pH influences the interfacial properties of blue whiting (M. poutassou) and whey protein hydrolysates determining the physical stability of fish oil-in-water emulsions
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AuthorRuiz Álvarez, José María; Castillo Santaella, Teresa del; Maldonado Valderrama, Julia; Guadix Escobar, Antonio María; Guadix Escobar, Emilia María; García Moreno, Pedro Jesús
Fish oil-in-water emulsionsProtein hydrolysatesEmulsifier peptidesInterfacial tensionInterfacial dilatational rheologyPhysical stability
J.M. Ruiz-Alvarez et al. pH influences the interfacial properties of blue whiting (M. poutassou) and whey protein hydrolysates determining the physical stability of fish oil-in-water emulsions. Food Hydrocolloids 122 (2022) 107075 [https://doi.org/10.1016/j.foodhyd.2021.107075]
SponsorshipSpanish Government CTQ2017-87076-R
This work investigates the influence of the interfacial properties of whey protein (WPH) and blue whiting protein (BPH) hydrolysates on the physical stability of fish oil-in-water emulsions stabilized with these hydrolysates at pH 2 or 8. Measurements of interfacial tension and dilatational rheology confirmed that pH is a key factor affecting these interfacial properties of WPH and BPH. WPH, when tested at 1 and 10 mg/mL, showed a higher interfacial activity at pH 8 when compared to pH 2 or to BPH at pH 8 or 2, despite having a lower protein content. Moreover, when tested at 0.1 and 1 mg/mL, the dilatational modulus of WPH was significantly higher at pH 8 than at pH 2. These findings correlate with the formation of smaller oil droplets and a more resistant interfacial peptide layer for WPH at pH 8, hence explaining the improved physical stability of the 5% fish oil-in water emulsion stabilized with WPH at pH 8. BPH did not show significant differences in interfacial activity with pH but exhibited significantly higher dilatational elasticity and viscosity at pH 2 compared to pH 8 (when measured at 0.1 mg/mL and 0.01 or 0.1 Hz). This correlates with the formation of stable 5% fish oil-in-water emulsions with BPH at pH 2 but not at pH 8.