## 1 Introduction  
A balanced human diet is one of the most important factors for the health and proper homeostasis of the body, as it provides all the necessary nutrients that play an important role in the biochemical and signaling pathways that influence growth, energy expenditure,and general functioning. According to the pyramid of proper nutrition, grains, fruits, and vegetables form the basis [1]. One of the most important vegetable groups used in the daily diet as a major source of antioxidants--such as flavonoids, fiber, minerals, carotenoids, and vitamins--is vegetables from the _Brassicaceae_ family, with broccoli (_Brassic oleracea_ var. _italica_) being the most common representative [2]. Broccoli has a high nutritional value [3], is anti-inflammatory and anti-cancer [4], and has antibacterial properties [5]. Eaten raw, e.g., in the form of microgreens, Brassica vegetables provide the greatest nutritional value, while various thermal processing methods reduce the content of \"healthy\" compounds [6]. However, vegetables are usually thermally processed before consumption to improve their flavor and safety [7]. The most commonly used thermal processing techniques today are boiling, blanching, steaming, pan-frying, and air-frying [8]. Each of these techniques significantly affects the nutrient content as many of the bioavailable compounds are heat-sensitive. Therefore, it is important to determine which thermal processing techniques preserve the most bioactive plant compounds for optimal nutritional value [9]. The most commonly used thermal processing techniques are boiling and steaming, which affect the physical and chemical properties of vegetables. Some boiled and steamed vegetables, such as sathkora (_Citrus macroptera_), pumpkin (_Cucurbita maxima_), green peas (_Pisum sativum_), pepper (_Capsicum annuum_), and spinach (_Spinacia oleracea_), have been shown to contain more \(\beta\)-carotene than fresh vegetables. However, the total content of polyphenols and flavonoids decreased by up to 70.3% and 82.27%, respectively, during boiling compared to steaming, with a significant reduction in free radical scavenging activity by up to 56.73%, with the exception of carrots [10]. Although hot water was used in both techniques, steaming was more gentle because the vegetables were not immersed in water, and the nutrient loss was far lower than with boiling [11]. Using mature broccoli as an example, boiling caused a greater loss of chlorophyll, vitamin C, and glucosinolates than steaming [12]. Blanching is a technique similar to boiling, with the main difference being the time the vegetables are immersed in boiling water. Blanched white cauliflower had a stronger antioxidant potential with higher levels of total phenolics, protocatechic acid, quercetin, pyrogallol, vanillic acid, coumaric acid, and kaempfer than boiled cauliflower [13]. In recent years, pan-frying and air-frying have become increasingly popular alternatives for the thermal processing of vegetables, often used for green pepper seeds and mustard. It has been shown that these techniques usually lower the radical scavenging ability [14]. However, the antioxidant potential, measured by ABTS, of pepper seeds and mustard was not significantly affected by pan-frying and air-frying [15,16]. In addition, a study on dried colored bell peppers (_Capsicum annuum_) showed that the scavenging potential measured with DPPH almost did not decrease, but the ability to scavenge the ABTS radical was drastically reduced [17]. [PERSON] et al. [18] showed that the antioxidant capacity of red peppers (_Capsicum annuum_), measured by ABTS and DPPH, decreased after boiling and steaming, while air-frying significantly reduced it. This shows that different thermal processing methods specifically influence the nutritional value of different vegetables. Therefore, it is necessary to evaluate the polyphenol content and antioxidant capacity of each individual vegetable type with no unique \"rule of thumb\" to assess their nutritional potential after thermal processing [18,19].