Unit Operations in Dairy and Food Engineering

Green peas are blanched in hot water at $90.0^\circ\text{C}$ to inactivate peroxidase. At $90.0^\circ\text{C}$, the decimal reduction time of peroxidase is $D_{90} = 0.50\text{ minutes}$. To achieve a $4D$ reduction ($99.99\%$ inactivation) of peroxidase activity, the required blanching time in minutes is ________ (answer in integer).