Glucosinolates (GSL) are sulfur-containing compounds that are predominantly found in cruciferous vegetables such as broccoli, kale, and Brussels sprouts, and are known for their health benefits.
After consumption, GSL are broken down by the enzyme myrosinase, resulting in the formation of bioactive compounds such as isothiocyanates and breakdown products of indole glucosinolates. All of them have a beneficial effect on health, including anti-cancer, anti-inflammatory, and cardioprotective effects.
The recommended intake of cruciferous vegetables varies from 100 to 300 g per day depending on specific health goals.
It has been established that consuming 100-200 g of cruciferous vegetables per day, including broccoli and various types of cabbage, significantly reduces the risk of developing cancer, especially in the lungs and gastrointestinal tract.
Similarly, daily consumption of 200 g of broccoli, cauliflower, and Brussels sprouts is associated with an 8-19% reduction in the risk of colorectal and stomach cancer.
For cardiovascular health, consuming 300 g of cruciferous vegetables per day demonstrates significant benefits. Studies have shown that this level of consumption lowers systolic blood pressure and improves vascular function in individuals with moderately elevated blood pressure.
Even lower quantities, such as 30 g of broccoli and radish per day, can protect against types of cancer such as colorectal and breast cancer due to the high content of bioactive compounds like sulforaphane.
The most significant loss of GSL from these vegetables occurs during home cooking. It has been noticed that in fully cooked broccoli, the bioavailability of isothiocyanates is only one-third of their content in raw or undercooked vegetables. Furthermore, nitriles, not isothiocyanates, are formed at high temperatures.
The cooking time also plays a crucial role and should be kept to a minimum to preserve the beneficial properties. Comparative studies of different cooking methods have shown that the sulforaphane content in broccoli decreases by 20% when steamed, 36% when fried, and 88% when boiled.
Boiling leads to significant cell destruction and loss of glucosinolates, resulting in a reduction of up to 60% in cabbage and broccoli.
Boiling leads to a loss of up to 57% of glucosinolates, while steaming allows better preservation of these compounds, and blending results in only 18-36% losses.
This highlights how different cooking methods impact the preservation of beneficial glucosinolates. Overall, blending or steaming better preserves the nutritional properties of cruciferous vegetables, while boiling, even for short periods (1-10 minutes) at temperatures from 50°C to 100°C, leads to the worst conditions for preserving glucosinolates due to their water solubility and easy diffusion into the cooking medium.
Studies on microwave cooking have shown that this technology can be useful for preparing cruciferous vegetables using low power (540 W) and short periods, without water. Under such conditions, GSL losses are less than 18%, and myrosinase remains active, promoting the formation of isothiocyanates instead of nitriles.
Cooking food in the microwave at low power retains 82% of glucosinolates compared to only 36% when boiling broccoli.
A recent study has shown that air frying is a good cooking method for cruciferous vegetables, including various types of cabbage, Brussels sprouts, and broccoli, especially for the overall content of flavonoids and phenols, although glucosinolate losses ranged from 30% to 70%.