Effects of Pressure Cooking on Food: Nutrient Loss or Retention?
No question about it, pressure cooking is one of the fastest and cheapest ways to prepare a hot meal. But how healthy are foods prepared this way? From a nutritional point of view, how do pressure cooked foods compare, for example, with meals cooked in a traditional stove-top steamer? Let's find out!
Health Benefits of Using a Pressure Cooker
Using a stove-top or electric pressure cooker to cook food is one of the fastest methods of cooking vegetables, beans, meat and poultry. In some cases, using a pressure cooker can reduce the cooking time of a food by up to 70 percent, compared with other conventional cooking methods! Despite the speed of this method, the food will be thoroughly cooked, with wonderful flavor similar to what you get when you use slow-cooking methods such as simmering at low heat. The effect a pressure cooker can have on the time you spend in the kitchen also leads to one of the greatest health benefits of using a pressure cooker: avoiding the need to resort to junky fast food meals when you are under time pressure (pardon the pun)!
But, reducing the time needed to cook healthy foods with notoriously long cooking times (such as beans and brown rice) is hardly the only health benefit of preparing food this way: scientific studies show that pressure cooking can also have some positive effects on the nutritional value of foods, when compared with other common food preparation methods such as steaming, boiling and roasting (surprising – but true!). The rest of this article explains in detail why this rediscovered cooking method is considered so healthy.
High Retention of Antioxidants and Vitamins (Compared with Steaming)
Steaming is considered one of the healthiest methods of preparing food as it helps your vegetables retain the nutrients they contain. Boiling, by contrast, can result in significant nutrient losses as many of the vitamins and minerals leach out of the vegetables into the cooking water. Of course, if you are planning to use the cooking water as well, this is not a problem, but in many (if not most) cases the nutrient-dense water produced during boiling ends up going down the drain.
Steaming food in a pressure cooker has the same advantage as cooking food in an electric steamer or the more traditional bamboo steamer: improved nutrient retention thanks to minimal direct contact of food with the cooking water.
But, the short cooking time associated with pressure cooking may have an additional benefit: an increase in the antioxidant capacity of the food. In one study, researchers from North Dakota State University found that both conventional boiling and steaming caused significant decreases in total phenolic content and antioxidant capacity – expressed as ORAC units – of the tested legumes, while pressure boiling and pressure steaming increased the ORAC values of the tested legumes. This study, published in the September 2008 issue of the journal Food Chemistry, focused on cool season legumes including green peas, yellow peas, chickpeas and lentils.
In another study, published in the March 2007 edition of the Journal of Food Science, pressure cooking broccoli was found to retain 92% of its vitamin C content, compared to retention rates of 78% and 66% for conventional steaming and boiling, respectively. During pressure cooking, broccoli also retained most of its sulforaphane, which was not the case when the broccoli samples were steamed or boiled using conventional methods. (In case you missed the memo, sulforaphane is a powerful, health-promoting phytochemical that has been linked to many of broccoli's health benefits, in particular its anti-cancer effects.)
Pressure-Cooked Foods Contain Little Acrylamide
When heated to high temperatures, starchy foods typically form acrylamide, a harmful chemical that, when consumed in high amounts, may lead to diseases and conditions like cancer, infertility and certain neurological disorders. The good news is that water vapor appears to hinder formation of acrylamide in foods. This is why steamed and boiled foods, including foods cooked by pressurized steam, contain little acrylamide. By contrast, foods prepared by baking or roasting may contain significant levels of this carcinogenic, neurotoxic substance.
Pressure Cooking Destroys Lectins
A study published in the May 1996 issue of the Journal of the Science of Food and Agriculture found that pressure cooking was as good as fermentation at reducing the lectin content of peas. Lectins are anti-nutrients that can reduce the nutritional value of food by hindering the absorption of certain minerals. In addition to peas, lectins are found in significant amounts in foods like wheat, seeds, beans and lentils.