Extraction method of bromelain

The invention discloses an extraction method of bromelain, and belongs to the technical field of bromelain. The method comprises the following steps: step 1, pretreatment: taking pineapple squeezed juice with an ice block structure, putting the pineapple squeezed juice into an enzyme separation tank, adding purified water, adjusting the temperature of the enzyme separation tank to 4-15 DEG C, and unfreezing the pineapple squeezed juice; step 2, preparing a pineapple juice treatment solution, adding a proper amount of a sodium benzoate solution and a sodium pyrosulfite solution into an enzyme separation tank, and stirring to obtain the pineapple juice treatment solution; step 3, performing enzyme precipitation treatment, adding a proper amount of tannic acid solution while stirring the pineapple juice treatment liquid, and continuously stirring for 1-2 minutes after the tannic acid solution is added; step 4, settling treatment: standing and settling for 0.5-1 hour at the temperature of 4-15 DEG C, removing sup