chl-Zn2+) by complexation with whey protein isolate (WPI) and alginate (ALG). Encapsulation of Chl-Zn2+ with WPI prevented its precipitation between pH 3 and pH 7, except at the isoelectric point (pI) of WPI (around pH 4.5). The visual appearance, colorimetric measurements, and absorbance spectra indicated that Chl-Zn2+ formed stable complexes with WPI at various pH. Additionally, the inclusion of ALG prevented isoelectric precipitation at pH 4.5, likely due to electrostatic interactions between WPI and ALG, leading to the formation of stable Chl-WPI-ALG complexes. These complexes significantly improved the color stability and solubility of Chl-Zn2+ during storage under both neutral and acidic conditions. Fluorescence spectroscopy and particle size measurements confirmed the formation of these complexes and their enhanced stability. This study suggests that the use of WPI and ALG to encapsulate Chl-Zn2+ could be an effective method to expand its application in acidic food products, providing a stable and vibrant natural colorant.