Gelling Properties of Tyrosinase-Treated Dairy Proteins

Abstract

Protein-based viscous gels can augment or replace carbohydrate-based ones for specific nutritional formulations such as in reduced calorie or low-fat food applications. In this study, slurries of whey protein isolates and calcium caseinate mixed with alginic acid (20% T.S.) were subjected to high-shear homogenization (microparticulation) at 27,000 rpm for 2, 3, 4, and 6 min. The resulting slurries were incubated with mushroom tyrosinase (E.C. 1.14.18.1) at levels of 3, 6, and 9 mg/100 g for 15, 30, and 60 min to facilitate gel formation of the alginic acid with the homogenized dairy proteins. The results indicate that the time of high-shear homogenization had significant (P< 0.05) effect on the viscosities of the gels. Highest gel viscosity was obtained with 6 mg tyrosinase at 60 min, but increases in gel viscosity depended on time of shear, with 2 and 4 min shear resulting in higher viscosity (484 and 6,143 cP) and stronger complex viscosity (49 and 38 Pa.s at 1 rad/s), respectively, compared to the control (69 cP) and (12 Pa.s at 1 rad/s). Gels were stable in refrigerated storage up to 240 h, strengthened with time of refrigeration storage, and became significantly more viscoelastic. Optimal viscous properties were obtained at 4 min microparticulation, 60 min incubation, and 6 mg tyrosinase treatment.

In vitro digestibility and rheological properties of caseinates treated by an oxidative system containing horseradish peroxidase, glucose oxidase and glucose

“…Oxidation of tyrosine residues result in an increase in molar mass, steric hindrance of the protein molecules and a higher viscous aqueous solutions (Fargemand et al, 1998). Milk proteins treated by mushroom tyrosinase resulted in the dispersion a higher viscosity (Onwulata & Tomasula, 2010). Laccase, peroxidase (Fargemand et al, Fig.…”

Effect of protein structural integrity on cross-linking by tyrosinase evidenced by multidimensional heteronuclear magnetic resonance spectroscopy

“…Tyrosinases have been also investigated in dairy processing (Thalmann and Lötzbeyer, 2002;Onwulata and Tomasula, 2010;Ercili Cura et al, 2010) to improve the texture of products. However, due to the brownish color formation during the reactions, the applicability of tyrosinases in certain food applications may be limited (Martinez and Whitaker, 1995;McEvily et al, 1992;Falguera al., 2010).…”

Effect of Trichoderma reesei tyrosinase on rheology and microstructure of acidified milk gels

“…Selinheimo et al (2007a) showed that tyrosinase from P. sanguineus and T. reesei could cross-link a-casein while tyrosinase from A. bisporus and plant tyrosinases were able to create cross-links only in the presence of an auxiliary compound. Mushroom tyrosinase was reported to increase the viscosity of heatinduced milk protein gels prepared by addition of alginic acid and high-shear homogenization (Onwulata & Tomasula, 2008). Moreover, tyrosinases were also reported to induce formation of proteineoligosaccharide conjugates (Selinheimo, Lampila, Mattinen, & Buchert, 2008) and grafting of peptides onto polysaccharides (Aberg, Chen, Olumide, Raghavan, & Payne, 2004).…”

“…Therefore, enzymatic tailoring of the interactions between casein molecules is expected to alter the structural properties of the milk protein-based systems. To our knowledge, there are only a few reports (Ercili Cura et al, 2009;Onwulata & Tomasula, 2008;Steffensen, Andersen, Degn, & Nielsen, 2008) focused on the utilization of oxidative enzymes in structure modification of dairy systems. The aim of this work was to elucidate the gelation of milk proteins upon modification by two tyrosinases of different origin, i.e., T. reesei tyrosinase and A. bisporus tyrosinase.…”