What's the purpose of blanching vegetables before roasting?

Question

Understand when and why blanching helps texture or color before roasting.

Answer 1

The purpose of blanching vegetables before roasting is usually to partially cook denser or tougher vegetables to ensure they become tender during roasting, especially if they are cooked alongside quicker-cooking items or if a very crispy exterior with a soft interior is desired (e.g., potatoes).

Detailed Explanation:

Blanching (briefly boiling then shocking in ice water) is a technique that can be beneficial before roasting certain vegetables, though it's not always necessary:

• Ensuring Tenderness (especially for dense vegetables): For very dense or large-cut vegetables like potatoes (as detailed in 'crispy roasted potatoes'), parsnips, or even thick-cut carrots, blanching (or par-boiling) them until just tender ensures they cook all the way through during roasting without the outside burning. This is particularly useful if you're aiming for a very crispy exterior with a perfectly tender (not raw or crunchy) interior.
• Even Cooking in Mixed Roasts: If you're roasting a medley of vegetables with vastly different cooking times, blanching the denser vegetables can help them cook at a similar pace to the quicker-cooking ones.
• Preserving Color and Texture (less common for roasting): In other culinary contexts, blanching is used to set the color of green vegetables and retain a crisp-tender bite. While less critical for roasting, it can sometimes contribute to a more vibrant final color.
• Creating a Starchy Exterior (e.g., Potatoes): For potatoes, blanching followed by roughing them up creates a starchy, porous surface that gets incredibly crispy when roasted.

For most common vegetables like broccoli, cauliflower, Brussels sprouts, or bell peppers, if cut into appropriate sizes, direct high-heat roasting without blanching is usually sufficient to achieve tender-crisp results.

Pro Tip:

If you do blanch, always ensure the vegetables are thoroughly dried after draining (and ideally, after shocking in ice water if you use that step) before tossing with oil and roasting. Excess moisture is the enemy of crispness.