Recently an AnswerLine client called with concerns related to the safety of microwaving steam bag vegetables such as those sold under the Birds Eye Steamfresh label. These bags are sold with the vegetables inside as stand-alone products containing just vegetables or with sauces or seasonings. In general, microwaving foods in plastic containers may carry some health risks due to the transmission of BPA and pthalates from the plastic to the food. However, the bags being used for the steamed vegetable products are specifically manufactured for microwave steaming and do not contain BPA or pthalates. These bags are designed for a one-time use. If there is any concern, the packages can be opened and the vegetables steamed or prepared by another method.
Whether you purchase the microwave steam bag vegetables or not, there are advantages to steaming vegetables. Frozen vegetables are usually flash frozen right after picking. As a result, frozen vegetables may be more nutrient dense than fresh vegetables that have spent time in transit, sitting in a warehouse, or on display at the store.
Steaming by way of the microwave, stove top, or pressure cooker are healthy ways to cook vegetables to prevent nutrient loss and retain flavor, texture, and color. Steaming also helps to retain the water-soluble vitamins and minerals that would otherwise leech into cooking water. Water soluble vitamins are also heat sensitive, so quick cooking times helps to reduce nutrient loss. Vegetable nutrients along with fiber and phytochemicals, help to lower risk of high cholesterol, high blood pressure, heart disease, stroke, obesity, cancer, and vision loss.
Steam bag vegetables can be used in the same way as any frozen vegetable. While steam bags do add cost to the vegetables, there definitely is convenience in using the steam bag packaging as there is virtually no clean up involved. One doesn’t need to be confined to using an entire bag when a smaller amount is needed. The bag can be opened and a smaller portion taken out and steamed using another method. For additional information on steaming vegetables, check out Cooking Fresh Vegetables by Purdue University.
Steaming is also a great way to prepare frozen vegetables for use in a salad. One should not thaw frozen vegetables and eat them without cooking. Blanching prior to freezing stops the aging of vegetables but does not necessarily take care of contaminants that may be found in the field such as salmonella, listeria, and E.coli; contaminants can penetrate the tiny cell walls which are broken when the vegetables are blanched. All vegetables are packaged as ready-to-cook, not as ready-to-eat. Therefore, vegetables should be cooked to 165 degrees for that reason. In most cases this temperature can be reached by steaming the vegetables to tender-crisp and then letting them sit in a closed container for 5 minutes before serving.
Bottom line is that the best cooking method for frozen (and fresh) vegetables is steaming. If accomplishing that is by using pre-packaged steam bag vegetables, know that it is safe when package directions are followed. Besides nutrient retention, steamed vegetables will have better flavor and more desirable textures.