Set Recipient in Sprout Email Notification
This is possible with the Sprout Forms Invisible Field (be sure to update to the latest version). Using the Invisible Field will ensure your email address never shows up in the template. To set this up:

1) Add an Invisible Field (invisibleFieldHandle) to your form and set its value to {recipient}

2) Setup a Notification Email and set your Recipient field to the name of your Invisible Field Handle: {invisibleFieldHandle}

3) Before your Sprout Forms displayForm tag, set the value of the Email Address where you want to trigger the Notification Email:

{% do craft.sproutForms.addFieldVariables({ 
  recipient: 'email@website.com'
}) %}

{% craft.sproutForms.displayForm('contact') %}