Quality indices of the set-yoghurt prepared from bovine milk treated with horseradish peroxidase.

Horseradish peroxidase (HRP, EC 1.11.1.7) was applied to treat whole bovine milk in the presence or absence of ferulic acid (FA). The treated milk exhibited different rheological properties from the control milk, and was used to prepare set-yoghurt with commercial direct vat set starter. Some chemical, textural and rheological properties of the yoghurt prepared were measured and compared. Compared to that prepared with the control milk, the yoghurt prepared with the HRP- or HRP and FA-treated bovine milk exhibited an increased hardness and adhesiveness, lower syneresis extent, higher apparent viscosity, and higher storage modulus and viscous modulus. Observation of the microstructure of the yoghurt samples under scanning electron microscopy illustrated that HRP treatment of bovine milk led to the prepared yoghurt a more compact and uniform structure. The results in the present work stated that treatment of bovine milk with HRP in the presence of ferulic acid could be applied to improve the quality of set-yoghurt.