We are accustomed to hearing about how healthy fresh foods are and how research aims to preserve the organoleptic and nutritional quality of processed foods. A significant amount of public and private money is invested in trying to achieve healthier foods from the field itself, researching agricultural processes to health. This is done to increase or preserve compounds such as carotenoids, glucosinolates, (poly)phenols, fatty acids, vitamins, minerals, etc., classified as beneficial metabolites for human health.
This is due to the ability of these bioactive compounds to prevent cardiovascular diseases (CVD), tumor formation, high blood cholesterol, and other pathologies.
However, what happens when a fresh product, like broccoli, leaves the company with all its properties improved and optimized? Firstly, it is usually transported in controlled conditions to the warehouse or distributed to the final point of sale. Up to this point, it can be assumed that nutritional characteristics are maintained, as both trucks and shelves must maintain specific conditions to ensure proper product preservation (refrigeration in this case).
Nevertheless, after being acquired by the end consumer or the restaurant, they usually undergo culinary treatments that transform the food into a cooked dish ready to eat. Domestic cooking methods have been developed to make the final product more attractive in terms of taste, appearance, and consistency. At the same time, this process makes foods more digestible, microbiologically safer, but also more or less nutritious, depending on the selected technology. Therefore, at this point in the food chain, there can be significant losses of bioactive compounds, and the person who cooks takes center stage. They can, in a moment, invalidate all the care and investment mentioned earlier.
The most common cooking methods, specifically for broccoli (the food in question), involve the use of heat, as it is rarely consumed (or was consumed) raw. In general, the most commonly used methods are boiling (i.e., immersion in water), pressure cooking (which shortens the time), steaming (without contact with water), microwaving (which requires some water to achieve an acceptable texture), or sautéing.
Studies have shown that, in general, the most negative effects come from direct contact with water, excessive cooking time, and very high temperatures. Therefore, it is advisable to minimize these factors as much as possible.
In this regard, it has been observed that under normal cooking conditions of 200 g of broccoli, the microwave (for 4 minutes at maximum power, with water) is the worst system, as it can lead to a loss of up to 65% of bioactive compounds (polyphenols, glucosinolates, or vitamin C). In second place are boiling and pressure cooking, where losses range from 20 to 45%, and finally, the best method has proven to be steaming, where only losses of 5% are obtained.
An intermediate example, where water is not involved, is sautéing. In this regard, the type of oil is decisive, with extra virgin olive oil being the most suitable, ahead of refined, coconut, sunflower, etc. Although losses are always higher than 20%.
As mentioned earlier, all cooking methods can be improved by trying to reduce temperature or time, depending on personal preferences, but one should always try to achieve a texture that is as crispy as possible.
Therefore, when we have broccoli at home, let’s not be the ones to spoil all the previous work and investment with poor cooking, as proper home practice can help increase the intake of bioactive compounds, improving functionality, and reducing the risk of chronic diseases.
Dr. Cristina García-Viguera
Research Professor at CSIC
Laboratory of Phytochemistry and Healthy Foods (LabFAS), CEBAS-CSIC
Campus de Espinardo 25, 30100, Espinardo-Murcia