The only difference between a bamboo steamer and a metal/plastic steamer is that a bamboo steamer will absorb (some of them) moisture from the steam, rather than allowing it to recondense and drop into the food.
It’s possible that recondensed moisture could take a small number of water-soluble nutrients with it, but between the limited ability of bamboo to absorb water and the limited amount of time that water would be in contact with the food, I don’t imagine it adds up to much.
What it may add up to is a slightly different cooking process in total. A metal steamer gets a bit hotter than a bamboo one, meaning the bottom of the food might be a bit crisper. That can be useful, or not – making dumplings or other bread products, lower heat means less sticking to the wrapper/steamer. A bamboo steamer will absorb some of the flavors of what you’re cooking (and keep it), meaning it can add some interesting flavors to other things you cook (which can be good or bad), although that’s controversial and appears to be only a minimal effect.
Many stainless steel cookware sets will usually come with a metal steamer included. To use, the saucepan is filled with water and the steamer fits snugly on top.
Once the water comes to a boil, the food is placed inside the metal steamer and the lid placed on top to close in the steam, which will lightly cook the food (usual vegetables) inside.
Your choice of the steamer for cooking vegetables will not depend so much on the materials. However, the traditional way to steam is to use a Chinese steamer.
The concept of cooking with a bamboo steamer is somewhat similar. A wide pan, or wok, is partially filled with about 2-inches of water and on medium heat, without the steamer on top of any sort of cover, allow the water to come to a simmer (do not let it come to a boil). Place the steamer, with the lid on top, cover the pot. The simmering water will steam (lightly cook) the food in the bamboo steamer. The length of time it will take to steam will depend on the particular food.
It is important to watch the water level in the pan/wok (whether using a bamboo or metal steamer) so that it does not run dry (add more water as necessary).
There is a lot of discussion about the differences (if any) between a stainless steel steamer (used with a lid and saucepan) and a bamboo steamer (often used with a wok or other wide-type pan).
While a metal pan may heat the water and trap the steam faster and possibly even more efficiently, the end goal of steaming isn’t about the speed; overcooking is so easy to do in a metal container which is heated from all sides and that defeats much of the purpose of using a steamer to cook in a healthier way.
Have you ever felt that your food had an aftertaste from the metal pots you cook in? Well, that may not actually be your imagination! According to this article by Cooks Illustrated, when certain ingredients are cooked in metallic pans, such as those made of aluminum or unseasoned cast iron, small amounts of molecules from the metal can seep into the food. These tiny amounts aren’t toxic, but they will add an unwanted and lasting aftertaste to your meal.
There are also electric steamers on the market, but a bamboo steamer is a better choice for those who would rather stay away plastic, and instead want to opt for natural, environmentally-friendly materials.
